Anomalous Behaviors of Block Copolymers at the Interface of an Immiscible Polymer Blend

Science.gov (United States)

Ryu, Ji Ho; Lee, Won Bo

We investigate the effects of structure and stiffness of block copolymers on the interface of an immiscible polymer blend using coarse-grained molecular dynamics (CGMD) simulation. The diblock and grafted copolymers, which are described by Kremer and Grest bead spring model, are used to compare the compatibilization efficiency, that is, reduction of the interfacial tension. It is found that, overall, the grafted copolymers are located more compactly at the interface and show better compatibilization efficiency than diblock copolymers. In addition, it is noted that an increase in the stiffness of one block of diblock copolymer causes inhomogeneous interfacial coverage due to bundle formation among the stiff blocks and orientational constraint on bundled structures near the interface, which makes copolymers poor compatibilizers. The dependence of anomalous orientational constraint on the chain length of homopolymers is also investigated. Theoretical and Computational Soft Matters Lab.

Functional porous composites by blending with solution-processable molecular pores.

Science.gov (United States)

Jiang, S; Chen, L; Briggs, M E; Hasell, T; Cooper, A I

2016-05-25

We present a simple method for rendering non-porous materials porous by solution co-processing with organic cage molecules. This method can be used both for small functional molecules and for polymers, thus creating porous composites by molecular blending, rather than the more traditional approach of supporting functional molecules on pre-frabricated porous supports.

Stability of monolayers and bilayers in a copolymer-homopolymer blend model

NARCIS (Netherlands)

Gennip, van Y.; Peletier, M.A.

2007-01-01

We study the stability of layered structures in a variational model for diblock copolymer- homopolymer blends. The main step consists of calculating the first and second derivative of a sharp-interface Ohta-Kawasaki energy for straight mono- and bilayers. By developing the interface perturbations in

A poly(vinyl alcohol)/sodium alginate blend monolith with nanoscale porous structure.

Science.gov (United States)

Sun, Xiaoxia; Uyama, Hiroshi

2013-10-04

A stimuli-responsive poly(vinyl alcohol) (PVA)/sodium alginate (SA) blend monolith with nanoscale porous (mesoporous) structure is successfully fabricated by thermally impacted non-solvent induced phase separation (TINIPS) method. The PVA/SA blend monolith with different SA contents is conveniently fabricated in an aqueous methanol without any templates. The solvent suitable for the fabrication of the present blend monolith by TINIPS is different with that of the PVA monolith. The nanostructural control of the blend monolith is readily achieved by optimizing the fabrication conditions. Brunauer Emmett Teller measurement shows that the obtained blend monolith has a large surface area. Pore size distribution plot for the blend monolith obtained by the non-local density functional theory method reveals the existence of the nanoscale porous structure. Fourier transform infrared analysis reveals the strong interactions between PVA and SA. The pH-responsive property of the blend monolith is investigated on the basis of swelling ratio in different pH solutions. The present blend monolith of biocompatible and biodegradable PVA and SA with nanoscale porous structure has large potential for applications in biomedical and environmental fields.

Nanoparticle Encapsulation in Diblock Copolymer/Homopolymer Blend Thin Film Mixtures

Science.gov (United States)

Zhao, Junnan; Chen, Xi; Green, Peter

2014-03-01

We investigated the organization of low concentrations of poly (2-vinylpyridine) (P2VP) grafted gold nanoparticles within a diblock copolymer polystyrene-b-poly (2-vinylpyridine) (PS-b-P2VP)/homopolymer polystyrene (PS) blend thin film. The PS-b-P2VP copolymers formed micelles, composed of inner cores of P2VP block and outer coronae of PS blocks, throughout the homopolymer PS. All nanoparticles were encapsulated within micelle cores and each micelle contained one or no nanoparticle, on average. When the host PS chains are much longer than corona chains, micelles tended to self-organize at the interfaces. Otherwise, they were dispersed throughout the PS host. In comparison to the neat PS-b-P2VP/PS blend, the nanoparticles/PS-b-P2VP/PS system had a higher density of smaller micelles, influenced largely by the number of nanoparticles in the system. The behavior of this system is understood in terms of the maximization of the nanoparticle/micelle core interactions and of the translational entropies of the micelles and the nanoparticles.

Comparing blends and blocks: Synthesis of partially fluorinated diblock polythiophene copolymers to investigate the thermal stability of optical and morphological properties

Directory of Open Access Journals (Sweden)

Pierre Boufflet

2016-10-01

Full Text Available The microstructure of the active blend layer has been shown to be a critically important factor in the performance of organic solar devices. Block copolymers provide a potentially interesting avenue for controlling this active layer microstructure in solar cell blends. Here we explore the impact of backbone fluorination in block copolymers of poly(3-octyl-4-fluorothiophenes and poly(3-octylthiophene (F-P3OT-b-P3OT. Two block co-polymers with varying block lengths were prepared via sequential monomer addition under Kumada catalyst transfer polymerisation (KCTP conditions. We compare the behavior of the block copolymer to that of the corresponding homopolymer blends. In both types of system, we find the fluorinated segments tend to dominate the UV–visible absorption and molecular vibrational spectral features, as well as the thermal behavior. In the block copolymer case, non-fluorinated segments appear to slightly frustrate the aggregation of the more fluorinated block. However, in situ temperature dependent Raman spectroscopy shows that the intramolecular order is more thermally stable in the block copolymer than in the corresponding blend, suggesting that such materials may be interesting for enhanced thermal stability of organic photovoltaic active layers based on similar systems.

Structure–Conductivity Relationships in Ordered and Disordered Salt-Doped Diblock Copolymer/Homopolymer Blends

Energy Technology Data Exchange (ETDEWEB)

Irwin, Matthew T.; Hickey, Robert J.; Xie, Shuyi; So, Soonyong; Bates, Frank S.; Lodge, Timothy P. (UMM)

2016-11-21

We examine the relationship between structure and ionic conductivity in salt-containing ternary polymer blends that exhibit various microstructured morphologies, including lamellae, a hexagonal phase, and a bicontinuous microemulsion, as well as the disordered phase. These blends consist of polystyrene (PS, M_n ≈ 600 g/mol) and poly(ethylene oxide) (PEO, M_n ≈ 400 g/mol) homopolymers, a nearly symmetric PS–PEO block copolymer (M_n ≈ 4700 g/mol), and lithium bis(trifluoromethane)sulfonamide (LiTFSI). These pseudoternary blends exhibit phase behavior that parallels that of well-studied ternary polymer blends consisting of A and B homopolymers compatibilized by an AB diblock copolymer. The utility of this framework is that all blends have nominally the same number of ethylene oxide, styrene, Li⁺, and TFSI– units, yet can exhibit a variety of microstructures depending on the relative ratio of the homopolymers to the block copolymer. For the systems studied, the ratio r = [Li⁺]/[EO] is maintained at 0.06, and the volume fraction of PS homopolymer is kept equal to that of PEO homopolymer plus salt. The total volume fraction of homopolymer is varied from 0 to 0.70. When heated through the order–disorder transition, all blends exhibit an abrupt increase in conductivity. However, analysis of small-angle X-ray scattering data indicates significant structure even in the disordered state for several blend compositions. By comparing the nature and structure of the disordered states with their corresponding ordered states, we find that this increase in conductivity through the order–disorder transition is most likely due to the elimination of grain boundaries. In either disordered or ordered states, the conductivity decreases as the total amount of homopolymer is increased, an unanticipated observation. This trend with increasing homopolymer loading is hypothesized to result from an increased density of �

High-throughput preparation of complex multi-scale patterns from block copolymer/homopolymer blend films

Science.gov (United States)

Park, Hyungmin; Kim, Jae-Up; Park, Soojin

2012-02-01

A simple, straightforward process for fabricating multi-scale micro- and nanostructured patterns from polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP)/poly(methyl methacrylate) (PMMA) homopolymer in a preferential solvent for PS and PMMA is demonstrated. When the PS-b-P2VP/PMMA blend films were spin-coated onto a silicon wafer, PS-b-P2VP micellar arrays consisting of a PS corona and a P2VP core were formed, while the PMMA macrodomains were isolated, due to the macrophase separation caused by the incompatibility between block copolymer micelles and PMMA homopolymer during the spin-coating process. With an increase of PMMA composition, the size of PMMA macrodomains increased. Moreover, the P2VP blocks have a strong interaction with a native oxide of the surface of the silicon wafer, so that the P2VP wetting layer was first formed during spin-coating, and PS nanoclusters were observed on the PMMA macrodomains beneath. Whereas when a silicon surface was modified with a PS brush layer, the PS nanoclusters underlying PMMA domains were not formed. The multi-scale patterns prepared from copolymer micelle/homopolymer blend films are used as templates for the fabrication of gold nanoparticle arrays by incorporating the gold precursor into the P2VP chains. The combination of nanostructures prepared from block copolymer micellar arrays and macrostructures induced by incompatibility between the copolymer and the homopolymer leads to the formation of complex, multi-scale surface patterns by a simple casting process.A simple, straightforward process for fabricating multi-scale micro- and nanostructured patterns from polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP)/poly(methyl methacrylate) (PMMA) homopolymer in a preferential solvent for PS and PMMA is demonstrated. When the PS-b-P2VP/PMMA blend films were spin-coated onto a silicon wafer, PS-b-P2VP micellar arrays consisting of a PS corona and a P2VP core were formed, while the PMMA macrodomains were isolated, due to the

Bulk and monolayer ordering of block copolymer blends

Science.gov (United States)

Onikoyi, Adetunji J.

The control of the nanoscale structure or morphology of a block copolymer is a desired goal for nanolithography applications. In this work, we are particularly interested in providing guides for controlling domain size, domain shape and defect densities in block copolymers and their blends for thin film applications. To reach this goal, a sphere forming PS-b-P2VP (having a PS majority block) and its blends with PS homopolymer or cylinder forming PS-b-P2VP are studied in both the bulk and thin films. Structure characterization is performed using a variety of experimental techniques including small angle X-ray scattering, scanning force microscopy and transmission electron microscopy. In the bulk, the spherical domains of the pure, sphere forming PS-b-P2VP arrange on a BCC lattice. On adding PS homopolymer (hPS), the lattice parameter of the BCC spheres increases, while the order-to-disorder temperature (ODT) of the BCC lattice simultaneously decreases. At a given hPS composition, the use of larger sized hPS leads to larger increases in the lattice parameter and larger decreases in the ODT. In bulk blends of cylinder forming PS-b-P2VP with sphere forming PS-b-P2VP, the ordered morphology changes (e.g., cylindrical morphology → coexisting spherical and cylindrical morphologies → spherical morphology) as the sphere forming PS-b-P2VP volume fraction phis increases, while the ODT of the cylindrical morphology decreases. The phase boundaries of these morphologies in monolayers shift to lower phis compared to those of the bulk, apparently caused by a selective adsorption of the cylindrical PS-b-P2VP to form a brush on the substrate. This selective adsorption leads to a preference for spherical domains in diamond-shaped lateral confinements when cylindrical domains are stabilized outside the confinements on the same substrate. Finally, we explore the use of graphoepitaxy to order monolayers of sphere forming PS-b-P2VP and its blends with hPS. The probability of forming

Modification of PE/PP Polymer Blend Nanocomposites with EPR and EVA Copolymers

Directory of Open Access Journals (Sweden)

Jelenčić, J.

2010-04-01

Full Text Available During the last decade, the use of polyolephinic polymers has been growing in a wide range of fields of applicability and the most widely used polymers are polyethylene and polypropylene. They can be processed separately to produce items with certain properties as well as in the form of blends, where special combinations of properties and price are intended. As it is known, polyethylene (PE and polypropylene (PP are incompatible and the weak interfacial bond strength between the phases directly linked to the blend morphology and results in poor mechanical properties. The properties of many polymer blends arise from the fine-scale structural arrangements or blend morphologies obtained during processing in addition to the proportion of each polymer type present. Compounding PE/PP blends with a single compatibilizer or their combination or some other additives as nanofiller, results in multi-component composites of great interest to research as they enable simultaneous improvement in the final properties of the blend. In addition, it is well known that the extrusion process has a significant effect on the dispersion of the filler in the blends. In this work, the mutual effect of the nanofiller silicium-dioxide (SiO2 and the compatibilizers ethylene-propylene copolymer (EPR and ethylene-vinyl acetate copolymer (EVA on the properties of blends based on polyethylene and polypropylene were studied. The morphology of the samples prepared with nanofiller and compatibilizers is much finer in comparison to the virgin blend. Better dispersion of nanofiller will result in better stability of the polymer blend and decrease in polymer flammability. The addition of the nanofiller and compatibilizers produced an increase in the elasticity especially for the samples prepared in the two-stage extrusion process where the nanofiller was first extruded with PE matrix and then with other polymers of the blends. SEM micrographs confirm finer morphology of samples

Bicontinuous Phases in Diblock Copolymer/Homopolymer Blends: Simulation and Self-Consistent Field Theory

KAUST Repository

Martínez-Veracoechea, Francisco J.; Escobedo, Fernando A.

2009-01-01

A combination of particle-based simulations and self-consistent field theory (SCFT) is used to study the stabilization of multiple ordered bicontinuous phases in blends of a diblock copolymer (DBC) and a homopolymer. The double-diamond phase (DD

Thermal, thermo-mechanical, and dynamic mechanical properties of polypropylene/cycloolefin copolymer blends

Czech Academy of Sciences Publication Activity Database

Fambri, L.; Kolařík, Jan; Pegoretti, A.; Penati, A.

2011-01-01

Roč. 122, č. 5 (2011), s. 3406-3414 ISSN 0021-8995 R&D Projects: GA ČR GA106/09/1348 Institutional research plan: CEZ:AV0Z40500505 Keywords : blends * poly (propylene) * cycloolefin copolymer Subject RIV: JI - Composite Materials Impact factor: 1.289, year: 2011

Biodegradable blends of poly (lactic acid) (PLA) / polyhydroxybutrate (PHB) copolymer and its effects on rheological, thermal and mechanical properties

Science.gov (United States)

Sood, Nitin K.

Poly (Lactic acid) is the most important plastic derived from the renewable resources. PLA based products have extensively been used in the medical industry. However, PLA has a few disadvantages such as inherent brittleness and low toughness despite a high modulus. A focus of this experiment was to study the improvement in toughness of PLA and to study the changes in thermal and rheological properties by blending PLA with a PHB copolymer. Where, PLA and PHB copolymer were melt blended using a twin screw Brabender extruder in the ratios of 100/0, 70/30, 50/50, 30/70, 0/100. Further, the blends were injection molded into tensile bar and impact bars for mechanical testing. Rheological properties were studied using a Galaxy capillary rheometer for melt viscosities and temperature dependence indicated a shear-thinning behavior along with power law model and consistency index. Blends were characterized to study the phase model using a differential scanning calorimetric (DSC), showed two separate phases. Mechanical properties were analyzed using a Tensile and Izod impact test indicating decrease in elastic modulus with increase in toughness and elongation as the PHB copolymer content was increased in the blend.

Comparative Study of the Physical, Topographical and Biological Properties of Electrospinning PCL, PLLA, their Blend and Copolymer Scaffolds

Science.gov (United States)

Bolbasov, E.; Goreninskii, S.; Tverdokhlebov, S.; Mishanin, A.; Viknianshchuk, A.; Bezuidenhout, D.; Golovkin, A.

2018-05-01

Biodegradable polymers (blends, copolymers) could be the ideal materials for manufacturing of scaffolds for small diameter vascular graft. Such material characteristics as mechanical properties, chemical structure, nano- and micro topography, surface charge, porosity, wettability etc. are becoming the most important aspects for effectiveness of prosthesis biofunctionalization because of their great impact on cell adhesion, spreading, cell proliferation, differentiation and cell function. The aim of the study is to compare physical, topographical and biological properties of polycaprolactone (PCL), poly-L-lactic acid (PLLA), polycaprolactone + poly-L-lactic acid blend (PCL PLLA), L-lactide/Caprolactone copolymer (PLC7015) scaffolds fabricated with the same fiber thickness using electrospun technology. PCL PLLA scaffolds had the highest average pore area (pactive phase of adhesion process. We propose that physical and topographical properties of PCL, PLLA, their blend and copolymer are of a great dependence of chemical structure but could be changed during the manufacturing process that will lead to changes in biological properties.

Phase Behavior of Binary Blends of AB+AC Block Copolymers with compatible B and C blocks

Science.gov (United States)

Pryamitsyn, Victor; Ganesan, Venkat

2012-02-01

Recently the experimental studies of phase behavior of binary blends of PS-b-P2VP and PS-b-PHS demonstrated an interesting effect: blends of symmetric PS-b-P2VP and shorter symmetric (PS-b-PHS) formed cylindrical HEX and spherical BCC phases, while each pure component formed lamellas. The miscibility of P2VP and PHS is caused by the hydrogen bonding between P2VP and PHS,which can be described as a negative Flory ?-parameter between P2VP and PHS. We developed a theory of the microphase segregation of AB+AC blends of diblock copolymers based on strong stretching theory. The main result of our theory is that in the copolymer brush-like layer formed by longer B chain and shorter C chains, the attraction between B and shorter C chains causes relative stretching of short C chains and compression of longer B chains. The latter manifests in an excessive bending force towards the grafting surface (BC|AA interface). Such bending force causes a transition from a symmetric lamella phase to a HEX cylinder or BCC spherical phases with the BC phase being a ``matrix'' component. In a blend of asymmetric BCC sphere forming copolymers (where B and C segments are the minor components), such bending force may unfold BCC spherical phase to a HEX cylinder phase, or even highly uneven lamella phases.

Improvements of fill factor in solar cells based on blends of polyfluorene copolymers as electron donors

International Nuclear Information System (INIS)

Gadisa, Abay; Zhang, Fengling; Sharma, Deepak; Svensson, Mattias; Andersson, Mats R.; Inganaes, Olle

2007-01-01

The photovoltaic characteristics of solar cells based on alternating polyfluorene copolymers, poly(2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3' -benzothia diazole)) (APFO-3), and poly(2,7-(9,9-didodecyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3' -benzothiadiazole)) (APFO-4), blended with an electron acceptor fullerene molecule [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM), have been investigated and compared. The two copolymers have the same aromatic backbone structure but differ by the length of their alkyl side chain. The overall photovoltaic performance of the solar cells is comparable irrespective of the copolymer used in the active layer. However, the fill factor (FF) values of the devices are strongly affected by the copolymer type. Higher FF values were realized in solar cells with APFO-4 (with longer alkyl side chain)/PCBM bulk heterojunction active layer. On the other hand, devices with blends of APFO-3/APFO-4/PCBM were found to render fill factor values that are intermediate between the values obtained in solar cells with APFO-3/PCBM and APFO-4/PCBM active film. Upon using APFO-3/APFO-4 blends as electron donors, the cell efficiency can be enhanced by about 16% as compared to cells with either APFO-3 or APFO-4. The transport of holes in each polymer obeys the model of hopping transport in disordered media. However, the degree of energetic barrier against hopping was found to be larger in APFO-3. The tuning of the photovoltaic parameters will be discussed based on studies of hole transport in the pure polymer films, and morphology of blend layers. The effect of bipolar transport in PCBM will also be discussed

Preparation and Properties of Poly (vinylidene fluoride)/poly(dimethylsiloxane) graft (poly(propylene oxide)-block-poly(ethylene oxide)) blend porous separators and corresponding electrolytes

International Nuclear Information System (INIS)

Li, Hao; Zhang, Hong; Liang, Zhi-Ying; Chen, Yue-Ming; Zhu, Bao-Ku; Zhu, Li-Ping

2014-01-01

Highlights: •This work aims exploring microporous PVDF separators for lithium ion batteries. •Comb structure polymer PDMS-g-(PPO-PEO) was used in PVDF blend separators. •The influence of polyether side chains on interfacial resistance was studied. -- Abstract: This work aims exploring the high performance porous separators that can be activated into gel electrolyte membranes for lithium ion batteries. A comb-like copolymer poly (dimethylsiloxane) graft poly (propylene oxide)-block-poly (ethylene oxide) (PDMS-g-(PPO-PEO)) was synthesized and blended with poly (vinylidene fluoride) (PVDF) to fabricate porous separators via a typical phase inversion process, and then the separators absorbed liquid electrolyte solution and formed into polymer electrolyte membranes. By measuring the composition, morphology and ion conductivity etc, the influence of PDMS-g-(PPO-PEO) on structure and properties of blend separators were discussed. Compared with pure PVDF separator with comparable porous structure, the adoption of PDMS-g-(PPO-PEO) decreased the crystallinity and increased the liquid electrolyte uptake and stability effectively. It was also found that the electrode/electrolyte interfacial resistance could be reduced greatly. The resulting electrolyte membrane using separator with PVDF/PDMS-g-(PPO-PEO) mass ratio in 8/2 exhibited highest ionic conductivity in 4.5 × 10 −3 S/cm at room temperature, while the electrochemical stability was up to 4.7 V (vs. Li/Li + ). Coin cells assembled with such separators also exhibited stable cycle performance and improved rate capabilities, especially when discharge rate higher than 0.5 C

Characteristics of PVdF copolymer/Nafion blend membrane for direct methanol fuel cell (DMFC)

International Nuclear Information System (INIS)

Cho, Ki-Yun; Eom, Ji-Yong; Jung, Ho-Young; Choi, Nam-Soon; Lee, Yong Min; Park, Jung-Ki; Choi, Jong-Ho; Park, Kyung-Won; Sung, Yung-Eun

2004-01-01

For direct methanol fuel cell, blends of vinylidene fluoride-hexafluoropropylene copolymer (P(VdF-co-HFP)) and Nafion were prepared the different equivalent weight of Nafion. The investigations of the blend morphology were performed by means of permeability test, uptake measurement, differential-scanning calorimetry (DSC), and scanning electron microscopy. In the blend membranes, many pores were created as the content of Nafion in blend increased. Then, the methanol uptake was sharply increased. But the methanol permeability was not sharply increased because the methanol permeation through blend membranes is diffusion-controlled process. The methanol permeability of N10 (low equivalent weight) series was similar to that of N11 series (high equivalent weight). The proton conductivity of N10 series was around one and a half times higher than that of N11 series. The cell performance of the blend was much enhanced when the equivalent weight of Nafion was 1000

The relationship between sol fraction and radiation dose in radiation crosslinking of low-density polyethylene (LDPE)/ethylenevinylacetate copolymer (EVA) blend

International Nuclear Information System (INIS)

Zhang, W.X.; Liu, Y.T.; Sun, J.Z.

1990-01-01

In this paper, two different methods were used to prepare the blend of low-density polyethylene (LDPE) and ethylene vinyl acetate copolymer (EVA). One of them was mechanical blending, and the other was solution blending. The relationship between sol fraction and radiation dose of different weight ratio polymer blends has been studied. The method to calculate the β b value of polymer blend system (LDPE/EVA) has been established. (author)

Cycloolefin-Copolymer/Polyethylene (COC/PE) Blend Assists with the Creation of New Articular Cartilage

Czech Academy of Sciences Publication Activity Database

Petrtýl, M.; Bastl, Zdeněk; Kruliš, Zdeněk; Hulejová, H.; Polanská, M.; Lísal, J.; Danešová, J.; Černý, P.

294-I, - (2010), s. 120-132 ISSN 1022-1360 R&D Projects: GA ČR GA106/06/0761 Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z40500505 Keywords : articular cartilage * biomaterials * cycloolefin-copolymer blend Subject RIV: CF - Physical ; Theoretical Chemistry

Asymmetric block copolymer membranes with ultrahigh porosity and hierarchical pore structure by plain solvent evaporation

KAUST Repository

Yu, H.

2016-09-14

Membranes with a hierarchical porous structure could be manufactured from a block copolymer blend by pure solvent evaporation. Uniform pores in a 30 nm thin skin layer supported by a macroporous structure were formed. This new process is attractive for membrane production because of its simplicity and the lack of liquid waste.

Asymmetric block copolymer membranes with ultrahigh porosity and hierarchical pore structure by plain solvent evaporation

KAUST Repository

Yu, H.; Qiu, Xiaoyan; Behzad, Ali Reza; Musteata, Valentina-Elena; Smilgies, D.-M.; Nunes, Suzana Pereira; Peinemann, Klaus-Viktor

2016-01-01

Membranes with a hierarchical porous structure could be manufactured from a block copolymer blend by pure solvent evaporation. Uniform pores in a 30 nm thin skin layer supported by a macroporous structure were formed. This new process is attractive for membrane production because of its simplicity and the lack of liquid waste.

One-step route to the fabrication of highly porous polyaniline nanofiber films by using PS-b-PVP diblock copolymers as templates.

Science.gov (United States)

Li, Xue; Tian, Shengjun; Ping, Yang; Kim, Dong Ha; Knoll, Wolfgang

2005-10-11

We report a new method to control both the nucleation and growth of highly porous polyaniline (PANI) nanofiber films using porous poly(styrene-block-2-vinylpyridine) diblock copolymer (PS-b-P2VP) films as templates. A micellar thin film composed of P2VP spheres within a PS matrix is prepared by spin coating a PS-b-P2VP micellar solution onto substrates. The P2VP domains are swollen in a selective solvent of acetic acid, which results in the formation of pores in the block copolymer film. PANI is then deposited onto the substrates modified with such a porous film using electrochemical methods. During the deposition, the nucleation and growth of PANI occur only at the pores of the block copolymer film. After the continued growth of PANI by the electrochemical deposition, a porous PANI nanofiber film is obtained.

The effect of copolymers on the interfaces in incompatible homopolymers blend: Molecular dynamics study

Science.gov (United States)

Ryu, Jiho; Lee, Won Bo

2015-03-01

Using molecular dynamics simulations the effect of copolymers as compatibilizer for reducing interfacial tension and enhancement of interfacial adhesion at the interface of thermodynamic unfavorable homopolymers blend is studied with block- and graft-copolymers. We have calculated local pressure tensor of system along the axis perpendicular to interface, varying bending potential energy of one part, which consist of just one kind of beads, of copolymer chain to examine the effect of stiffness of surfactin molecules. Here we consider symmetric diblock copolymer (f =1/2) having 1/2 N make of beads of type A and the other part made of beads of type B, and graft copolymer having backbone linear chain consist of 1/2 N beads of type of A and branched with two side-chain consist of 1/4 N beads of type B. All simulations were performed under the constant NPT ensemble at T* =1, ρ* ~0.85. Also we studied changes of effect of copolymers with increasing pairwise repulsive interaction potential between two beads of types A and B while homopolymers chain length are fixed, N =30. Chemical and Biomolecular Engineering, Sogang University, Seoul, South Korea.

Reversible Micro- and Nano- Phase Programming of Anthraquinone Thermochromism Using Blended Block Copolymers.

Science.gov (United States)

Zhang, Yumiao; Lovell, Jonathan F

2015-12-22

Here, we present an approach to generate materials with programmable thermochromic transition temperatures (TTTs), based on the reversible microcrystallization of anthraquinone dyes with the assistance of blended Pluronic block copolymers. At temperatures above block copolymer critical micellization temperature (CMT), hydrophobic anthraquinone dyes, including Sudan blue II, were dispersed in copolymer micelles, whereas at lower temperature, the dyes formed microcrystals driven by dye-dye and dye-Pluronic molecular interactions. The crystallization process altered the optical properties of the dye with bathochromatic shifts detectable by eye and the thermochromic process was fully reversible. Not only could Pluronic reversibly incorporate the anthraquinone dyes into micelles at elevated temperatures, but it also modulated the crystallization process and resulting morphology of microcrystals via tuning the molecular interactions when the temperature was lowered. Crystal melting transition points (and TTTs) were in agreement with the CMTs, demonstrating that the thermochromism was dependent on block copolymer micellization. Thermochromism could be readily programmed over a broad range of temperatures by changing the CMT by using different types and concentrations of Pluronics and combinations thereof.

Triplet State Formation in Photovoltaic Blends of DPP-Type Copolymers and PC71BM

KAUST Repository

Ochsmann, Julian R.

2015-04-29

The exciton dynamics in pristine films of two structurally related low-bandgap diketopyrrolopyrrole (DPP)-based donor–acceptor copolymers and the photophysical processes in bulk heterojunction solar cells using DPP copolymer:PC71BM blends are investigated by broadband transient absorption (TA) pump-probe experiments covering the vis–near-infrared spectral and fs–μs dynamic range. The experiments reveal surprisingly short exciton lifetimes in the pristine poly­mer films in conjunction with fast triplet state formation. An in-depth analysis of the TA data by multivariate curve resolution analysis shows that in blends with fullerene as acceptor ultrafast exciton dissociation creates charge carriers, which then rapidly recombine on the sub-ns timescale. Furthermore, at the carrier densities created by pulsed laser excitation the charge carrier recombination leads to a substantial population of the polymer triplet state. In fact, virtually quantitative formation of triplet states is observed on the sub-ns timescale. However, the quantitative triplet formation on the sub-ns timescale is not in line with the power conversion efficiencies of devices indicating that triplet state formation is an intensity-dependent process in these blends and is reduced under solar illumination conditions, as free charge carriers can be extracted from the photoactive layer in devices.

Interaction between poly(vinyl pyridine) and poly(2,6-dimethyl-1,4-phenylene oxide) : A copolymer blend miscibility study

NARCIS (Netherlands)

de Wit, Joost; van Ekenstein, Gert Alberda; ten Brinke, Gerrit

2007-01-01

The phase behavior of blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with random copolymers of styrene and 2-vinyl pyridine, Poly(S-co-2VP), as well as with random copolymers of styrene and 4-vinyl pyridine, Poly(S-co-4VP), has been investigated in order to estimate the values of the

Preparation, Characterization and Permeation Behavior of Poly(methyl acrylate-Poly(dimethyl siloxane-Poly(methyl acrylate Block Copolymer/Poly(vinyl acetate Blend Membranes

Directory of Open Access Journals (Sweden)

Mohammad Ali Semsarzadeh

2015-03-01

Full Text Available Structure of polymeric materials is of the most important factors in determination of the characteristics and properties of the membranes. Various research and developments on polymeric membranes confirm the direct correlation between structure-properties of polymeric membranes. In this research, the structural outcome of poly(methyl acrylate-poly(dimethyl siloxane-poly(methyl acrylate/poly(vinyl acetate blend membranes and its relationship with gas permeation behavior of the blends were investigated. The flexible block copolymer of poly(methyl acrylate-poly(dimethyl siloxane-poly(methyl acrylate (PMA-PDMS-PMA was synthesized via atom transfer radical polymerization. Morphology and chemical structure of the synthesized block copolymer was investigated by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography, X-ray diffraction analysis, differential scanning calorimetry and scanning electron microscopy. Blend membranes of PMA-PDMS-PMA and poly(vinyl acetate (PVAc were prepared by solution casting method in different compositions. By adding poly(vinyl acetate to PMA-PDMS-PMA block copolymer, the selectivity of the membranes for carbon dioxide/methane pair gases were increased by 55%. Fractional free volume (an indication of chain packing efficiency in blend membranes and dielectric constant (an indication of the molar volume and molar polarization of the blend membranes were obtained as the factors reflected the microstructural effect of PMA-PDMS-PMA and PVAc blend membranes. The efforts were directed toward expressing more precise structure-properties relationship of PMA-PDMS-PMA/PVAc blend membranes. The experimental permeability values of the blend membranes reported in this research were compared with the modified logarithmic model. The modified logarithmic model was evaluated for other blend membranes.

A poly(vinyl alcohol)/sodium alginate blend monolith with nanoscale porous structure

OpenAIRE

Sun, Xiaoxia; Uyama, Hiroshi

2013-01-01

A stimuli-responsive poly(vinyl alcohol) (PVA)/sodium alginate (SA) blend monolith with nanoscale porous (mesoporous) structure is successfully fabricated by thermally impacted non-solvent induced phase separation (TINIPS) method. The PVA/SA blend monolith with different SA contents is conveniently fabricated in an aqueous methanol without any templates. The solvent suitable for the fabrication of the present blend monolith by TINIPS is different with that of the PVA monolith. The nanostructu...

The Plumber’s Nightmare Phase in Diblock Copolymer/Homopolymer Blends. A Self-Consistent Field Theory Study.

KAUST Repository

Martinez-Veracoechea, Francisco J.; Escobedo, Fernando A.

2009-01-01

Using self-consistent field theory, the Plumber's Nightmare and the double diamond phases are predicted to be stable in a finite region of phase diagrams for blends of AB diblock copolymer (DBC) and A-component homopolymer. To the best of our

nanocomposites of PA6/ABS blends compatibilized with styrene-maleic anhydride copolymer

International Nuclear Information System (INIS)

Oliveira, Amanda D. de; Pessan, Luiz A.

2009-01-01

To achieve a balance between stiffness and toughness, ternary nanocomposites based on blends of polyamide 6 (PA6) and acrylonitrile-butadiene-styrene (ABS) were prepared by the melt intercalation using the organoclay Cloisite R 30B (OMMT) and the styrene-maleic anhydride copolymer (SMA) as compatibilizer. Four blending sequences were used to prepare studied systems and their mechanical properties studied through the Young's modulus and notched Izod impact. It was observed that the materials prepared by all blending sequences studied showed an increase in the Young's modulus compared to the neat PA6. However, a decrease in the toughness was observed for the systems with the addition of the organoclay. The DRX results showed an intercalated structure for the some systems that used ABS in their compositions. HDT measurements of the nanocomposites showed an increase in this property compared to the neat PA6. The use of nanoclay lead to a reinforcement of the polymeric matrix. (author)

Magnetic field alignment of coil-coil diblock copolymers and blends via intrinsic chain anisotropy

Science.gov (United States)

Rokhlenko, Yekaterina; Majewski, Pawel; Larson, Steven; Yager, Kevin; Gopalan, Padma; Avgeropoulos, Apostolos; Chan, Edwin; Osuji, Chinedum

Magnetic fields can control alignment of self-assembled soft materials such as block copolymers provided there is a suitably large magnetic susceptibility anisotropy present in the system. Recent results have highlighted the existence of a non-trivial intrinsic anisotropy in coil-coil diblock copolymers, specifically in lamellar-forming PS-b-P4VP, which enables alignment at field strengths of a few tesla in systems lacking mesogenic components. Alignment is predicated on correlation in the orientation of end-end vectors implied by the localization of block junctions at the microdomain interface and is observed on cooling across the order-disorder transition in the presence of the field. For appropriate combinations of field strength and grain size, we can leverage intrinsic chain anisotropy to magnetically direct self-assembly of many non-mesogenic systems, including other coil-coil BCPs like PS-b-PDMS and PS-b-PMMA, blends of BCPs of disparate morphologies and MWs, and blends of BCPs with homopolymers. This is noteworthy as blends of PS-b-P4VP with PEO provide a route to form functional materials such as nanoporous films by dissolution of PEO, or aligned ion conduction materials. We survey these various systems using TEM and in-situ X-ray scattering to study the phase behavior and temperature-, time- and field- dependent dynamics of alignment.

Morphology in binary blends of poly(vinyl methyl ether) and epsilon-caprolactone-trimethylene carbonate diblock copolymer

NARCIS (Netherlands)

Luyten, MC; Bogels, EJF; vanEkenstein, GORA; tenBrinke, G; Bras, W; Komanschek, BE; Ryan, AJ

The morphology of symmetric diblock copolymer of epsilon-caprolactone (PCL) and trimethylene carbonate (PTMC), in blends with poly(vinyl methyl ether) (PVME) is investigated with (modulated) differential scanning calorimetry (d.s.c.), time resolved small angle (SAXS) and wide angle (WAXS) X-ray

Morphology in binary blends of poly(vinyl methyl ether) and ε-caprolactone-trimethylene carbonate diblock copolymer

NARCIS (Netherlands)

Luyten, M.C.; Bögels, E.J.F.; Alberda van Ekenstein, G.O.R.; Brinke, G. ten; Bras, W.; Komanschek, B.E.; Ryan, A.J.

1997-01-01

The morphology of symmetric diblock copolymer of ε-caprolactone (PCL) and trimethylene carbonate (PTMC), in blends with poly(vinyl methyl ether) (PVME) is investigated with (modulated) differential scanning calorimetry (d.s.c.), time resolved small angle (SAXS) and wide angle (WAXS) X-ray

Compatibilization of low-density polyethylene/polystyrene blends by segmented EB(PS-block-EB)(n) block copolymers

NARCIS (Netherlands)

Kroeze, E; ten Brinke, G.; Hadziioannou, G

Hydrogenated segmented poly[butadiene-block-(styrene-block-butadiene)(n)] block copolymers, which were developed by use of a polymeric iniferter technique, were tested on their compatibilizing effectiveness for (10/90) LDPE/PS blends. They were found to be effective compatibilizers for this mixture,

Towards quantification of butadiene content in styrene-butadiene block copolymers and their blends with general purpose polystyrene (GPPS) and the relation between mechanical properties and NMR relaxation times

Energy Technology Data Exchange (ETDEWEB)

Nestle, Nikolaus [BASF Aktiengesellschaft, GKP/P-G 201, D-67056 Ludwigshafen (Germany)], E-mail: nikolaus.nestle@basf.com; Heckmann, Walter; Steininger, Helmut; Knoll, Konrad [BASF Aktiengesellschaft, GKP/P-G 201, D-67056 Ludwigshafen (Germany)

2007-11-26

The properties of styrene-butadiene-styrene (SBS) block copolymers do not only depend on the butadiene content and the degree of polymerisation but also on their chain architecture. In this contribution we present the results of a low-field time domain (TD) NMR study in which the transverse relaxation behaviour of different SBS block copolymers was analysed and correlated with findings from mechanical testing on pure and blended materials and transmission electron microscopy data which provide information on the microphase separation. The results indicate that while a straightforward determination of the butadiene content as in blended materials like ABS is not possible for these materials, the TD-NMR results correlate quite well with the mechanical performance of blends from SBS block copolymers with general purpose polystyrene (GPPS), i.e. industrial grade homopolymer polystyrene. Temperature-dependent experiments on pure and blended materials revealed a slight reduction in the softening temperature of the GPPS fraction in the blends.

Monte Carlo studies on the interfacial properties and interfacial structures of ternary symmetric blends with gradient copolymers.

Science.gov (United States)

Sun, Dachuan; Guo, Hongxia

2012-08-09

Using Monte Carlo simulation methods, the effects of the comonomer sequence distribution on the interfacial properties (including interfacial tension, interfacial thickness, saturated interfacial area per copolymer, and bending modulus) and interfacial structures (including chain conformations and comonomer distributions of the simulated copolymers at the interfaces) of a ternary symmetric blend containing two immiscible homopolymers and one gradient copolymer are investigated. We find that copolymers with a larger composition gradient width have a broader comonomer distribution along the interface normal, and hence more pronouncedly enlarge the interfacial thickness and reduce the interfacial tension. Furthermore, the counteraction effect, which arises from the tendency of heterogeneous segments in gradient copolymers to phase separate and enter their miscible phases to reduce the local enthalpy, decreases the stretching of copolymers along the interface normal direction. As a result, copolymers with a larger width of gradient composition can occupy a larger interfacial area and form softer monolayers at saturation and are more efficient in facilitating the formation of bicontinuous microemulsions. Additionally, chain length ratio, segregation strength, and interactions between homopolymers and copolymers can alter the interfacial character of gradient copolymers. There exists a strong coupling between the comonomer sequence distribution, chain conformation, and interfacial properties. Especially, bending modulus is mainly determined by the complicated interplay of interfacial copolymer density and interfacial chain conformation.

Complex Macrophase-Separated Nanostructure Induced by Microphase Separation in Binary Blends of Lamellar Diblock Copolymer Thin Films

DEFF Research Database (Denmark)

Zhang, Jianqi; Posselt, Dorthe; Smilgies, Detlef-M.

2014-01-01

The nanostructures of thin films spin-coated from binary blends of compositionally symmetric polystyrene-b-polybutadiene (PS-b-PB) diblock copolymer having different molar masses are investigated by means of atomic force microscopy (AFM) and grazing-incidence small-angle X-ray scattering (GISAXS)...

Application of the Ornstein-Zernike formalism to polymer and copolymer blends

International Nuclear Information System (INIS)

Benmouna, M.

1988-09-01

The Ornstein Zernike formalism is shown to be applicable to polymer and copolymer blends. Direct correlation functions are obtained from the solution problem by using a simple procedure which was suggested before (M. Benmouna, H. Benoit and W. Wu, to be published in Macromolecules). This procedure consists essentially of replacing the volume fraction of solvent by the quantity φ c N c P c (q) where φ c , N c and P c (q) are the volume fraction, the degree of polymerization and the form factor as a function of momentum transfer q, respectively. (author). 9 refs

Tissue engineering of bovine articular cartilage within porous poly(ether ester) copolymer scaffolds with different structures

NARCIS (Netherlands)

Mahmood, Tahir A.; Shastri, V. Prasad; van Blitterswijk, Clemens; Langer, Robert; Riesle, J.U.

2005-01-01

The potential of porous poly(ether ester) scaffolds made from poly(ethylene glycol) terephthalate: poly(butylene terephthalate) (PEGT:PBT) block copolymers produced by various methods to enable cartilaginous tissue formation in vitro was studied. Scaffolds were fabricated by two different processes:

Hg(II) adsorption using amidoximated porous acrylonitrile/itaconic copolymers prepared by suspended emulsion polymerization.

Science.gov (United States)

Ji, Chunnuan; Qu, Rongjun; Chen, Hou; Liu, Xiguang; Sun, Changmei; Ma, Caixia

2016-01-01

Initially, porous acrylonitrile/itaconic acid copolymers (AN/IA) were prepared by suspended emulsion polymerization. Successively, the cyano groups in AN/IA copolymers were converted to amidoxime (AO) groups by the reaction with hydroxylamine hydrochloride. The structures of the AN/IA and amidoximated AN/IA (AO AN/IA) were characterized by infrared spectroscopy, scanning electron microscopy, and porous structural analysis. The adsorption properties of AO AN/IA for Hg(II) were investigated. The results show that AO AN/IA has mesopores and macropores, and surface area of 11.71 m(2) g(-1). It was found that AO AN/IA has higher affinity for Hg(II), with the maximum adsorption capacity of 84.25 mg g(-1). The AO AN/IA also can effectively remove Hg(II) from different binary metal ion mixture systems. Furthermore, the adsorption kinetics and thermodynamics were studied in detail. The adsorption equilibrium can quickly be achieved in 4 h determined by an adsorption kinetics study. The adsorption process is found to belong to the second-order model, and can be described by the Freundlich model.

Preparation of degradable porous structures based on 1,3-trimethylene carbonate and D,L-lactide (co)polymers for heart tissue engineering

NARCIS (Netherlands)

Pego, AP; Siebum, B; Van Luyn, MJA; Van Seijen, XJGY; Poot, AA; Grijpma, DW; Feijen, J

2003-01-01

Biodegradable porous scaffolds for heart tissue engineering were prepared from amorphous elastomeric (co)polymers of 1,3-trimethylene carbonate (TMC) and D,L-lactide (DLLA). Leaching of salt from compression-molded polymer-salt composites allowed the preparation of highly porous structures in a

Compositional and electric field dependence of the dissociation of charge transfer excitons in alternating polyfluorene copolymer/fullerene blends

NARCIS (Netherlands)

Veldman, D.; Ipek, Ö.; Meskers, S.C.J.; Sweelssen, J.; Koetse, M.M.; Veenstra, S.C.; Kroon, J.M.; Bavel, S.S. van; Loos, J.; Janssen, R.A.J.

2008-01-01

The electro-optical properties of thin films of electron donor-acceptor blends of a fluorene copolymer (PF10TBT) and a fullerene derivative (PCBM) were studied. Transmission electron microscopy shows that in these films nanocrystalline PCBM clusters are formed at high PCBM content. For all

Disorder-order-crystalline state transitions of PEO-b-PPO-b-PEO copolymers and their blends: SAXS/WAXS/DSC study

Czech Academy of Sciences Publication Activity Database

Baldrian, Josef; Steinhart, M.; Amenitsch, H.; Bernstorff, S.

2009-01-01

Roč. 48, č. 1 (2009), s. 174-184 ISSN 0022-2348 Institutional research plan: CEZ:AV0Z40500505 Keywords : triblock copolymers * blends with homopolymer * structure development Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.716, year: 2009

Preparation of 3D fibroin/chitosan blend porous scaffold for tissue engineering via a simplified method.

Science.gov (United States)

Ruan, Yuhui; Lin, Hong; Yao, Jinrong; Chen, Zhengrong; Shao, Zhengzhong

2011-03-10

In this work, we developed a simple and flexible method to manufacture a 3D porous scaffold based on the blend of regenerated silk fibroin (RSF) and chitosan (CS). No crosslinker or other toxic reagents were used in this method. The pores of resulted 3D scaffolds were connected with each other, and their sizes could be easily controlled by the concentration of the mixed solution. Compared with pure RSF scaffolds, the water absorptivities of these RSF/CS blend scaffolds with significantly enhanced mechanical properties were greatly increased. The results of MTT and RT-PCR tests indicated that the chondrocytes grew very well in these blend RSF/CS porous scaffolds. This suggested that the RSF/CS blend scaffold prepared by this new method could be a promising candidate for applications in tissue engineering. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermoplastic elastomers blends based on linear low density polyethylene, ethylene-1-octene copolymers and ground rubber tire

Directory of Open Access Journals (Sweden)

Marisa Cristina Guimarães Rocha

2014-01-01

Full Text Available Blends of linear low density polyethylene (LLDPE ethylene-1-octene copolymers (EOC, with different 1-octene (OC content, and ground rubber tire (GRT were prepared by melt mixing in a twin screw extruder. Five different compositions of LLDPE/EOC/GRT blends were processed in the extruder to evaluate the effect of EOC addition to the LLDPE/GRT blends. The addition of EOC to LLDPE/GRT blends improves the mechanical properties. Besides, the replacement of 5% of GRT by EOC grades (OC = 20 or 30 wt % in the 50/50 LLDPE/GRT blend, leads to a significant increase of ultimate tensile properties. The EOC comonomer content affects the properties of LLDPE/EOC and LLDPE/EOC/GRT blends. Dynamical-mechanical analyses showed that, with the addition of EOC to LLDPE/GRT blends, the Tg of GRT and the Tg of EOC are closer. This effect is more pronounced when the EOC with the highest content of comonomer (30 wt % is added to LLDPE/GRT blend. In this case, only one peak related to the Tg of the rubber phase can be visualized in the amorphous region. These findings indicate that EOC may act as compatibilizer agent for LLDPE/GRT blends.

Functional porous structures based on the pyrolysis of cured templates of block copolymer and phenolic resin

NARCIS (Netherlands)

Kosonen, H; Valkama, S; Nykanen, A; Toivanen, M; ten Brinke, G; Ruokolainen, J; Ikkala, O; Nykänen, Antti

2006-01-01

Porous materials with controlled pore size and large surface area (see Figure) have been prepared by crosslinking phenolic resin in the presence of a self-assembled block-copolymer template, followed by pyrolysis. Many phenolic hydroxyl groups remain at the matrix and pore walls, which can be used

Neutral wetting brush layers for block copolymer thin films using homopolymer blends processed at high temperatures

International Nuclear Information System (INIS)

Ceresoli, M; Palermo, M; Ferrarese Lupi, F; Seguini, G; Perego, M; Zuccheri, G; Phadatare, S D; Antonioli, D; Gianotti, V; Sparnacci, K; Laus, M

2015-01-01

Binary homopolymer blends of two hydroxyl-terminated polystyrene (PS-OH) and polymethylmethacrylate (PMMA-OH) homopolymers (Mn ∼ 16000 g mol"−"1) were grafted on SiO_2 substrates by high-temperature (T > 150 °C), short-time (t < 600 s) thermal treatments. The resulting brush layer was tested to screen preferential interactions of the SiO_2 substrate with the different symmetric and asymmetric PS-b-PMMA block copolymers deposited on top of the grafted molecules. By properly adjusting the blend composition and the processing parameters, an efficient surface neutralization path was identified, enabling the formation, in the block copolymer film, of homogeneous textures of lamellae or cylinders perpendicularly oriented with respect to the substrate. A critical interplay between the phase segregation of the homopolymer blends and their grafting process on the SiO_2 was observed. In fact, the polar SiO_2 is preferential for the PMMA-rich phase that forms a homogeneous layer on the substrate, while the PS-rich phase is located at the polymer-air interface. During the thermal treatment, phase segregation and grafting proceed simultaneously. Complete wetting of the PS rich phase on the PMMA rich phase leads to the formation of a PS/PMMA bilayer. In this case, the progressive diffusion of PS chains toward the polymer-SiO_2 interface during the thermal treatment allows tuning of the brush layer composition. (paper)

A pulsed field gradient NMR study of a ternary homopolymer/diblock copolymer blend in the bicontinuous microemulsion phase

Czech Academy of Sciences Publication Activity Database

Gröger, S.; Rittig, F.; Stallmach, F.; Almdal, K.; Štěpánek, Petr; Papadakis, C. M.

2002-01-01

Roč. 117, č. 1 (2002), s. 396-406 ISSN 0021-9606 R&D Projects: GA AV ČR IAA1050902 Institutional research plan: CEZ:AV0Z4050913 Keywords : polymer blends * diblock copolymer * dynamic light scattering Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.998, year: 2002

Ion solvation in polymer blends and block copolymer melts: effects of chain length and connectivity on the reorganization of dipoles.

Science.gov (United States)

Nakamura, Issei

2014-05-29

We studied the thermodynamic properties of ion solvation in polymer blends and block copolymer melts and developed a dipolar self-consistent field theory for polymer mixtures. Our theory accounts for the chain connectivity of polymerized monomers, the compressibility of the liquid mixtures under electrostriction, the permanent and induced dipole moments of monomers, and the resultant dielectric contrast among species. In our coarse-grained model, dipoles are attached to the monomers and allowed to rotate freely in response to electrostatic fields. We demonstrate that a strong electrostatic field near an ion reorganizes dipolar monomers, resulting in nonmonotonic changes in the volume fraction profile and the dielectric function of the polymers with respect to those of simple liquid mixtures. For the parameter sets used, the spatial variations near an ion can be in the range of 1 nm or larger, producing significant differences in the solvation energy among simple liquid mixtures, polymer blends, and block copolymers. The solvation energy of an ion depends substantially on the chain length in block copolymers; thus, our theory predicts the preferential solvation of ions arising from differences in chain length.

Fluorinated Amphiphilic Polymers and Their Blends for Fouling-Release Applications: The Benefits of a Triblock Copolymer Surface

KAUST Repository

Sundaram, Harihara S.

2011-09-28

Surface active triblock copolymers (SABC) with mixed polyethylene glycol (PEG) and two different semifluorinated alcohol side chains, one longer than the other, were blended with a soft thermoplastic elastomer (TPE), polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS). The surface composition of these blends was probed by X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The surface reconstruction of the coatings in water was monitored qualitatively by dynamic water contact angles in air as well as air bubble contact angle measurements in water. By blending the SABC with SEBS, we minimize the amount of the SABC used while achieving a surface that is not greatly different in composition from the pure SABC. The 15 wt % blends of the SABC with long fluoroalkyl side chains showed a composition close to that of the pure SABC while the SABC with shorter perfluoroakyl side chains did not. These differences in surface composition were reflected in the fouling-release performance of the blends for the algae, Ulva and Navicula. © 2011 American Chemical Society.

Self-Assembled Asymmetric Block Copolymer Membranes: Bridging the Gap from Ultra- to Nanofiltration

KAUST Repository

Yu, Haizhou

2015-09-21

The self-assembly of block copolymers is an emerging strategy to produce isoporous ultrafiltration membranes. However, thus far, it has not been possible to bridge the gap from ultra- to nanofiltration and decrease the pore size of self-assembled block copolymer membranes to below 5 nm without post-treatment. It is now reported that the self-assembly of blends of two chemically interacting copolymers can lead to highly porous membranes with pore diameters as small as 1.5 nm. The membrane containing an ultraporous, 60 nm thin separation layer can fully reject solutes with molecular weights of 600 g mol−1 in aqueous solutions with a water flux that is more than one order of magnitude higher than the permeance of commercial nanofiltration membranes. Simulations of the membrane formation process by dissipative particle dynamics (DPD) were used to explain the dramatic observed pore size reduction combined with an increase in water flux.

Structuring of Interface-Modified Polymer Blends

DEFF Research Database (Denmark)

Lyngaae-Jørgensen, Jørgen

1999-01-01

The paper treats the case where blends of polystyrene (PS), poly (dimethylsiloxane) (PDMS) and a diblock copolymer of PS and PDMS are used as model materials. This modelsystem is predicted to be "stable" in discrete blends in simple shear flow. Stable in the sence that the block copolymer can not...

Modification of polymer blends by irradiation

International Nuclear Information System (INIS)

Zuchowska, D.; Zagorski, Z.P.

1999-01-01

Modification of polymers, especially of polyolefin-elastomer blends (e. g. ethylene/propylene/diene terpolymer, ethylene propylene copolymer, ethylene/vinyl acetate copolymer etc.), by irradiation with a beam of fast electrons is discussed. Irradiation of polymer blends usually results in enhanced interactions between the constituents, caused among other things, by grafting induced at the polymer interphase. As a result, mechanical properties are affected to an extent depending on the proportion and type of constituent polymers, stabilizer content and radiation dose. Breaking strength (σ) relative elongation at break (ε) and melt flow rate (MFR), were examined for a triblock styrene/butadiene/styrene (SBS) copolymer, polypropylene (PP), and a PP-SBS blend (50:50 by wt.). In PP, the content of the crystal phase was determined. Irradiation was found to make SBS crosslink, as a result, σ rose by 25% and ε remained unaffected. PP was found to become degraded upon irradiation (MFR rose as much as 16 times), thereby σ and ε decreased considerably. In pure PP, the content of the crystal phase was found to increase. The variations of σ and ε in the irradiated PP-SBS blend follow a tendency similar to that in the SBS copolymer examined. This fact suggests the SBS copolymer to have a decisive effect on the macroscopic properties of the PP-SBS blend. (author)

Dynamic mechanical analysis of binary and ternary polymer blends based on nylon copolymer/EPDM rubber and EPM grafted maleic anhydride compatibilizer

Directory of Open Access Journals (Sweden)

2007-10-01

Full Text Available The dynamic mechanical properties such as storage modulus, loss modulus and damping properties of blends of nylon copolymer (PA6,66 with ethylene propylene diene (EPDM rubber was investigated with special reference to the effect of blend ratio and compatibilisation over a temperature range –100°C to 150°C at different frequencies. The effect of change in the composition of the polymer blends on tanδ was studied to understand the extent of polymer miscibility and damping characteristics. The loss tangent curve of the blends exhibited two transition peaks, corresponding to the glass transition temperature (Tg of individual components indicating incompatibility of the blend systems. The morphology of the blends has been examined by using scanning electron microscopy. The Arrhenius relationship was used to calculate the activation energy for the glass transition of the blends. Finally, attempts have been made to compare the experimental data with theoretical models.

Time-resolved SAXS studies of morphological changes in a blend of linear polyethylene with homogeneous ethylene-1-octene copolymer

Energy Technology Data Exchange (ETDEWEB)

Ślusarczyk, Czesław, E-mail: cslusarczyk@ath.bielsko.pl

2015-12-01

Isothermal melt crystallization in the 15/85 (m/m) blend of a high density polyethylene (HDPE) and a homogeneous ethylene copolymer with 5.5 mol% 1-octene was studied by time-resolved SAXS method with synchrotron radiation over a wide-range of crystallization temperatures. The SAXS profile was analyzed by means of the correlation function which allows to elucidate the evolution of the morphological parameters of polyethylene lamellar structure (long period (LP), thicknesses of crystalline (L{sub C}) and amorphous (L{sub A}) layers) during a crystallization process. It was found that for the samples crystallized at 100 °C, 120 °C and 122 °C L{sub C} increases with time. The lamellar thickening rate strongly depends on crystallization temperature. At 40 °C thickening of the crystalline layers does not occur. The time evolution of the lamellar structure in the blend studied confirms the role of hexyl branches of homogeneous copolymer in the crystallization process of polyethylene. The branches introduce steric constraints which hinder the crystallization of HDPE, thus decreasing the size of the HDPE lamellar crystals.

Diblock Copolymer/Layered Silicate Nanocomposite Thin Film Stability

Science.gov (United States)

Limary, Ratchana; Green, Peter

2000-03-01

The stability of thin film symmetric diblock copolymers blended with layered silicate nanocomposites were examined using a combination of optical microscopy, atomic force microscopy (AFM), and X-ray diffraction (XRD). Two cases were examined PS-b-PMMA (polystyrene-b-polymethylacrylate) blended with montmorillonite stoichiometrically loaded with alkyl ammonium ions, OLS(S), and PS-b-PMMA blended with montmorillonite loaded with excess alkyl ammonium ions, OLS(E). XRD spectra show an increase in the gallery spacing of the OLSs, indicating that the copolymer chains have intercalated the layered silicates. AFM images reveal a distinct difference between the two nanocomposite thin films: regions in the vicinity of OLS(S) aggregates were depleted of material, while in the vicinity of OLS(E) aggregates, dewetting of the substrate occurred. We show that the stability of the copolymer/OLS nanocomposite films is determined by the enthalpic driving force associated with intercalation of the copolymer chains into the galleries of the modified OLS layers and by the substrate/organic modifier interactions.

Preparation and Drug-Release Kinetics of Porous Poly(L-lactic acid)/Rifampicin Blend Particles

OpenAIRE

Takashi Sasaki; Hiroaki Matsuura; Kazuki Tanaka

2014-01-01

Porous polymer spheres are promising materials as carriers for controlled drug release. As a new drug-carrier material, blend particles composed of poly(L-lactic acid) (PLLA) and rifampicin were developed using the freeze-drying technique. The blend particles exhibit high porosity with a specific surface area of 10–40 m2 g−1. Both the size and porosity of the particles depend on the concentration of the original solution and on the method of freezing. With respect to the latter, we used the d...

Radiation Effects on Mechanical Properties of LDPE/EVA blend

International Nuclear Information System (INIS)

Lee, Chung; Kim, Ki Yup; Im, Don Sun; Ryu, Boo Hyung

2005-01-01

Restricted properties and a limited use of homopolymers alone, have given rise to an exploration of composites, copolymers, blends, etc. Copolymers such as poly(ethylene-co-vinyl acetate) (EVA), poly(ethylene-co-butyl acrylate), poly(ethylene-co-ethyl acrylate) (EEA) have wide usages in different industry. Among the numerous ethylene copolymers, due to its wide range of properties depending on its vinyl acetate content, EVA has become one of the most useful copolymers in the electrical industry as a cable insulator, and in many other industries as a hot melt adhesive, a coating, etc. Several works looked at the influence of gamma rays on polymers. Zhang et al have blended EVA with PE because crosslinked PE has a low flexibility for use as a cable insulation. It was reported that the blend showed have a better elongation, flexibility and heat aging effect than PE, but its hardness and softening point were lower. In this study, the radiation degradation of LDPE/EVA blends as a function of the vinyl acetate contents was investigated by using TGA, gelation and elongation

Theory of melt polyelectrolyte blends and block copolymers: Phase behavior, surface tension, and microphase periodicity

Energy Technology Data Exchange (ETDEWEB)

Sing, Charles E. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Zwanikken, Jos W.; Olvera de la Cruz, Monica [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States)

2015-01-21

Polymer mixtures such as blends or block copolymers are of great interest in energy applications and functional materials, and often, one or more of these species contain charges. The traditional fashion in which such materials are studied uses Self-Consistent Field Theory (SCFT) methods that incorporate electrostatics using Poisson-Boltzmann (PB) theory. We adapt a new and rigorous approach that does not rely on the mean-field assumptions inherent in the PB theory and instead uses Liquid State (LS) integral equation theory to articulate charge correlations that are completely neglected in PB. We use this theory to calculate phase diagrams for both blends and block copolyelectrolytes using SCFT-LS and demonstrate how their phase behavior is highly dependent on chain length, charge fraction, charge size, and the strength of Coulombic interactions. Beyond providing phase behavior of blends and block copolyelectrolytes, we can use this theory to investigate the interfacial properties such as surface tension and block copolyelectrolyte lamellar spacing. Lamellar spacing provides a way to directly compare the SCFT-LS theory to the results of experiments. SCFT-LS will provide conceptual and mathematical clarification of the role of charge correlations in these systems and aid in the design of materials based on charge polymers.

Theory of melt polyelectrolyte blends and block copolymers: Phase behavior, surface tension, and microphase periodicity

International Nuclear Information System (INIS)

Sing, Charles E.; Zwanikken, Jos W.; Olvera de la Cruz, Monica

2015-01-01

Polymer mixtures such as blends or block copolymers are of great interest in energy applications and functional materials, and often, one or more of these species contain charges. The traditional fashion in which such materials are studied uses Self-Consistent Field Theory (SCFT) methods that incorporate electrostatics using Poisson-Boltzmann (PB) theory. We adapt a new and rigorous approach that does not rely on the mean-field assumptions inherent in the PB theory and instead uses Liquid State (LS) integral equation theory to articulate charge correlations that are completely neglected in PB. We use this theory to calculate phase diagrams for both blends and block copolyelectrolytes using SCFT-LS and demonstrate how their phase behavior is highly dependent on chain length, charge fraction, charge size, and the strength of Coulombic interactions. Beyond providing phase behavior of blends and block copolyelectrolytes, we can use this theory to investigate the interfacial properties such as surface tension and block copolyelectrolyte lamellar spacing. Lamellar spacing provides a way to directly compare the SCFT-LS theory to the results of experiments. SCFT-LS will provide conceptual and mathematical clarification of the role of charge correlations in these systems and aid in the design of materials based on charge polymers

Heat shrink ability of electron-beam-modified thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer and polyethylene

International Nuclear Information System (INIS)

Chattopadhyay, S.; Chaki, T.K.; Bhowmick, Anil K.

2000-01-01

The heat shrink ability of electron-beam-irradiated thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer (EVA) and low-density polyethylene (LDPE) has been investigated in this paper. The effects of temperature, time and extent of stretching and shrinkage temperature and time have been reported. Based on the above data, the optimized conditions in terms of high heat shrinkage and low amnesia rating have been evaluated. Influence of radiation doses (0-500 kGy), multifunctional sensitizer levels (ditri methylol propane tetraacrylate, DTMPTA), and blend proportions on heat shrink ability has been explained with the help of gel fraction and X-ray data. With the increase in radiation dose, gel fraction increases, which in turn gives rise to low values of heat shrinkage and amnesia rating. At a constant radiation dose and blend ratio, percent heat shrinkage is found to decrease with increase in DTMPTA level. Gel content increases with the increase in EVA content of the blend at a constant radiation dose and monomer level, giving rise to decrease in heat shrink ability. Heat shrinkage increases with the increase in percent crystallinity, although the amnesia rating follows the reverse trend.

Heat shrink ability of electron-beam-modified thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer and polyethylene

Energy Technology Data Exchange (ETDEWEB)

Chattopadhyay, S.; Chaki, T.K.; Bhowmick, Anil K. E-mail: anilkb@rtc.iitkgp.ernet.in

2000-11-01

The heat shrink ability of electron-beam-irradiated thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer (EVA) and low-density polyethylene (LDPE) has been investigated in this paper. The effects of temperature, time and extent of stretching and shrinkage temperature and time have been reported. Based on the above data, the optimized conditions in terms of high heat shrinkage and low amnesia rating have been evaluated. Influence of radiation doses (0-500 kGy), multifunctional sensitizer levels (ditri methylol propane tetraacrylate, DTMPTA), and blend proportions on heat shrink ability has been explained with the help of gel fraction and X-ray data. With the increase in radiation dose, gel fraction increases, which in turn gives rise to low values of heat shrinkage and amnesia rating. At a constant radiation dose and blend ratio, percent heat shrinkage is found to decrease with increase in DTMPTA level. Gel content increases with the increase in EVA content of the blend at a constant radiation dose and monomer level, giving rise to decrease in heat shrink ability. Heat shrinkage increases with the increase in percent crystallinity, although the amnesia rating follows the reverse trend.

Molecular Interaction Control in Diblock Copolymer Blends and Multiblock Copolymers with Opposite Phase Behaviors

Science.gov (United States)

Cho, Junhan

2014-03-01

Here we show how to control molecular interactions via mixing AB and AC diblock copolymers, where one copolymer exhibits upper order-disorder transition and the other does lower disorder-order transition. Linear ABC triblock copolymers possessing both barotropic and baroplastic pairs are also taken into account. A recently developed random-phase approximation (RPA) theory and the self-consistent field theory (SCFT) for general compressible mixtures are used to analyze stability criteria and morphologies for the given systems. It is demonstrated that the copolymer systems can yield a variety of phase behaviors in their temperature and pressure dependence upon proper mixing conditions and compositions, which is caused by the delicate force fields generated in the systems. We acknowledge the financial support from National Research Foundation of Korea and Center for Photofunctional Energy Materials.

Chain conformations of the component polymers and the microphase separation structures of homopolymer/block coplymer blends

International Nuclear Information System (INIS)

Torikai, Naoya; Mogi, Yasuhiro; Matsushita, Yushu; Noda, Ichiro; Han, C.C.

1993-01-01

Microdomain spacings of lamellar structures formed by styrene homopolymer/styrene-2-vinylpyridine diblock copolymer/2-vinylpyridine homopolymer blends were measured by small-angle X-ray scattering (SAXS) and single chain conformations of block copolymers in the same blend system were measured by small-angle neutron scattering (SANS). The molecular weight of diblock copolymers is 78K-72K, and three kinds of styrene homopolymer (S H ) and 2-vinylpyridine homopolymer (P H ) pairs were blended, their molecular weight ratios to that of host block chains were 0.17, 0.38, and 0.78, respectively. Two blend ratios of homopolymer (H)/block copolymer (B), i.e. 1/2 and 1/1 were examined. It was found that the domain spacings of all blends are larger than that of pure block copolymer and that they are increasing with increasing the molecular weight of homopolymers and/or with increasing the volume fraction of homopolymers. Further, block chains in the blends were confirmed to have almost the same chain dimension as that of block chain in pure block copolymer system in the direction parallel to the domain interface irrespective of molecular weight and volume fraction of homopolymers. (author)

Mistura reativa de poliamida 6 e policarbonato: reatividade do copolímero formado "in situ" Polyamide 6 and polycarbonate reactive blends: reactivity of the copolymer formed "in situ"

Directory of Open Access Journals (Sweden)

Dilma A. Costa

2004-01-01

Full Text Available As misturas físicas de poliamida 6 (PA6 e policarbonato (PC processadas a 240 ºC, durante 10, 30 e 60 minutos formam um copolímero de PA6-PC. A alta temperatura e o longo tempo de processamento podem causar modificações nas propriedades dessas misturas e degradar o copolímero, originando grupos isocianato e subseqüentemente CO2 e grupos NH2 terminais. A quantidade de copolímero PA6-PC formado durante o processo de mistura é maior com o aumento da proporção de PC na mistura. As ligações uretânicas de polímeros termoplásticos exibem mais baixas estabilidades térmica e oxidativa, resultando no aumento da concentração de grupos terminais NH2. A reatividade dessas misturas foi investigada através do torque durante o processo de mistura, da titulação potenciométrica dos grupos NH2 terminais e por microscopia eletrônica de varredura.Polyamide 6 (PA6 and polycarbonate (PC blends processed at 240 °C, during 10, 30 and 60 minutes produced a copolymer of PA6-PC. The high temperature and long processing time can cause modifications on the properties of these blends and degradation of the copolymer. It can also form isocyanate groups and subsequently CO2 and NH2 "end groups". The amount of PA6-PC copolymer formed during the blending process was found to increase when the PC content is increased. The thermoplastic urethanes normally exhibit smaller thermal and oxidative stability, resulting in an increase in the concentration of NH2 terminal groups. The reactivity of the blends was investigated by monitoring the torque during the blending, potentiometer titration of NH2 terminal groups and scanning electronic microscopy (SEM.

Assessment of Blend PVDF Membranes, and the Effect of Polymer Concentration and Blend Composition

Directory of Open Access Journals (Sweden)

Imtiaz Ali

2018-03-01

Full Text Available In this work, PVDF homopolymer was blended with PVDF-co-HFP copolymer and studied in terms of morphology, porosity, pore size, hydrophobicity, permeability, and mechanical properties. Different solvents, namely N-Methyl-2 pyrrolidone (NMP, Tetrahydrofuran (THF, and Dimethylformamide (DMF solvents, were used to fabricate blended PVDF flat sheet membranes without the introduction of any pore forming agent, through a non-solvent induced phase separation (NIPS technique. Furthermore, the performance of the fabricated membranes was investigated for pressure and thermal driven applications. The porosity of the membranes was slightly increased with the increase in the overall content of PVDF and by the inclusion of PVDF copolymer. Total PVDF content, copolymer content, and mixed-solvent have a positive effect on mechanical properties. The addition of copolymer increased the hydrophobicity when the total PVDF content was 20%. At 25% and with the inclusion of mixed-solvent, the hydrophobicity was adversely affected. The permeability of the membranes increased with the increase in the overall content of PVDF. Mixed-solvents significantly improved permeability.

Assessment of Blend PVDF Membranes, and the Effect of Polymer Concentration and Blend Composition.

Science.gov (United States)

Ali, Imtiaz; Bamaga, Omar A; Gzara, Lassaad; Bassyouni, M; Abdel-Aziz, M H; Soliman, M F; Drioli, Enrico; Albeirutty, Mohammed

2018-03-05

In this work, PVDF homopolymer was blended with PVDF-co-HFP copolymer and studied in terms of morphology, porosity, pore size, hydrophobicity, permeability, and mechanical properties. Different solvents, namely N-Methyl-2 pyrrolidone (NMP), Tetrahydrofuran (THF), and Dimethylformamide (DMF) solvents, were used to fabricate blended PVDF flat sheet membranes without the introduction of any pore forming agent, through a non-solvent induced phase separation (NIPS) technique. Furthermore, the performance of the fabricated membranes was investigated for pressure and thermal driven applications. The porosity of the membranes was slightly increased with the increase in the overall content of PVDF and by the inclusion of PVDF copolymer. Total PVDF content, copolymer content, and mixed-solvent have a positive effect on mechanical properties. The addition of copolymer increased the hydrophobicity when the total PVDF content was 20%. At 25% and with the inclusion of mixed-solvent, the hydrophobicity was adversely affected. The permeability of the membranes increased with the increase in the overall content of PVDF. Mixed-solvents significantly improved permeability.

Process of irradiating an ethylene-vinyl acetate copolymer to produce low melt index copolymers, and products of said process

International Nuclear Information System (INIS)

Potts, J.E.

1976-01-01

Application of ionizing radiation in a dose between 0.5 and 1.5 megareps to copolymers of ethylene and vinyl acetate lowers the melt index and increases the toughness and flexibility of the copolymers without substantially decreasing solubility or thermoplasticity. The increased toughness and flexibility carries over into blends with wax or polyethylene. (author)

Honeycomb structured porous interfaces as templates for protein adhesion

Energy Technology Data Exchange (ETDEWEB)

Rodriguez-Hernandez, J; Munoz-Bonilla, A; Ibarboure, E; Bordege, V; Fernandez-Garcia, M, E-mail: jrodriguez@ictp.csic.es

2010-11-01

We prepared breath figure patterns decorated with a statistical glycopolymer, (styrene-co-2-{l_brace}[(D-glucosamin-2-N-yl)carbonyl]oxy{r_brace}ethyl methacrylate, S-HEMAGl). The preparation of the glycopolymer occurs in one single step by using styrene and S-HEMAGl. Blends of this copolymer and high molecular weight polystyrene were spin coated from THF solutions leading to the formation of surfaces with both controlled functionality and topography. AFM studies revealed that both the composition of the blend and the relative humidity play a key role on the size and distribution of the pores at the interface. The porous films shows the hydrophilic glycomonomer units are oriented towards the pore interface since upon soft annealing in water, the holes are partially swelled. The self-organization of the glycopolymer within the pores was additionally confirmed both by reaction of carbohydrate hydroxyl groups with rhodamine-isocyanate and by means of the lectin binding test using Concanavalin A (Con A).

Miscibility, crystallization and mechanical properties of biodegradable blends of poly(L-lactic acid) and poly(butylene succinate-b-ethylene succinate) multiblock copolymer

International Nuclear Information System (INIS)

Jiao, Ling; Huang, Cai-Li; Zeng, Jian-Bing; Wang, Yu-Zhong; Wang, Xiu-Li

2012-01-01

Highlights: ► The blend of PLLA and PBES showed limited miscibility. ► The crystallization rate of PLLA was accelerated by blending with PBES. ► The crystal structures of PLLA and PBES did not change. - Abstract: Poly(L-lactic acid) (PLLA) is regarded as one of the most promising biobased and biodegradable polymers. However, its application was restricted due to the brittle nature. In the present study, PLLA was blended with a novel biodegradable flexible multiblock copolymer, poly(butylene succinate-b-ethylene succinate) (PBES) to produce new biodegradable materials. PLLA/PBES blends with different composition were prepared by solution blending and casting method with chloroform as a mutual solvent. Miscibility, crystallization behavior, and mechanical properties of the blends were investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and tensile tests. The results indicated that PLLA and PBES showed limited miscibility in the amorphous phase. The crystallization rate of PLLA was accelerated with the increase of PBES in the blends while the crystallization mechanism did not change. The results of tensile tests suggest that the blends showed longer elongation at break than neat PLLA. The elongation at break of PLLA was obtained to be 10%, and those of PLLA/PBES 80/20, 60/40, 40/60 and 20/80 were 29, 110, 442, and 455%, respectively.

Sorption of Different Dye Wastes By Poly(vinyl alcohol) /Poly (Carboxymethyl Cellulose) Blend Grafted Through A Radiation Method

International Nuclear Information System (INIS)

El-Salmawi Kariman, M.; Abu Zaid Magda, M.; Ibraheim Sayeda, M.; El-Naggar Abdel Wahab, M.; Zahran Abdel Hamid, H.

1999-01-01

The sorption of different dye wastes normaly released from industrial textile factories by a graft copolymer of poly(vinyl alcohol)/poly(carboxymethyl cellulose) blend with polystyrene has been investigated. The dye sorption was evaluated at different conditions. The amount of sorbed dye was determined by using a spectroscopic method. The blend graft copolymer showed a relatively high sorption for basic dye than other dyestuffs such as acid, reactive and direct. Moreover, it was found that the dye sorption did not depend on the weight of the blend graft copolymer or the volume of the waste solution. The treatment of the dye waste by using the prepared blend graft copolymer may be considered a practical one from the point of view of environmental methods

Nanostructured Polysulfone-Based Block Copolymer Membranes

KAUST Repository

Xie, Yihui

2016-05-01

The aim of this work is to fabricate nanostructured membranes from polysulfone-based block copolymers through self-assembly and non-solvent induced phase separation. Block copolymers containing polysulfone are novel materials for this purpose providing better mechanical and thermal stability to membranes than polystyrene-based copolymers, which have been exclusively used now. Firstly, we synthesized a triblock copolymer, poly(tert-butyl acrylate)-b-polsulfone-b-poly(tert-butyl acrylate) through polycondensation and reversible addition-fragmentation chain-transfer polymerization. The obtained membrane has a highly porous interconnected skin layer composed of elongated micelles with a flower-like arrangement, on top of the graded finger-like macrovoids. Membrane surface hydrolysis was carried out in a combination with metal complexation to obtain metal-chelated membranes. The copper-containing membrane showed improved antibacterial capability. Secondly, a poly(acrylic acid)-b-polysulfone-b-poly(acrylic acid) triblock copolymer obtained by hydrolyzing poly(tert-butyl acrylate)-b-polsulfone-b-poly(tert-butyl acrylate) formed a thin film with cylindrical poly(acrylic acid) microdomains in polysulfone matrix through thermal annealing. A phase inversion membrane was prepared from the same polymer via self-assembly and chelation-assisted non-solvent induced phase separation. The spherical micelles pre-formed in a selective solvent mixture packed into an ordered lattice in aid of metal-poly(acrylic acid) complexation. The space between micelles was filled with poly(acrylic acid)-metal complexes acting as potential water channels. The silver0 nanoparticle-decorated membrane was obtained by surface reduction, having three distinct layers with different particle sizes. Other amphiphilic copolymers containing polysulfone and water-soluble segments such as poly(ethylene glycol) and poly(N-isopropylacrylamide) were also synthesized through coupling reaction and copper0-mediated

Block coordination copolymers

Science.gov (United States)

Koh, Kyoung Moo; Wong-Foy, Antek G; Matzger, Adam J; Benin, Annabelle I; Willis, Richard R

2012-11-13

The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

Effect of grafting cellulose acetate and methylmethacrylate as compatibilizer onto NBR/SBR blends

International Nuclear Information System (INIS)

Khalf, A.I.; Nashar, D.E.El.; Maziad, N.A.

2010-01-01

Compatibilizer is used for improving of processability, interfacial interaction and mechanical properties of polymer blends. In this study acrylonitrile butadiene rubber (NBR) and styrene-butadiene rubber (SBR) blends were compatibilized by a graft copolymer of acrylonitrile butadiene rubber (NBR) grafted with cellulose acetate (CA) i.e. (NBR-g-CA) and acrylonitrile butadiene rubber (NBR) grafted with methylmethacrylate i.e. (NBR-g-MMA). Compatibilizers were prepared by gamma radiation induced grafting of NBR with cellulose acetate (CA) and methylmethacrylate (MMA) were added with different ratios to NBR/SBR (50/50) blend. The compatibilized blends were evaluated by rheometric characteristics, physico-mechanical properties, swelling behavior, scanning electron microscope (SEM) and thermal analysis. The results showed that, the blends with graft copolymer effect greatly on the rheological characteristics [optimum cure time (Tc 90 ), scorch time (Ts 2 ), and the cure rate index (CRI)]. The physico-mechanical properties of the investigated blends were enhanced by the incorporation of these graft copolymers, while the resistance to swelling in toluene became higher. SEM photographs confirm that, these compatibilizers improve the interfacial adhesion between NBR/SBR (50/50) blend which induce compatibilization in the immiscible blends. The efficiency of the compatibilizer was also evaluated by studying the thermogravimetric analysis.

Synchrotron SAXS studies on morphology formation in a binary blend of poly(ε-caprolactone) homopolymer and poly(ε-caprolactone)-block-polybutadiene copolymer

International Nuclear Information System (INIS)

Akaba, Michiaki; Nojima, Shuichi

2005-01-01

The process of morphology formation in a binary blend of poly(ε-caprolactone) homopolymer (PCL) and poly(ε-caprolactone)-block-polybutadiene copolymer (PCL-b-PB) has been investigated by synchrotron small-angle X-ray scattering (SR-SAXS). This blend shows an UCST-type phase separation and the crystallization of PCL chains (i.e., PCL and PCL blocks in PCL-b-PB) at a same temperature range, so that these two factors may work simultaneously to yield a complicated morphology formation. When the weight fraction of PCL (φ PCL ) is small (φ PCL PCL > 0.8), the blend can directly be quenched into crystallization temperatures without passing through the UCST region. Time-resolved SAXS curves in this case show that overall morphology formation is driven by the crystallization of PCL chains, where a crystallized PCL region always coexists with a crystallized PCL-b-PB region and the volume ratio of two regions is constant throughout. (author)

Renormalization of the one-loop theory of fluctuations in polymer blends and diblock copolymer melts.

Science.gov (United States)

Grzywacz, Piotr; Qin, Jian; Morse, David C

2007-12-01

Attempts to use coarse-grained molecular theories to calculate corrections to the random-phase approximation (RPA) for correlations in polymer mixtures have been plagued by an unwanted sensitivity to the value of an arbitrary cutoff length, i.e., by an ultraviolet (UV) divergence. We analyze the UV divergence of the inverse structure factor S(-1)(k) predicted by a "one-loop" approximation similar to that used in several previous studies. We consider both miscible homopolymer blends and disordered diblock copolymer melts. We show, in both cases, that all UV divergent contributions can be absorbed into a renormalization of the values of the phenomenological parameters of a generalized self-consistent field theory (SCFT). This observation allows the construction of an UV convergent theory of corrections to SCFT phenomenology. The UV-divergent one-loop contribution to S(-1)(k) is shown to be the sum of (i) a k -independent contribution that arises from a renormalization of the effective chi parameter, (ii) a k-dependent contribution that arises from a renormalization of monomer statistical segment lengths, (iii) a contribution proportional to k(2) that arises from a square-gradient contribution to the one-loop fluctuation free energy, and (iv) a k-dependent contribution that is inversely proportional to the degree of polymerization, which arises from local perturbations in fluid structure near chain ends and near junctions between blocks in block copolymers.

Effects of organoclay to miscibility, mechanical and thermal properties of poly(lactic acid) and propylene-ethylene copolymer blends

Science.gov (United States)

Wacharawichanant, S.; Ounyai, C.; Rassamee, P.

2017-07-01

The effects of propylene-ethylene copolymer (PEC or PEC3300) and clay surface modified with 25-30 wt% of trimethylstearyl ammonium (Clay-TSA) on morphology, thermal and mechanical properties of poly(lactic acid) (PLA) were investigated. The morphology analysis showed PLA/PEC3300 blends clearly demonstrated a two-phase separation of dispersed phase and the matrix phase and the addition of Clay-TSA could improve the miscibility of PLA and PEC3300 blends due to the decreased of the domain sizes of dispersed PEC3300 phase in the polymer matrix. From X-ray diffraction analysis showed the intercalation of PLA chains inside the Clay-TSA and this result implied that Clay-TSA platelets acted as an effective compatibilizer. The tensile properties showed the strain at break of PLA was improved after adding PEC3300 while Young’s modulus, tensile strength and storage modulus decreased. The addition of Clay-TSA could improve Young’s modulus of PLA/PEC3300 blends. The addition of Clay-TSA 7 phr showed the maximum of Young’s modulus of PLA/PEC3300/Clay-TSA composites. The thermal properties found that the addition of PEC3300 and Clay-TSA did not change significantly on the glass transition temperature and melting point temperature of PLA. The percent of crystallinity of PLA decreased with increasing PEC content. The thermal stability of PLA improved after adding PEC3300.

Styrene-Based Copolymer for Polymer Membrane Modifications

OpenAIRE

Harsha Srivastava; Harshad Lade; Diby Paul; G. Arthanareeswaran; Ji Hyang Kweon

2016-01-01

Poly(vinylidene fluoride) (PVDF) was modified with a styrene-based copolymer. The crystalline behavior, phase, thermal stability, and surface morphology of the modified membranes were analyzed. The membrane surface roughness showed a strong dependence on the styrene-acrylonitrile content and was reduced to 34% for a PVDF/styrene-acrylonitrile blend membrane with a 40/60 ratio. The thermal and crystalline behavior confirmed the blend miscibility of both polymers. It was observed in X-ray diffr...

The Plumber’s Nightmare Phase in Diblock Copolymer/Homopolymer Blends. A Self-Consistent Field Theory Study.

KAUST Repository

Martinez-Veracoechea, Francisco J.

2009-11-24

Using self-consistent field theory, the Plumber\\'s Nightmare and the double diamond phases are predicted to be stable in a finite region of phase diagrams for blends of AB diblock copolymer (DBC) and A-component homopolymer. To the best of our knowledge, this is the first time that the P phase has been predicted to be stable using self-consistent field theory. The stabilization is achieved by tuning the composition or conformational asymmetry of the DBC chain, and the architecture or length of the homopolymer. The basic features of the phase diagrams are the same in all cases studied, suggesting a general type of behavior for these systems. Finally, it is noted that the homopolymer length should be a convenient variable to stabilize bicontinuous phases in experiments. © 2009 American Chemical Society.

Phase behavior in blends of ethylene oxide-propylene oxide copolymer and poly(ether sulfone) studied by modulated-temperature DSC and NMR relaxometry.

Science.gov (United States)

Van Lokeren, Luk; Gotzen, Nicolaas-Alexander; Pieters, Ronny; Van Assche, Guy; Biesemans, Monique; Willem, Rudolph; Van Mele, Bruno

2009-01-01

The state diagram of a blend consisting of a copolymer containing ethylene oxide and propylene oxide, P(EO-ran-PO), and poly(ether sulfone), PES, is constructed by using modulated-temperature differential scanning calorimetry (MTDSC), T(2) NMR relaxometry, and light scattering. The apparent heat capacity signal in MTDSC is used for the characterization of polymer miscibility and morphology development. T(2) NMR relaxometry is used to detect the onset of phase separation, which is in good agreement with the onset of phase separation in the apparent heat capacity from MTDSC and the cloud-point temperature as determined from light scattering. The coexistence curve can be constructed from T(2) values at various temperatures by using a few blends with well-chosen compositions. These T(2) values also allow the detection of the boundary between the demixing zones with and without interference of partial vitrification and are in good agreement with stepwise quasi-isothermal MTDSC heat capacity measurements. Important interphases are detected in the heterogeneous P(EO-ran-PO)/PES blends.

Block copolymer membranes for aqueous solution applications

KAUST Repository

Nunes, Suzana Pereira

2016-03-22

Block copolymers are known for their intricate morphology. We review the state of the art of block copolymer membranes and discuss perspectives in this field. The main focus is on pore morphology tuning with a short introduction on non-porous membranes. The two main strategies for pore formation in block copolymer membranes are (i) film casting and selective block sacrifice and (ii) self-assembly and non-solvent induced phase separation (SNIPS). Different fundamental aspects involved in the manufacture of block copolymer membranes are considered, including factors affecting the equilibrium morphology in solid films, self-assembly of copolymer in solutions and macrophase separation by solvent-non-solvent exchange. Different mechanisms are proposed for different depths of the SNIPS membrane. Block copolymer membranes can be prepared with much narrower pore size distribution than homopolymer membranes. Open questions and indications of what we consider the next development steps are finally discussed. They include the synthesis and application of new copolymers and specific functionalization, adding characteristics to respond to stimuli and chemical environment, polymerization-induced phase separation, and the manufacture of organic-inorganic hybrids.

Block copolymer membranes for aqueous solution applications

KAUST Repository

Nunes, Suzana Pereira

2016-01-01

Block copolymers are known for their intricate morphology. We review the state of the art of block copolymer membranes and discuss perspectives in this field. The main focus is on pore morphology tuning with a short introduction on non-porous membranes. The two main strategies for pore formation in block copolymer membranes are (i) film casting and selective block sacrifice and (ii) self-assembly and non-solvent induced phase separation (SNIPS). Different fundamental aspects involved in the manufacture of block copolymer membranes are considered, including factors affecting the equilibrium morphology in solid films, self-assembly of copolymer in solutions and macrophase separation by solvent-non-solvent exchange. Different mechanisms are proposed for different depths of the SNIPS membrane. Block copolymer membranes can be prepared with much narrower pore size distribution than homopolymer membranes. Open questions and indications of what we consider the next development steps are finally discussed. They include the synthesis and application of new copolymers and specific functionalization, adding characteristics to respond to stimuli and chemical environment, polymerization-induced phase separation, and the manufacture of organic-inorganic hybrids.

Modification of PSf/SPSf Blended Porous Support for Improving the Reverse Osmosis Performance of Aromatic Polyamide Thin Film Composite Membranes

Directory of Open Access Journals (Sweden)

Li-Fen Liu

2018-06-01

Full Text Available In this study, modification of polysulfone (PSf/sulfonated polysulfone (SPSf blended porous ultrafiltration (UF support membranes was proposed to improve the reverse osmosis (RO performance of aromatic polyamide thin film composite (TFC membranes. The synergistic effects of solvent, polymer concentration, and SPSf doping content in the casting solution were investigated systematically on the properties of both porous supports and RO membranes. SEM and AFM were combined to characterize the physical properties of the membranes, including surface pore natures (porosity, mean pore radius, surface morphology, and section structure. A contact angle meter was used to analyze the membrane surface hydrophilicity. Permeate experiments were carried out to evaluate the separation performances of the membranes. The results showed that the PSf/SPSf blended porous support modified with 6 wt % SPSf in the presence of DMF and 14 wt % PSf had higher porosity, bigger pore diameter, and a rougher and more hydrophilic surface, which was more beneficial for fabrication of a polyamide TFC membrane with favorable reverse osmosis performance. This modified PSf/SPSf support endowed the RO membrane with a more hydrophilic surface, higher water flux (about 1.2 times, as well as a slight increase in salt rejection than the nascent PSf support. In a word, this work provides a new facile method to improve the separation performance of polyamide TFC RO membranes via the modification of conventional PSf porous support with SPSf.

Simultaneous determination of the styrene unit content and assessment of molecular weight of triblock copolymers in adhesives by a size exclusion chromatography method.

Science.gov (United States)

Wang, Mingfang; Wang, Yuerong; Luo, Pei; Zhang, Hongyang; Zhang, Min; Hu, Ping

2017-10-01

The content of styrene units in nonhydrogenated and hydrogenated styrene-butadiene-styrene and styrene-isoprene-styrene triblock copolymers significantly influences product performance. A size exclusion chromatography method was developed to determine the average styrene content of triblock copolymers blended with tackifier in adhesives. A complete separation of the triblock copolymer from the other additives was realized with size exclusion chromatography. The peak area ratio of the UV and refraction index signals of the copolymers at the same effective elution volume was correlated to the average styrene unit content using nuclear magnetic resonance spectroscopy with commercial copolymers as standards. The obtained calibration curves showed good linearity for both the hydrogenated and nonhydrogenated styrene-butadiene-styrene and styrene-isoprene-styrene triblock copolymers (r = 0.974 for styrene contents of 19.3-46.3% for nonhydrogenated ones and r = 0.970 for the styrene contents of 23-58.2% for hydrogenated ones). For copolymer blends, the developed method provided more accurate average styrene unit contents than nuclear magnetic resonance spectroscopy provided. These results were validated using two known copolymer blends consisting of either styrene-isoprene-styrene or hydrogenated styrene-butadiene-styrene and a hydrocarbon tackifying resin as well as an unknown adhesive with styrene-butadiene-styrene and an aromatic tackifying resin. The methodology can be readily applied to styrene-containing polymers in blends such as poly(acrylonitrile-butadiene styrene). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and characterization of compatibilizers for blends of PA and ABS

NARCIS (Netherlands)

Staal, M.P.B.

2005-01-01

Blends of polyamide (PA) and acrylonitrile-butadiene-styrene (ABS) copolymers yield polymeric materials that are highly solvent resistant, easy to process and have high impact strengths over a wide temperature range. These properties make these blends interesting materials for various applications

Functional Nanoporous Polymers from Block Copolymer Precursors

DEFF Research Database (Denmark)

Guo, Fengxiao

Abstract Self-assembly of block copolymers provides well-defined morphologies with characteristic length scales in the nanometer range. Nanoporous polymers prepared by selective removal of one block from self-assembled block copolymers offer great technological promise due to their many potential...... functionalities remains a great challenge due to the limitation of available polymer synthesis and the nanoscale confinement of the porous cavities. The main topic of this thesis is to develop methods for fabrication of functional nanoporous polymers from block copolymer precursors. A method has been developed......, where living anionic polymerization and atom transfer radical polymerization (ATRP) are combined to synthesize a polydimethylsiloxane-b-poly(tert-butyl acrylate)-b-polystyrene (PDMS-b-PtBA-b-PS) triblock copolymer precursor. By using either anhydrous hydrogen fluoride or trifluoroacetic acid, PtBA block...

Poly(4-vinylpyridine)-block-poly(N-acryloylpiperidine) diblock copolymers: synthesis, self-assembly and interaction

NARCIS (Netherlands)

Hofman, Anton H.; Alberda van Ekenstein, Gerhard; Woortman, Albert; ten Brinke, Gerrit; Loos, Katja

2015-01-01

Controlled radical polymerization of 4-vinylpyridine (4VP) and N-acryloylpiperidine (API) by the RAFT process allowed preparation of well-defined double hydrogen bond accepting P4VP-b-PAPI diblock copolymers. The miscibility of this new monomer pair was studied via a random copolymer blend approach

Crystalline structure of polypropylene in blends with thermoplastic elastomers after electron beam irradiation

International Nuclear Information System (INIS)

Steller, Ryszard; Zuchowska, Danuta; Meissner, Wanda; Paukszta, Dominik; Garbarczyk, Jozef

2006-01-01

Isotactic polypropylene (PP) was blended in extruder with 0-50% addition of styrene-ethylene/butylene-styrene (SEBS) and styrene-butadiene-styrene (SBS) block copolymers. Granulated blends were irradiated with electron beam (60 kGy) and 1 week later processed with injection molding machine. Properties of samples molded from irradiated and non-irradiated granulates were investigated using DSC, WAXS, MFR, SEM and mechanical and solubility tests. It was found that the SEBS based systems are more resistant to irradiation in comparison to similar blends with SBS copolymer. Such behavior can be explained by the presence of double bonds in elastic SBS block. Irradiation of PP-SBS blends leads to considerable structure changes of crystalline and amorphous PP phases and elastic SBS phase. It indicates creation of new (inter)phase consisting of products of grafting and cross-linking reactions. Irradiated PP-SBS blends show significant improvement of impact strength at low temperatures

Relationship between the mechanical properties of epoxy/PMMA-b-PnBA-b-PMMA block copolymer blends and their three-dimensional nanostructures

Directory of Open Access Journals (Sweden)

H. Kishi

2017-10-01

Full Text Available Nanostructures of diglycidyl ether of bisphenol-A epoxy/poly(methyl methacrylate-b-poly(n-butyl acrylate-b-poly(methyl methacrylate (PMMA-b-PnBA-b-PMMA triblock copolymer (BCP blends were studied in relation to their mechanical properties. Three types of self-assembled nanostructures, such as spheres, random cylinders, and curved lamella, were controlled in phenol novolac-cured epoxy blends with a wide range of BCP content. Three types of nanostructures were observed using two-dimensional and three-dimensional transmission electron microscopy (TEM. The 3D-TEM, dynamic viscoelastic analyses, and theoretical model on the elastic modulus clarified that the spheres and the random cylinders, consisted of epoxy-immiscible PnBA phases, were discontinuously dispersed in the epoxy matrix. In contrast, the curved lamella formed co-continuous nanostructure, in which both the PnBA and epoxy phases formed continuous channels. The fracture toughness (critical strain energy release rate, GIC and the flexural moduli of elasticity (E of the cured blends were evaluated for various amounts of BCP content. The highest GIC was obtained from the random cylindrical nanostructured blends in the three types of nanostructures with the same PnBA content. The lowest E was obtained for the curved lamella with co-continuous nanostructures. The details of deformation and fracture events were observed using optical and electron microscopy, and the mechanical properties are discussed in relation to the nanostructures.

RGB-Switchable Porous Electrospun Nanofiber Chemoprobe-Filter Prepared from Multifunctional Copolymers for Versatile Sensing of pH and Heavy Metals.

Science.gov (United States)

Liang, Fang-Cheng; Kuo, Chi-Ching; Chen, Bo-Yu; Cho, Chia-Jung; Hung, Chih-Chien; Chen, Wen-Chang; Borsali, Redouane

2017-05-17

Novel red-green-blue (RGB) switchable probes based on fluorescent porous electrospun (ES) nanofibers exhibiting high sensitivity to pH and mercury ions (Hg 2+ ) were prepared with one type of copolymer (poly(methyl methacrylatete-co-1,8-naphthalimide derivatives-co-rhodamine derivative); poly(MMA-co-BNPTU-co-RhBAM)) by using a single-capillary spinneret. The MMA, BNPTU, and RhBAM moieties were designed to (i) permit formation of porous fibers, (ii) fluoresce for Hg 2+ detection, and (iii) fluoresce for pH, respectively. The fluorescence emission of BNPTU (fluorescence resonance energy transfer (FRET) donor) changed from green to blue as it detected Hg 2+ . The fluorescence emission of RhBAM (FRET acceptor) was highly selective for pH, changing from nonfluorescent (pH 7) to exhibiting strong red fluorescence (pH 2). The full-color emission of the ES nanofibers included green, red, blue, purple, and white depending on the particular pH and Hg 2+ -concentration combination of the solution. The porous ES nanofibers with 30 nm pores were fabricated using hydrophobic MMA, low-boiling-point solvent, and at a high relative humidity (80%). These porous ES nanofibers had a higher surface-to-volume ratio than did the corresponding thin films, which enhanced their performance. The present study demonstrated that the FRET-based full-color-fluorescence porous nanofibrous membranes, which exhibit on-off switching and can be used as naked eye probes, have potential for application in water purification sensing filters.

Chitosan-Based Polymer Blends: Current Status and applications

International Nuclear Information System (INIS)

Hefian, E.A.E.; Nasef, M.M.

2014-01-01

This paper reviews the latest developments in chitosan-based blends and their potential applications in various fields. Various blends together with other derivatives, such as composites and graft copolymers, have been developed to overcome chitosans disadvantages, including poor mechanical properties and to improve its functionality towards specific applications. The progress made in blending chitosan with synthetic and natural polymers is presented. The versatility and unique characteristics, such as hydrophilicity, film-forming ability, biodegradability, biocompatibility, antibacterial activity and non-toxicity of chitosan has contributed to the successful development of various blends for medical, pharmaceutical, agricultural and environmental applications. (author)

Tough Blends of Polylactide and Castor Oil

Energy Technology Data Exchange (ETDEWEB)

Robertson, Megan L.; Paxton, Jessica M.; Hillmyer, Marc A. (UMM)

2012-10-10

Poly(l-lactide) (PLLA) is a renewable resource polymer derived from plant sugars with several commercial applications. Broader implementation of the material is limited due to its inherent brittleness. We show that the addition of 5 wt % castor oil to PLLA significantly enhances the overall tensile toughness with minimal reductions in the modulus and no plasticization of the PLLA matrix. In addition, we used poly(ricinoleic acid)-PLLA diblock copolymers, synthesized entirely from renewable resources, as compatibilizers for the PLLA/castor oil blends. Ricinoleic acid, the majority fatty acid comprising castor oil, was polymerized through a lipase-catalyzed condensation reaction. The resulting polymers contained a hydroxyl end-group that was subsequently used to initiate the ring-opening polymerization of L-lactide. The binary PLLA/castor oil blend exhibited a tensile toughness seven times greater than neat PLLA. The addition of block copolymer allowed for control over the morphology of the blends, and even further improvement in the tensile toughness was realized - an order of magnitude larger than that of neat PLLA.

Tough blends of polylactide and castor oil.

Science.gov (United States)

Robertson, Megan L; Paxton, Jessica M; Hillmyer, Marc A

2011-09-01

Poly(l-lactide) (PLLA) is a renewable resource polymer derived from plant sugars with several commercial applications. Broader implementation of the material is limited due to its inherent brittleness. We show that the addition of 5 wt % castor oil to PLLA significantly enhances the overall tensile toughness with minimal reductions in the modulus and no plasticization of the PLLA matrix. In addition, we used poly(ricinoleic acid)-PLLA diblock copolymers, synthesized entirely from renewable resources, as compatibilizers for the PLLA/castor oil blends. Ricinoleic acid, the majority fatty acid comprising castor oil, was polymerized through a lipase-catalyzed condensation reaction. The resulting polymers contained a hydroxyl end-group that was subsequently used to initiate the ring-opening polymerization of l-lactide. The binary PLLA/castor oil blend exhibited a tensile toughness seven times greater than neat PLLA. The addition of block copolymer allowed for control over the morphology of the blends, and even further improvement in the tensile toughness was realized-an order of magnitude larger than that of neat PLLA.

Block copolymer/homopolymer dual-layer hollow fiber membranes

KAUST Repository

Hilke, Roland; Neelakanda, Pradeep; Behzad, Ali Reza; Nunes, Suzana Pereira; Peinemann, Klaus-Viktor

2014-01-01

We manufactured the first time block copolymer dual-layer hollow fiber membranes and dual layer flat sheet membranes manufactured by double solution casting and phase inversion in water. The support porous layer was based on polystyrene

Impacts of side chain and excess energy on the charge photogeneration dynamics of low-bandgap copolymer-fullerene blends

International Nuclear Information System (INIS)

Huo, Ming-Ming; Zhang, Jian-Ping; Hu, Rong; Xing, Ya-Dong; Liu, Yu-Chen; Ai, Xi-Cheng; Hou, Jian-Hui

2014-01-01

Primary charge photogeneration dynamics in neat and fullerene-blended films of a pair of alternating benzo[1,2-b:4,5-b ′ ]dithiophene (BDT) and thieno[3,4-b]thiophene (TT) copolymers are comparatively studied by using near-infrared, time-resolved absorption (TA) spectroscopy under low excitation photon fluence. PBDTTT-E and PBDTTT-C, differed merely in the respective TT-substituents of ester (-E) and carbonyl (-C), show distinctly different charge photogeneration dynamics. The pair of neat PBDTTT films show exciton lifetimes of ∼0.1 ns and fluorescence quantum yields below 0.2%, as well as prominent excess-energy enhanced exciton dissociation. In addition, PBDTTT-C gives rise to >50% higher P •+ yield than PBDTTT-E does irrespective to the excitation photon energy. Both PBDTTT-E:PC 61 BM and PBDTTT-C:PC 61 BM blends show subpicosecond exciton lifetimes and nearly unitary fluorescence quenching efficiency and, with respect to the former blend, the latter one shows substantially higher branching ratio of charge separated (CS) state over interfacial charge transfer (ICT) state, and hence more efficient exciton-to-CS conversion. For PBDTTT-C:PC 61 BM, the ultrafast charge dynamics clearly show the processes of ICT-CS interconversion and P •+ migration, which are possibly influenced by the ICT excess energy. However, such processes are relatively indistinctive in the case of PBDTTT-E:PC 61 BM. The results strongly prove the importance of ICT dissociation in yielding free charges, and are discussed in terms of the film morphology and the precursory solution-phase macromolecular conformation

Mechanical properties of polyamide 6,6/low density polyethylene blend by ionizing radiation

International Nuclear Information System (INIS)

Pino, Eddy S.; Feitosa, Marcos A.F.

2007-01-01

Polymer blending is a growing scientific and commercial development activity. In most of the cases, polymeric blends are formed by thermodynamically immiscible components. Such blends require the use of compatibilizers that, often, are copolymers, graft copolymers or any mean that improves the dispersion and adhesion of the blend phases. Compatibility of a polymer blend plays an important role in determining the blend properties for its end use. In this work, the improvement of mechanical properties of PA 6,6/LDPE 75/25% wt/wt composition blend, using electron radiation, was studied. Samples for mechanical test were melt-mixed in an extruder and then injection-molded. These samples were electron irradiated to overall doses of 50, 100, 150, 200 and 250 kGy. Tensile measurements have shown that the strength at break increases with an increase of radiation dose. Hardness Shore D measurements show that this property also increases as a function of radiation dose. On the other hand, Impact Izod tests show that the resistance to impact decreases with the increase of radiation dose. The behavior of these bulk and surface properties implies that ionizing radiation produces changes in the mechanical performance of the irradiated blend due to a combined radiation inducing effects, cross-linking and the compatibility of blend components. (author)

21 CFR 177.1990 - Vinylidene chloride/methyl acrylate copolymers.

Science.gov (United States)

2010-04-01

... SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances... (unsupported film, barrier layer, or as a copolymer for blending) will not exceed 10 parts per million and 5... producing, manufacturing, processing, preparing, treating, packaging, transporting, or holding food...

Study of micro-phase separation of two polystyrene-based copolymer mixture using the combination of PALS and FT-IR

International Nuclear Information System (INIS)

Jiang, Z.Y.; Jiang, X.Q.; Yang, Y.X.; Huang, Y.J.; Huang, H.B.; Hsia, Y.F.

2005-01-01

Positron annihilation lifetime (PAL) spectroscopy, Fourier transform infrared (FT-IR) and differential scanning calorimetry (DSC) have been applied to study the micro-phase separation in the blends of poly(styrene-co-methylmethacrylate) (SMMA) copolymer and poly(styrene-co-maleic anhydride) (SMA) copolymer. The DSC results indicate that the SMA/SMMA blends are miscible and weak intermolecular interactions exist between SMA and SMMA. The strength of intermolecular interactions to some degree exhibits somewhat non-monotonic variation with increasing of SMA component in the blends. The results of PAL measurement present the blend containing 20 wt% SMA is phase-separated in molecular level, which is interpreted by the results of FT-IR analysis. It was concluded that it is helpful to study the miscibility of polymer blends in molecular level by means of PAL method, accompanied with the requisite measurement of DSC and FT-IR

Composites and blends from biobased materials

Energy Technology Data Exchange (ETDEWEB)

Kelley, S.S. [National Renewable Energy Laboratory, Golden, CO (United States)

1995-05-01

The program is focused on the development of composites and blends from biobased materials to use as membranes, high value plastics, and lightweight composites. Biobased materials include: cellulose derivative microporous materials, cellulose derivative copolymers, and cellulose derivative blends. This year`s research focused on developing an improved understanding of the molecular features that cellulose based materials with improved properties for gas separation applications. Novel cellulose ester membrane composites have been developed and are being evaluated under a collaborative research agreement with Dow Chemicals Company.

Improved surface property of PVDF membrane with amphiphilic zwitterionic copolymer as membrane additive

Energy Technology Data Exchange (ETDEWEB)

Li Jianhua, E-mail: jhli_2005@163.com [Institute of Biomedical and Pharmaceutical Technology and College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350001 (China); Li Mizi; Miao Jing; Wang Jiabin; Shao Xisheng [Institute of Biomedical and Pharmaceutical Technology and College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350001 (China); Zhang Qiqing, E-mail: zhangqiq@126.com [Institute of Biomedical and Pharmaceutical Technology and College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350001 (China) and Institute of Biomedical Engineering, Chinese Academy of Medical Science, Peking Union Medical College, Tianjin 300192 (China)

2012-06-15

An attempt to improve hydrophilicity and anti-fouling properties of PVDF membranes, a novel amphiphilic zwitterionic copolymer poly(vinylidene fluoride)-graft-poly(sulfobetaine methacrylate) (PVDF-g-PSBMA) was firstly synthesized by atom transfer radical polymerization (ATRP) and used as amphiphilic copolymer additive in the preparation of PVDF membranes. The PVDF-g-PSBMA/PVDF blend membranes were prepared by immersion precipitation process. Fourier transform infrared attenuated reflection spectroscopy (FTIR-ATR) and X-ray photoelectronic spectroscopy (XPS) measurements confirmed that PSBMA brushes from amphiphilic additives were preferentially segregated to membrane-coagulant interface during membrane formation. The morphology of membranes was characterized by scanning electron microscopy (SEM). Water contact angle measurements showed that the surface hydrophilicity of PVDF membranes was improved significantly with the increasing of amphiphilic copolymer PVDF-g-PSBMA in cast solution. Protein static adsorption experiment and dynamic fouling resistance experiment revealed that the surface enrichment of PSBMA brush endowed PVDF blend membrane great improvement of surface anti-fouling ability.

Improved surface property of PVDF membrane with amphiphilic zwitterionic copolymer as membrane additive

International Nuclear Information System (INIS)

Li Jianhua; Li Mizi; Miao Jing; Wang Jiabin; Shao Xisheng; Zhang Qiqing

2012-01-01

An attempt to improve hydrophilicity and anti-fouling properties of PVDF membranes, a novel amphiphilic zwitterionic copolymer poly(vinylidene fluoride)-graft-poly(sulfobetaine methacrylate) (PVDF-g-PSBMA) was firstly synthesized by atom transfer radical polymerization (ATRP) and used as amphiphilic copolymer additive in the preparation of PVDF membranes. The PVDF-g-PSBMA/PVDF blend membranes were prepared by immersion precipitation process. Fourier transform infrared attenuated reflection spectroscopy (FTIR-ATR) and X-ray photoelectronic spectroscopy (XPS) measurements confirmed that PSBMA brushes from amphiphilic additives were preferentially segregated to membrane-coagulant interface during membrane formation. The morphology of membranes was characterized by scanning electron microscopy (SEM). Water contact angle measurements showed that the surface hydrophilicity of PVDF membranes was improved significantly with the increasing of amphiphilic copolymer PVDF-g-PSBMA in cast solution. Protein static adsorption experiment and dynamic fouling resistance experiment revealed that the surface enrichment of PSBMA brush endowed PVDF blend membrane great improvement of surface anti-fouling ability.

Effects of electron beam irradiation on ethylene-octene copolymers (octene rubber)

International Nuclear Information System (INIS)

Harris C Raj Kumar; Mansor Ahmad; Khairul Zaman Mohd Dahlan

2002-01-01

The effect of electron irradiation on a ethylene-octene copolymer was investigated. The optimal blending speed, blending temperature and hot press temperature were first optimized to 40 rpm, 185 degree C and 180 degree C, respectively. The ethylene octene copolymer was then irradiated with electron beam from doses in the range of 20 kGy up to 200 kGy. The physical changes occurred were examined from the point of tensile strength tests, elongation at break, tensile modulus, hardness (Shore A) and gel content, and compared with a set of un-irradiated sample. Almost all the tests signify that cross-linking was the predominant reaction rather than chain scission, especially in gel content test. The hardness test was inconclusive as there were no significant changes that occurred. (Author)

Flame-retardant copolymers of dialkyl (meth)acryloyloxyalkyl phosphate or dialkyl (meth)acryloyloxyalkyl phosphonate monomers and polymer foams based made therefrom

Energy Technology Data Exchange (ETDEWEB)

Qi, Yudong; Li, Yan; Bunker, Shana P.; Costeux, Stephane; Morgan, Ted A.

2017-12-12

Polymer foam bodies are made from phosphorus-containing thermoplastic random copolymers of a dialkyl (meth)acryloyloxyalkyl phosph(on)ate. Foam bodies made from these copolymers exhibit increased limiting oxygen indices and surprisingly have good properties. In certain embodiments, the phosphorus-containing thermoplastic copolymer is blended with one or more other polymers and formed into nanofoams.

Proton exchange membranes based on PVDF/SEBS blends

Energy Technology Data Exchange (ETDEWEB)

Mokrini, A.; Huneault, M.A. [Industrial Materials Institute, National Research Council of Canada, 75 de Mortagne Blvd., Boucherville, Que. (Canada J4B 6Y4)

2006-03-09

Proton-conductive polymer membranes are used as an electrolyte in the so-called proton exchange membrane fuel cells. Current commercially available membranes are perfluorosulfonic acid polymers, a class of high-cost ionomers. This paper examines the potential of polymer blends, namely those of styrene-(ethylene-butylene)-styrene block copolymer (SEBS) and polyvinylidene fluoride (PVDF), in the proton exchange membrane application. SEBS/PVDF blends were prepared by twin-screw extrusion and the membranes were formed by calendering. SEBS is a phase-segregated material where the polystyrene blocks can be selectively functionalized offering high ionic conductivity, while PVDF insures good dimensional stability and chemical resistance to the films. Proton conductivity of the films was obtained by solid-state grafting of sulfonic acid moieties. The obtained membranes were characterized in terms of conductivity, ionic exchange capacity and water uptake. In addition, the membranes were characterized in terms of morphology, microstructure and thermo-mechanical properties to establish the blends morphology-property relationships. Modification of interfacial properties between SEBS and PVDF was found to be a key to optimize the blends performance. Addition of a methyl methacrylate-butyl acrylate-methyl methacrylate block copolymer (MMA-BA-MMA) was found to compatibilize the blend by reducing the segregation scale and improving the blend homogeneity. Mechanical resistance of the membranes was also improved through the addition of this compatibilizer. As little as 2wt.% compatibilizer was sufficient for complete interfacial coverage and lead to improved mechanical properties. Compatibilized blend membranes also showed higher conductivities, 1.9x10{sup -2} to 5.5x10{sup -3}Scm{sup -1}, and improved water management. (author)

Phase equilibria and phase structures of polymer blends

International Nuclear Information System (INIS)

Chalykh, Anatolii E; Gerasimov, Vladimir K

2004-01-01

Experimental, methodical and theoretical studies dealing with phase equilibria and phase structures of polymer blends are generalised. The general and specific features of the change in solubility of polymers with changes in the molecular mass and copolymer composition and upon the formation of three-dimensional cross-linked networks are described. The results of the effect of the prehistory on the phase structure and the non-equilibrium state of polymer blends are considered in detail.

Amino-Functional Polybenzimidazole Blends with Enhanced Phosphoric Acid Mediated Proton Conductivity as Fuel Cell Electrolytes

DEFF Research Database (Denmark)

Aili, David; Javakhishvili, Irakli; Han, Junyoung

2016-01-01

A new amino-functional polybenzimidazole copolymer is synthesized by homogeneous solution condensation polymerization from a novel monomer, N,N′-bis (2,4-diaminophenyl)-1,3-diaminopropane. The copolymer readily dissolves in organic solvents and shows good film forming characteristics. To balance...... the phosphoric acid uptake and to obtain mechanically robust membranes, the amino-functional polybenzimidazole derivative is blended with high molecular weight poly [2,2′-(m-phenylene)-5,5′-bisbenzimidazole] at different ratios. Due to the high acid uptake, the homogenous blend membranes show enhanced proton...

COPOLYMER BLENDS OF STYRENE AND ORTHO-FLUOROSTYRENE

NARCIS (Netherlands)

TENBRINKE, G; KARASZ, FE

1991-01-01

The traditional method, using differential scanning calorimetry, to study phase behaviour in blends containing styrene and fluorinated styrene is hampered by the fact that the glass transition temperatures of fluorinated polystyrenes are almost independent of the degree of fluorination. To deal with

Origin of thermally stable ferroelectricity in a porous barium titanate thin film synthesized through block copolymer templating

Directory of Open Access Journals (Sweden)

Norihiro Suzuki

2017-07-01

Full Text Available A porous barium titanate (BaTiO3 thin film was chemically synthesized using a surfactant-assisted sol-gel method in which micelles of amphipathic diblock copolymers served as structure-directing agents. In the Raman spectrum of the porous BaTiO3 thin film, a peak corresponding to the ferroelectric tetragonal phase was observed at around 710 cm−1, and it remained stable at much higher temperature than the Curie temperature of bulk single-crystal BaTiO3 (∼130 °C. Measurements revealed that the ferroelectricity of the BaTiO3 thin film has high thermal stability. By analyzing high-resolution transmission electron microscope images of the BaTiO3 thin film by the fast Fourier transform mapping method, the spatial distribution of stress in the BaTiO3 framework was clearly visualized. Careful analysis also indicated that the porosity in the BaTiO3 thin film introduced anisotropic compressive stress, which deformed the crystals. The resulting elongated unit cell caused further displacement of the Ti4+ cation from the center of the lattice. This displacement increased the electric dipole moment of the BaTiO3 thin film, effectively enhancing its ferro(piezoelectricity.

Phase Behavior of Diblock Copolymer–Homopolymer Ternary Blends: Congruent First-Order Lamellar–Disorder Transition

Energy Technology Data Exchange (ETDEWEB)

Hickey, Robert J.; Gillard, Timothy M.; Irwin, Matthew T.; Morse, David C.; Lodge, Timothy P.; Bates, Frank S. (UMM)

2016-10-13

We have established the existence of a line of congruent first-order lamellar-to-disorder (LAM–DIS) transitions when appropriate amounts of poly(cyclohexylethylene) (C) and poly(ethylene) (E) homopolymers are mixed with a corresponding compositionally symmetric CE diblock copolymer. The line of congruent transitions, or the congruent isopleth, terminates at the bicontinuous microemulsion (BμE) channel, and its trajectory appears to be influenced by the critical composition of the C/E binary homopolymer blend. Blends satisfying congruency undergo a direct LAM–DIS transition without passing through a two-phase region. We present complementary optical transmission, small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and dynamic mechanical spectroscopy (DMS) results that establish the phase behavior at constant copolymer volume fraction and varying C/E homopolymer volume ratios. Adjacent to the congruent composition at constant copolymer volume fraction, the lamellar and disordered phases are separated by two-phase coexistence windows, which converge, along with the line of congruent transitions, at an overall composition in the phase prism coincident with the BμE channel. Hexagonal and cubic (double gyroid) phases occur at higher diblock copolymer concentrations for asymmetric amounts of C and E homopolymers. These results establish a quantitative method for identifying the detailed phase behavior of ternary diblock copolymer–homopolymer blends, especially in the vicinity of the BμE.

Position transitions of polymer-grafted nanoparticles in diblock-copolymer nanocomposites

Directory of Open Access Journals (Sweden)

2011-04-01

Full Text Available Self-assembly of block copolymer/nanoparticle blends has promising applications in the design and fabrication of novel functional nanomaterials. Precise control of the spatial positions of nanoparticles within block copolymer-based nanomaterials is crucial to achieve some special physical properties and functions. Here, we employ the self-consistent field method to theoretically investigate the self-assembly of polymer grafted-nanoparticles in a diblock copolymer. It is found that by varying the size and selectivity of nanoparticles, one can not only produce various self-assembled nanostructures but also modulate the spatial positions of the nanoparticles, either at the copolymer interfaces or in the center of one copolymer phase, within the nanostructures. A denser grafted polymer brush plays a role of shielding effect on nanoparticles and can position them into the center of one copolymer phase. The nanostructural transition we observed is dictated by the competition between entropy and enthalpy. On the basis of a number of simulations, two phase diagrams of self-assembled nanostructures are constructed. This study may be helpful for optimal design of advanced materials with desired nanostructures and enhanced performance.

Synthesis and Characterization of Block Copolymers with Unique Chemical Functionalities and Entropically-Hindering Moieties

Science.gov (United States)

2017-08-14

methanol as a function of chemistry , morphology and hydration levels. Accomplishments: This section is included in the "upload" section. Training...Copolymer Blend Membranes.” In Press, Polymer Engineering and Science, DOI: 10.1002 /pen.24508, 2017. 5. M. Pérez-Pérez and D. Suleiman. “Synthesis and...Synthesis and Characterization of Sulfonated Amine Block Copolymers for Energy Efficient Applications". Chemical Engineering Symposium, University of

Recycling of plastic wastes with poly (ethylene-co-methacrylic acid) copolymer as compatibilizer and their conversion into high-end product.

Science.gov (United States)

Rajasekaran, Divya; Maji, Pradip K

2018-04-01

This paper deals with the utilization of plastic wastes to a useful product. The major plastic pollutants that are considered to be in maximum use i.e. PET bottle and PE bags have been taken for consideration for recycling. As these two plastic wastes are not compatible, poly (ethylene-co-methacrylic acid) copolymer has been used as compatibilizer to process these two plastic wastes. Effect of dose of poly (ethylene-co-methacrylic acid) copolymer as compatibilizer has been studied here. It has been shown that only 3 wt% of poly (ethylene-co-methacrylic acid) copolymer is sufficient to make 3:1 mass ratio of PET bottle and polyethylene bags compatible. Compatibility has been examined through mechanical testing, thermal and morphological analysis. After analysing the property of recyclates, better mechanical and thermal property has been observed. Almost 500% of tensile property has been improved by addition of 3 wt% of poly (ethylene-co-methacrylic acid) copolymer in 3:1 mass ratio blend of PET bottle and PE bags than that of pristine blend. Morphological analysis by FESEM and AFM has also confirmed the compatibility of the blend. Experimental data showed better performance than available recycling process. Copyright © 2018 Elsevier Ltd. All rights reserved.

Recycling cycle of materials applied to acrylonitrile-butadiene-styrene/policarbonate blends with styrene-butadiene-styrene copolymer addition

Science.gov (United States)

Cândido, L. H. A.; Ferreira, D. B.; Júnior, W. Kindlein; Demori, R.; Mauler, R. S.

2014-05-01

The scope of this research is the recycling of polymers from mobile phones hulls discarded and the performance evaluation when they are submitted to the Recycling Cycle of Materials (RCM). The studied material was the ABS/PC blend in a 70/30 proportion. Different compositions were evaluated adding virgin material, recycled material and using the copolymer SBS as impact modifier. In order to evaluate the properties of material's composition, the samples were characterized by TGA, FTIR, SEM, IZOD impact strength and tensile strength tests. At the first stage, the presented results suggest the composition containing 25% of recycled material and 5% of SBS combines good mechanical performance to the higher content of recycled material and lower content of impact modifier providing major benefits to recycling plans. Five cycles (RCM) were applied in the second stage; they evidenced a decrease trend considering the impact strength. At first and second cycle the impact strength was higher than reference material (ABS/PC blend) and from the fourth cycle it was lower. The superiority impact strength in the first and second cycles can be attributed to impact modifier effect. The thermal tests and the spectrometry didn't show the presence of degradation process in the material and the TGA curves demonstrated the process stability. The impact surface of each sample was observed at SEM. The microstructures are not homogeneous presenting voids and lamellar appearance, although the outer surface presents no defects, demonstrating good moldability. The present work aims to assess the life cycle of the material from the successive recycling processes.

Two-Dimensional Liquid Chromatography Analysis of Polystyrene/Polybutadiene Block Copolymers.

Science.gov (United States)

Lee, Sanghoon; Choi, Heejae; Chang, Taihyun; Staal, Bastiaan

2018-05-15

A detailed characterization of a commercial polystyrene/polybutadiene block copolymer material (Styrolux) was carried out using two-dimensional liquid chromatography (2D-LC). The Styrolux is prepared by statistical linking reaction of two different polystyrene- block-polybutadienyl anion precursors with a multivalent linking agent. Therefore, it is a mixture of a number of branched block copolymers different in molecular weight, composition, and chain architecture. While individual LC analysis, including size exclusion chromatography, interaction chromatography, or liquid chromatography at critical condition, is not good enough to resolve all the polymer species, 2D-LC separations coupling two chromatography methods were able to resolve all polymer species present in the sample; at least 13 block copolymer species and a homopolystyrene blended. Four different 2D-LC analyses combining a different pair of two LC methods provide their characteristic separation results. The separation characteristics of the 2D-LC separations are compared to elucidate the elution characteristics of the block copolymer species.

Block copolymer/homopolymer dual-layer hollow fiber membranes

KAUST Repository

Hilke, Roland

2014-12-01

We manufactured the first time block copolymer dual-layer hollow fiber membranes and dual layer flat sheet membranes manufactured by double solution casting and phase inversion in water. The support porous layer was based on polystyrene and the selective layer with isopores was formed by micelle assembly of polystyrene-. b-poly-4-vinyl pyridine. The dual layers had an excellent interfacial adhesion and pore interconnectivity. The dual membranes showed pH response behavior like single layer block copolymer membranes with a low flux for pH values less than 3, a fast increase between pH4 and pH6 and a constant high flux level for pH values above 7. The dry/wet spinning process was optimized to produce dual layer hollow fiber membranes with polystyrene internal support layer and a shell block copolymer selective layer.

Supercapacitor Electrode Materials from Highly Porous Carbon Nanofibers with Tailored Pore Distributions

Science.gov (United States)

Chathurika Abeykoon, Nimali

Environmental and human health risks associated with the traditional methods of energy production (e.g., oil and gas) and intermittency and uncertainty of renewable sources (e.g., solar and wind) have led to exploring effective and alternative energy sources to meet the growing energy demands. Electricity based on energy storage devices are the most promising solutions for realization of these objectives. Among the energy storage devices, electrochemical double layer capacitors (EDLCs) or supercapacitors have become an attractive research interest due to their outstanding performance, especially high power densities, long cycle life and rapid charge and discharge times, which enables them to utilize in many applications including consumer electronics and transportation, where high power is needed. However, low energy density of supercapacitors is a major obstacle to compete with the commercially existing high energy density energy storage device such as batteries. The fabrication of advanced electrodes materials with very high surface area from novel precursors and utilization of electrolytes with higher operating voltages are essential to enhance energy density of supercapacitors. In this work, carbon nanofibers (CNFs) from different polymer precursors with new fabrication techniques are explored to develop highly porous carbon with tailored pore distributions to match with employed ionic liquid electrolytes (which possess high working voltages), to realize high energy storage capability. Novel electrode materials derived from electrospun immiscible polymer blends and synthesized copolymers and terpolymers were described. Pore distributions of CNFs were tailored by varying the composition of polymers in immiscible blends or varying the monomer ratios of copolymer or terpolymers. Chapter 1 gives the detailed introduction of supercapacitors including history and storage principle of EDLCs, fabrication of carbon nanofiber based electrodes and electrolytes employed

Enhancing relative permittivity by incorporating PDMS-PEG multi block copolymers in binary polymer blends

DEFF Research Database (Denmark)

A Razak, Aliff Hisyam; Szabo, Peter; Skov, Anne Ladegaard

Polydimethylsiloxanes (PDMS) are well-known to actuate with relatively large strains due to low modulus, but they possess lowpermittivity. Contrary, polyethyleneglycols (PEG) are not stretchable but possess high permittivity. Combination of the two polymers in a block copolymer depicts a possibil......Polydimethylsiloxanes (PDMS) are well-known to actuate with relatively large strains due to low modulus, but they possess lowpermittivity. Contrary, polyethyleneglycols (PEG) are not stretchable but possess high permittivity. Combination of the two polymers in a block copolymer depicts...... a possibility for substantial improvement of properties such as high permittivity, stretchability and non-conductivity – if carefully designed. The objective is to synthesize PDMS-PEG multiblock copolymer assembling into discontinuous morphologies in PEG based on variation of volume fractions of PDMS....... The utilized synthesis of PDMS-PEG multiblock copolymer is based on hydrosilylation reaction, which is amended from Klasner et al.1 and Jukarainen etal.2 Variation in the ratio between the two constituents introduces distinctive properties in terms of dielectric permittivity and rheological behaviour. PDMS...

Barriers to defect melting in chemo-epitaxial directed self-assembly of lamellar-forming diblock copolymer/homopolymer blends

Science.gov (United States)

Izumi, Kenichi; Kim, Bongkeun; Laachi, Nabil; Delaney, Kris T.; Carilli, Michael; Fredrickson, Glenn H.

2015-03-01

We investigate energy barriers and minimum energy paths (MEPs) for transitions from dislocation-pair defects to perfect lamellae in self-assembly of AB-diblock copolymer plus A- or B-homopolymer blends using self-consistent field theory (SCFT) and the numerical string method. For neutral substrates, all minimum energy paths discovered by the string method show two successive energy barriers. The two-barrier qualitative nature of the MEPs appears not to depend on the presence or absence of small amounts of homopolymer. For the first energy barrier, the barrier height shows pronounced increase with addition of A-homopolymer due to localization of A-homopolymer on the T-junction core of the dislocation. For chemo-epitaxially patterned substrates (stripes of A-attractive substrate alternating with neutral substrate), the presence of A-attractive stripes helps draw the system towards a perfect lamellar configuration, and energy barriers along the MEP are reduced, in some cases disappearing entirely. Our findings provide guidance on how the presence of homopolymer and chemo-epitaxial prepatterns affect the stability of defective morphologies.

Application of Bottlebrush Block Copolymers as Photonic Crystals.

Science.gov (United States)

Liberman-Martin, Allegra L; Chu, Crystal K; Grubbs, Robert H

2017-07-01

Brush block copolymers are a class of comb polymers that feature polymeric side chains densely grafted to a linear backbone. These polymers display interesting properties due to their dense functionality, low entanglement, and ability to rapidly self-assemble to highly ordered nanostructures. The ability to prepare brush polymers with precise structures has been enabled by advancements in controlled polymerization techniques. This Feature Article highlights the development of brush block copolymers as photonic crystals that can reflect visible to near-infrared wavelengths of light. Fabrication of these materials relies on polymer self-assembly processes to achieve nanoscale ordering, which allows for the rapid preparation of photonic crystals from common organic chemical feedstocks. The characteristic physical properties of brush block copolymers are discussed, along with methods for their preparation. Strategies to induce self-assembly at ambient temperatures and the use of blending techniques to tune photonic properties are emphasized. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaluation of miscibility of poly(epichlorohydrin-co-ethylene oxide) and poly(methylmethacrylate) blends

International Nuclear Information System (INIS)

Turchete, Renato; Felisberti, Maria Isabel

1999-01-01

The miscibility of blends of poly(methylmethacrylate), (PMMA) and poly(epichlorohydrin-co-ethylene oxide), (ECO) were investigated by differential scanning calorimetry. The ECO was fractionated using two different systems: a solvent-non solvent system and by cooling the solution in tetrahydrofuran in the temperature range from 20 to 0 deg C. The fractions with different composition and molecular weight were used to prepare the blends by casting from solution in tetrahydrofuran. The blends exhibit two glass transitions shifted in relation to the glass transitions of the pure polymers, indicating a partial miscibility. Blends containing copolymer richer in epichlorohydrin segments were more miscible than blends of non-fractionated ECO. (author)

Anti-biofouling 3D porous systems: the blend effect of oxazoline-based oligomers on chitosan scaffolds.

Science.gov (United States)

Correia, Vanessa G; Coelho, Margarida; Barroso, Telma; Raje, Vivek P; Bonifácio, Vasco D B; Casimiro, Teresa; Pinho, Mariana G; Aguiar-Ricardo, Ana

2013-01-01

The production, characterization and anti-biofouling activity of 3D porous scaffolds combining different blends of chitosan and oxazoline-based antimicrobial oligomers is reported. The incorporation of ammonium quaternized oligo(2-oxazoline)s into the composition of the scaffold enhances the stability of the chitosan scaffold under physiological conditions as well as its ability to repel protein adsorption. The blended scaffolds showed mean pore sizes in the range of 18-32 μm, a good pore interconnectivity and high porosity, as well as a large surface area, ultimate key features for anti-biofouling applications. Bovine serum albumin (BSA) adhesion profiles showed that the composition of the scaffolds plays a critical role in the chitosan-oligooxazoline system. Oligobisoxazoline-enriched scaffolds (20% w/w, CB8020) decreased protein adsorption (BSA) by up to 70%. Moreover, 1 mg of CB8020 was able to kill 99.9% of Escherichia coli cells upon contact, demonstrating its potential as promising material for production of tailored non-fouling 3D structures to be used in the construction of novel devices with applications in the biomedical field and water treatment processes.

Synthesis and Characterization of New ‎Copolymers as Asphalt Additives

Directory of Open Access Journals (Sweden)

Firyal M. ‎ A

2017-12-01

Full Text Available Rheological properties of asphalt S50  were improved by adding different prepared copolymers as additives with high homogeneity of asphalts  samples.  Three types of copolymers were prepared  Poly  (Indene –Co- maleic anhydride(A1 Poly (Acrylonitrile –Co- Maleic anhydride (A2 and Poly (Dipentine –Co-Maleic anhydride (A3, the cross linking of (A3 to (A3d. by using sulfur.              These copolymers  were designed by inserting Maleic anhydride as  rings  containing through backbone of polymer chains to be high potentially to react with water to protect the crack of pavement .And moisture with inhibit bonding of crack of pavement, Many factors should be considered when prepared the additives to enhanced performance to be convenience cost, beneficial thermal safety ,   extended life of the asphalt, preparing conditions which gave high thermal resistance with more stabilities, all these prepared copolymer have been characterized by FTIR and H-NMR spectroscopies .Intrinsic viscosities were calculated. softening point and penetration were observed for all asphalts blends which were  compared with the  asphalt samples, which gave high thermal resistance with more stabilities.                                          The results  showed high properties of these blends when  compared with the original asphalt. The physical properties of a specific polymers are determined by the sequence and chemical structure , When polymers are added to asphalt , the properties of the modified asphalt cement depend on polymer characteristic of asphalt and compatibility of polymer with asphalt. All these prepared copolymers were tested by softening points and penetration for all  asphalt blends which were compared with the asphalt sample. All the Improvements made by adding polymers to asphalt included the Increasing the viscosity of the binder service, the thermal susceptibility of the binder

High performance lignin-acrylonitrile polymer blend materials

Energy Technology Data Exchange (ETDEWEB)

Naskar, Amit K.; Tran, Chau D.

2017-11-14

A polymer blend material comprising: (i) a lignin component having a weight-average molecular weight of up to 1,000,000 g/mol; and (ii) an acrylonitrile-containing copolymer rubber component comprising acrylonitrile units in combination with diene monomer units, and having an acrylonitrile content of at least 20 mol %; wherein said lignin component is present in an amount of at least 5 wt % and up to about 95 wt % by total weight of components (i) and (ii); and said polymer blend material possesses a tensile yield stress of at least 5 MPa, or a tensile stress of at least 5 MPa at 10% elongation, or a tensile stress of at least 5 MPa at 100% elongation. Methods for producing the polymer blend, molded forms thereof, and articles thereof, are also described.

Vertical stratification and its impact on device performance in a polycarbazole based copolymer solar cells

OpenAIRE

Wang, T.; Scarratt, N.W.; Yi, H.; Coleman, I.F.; Zhang, Y.; Grant, R.T.; Yao, J.; Skoda, M.W.A.; Dunbar, A.D.F.; Jones, R.A.L.; Iraqi, A.; Lidzey, D.G.

2015-01-01

Using neutron-reflectivity, we study vertical stratification and device performance in bulk hetero-junction organic photovoltaic (OPV) cells consisting of a blend of PC71BM with a carbazole-based donor–acceptor copolymer PCDTBT1. We find that when the blend is cast on a PEDOT:PSS/ITO anode, a PC71BM-depleted (polymer-rich) layer is formed at the PEDOT:PSS interface, whilst a PC71BM-depleted layer is instead located at the air-interface when the same blend is cast on a solution processed MoOx ...

Studies on the effect of compatibilizers on mechanical, thermal and flow properties of polycarbonate/poly (butylene terephthalate) blends

Science.gov (United States)

Kumar, Ravindra; Kar, Kamal K.; Kumar, Vijai

2018-01-01

Bisphenol-A polycarbonate (PC) and poly(butylene terephthalate) (PBT) were melt blended with ethylene-n-butylacrylate-glycidylmethacrylate terpolymer (E-BA-GMA) at various proportions in order to study the effects of compatibilizers on mechanical, thermal and flow properties of blends. Furthermore, on the basis of this study, PC and PBT were melt-blended at 60/40 proportion with three different compatibilizers viz., ethylene-n-butylacrylate copolymer (E-BA), E-BA-GMA and random copolymer of ethylene and glycidylmethacrylate (E-GMA) at 3 phr loading in a co-rotating twin screw extruder. Tensile, flexural and impact tests were carried out on injection molded samples of PC/PBT blends. The notched izod impact strength increases enormously (˜2-3 times) on addition of any one of the three compatibilizers, and elongation at break (%) also improves tremendously (3, 5 and 4 times) on incorporation of E-BA, E-BA-GMA and E-GMA copolymer, respectively while other mechanical properties decreases slightly (3%-8%) on addition of any one of these compatibilizers. The heat deflection temperature (HDT) raises ˜8 °C-9 °C on addition of either E-BA-GMA or E-GMA, while E-BA shows a negative effect on HDT. The melt flow index diminishes significantly (˜5%-20%) on incorporation of these compatibilizers. The morphology studies via scanning electron microscopy of these four blends were carried out to confirm the mechanical results.

Microstructure and in vitro cellular response to novel soy protein-based porous structures for tissue regeneration applications.

Science.gov (United States)

Olami, Hilla; Zilberman, Meital

2016-02-01

Interest in the development of new bioresorbable structures for various tissue engineering applications is on the rise. In the current study, we developed and studied novel soy protein-based porous blends as potential new scaffolds for such applications. Soy protein has several advantages over the various types of natural proteins employed for biomedical applications due to its low price, non-animal origin and relatively long storage time and stability. In the present study, blends of soy protein with other polymers (gelatin, pectin and alginate) were added and chemically cross-linked using the cross-linking agents carbodiimide or glyoxal, and the porous structure was obtained through lyophilization. The resulting blend porous structures were characterized using environmental scanning microscopy, and the cytotoxicity of these scaffolds was examined in vitro. The biocompatibility of the scaffolds was also evaluated in vitro by seeding and culturing human fibroblasts on these scaffolds. Cell growth morphology and adhesion were examined histologically. The results show that these blends can be assembled into porous three-dimensional structures by combining chemical cross-linking with freeze-drying. The achieved blend structures combine suitable porosity with a large pore size (100-300 µm). The pore structure in the soy-alginate scaffolds possesses adequate interconnectivity compared to that of the soy-gelatin scaffolds. However, porous structure was not observed for the soy-pectin blend, which presented a different structure with significantly lower porosities than all other groups. The in vitro evaluation of these porous soy blends demonstrated that soy-alginate blends are advantageous over soy-gelatin blends and exhibited adequate cytocompatibility along with better cell infiltration and stability. These soy protein scaffolds may be potentially useful as a cellular/acellular platform for skin regeneration applications. © The Author(s) 2015.

Coarse-grained modeling of hybrid block copolymer system

Science.gov (United States)

Su, Yongrui

This thesis is comprised of three major projects of my research. In the first project, I proposed a nanoparticle model and combined it with the Theoretically Informed Coarse Grained (TICG) model for pure polymer systems and the grand canonical slip springs model developed in our group to build a new model for entangled nanocomposites. With Molecule Dynamics(MD) simulation, I studied the mechanic properties of the nanocomposites, for example the influence of nanoparticles size and volume fraction on entanglements, the diffusion of polymers and nanoparticles, and the influence of nanoparticles size and volume fraction on viscosity et al.. We found that the addition of small-size nanoparticles reduces the viscosity of the nanocomposites, which is in contrary to what Einstein predicted a century ago. However, when particle increases its size to micrometers the Einstein predictions is recovered. From our simulation, we believe that small-size nanoparticles can more effectively decrease the entanglements of nanocomposites than larger particles. The free volume effect introduced by small-size nanoparticles also helps decrease the viscosity of the whole system. In the second project, I combined the Ohta-Kawasaki (OK) model [3] and the Covariance Matrix Adaptation Evolutionary Strategy(CMA-ES) to optimize the block copolymer blends self-assembly in the hole-shrink process. The aim is to predict the optimal composition and the optimal surface energy to direct the block copolymer blends self-assembly process in the confined hole. After optimization in the OK model, we calibrated the optimal results by the more reliable TICG model and got the same morphology. By comparing different optimization process, we found that the homopolymers which are comprised of the same monomers as either block of the block copolymer can form a perfect perforated hole and might have better performance than the pure block copolymer. While homopolymers which are comprised of a third-party monomers

Effect of compatibilizer on impact and morphological analysis of recycled HDPE/PET blends

Energy Technology Data Exchange (ETDEWEB)

Salleh, Mohd Nazry [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia and School of Materials Engineering, Universiti Malaysia Perlis, 02600 Jejawi, Perlis (Malaysia); Ahmad, Sahrim; Ghani, Mohd Hafizuddin Ab; Chen, Ruey Shan [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia)

2013-11-27

Blends based on recycled high density polyethylene (rHDPE) and recycled polyethylene terephthalate (rPET) were prepared using a corotating twin screw extruder. PET and HDPE are incompatible polymers and their blends showed poor properties. Compatibilization is a step to obtain blends with good mechanical properties and in this work, ethylene glycidyl methacrylate copolymer (E-GMA) was used as a compatibilizing agent. The effect of blends based on rHDPE and rPET with and without a compatibilizer, E-GMA were examined. From the studies clearly showed that the addition of 5% E-GMA increased the impact strength. SEM analysis of rHDPE/rPET blends confirmed the morphological interaction and improved interfacial bonding between two phases.

Morphology and properties of nanocomposites based on polymer blend and organoclay

CSIR Research Space (South Africa)

Gcwabaza, T

2008-10-01

Full Text Available improved properties.1-4 such a compatibilizer may be a homopolymer, a block, graft or star copolymer. However, there are few reports on clay containing nanocomposites based on polymer blends, whether miscible or immiscible. Such composite materials offer...

Microbial production of polyhydroxyalkanoate block copolymer by recombinant Pseudomonas putida.

Science.gov (United States)

Li, Shi Yan; Dong, Cui Ling; Wang, Shen Yu; Ye, Hai Mu; Chen, Guo-Qiang

2011-04-01

Polyhydroxyalkanoate (PHA) synthesis genes phaPCJ(Ac) cloned from Aeromonas caviae were transformed into Pseudomonas putida KTOY06ΔC, a mutant of P. putida KT2442, resulting in the ability of the recombinant P. putida KTOY06ΔC (phaPCJ(A.c)) to produce a short-chain-length and medium-chain-length PHA block copolymer consisting of poly-3-hydroxybutyrate (PHB) as one block and random copolymer of 3-hydroxyvalerate (3HV) and 3-hydroxyheptanoate (3HHp) as another block. The novel block polymer was studied by differential scanning calorimetry (DSC), nuclear magnetic resonance, and rheology measurements. DSC studies showed the polymer to possess two glass transition temperatures (T(g)), one melting temperature (T(m)) and one cool crystallization temperature (T(c)). Rheology studies clearly indicated a polymer chain re-arrangement in the copolymer; these studies confirmed the polymer to be a block copolymer, with over 70 mol% homopolymer (PHB) of 3-hydroxybutyrate (3HB) as one block and around 30 mol% random copolymers of 3HV and 3HHp as the second block. The block copolymer was shown to have the highest tensile strength and Young's modulus compared with a random copolymer with similar ratio and a blend of homopolymers PHB and PHVHHp with similar ratio. Compared with other commercially available PHA including PHB, PHBV, PHBHHx, and P3HB4HB, the short-chain- and medium-chain-length block copolymer PHB-b-PHVHHp showed differences in terms of mechanical properties and should draw more attentions from the PHA research community. © Springer-Verlag 2010

A new supramolecular route for using Rod-Coil block copolymers in photovoltaic applications

Energy Technology Data Exchange (ETDEWEB)

Sary, Nicolas [Department of Physics and FRIMAT Center for Nanomaterials, University of Fribourg (Switzerland); Richard, Fanny; Brochon, Cyril; Leclerc, Nicolas; Hadziioannou, Georges [Laboratoire d' Ingenierie des Polymeres pour les Hautes Technologies Universite de Strasbourg, Ecole Europeenne de Chimie Polymeres et Materiaux (France); Leveque, Patrick; Heiser, Thomas [Institut d' Electronique du Solide et des Systemes Centre National de la Recherche Scientifique, Universite de Strasbourg (France); Audinot, Jean-Nicolas [Science and Analysis of Materials Department Public Research Centre Gabriel Lippmann, Belvaux (Luxembourg); Berson, Solenn [Laboratoire des Composants Solaires, Institut de l' Energie Solaire Commissariat a l' energie atomique, Le Bourget Du Lac (France); Mezzenga, Raffaele [Department of Physics and FRIMAT Center for Nanomaterials, University of Fribourg (Switzerland); Nestle Research Center, Lausanne (Switzerland)

2010-02-09

A new polymer blend formed by poly(3-hexylthiophene)-poly(4-vinylpyridine) (P3HT- P4VP) block copolymers and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is reported. The P4VP and PCBM are mixed together by weak supramolecular interactions, and the resulting materials exhibit microphase separated morphologies of electron-donor and electron-acceptor rich domains. The properties of the blend, used in photovoltaic devices as active layers, are also discussed. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

Influence of compatibilizer on blends degradation during processing

Directory of Open Access Journals (Sweden)

Walter R. Waldman

2013-01-01

Full Text Available The thermomechanical degradation of blends made from polypropylene and polystyrene, with or without compatibilizer, was studied using an internal mixer coupled to a torque rheometer. The blends processed without compatibilizer presented regular and expected results regarding torque reduction, with evidence of chain scission. The blends processed with the block copolymer of styrene and butadiene, SBS, as a compatibilizer presented unchanged or less reduced variation on torque values during processing. The extraction of stabilizers from the compatibilizer before processing did not affect the results. The compatibilizer concentration in the blends was varied, with its influence still being observed in concentrations as low as 0.03 parts per hundred. Similar results were obtained in an experiment comparing the performance of a primary commercial anti-oxidant, Irganox 1076, and the compatibilizer SBS. Therefore, the compatibilizer can be considered as a processing aid agent with positive influence on avoiding thermomechanical degradation.

Responsive copolymers for enhanced petroleum recovery. Annual report

Energy Technology Data Exchange (ETDEWEB)

McCormick, C.; Hester, R.

1994-08-01

A coordinated research program involving synthesis, characterization, and rheology has been undertaken to develop advanced polymer system which should be significantly more efficient than polymers presently used for mobility control and conformance. Unlike the relatively inefficient, traditional EOR polymers, these advanced polymer systems possess microstructural features responsive to temperature, electrolyte concentration, and shear conditions. Contents of this report include the following chapters. (1) First annual report responsive copolymers for enhanced oil recovery. (2) Copolymers of acrylamide and sodium 3-acrylamido-3-methylbutanoate. (3) Terpolymers of NaAMB, Am, and n-decylacrylamide. (4) Synthesis and characterization of electrolyte responsive terpolymers of acrylamide, N-(4-butyl)phenylacrylamide, and sodium acrylate, sodium-2-acrylamido-2-methylpropanesulphonate or sodium-3-acrylamido-3-methylbutanoate. (5) Synthesis and solution properties of associative acrylamido copolymers with pyrensulfonamide fluorescence labels. (6) Photophysical studies of the solution behavior of associative pyrenesulfonamide-labeled polyacrylamides. (7) Ampholytic copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate with [2-(acrylamido)-2-methypropyl]trimethylammonium chloride. (8) Ampholytic terpolymers of acrylamide with sodium 2-acrylamido-2-methylpropanesulphoante and 2-acrylamido-2-methylpropanetrimethyl-ammonium chloride and (9) Polymer solution extensional behavior in porous media.

CO2-Philic Thin Film Composite Membranes: Synthesis and Characterization of PAN-r-PEGMA Copolymer

Directory of Open Access Journals (Sweden)

Madhavan Karunakaran

2017-07-01

Full Text Available In this work, we report the successful fabrication of CO2-philic polymer composite membranes using a polyacrylonitrile-r-poly(ethylene glycol methyl ether methacrylate (PAN-r-PEGMA copolymer. The series of PAN-r-PEGMA copolymers with various amounts of PEG content was synthesized by free radical polymerization in presence of AIBN initiator and the obtained copolymers were used for the fabrication of composite membranes. The synthesized copolymers show high molecular weights in the range of 44–56 kDa. We were able to fabricate thin film composite (TFC membranes by dip coating procedure using PAN-r-PEGMA copolymers and the porous PAN support membrane. Scanning electron microscopy (SEM and atomic force microscopy (AFM were applied to analyze the surface morphology of the composite membranes. The microscopy analysis reveals the formation of the defect free skin selective layer of PAN-r-PEGMA copolymer over the porous PAN support membrane. Selective layer thickness of the composite membranes was in the range of 1.32–1.42 μm. The resulting composite membrane has CO2 a permeance of 1.37 × 10−1 m3/m2·h·bar and an ideal CO2/N2, selectivity of 65. The TFC membranes showed increasing ideal gas pair selectivities in the order CO2/N2 > CO2/CH4 > CO2/H2. In addition, the fabricated composite membranes were tested for long-term single gas permeation measurement and these membranes have remarkable stability, proving that they are good candidates for CO2 separation.

CO2-Philic Thin Film Composite Membranes: Synthesis and Characterization of PAN-r-PEGMA Copolymer

KAUST Repository

Karunakaran, Madhavan

2017-07-06

In this work, we report the successful fabrication of CO2-philic polymer composite membranes using a polyacrylonitrile-r-poly(ethylene glycol) methyl ether methacrylate (PAN-r-PEGMA) copolymer. The series of PAN-r-PEGMA copolymers with various amounts of PEG content was synthesized by free radical polymerization in presence of AIBN initiator and the obtained copolymers were used for the fabrication of composite membranes. The synthesized copolymers show high molecular weights in the range of 44-56 kDa. We were able to fabricate thin film composite (TFC) membranes by dip coating procedure using PAN-r-PEGMA copolymers and the porous PAN support membrane. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were applied to analyze the surface morphology of the composite membranes. The microscopy analysis reveals the formation of the defect free skin selective layer of PAN-r-PEGMA copolymer over the porous PAN support membrane. Selective layer thickness of the composite membranes was in the range of 1.32-1.42 mu m. The resulting composite membrane has CO2 a permeance of 1.37 x 10(-1) m(3)/m(2).h.bar and an ideal CO2/N-2, selectivity of 65. The TFC membranes showed increasing ideal gas pair selectivities in the order CO2/N-2 > CO2/CH4 > CO2/H-2. In addition, the fabricated composite membranes were tested for long-term single gas permeation measurement and these membranes have remarkable stability, proving that they are good candidates for CO2 separation.

Triblock copolymers based on ε-caprolactone and trimethylene carbonate for the 3D printing of tissue engineering scaffolds.

Science.gov (United States)

Güney, Aysun; Malda, Jos; Dhert, Wouter J A; Grijpma, Dirk W

2017-05-09

Biodegradable PCL-b-PTMC-b-PCL triblock copolymers based on trimethylene carbonate (TMC) and ε-caprolactone (CL) were prepared and used in the 3D printing of tissue engineering scaffolds. Triblock copolymers of various molecular weights containing equal amounts of TMC and CL were prepared. These block copolymers combine the low glass transition temperature of amorphous PTMC (approximately -20°C) and the semi-crystallinity of PCL (glass transition approximately -60°C and melting temperature approximately 60°C). PCL-b-PTMC-b-PCL triblock copolymers were synthesized by sequential ring opening polymerization (ROP) of TMC and ε-CL. From these materials, films were prepared by solvent casting and porous structures were prepared by extrusion-based 3D printing. Films prepared from a polymer with a relatively high molecular weight of 62 kg/mol had a melting temperature of 58°C and showed tough and resilient behavior, with values of the elastic modulus, tensile strength and elongation at break of approximately 120 MPa, 16 MPa and 620%, respectively. Porous structures were prepared by 3D printing. Ethylene carbonate was used as a crystalizable and water-extractable solvent to prepare structures with microporous strands. Solutions, containing 25 wt% of the triblock copolymer, were extruded at 50°C then cooled at different temperatures. Slow cooling at room temperature resulted in pores with widths of 18 ± 6 μm and lengths of 221 ± 77 μm, rapid cooling with dry ice resulted in pores with widths of 13 ± 3 μm and lengths of 58 ± 12 μm. These PCL-b-PTMC-b-PCL triblock copolymers processed into porous structures at relatively low temperatures may find wide application as designed degradable tissue engineering scaffolds. In this preliminary study we prepared biodegradable triblock copolymers based on 1,3-trimethylene carbonate and ε-caprolactone and assessed their physical characteristics. Furthermore, we evaluated their potential as melt-processable thermoplastic

Funding initiates production of tunable nano-porous block copolymer membranes

KAUST Repository

Peinemann, Klaus-Viktor

2013-01-01

- on top of a non-ordered sponge-like layer. It is fabricated in a fast, one-step process by combining the self-assembly of an amphiphilic block copolymer (PS- b-P4VP) with non-solvent-induced phase separation. The university's "Seed Fund" has helped

Porous PEOT/PBT scaffolds for bone tissue engineering: preparation, characterization, and in vitro bone marrow cell culturing

NARCIS (Netherlands)

Claase, M.B.; Grijpma, Dirk W.; Mendes, S.C.; Mendes, Sandra C.; de Bruijn, Joost Dick; Feijen, Jan

2003-01-01

The preparation, characterization, and in vitro bone marrow cell culturing on porous PEOT/PBT copolymer scaffolds are described. These scaffolds are meant for use in bone tissue engineering. Previous research has shown that PEOT/PBT copolymers showed in vivo degradation, calcification, and bone

Sulfonation and characterization of styrene-indene copolymers for the development of proton conducting polymer membranes

Directory of Open Access Journals (Sweden)

Cristiane M. Becker

2012-01-01

Full Text Available The aim of this work is to obtain polymer precursors based on styrene copolymers with distinct degrees of sulfonation, as an alternative material for fuel cell membranes. Acetyl sulfate was used to carry out the sulfonation and the performance of the polyelectrolyte was evaluated based on the content of acid polar groups incorporated into the macromolecular chain. Polymeric films were produced by blending the sulfonated styrene-indene copolymer with poly(vinylidene fluoride. The degree of sulfonation of the polymer was strongly affected by the sulfonation reaction parameters, with a direct impact on the ionic exchange capacity and the ionic conductivity of the sulfonated polymers and the membranes obtained from them. The films produced with the blends showed more suitable mechanical properties, although the conductivity of the membranes was still lower than that of commercially available membranes used in fuel cells.

Bio-safe processing of polylactic-co-caprolactone and polylactic acid blends to fabricate fibrous porous scaffolds for in vitro mesenchymal stem cells adhesion and proliferation

Energy Technology Data Exchange (ETDEWEB)

Salerno, Aurelio, E-mail: asalerno@unina.it [Centre for Advanced Biomaterials for Health Care, Istituto Italiano di Tecnologia, Largo Barsanti e Matteucci 53, 80125 Napoli (Italy); Institute of Materials Science of Barcelona (ICMAB-CSIC), Campus de la UAB s/n, Bellaterra 08193 (Spain); Guarino, Vincenzo; Oliviero, Olimpia; Ambrosio, Luigi [Institute of Polymers, Composites and Biomaterials, National Research Council of Italy, V.le Kennedy 54, Pad 20, Mostra d' Oltremare, 80125 Naples (Italy); Domingo, Concepción [Institute of Materials Science of Barcelona (ICMAB-CSIC), Campus de la UAB s/n, Bellaterra 08193 (Spain)

2016-06-01

In this study, the design and fabrication of porous scaffolds, made of blends of polylactic-co-caprolactone (PLC) and polylactic acid (PLA) polymers, for tissue engineering applications is reported. The scaffolds are prepared by means of a bio-safe thermally induced phase separation (TIPS) approach with or without the addition of NaCl particles used as particulate porogen. The scaffolds are characterized to assess their crystalline structure, morphology and mechanical properties, and the texture of the pores and the pore size distribution. Moreover, in vitro human mesenchymal stem cells (hMSCs) culture tests have been carried out to demonstrate the biocompatibility of the scaffolds. The results of this study demonstrate that all of the scaffold materials processed by means of TIPS process are semi-crystalline. Furthermore, the blend composition affected polymer crystallization and, in turn, the nano and macro-structural properties of the scaffolds. Indeed, neat PLC and neat PLA crystallize into globular and randomly arranged sub micro-size scale fibrous conformations, respectively. Concomitantly, the addition of NaCl particles during the fabrication route allows for the creation of an interconnected network of large pores inside the primary structure while resulted in a significant decrease of scaffolds mechanical response. Finally, the results of cell culture tests demonstrate that both the micro and macro-structure of the scaffold affect the in vitro hMSCs adhesion and proliferation. - Highlights: • Porous scaffolds are prepared by polymer blending, phase separation and NaCl leaching. • The process avoids the use of toxic solvents. • Blend composition dictates polymer crystallization and scaffold properties. • Scaffolds are provided of a sub micro-scale fibers structure and interconnected macropores. • Stem cells adhesion and proliferation depend on scaffolds composition and structure.

Impact behaviour of polystyene/EPDM-rubber blends : influence of electron beam irradiation

NARCIS (Netherlands)

Gisbergen, van J.G.M.; Borgmans, C.P.J.H.; Sanden, van der M.C.M.; Lemstra, P.J.

1990-01-01

Electron beam irradiation of polystyrene/ethylene propylene diene monomer (PS/EPDM) blends, using polystyrene/polybutadiene block copolymers as compatibilizers, resulted in a two to three fold increase in Izod impact value. This greatly increased impact resistance is probably related to

Self-assembled structures in d8-polystyreneblock- polyisoprene/polystyrene blends in the weak segregation regime: SAXS and TEM study

Czech Academy of Sciences Publication Activity Database

Holoubek, Jaroslav; Baldrian, Josef; Hromádková, Jiřina; Steinhart, Miloš

2009-01-01

Roč. 58, č. 7 (2009), s. 762-774 ISSN 0959-8103 R&D Projects: GA ČR GA202/09/2078; GA ČR GESON/06/E005 Institutional research plan: CEZ:AV0Z40500505 Keywords : diblock copolymers * homopolymer/copolymer blends * SAXS Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.137, year: 2009

Hybrid, Nanoscale Phospholipid/Block Copolymer Vesicles

Directory of Open Access Journals (Sweden)

Bo Liedberg

2013-09-01

Full Text Available Hybrid phospholipid/block copolymer vesicles, in which the polymeric membrane is blended with phospholipids, display interesting self-assembly behavior, incorporating the robustness and chemical versatility of polymersomes with the softness and biocompatibility of liposomes. Such structures can be conveniently characterized by preparing giant unilamellar vesicles (GUVs via electroformation. Here, we are interested in exploring the self-assembly and properties of the analogous nanoscale hybrid vesicles (ca. 100 nm in diameter of the same composition prepared by film-hydration and extrusion. We show that the self-assembly and content-release behavior of nanoscale polybutadiene-b-poly(ethylene oxide (PB-PEO/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC hybrid phospholipid/block copolymer vesicles can be tuned by the mixing ratio of the amphiphiles. In brief, these hybrids may provide alternative tools for drug delivery purposes and molecular imaging/sensing applications and clearly open up new avenues for further investigation.

RANDOM COPOLYMER BLENDS OF STYRENE, PARA-FLUORO STYRENE AND ORTHO-FLUORO STYRENE

NARCIS (Netherlands)

OUDHUIS, AACM; TENBRINKE, G; KARASZ, FE

1993-01-01

This study completes the investigation of the phase behaviour of polymer blends involving styrene (S), ortho-fluoro styrene (oFS) and para-fluoro styrene (pFS). As before, due to the proximity of the glass transition temperatures of most blends investigated, the miscibility or immiscibility is

Nanostructured synthetic carbons obtained by pyrolysis of spherical acrylonitrile/divinylbenzene copolymers.

Directory of Open Access Journals (Sweden)

Danish J Malik

Full Text Available Novel carbon materials have been prepared by the carbonization of acrylonitrile (AN/divinylbenzene (DVB suspension porous copolymers having nominal crosslinking degrees in the range of 30-70% and obtained in the presence of various amounts of porogens. The carbons were obtained by pre-oxidation of AN/DVB copolymers at 250-350°C in air followed by pyrolysis at 850°C in an N(2 atmosphere. Both processes were carried out in one furnace and the resulting material needed no further activation. Resulting materials were characterized by XPS and low temperature nitrogen adsorption/desorption. It was found that maximum pyrolysis yield was ca. 50% depending on the oxidation conditions but almost independent of the crosslinking degree of the polymers. Porous structure of the carbons was characterized for the presence of micropores and macropores, when obtained from highly crosslinked polymers or polymers oxidized at 350°C and meso- and macropores in all other cases. The latter pores are prevailing in the structure of carbons obtained from less porous AN/DVB resins. Specific surface area (BET of polymer derived carbons can vary between 440 m(2/g and 250 m(2/g depending on the amount of porogen used in the synthesis of the AN/DVB polymeric precursors.

A polyacrylonitrile copolymer-silica template for three-dimensional hierarchical porous carbon as a Pt catalyst support for the oxygen reduction reaction.

Science.gov (United States)

Liu, Minmin; Li, Jian; Cai, Chao; Zhou, Ziwei; Ling, Yun; Liu, Rui

2017-08-01

Herein, we report a novel route to construct a hierarchical three-dimensional porous carbon (3DC) through a copolymer-silica assembly. In the synthesis, silica acts as a hard template and leads to the formation of an interconnected 3D macropore, whereas styrene-co-acrylonitrile polymer has been used as both a carbon source and a soft template for micro- and meso-pores. The obtained 3DC materials possess a large surface area (∼550.5 m 2 g -1 ), which facilitates high dispersion of Pt nanoparticles on the carbon support. The 3DC-supported Pt electrocatalyst shows excellent performance in the oxygen reduction reaction (ORR). The easy processing ability along with the characteristics of hierarchical porosity offers a new strategy for the preparation of carbon nanomaterials for energy application.

Facile preparation of nitrogen-doped hierarchical porous carbon with high performance in supercapacitors

International Nuclear Information System (INIS)

Yan, Kun; Kong, Ling-Bin; Shen, Kui-Wen; Dai, Yan-Hua; Shi, Ming; Hu, Bing; Luo, Yong-Chun; Kang, Long

2016-01-01

Graphical abstract: Preparing and activating process of nitrogen-doped hierarchical porous carbon (NHPC). - Highlights: • The well-defined PAN-b-PMMA copolymer was synthesized by atom transfer radical polymerization with narrow molecular weight distribution. • Nitrogen-doped hierarchical porous structure (NHPC) was prepared through a simple carbonization procedure of PAN-b-PMMA precursor. • NHPC possessed hierarchical porous structure with high BET surface area of 257 m"2 g"−"1 and DFT mesopore size of 14.61 nm. • Effects of activation conditions on supercapacitive behavior were systematically studied. - Abstract: The nitrogen-doped hierarchical porous carbon (NHPC) material was successfully prepared through a simple carbonization procedure of well-defined diblock copolymer precursor containing nitrogen-enriched carbon source, i.e., polyacrylonitrile (PAN), and asacrificial block, i.e., polymethylmethacrylate (PMMA). PAN-b-PMMA diblock copolymer was synthesized by atom transfer radical polymeriation (ATRP) with narrow molecular weight distribution. The as-obtained NHPC possessed nitrogen-doped hierarchical porous structure with high BET surface area of 257 m"2 g"−"1 and Nonlocal density functional theory (NLDFT) mesopore size of 14.61 nm. Surface activated nitrogen-doped hierarchical porous carbon (A-NHPC) materials were obtained by subsequent surface activation with HNO_3 solution. The effects of activation conditions on supercapacitive behavior were systematically studied, a maximum specific capacitance of 314 F g"−"1 at a current density of 0.5 A g"−"1 was achieved in 2 M KOH aqueous electrolyte. Simultaneously, it exhibited excellent rate capability of 67.8% capacitance retention as the current density increased from 0.5 to 20 A g"−"1 and superior cycling performance of 90% capacitance retention after 10,000 cycles at the current density of 2 A g"−"1.

Facile preparation of nitrogen-doped hierarchical porous carbon with high performance in supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Yan, Kun [State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); Kong, Ling-Bin, E-mail: konglb@lut.cn [State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); Shen, Kui-Wen; Dai, Yan-Hua; Shi, Ming; Hu, Bing [State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); Luo, Yong-Chun; Kang, Long [School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China)

2016-02-28

Graphical abstract: Preparing and activating process of nitrogen-doped hierarchical porous carbon (NHPC). - Highlights: • The well-defined PAN-b-PMMA copolymer was synthesized by atom transfer radical polymerization with narrow molecular weight distribution. • Nitrogen-doped hierarchical porous structure (NHPC) was prepared through a simple carbonization procedure of PAN-b-PMMA precursor. • NHPC possessed hierarchical porous structure with high BET surface area of 257 m{sup 2} g{sup −1} and DFT mesopore size of 14.61 nm. • Effects of activation conditions on supercapacitive behavior were systematically studied. - Abstract: The nitrogen-doped hierarchical porous carbon (NHPC) material was successfully prepared through a simple carbonization procedure of well-defined diblock copolymer precursor containing nitrogen-enriched carbon source, i.e., polyacrylonitrile (PAN), and asacrificial block, i.e., polymethylmethacrylate (PMMA). PAN-b-PMMA diblock copolymer was synthesized by atom transfer radical polymeriation (ATRP) with narrow molecular weight distribution. The as-obtained NHPC possessed nitrogen-doped hierarchical porous structure with high BET surface area of 257 m{sup 2} g{sup −1} and Nonlocal density functional theory (NLDFT) mesopore size of 14.61 nm. Surface activated nitrogen-doped hierarchical porous carbon (A-NHPC) materials were obtained by subsequent surface activation with HNO{sub 3} solution. The effects of activation conditions on supercapacitive behavior were systematically studied, a maximum specific capacitance of 314 F g{sup −1} at a current density of 0.5 A g{sup −1} was achieved in 2 M KOH aqueous electrolyte. Simultaneously, it exhibited excellent rate capability of 67.8% capacitance retention as the current density increased from 0.5 to 20 A g{sup −1} and superior cycling performance of 90% capacitance retention after 10,000 cycles at the current density of 2 A g{sup −1}.

Enhancing relative permittivity by incorporating PDMS-PEG multiblock copolymers in binary polymer blends

DEFF Research Database (Denmark)

A Razak, Aliff Hisyam; Szabo, Peter; Skov, Anne Ladegaard

Polydimethylsiloxane (PDMS) elastomers are well-known to be soft and highly stretchable, yet they never achieve maximum elongation when utilised as dielectric elastomers, simply because their dielectric permittivity remains rather low. Conversely, polyethyleneglycols (PEG) are not stretchable......, but they do possess high permittivity. Combining two such polymers in a block copolymer allows for further crosslinking and presents the possibility of substantial improvements in the actuation response of the resulting dielectric elastomer – if carefully designed. The objective is to synthesise a PDMS......, the discontinuity in PEG can be acquired and the relative permittivity (ε’) is significantly enhanced (60%) with 5wt% of PDMS-PEG block copolymer incorporated into the silicone elastomer....

Bicontinuous Phases in Diblock Copolymer/Homopolymer Blends: Simulation and Self-Consistent Field Theory

KAUST Repository

Martínez-Veracoechea, Francisco J.

2009-03-10

A combination of particle-based simulations and self-consistent field theory (SCFT) is used to study the stabilization of multiple ordered bicontinuous phases in blends of a diblock copolymer (DBC) and a homopolymer. The double-diamond phase (DD) and plumber\\'s nightmare phase (P) were spontaneously formed in the range of homopolymer volume fraction simulated via coarse-grained molecular dynamics. To the best of our knowledge, this is the first time that such phases have been obtained in continuum-space molecular simulations of DBC systems. Though tentative phase boundaries were delineated via free-energy calculations, macrophase separation could not be satisfactorily assessed within the framework of particle-based simulations. Therefore, SCFT was used to explore the DBC/homopolymer phase diagram in more detail, showing that although in many cases two-phase coexistence of a DBC-rich phase and a homopolymer-rich phase does precede the stability of complex bicontinuous phases the DD phase can be stable in a relatively wide region of the phase diagram. Whereas the P phase was always metastable with respect to macrophase separation under the thermodynamic conditions explored with SCFT, it was sometimes nearly stable, suggesting that full stability could be achieved in other unexplored regions of parameter space. Moreover, even the predicted DD- and P-phase metastability regions were located significantly far from the spinodal line, suggesting that these phases could be observed in experiments as "long-lived" metastable phases under those conditions. This conjecture is also consistent with large-system molecular dynamics simulations that showed that the time scale of mesophase formation is much faster than that of macrophase separation. © 2009 American Chemical Society.

Nickel ion removal using nanoporous poly(styrene-co divinyl benzene) copolymer

Energy Technology Data Exchange (ETDEWEB)

Bagherian, Abbas; Ghorbani, Mohsen; Mirzababaei, Seyed Nima [Babol University of Technology, Babol (Iran, Islamic Republic of)

2015-10-15

To achieve a suitable porous structure and high mechanical strength that is extremely valuable properties in adsorbent polymeric particles, poly(styrene-co-divinylbenzene) with high amounts of cross-linker and diverse proportions of diluent agent (porogen) were synthesized according to the methodology of the suspension polymerization technique. The structural characteristics of the particles and their adsorption properties for adsorption of Nickel ions were studied. Effect of solvent type and monomeric fraction on particles morphology and porosity was discussed. The solvents including n-heptane (HEP) and acetonitrile and monomer fraction was 50% and 30% of divinylbenzene (DVB). From the results obtained, we decided to apply an adsorbent with high mechanical strength and a porous structure appropriate for absorbing the Ni(II). The copolymer was characterized by Fourier transform infrared (FT-IR) analysis. We used scanning electron microscopy (SEM) and transmission electron microscopy (TEM) tests to study the morphology and particle size of the nanoparticles. According to the results, the copolymers synthesized with n-heptane have more porosity. Also an increase in the percentage of DVB caused finer pores. After synthesis of copolymer the applicability of these polymer beads to separation and concentration of Ni(II) is discussed. In separation of Ni(II) from aqueous solution, the effects of pH, temperature and time are discussed and thermodynamic and kinetic calculations are done and its isotherm are fitted with various equations.

Fracture mechanics and statistical modeling of ternary blends of polylactide/ethylene-acrylate copolymer /wood-flour composites

Science.gov (United States)

Afrifah, Kojo Agyapong

This study examined the mechanisms of toughening the brittle bio-based poly(lactic acid) (PLA) with a biodegradable rubbery impact modifier to develop biodegradable and cost effective PLA/wood-flour composites with improved impact strength, toughness, high ductility, and flexibility. Semicrystalline and amorphous PLA grades were impact modified by melt blending with an ethylene-acrylate copolymer (EAC) impact modifier. EAC content was varied to study the effectiveness and efficiency of the impact modifier in toughening the semicrystalline and amorphous grades of the PLA. Impact strength was used to assess the effectiveness and efficiency of the EAC in toughening the blends, whereas the toughening mechanisms were determined with the phase morphologies and the miscibilities of the blends. Subsequent tensile property analyses were performed on the most efficiently toughened PLA grade. Composites were made from PLA, wood flour of various particle sizes, and EAC. Using two-level factorial design the interaction between wood flour content, wood flour particle size, and EAC content and its effect on the mechanical properties of the PLA/wood-flour composites was statistically studied. Numerical optimization was also performed to statistically model and optimize material compositions to attain mechanical properties for the PLA/wood-flour composites equivalent to at least those of unfilled PLA. The J-integral method of fracture mechanics was applied to assess the crack initiation (Jin) and complete fracture (J f) energies of the composites to account for imperfections in the composites and generate data useful for engineering designs. Morphologies of the fractured surfaces of the composites were analyzed to elucidate the failure and toughening mechanisms of the composites. The EAC impact modifier effectively improved the impact strength of the PLA/EAC blends, regardless of the PLA type. However, the EAC was more efficient in the semicrystalline grades of PLA compared to the

Structural transition with thickness in films of poly-(styrene-b-2vinylpyridine) (PS-b-P2VP) diblock copolymer/homopolymer blends

Science.gov (United States)

Mishra, Vindhya; Kramer, Edward; Hur, Su-Mi; Fredrickson, Glenn; Sprung, Michael

2009-03-01

In multilayer thin films of spherical morphology block copolymers, the surface layers prefer hexagonal symmetry while the inner layers prefer BCC. Thin films with spherical morphology of PS-b-P2VP blends with short homopolymer polystyrene (hPS) chains have an HCP structure up to a thickness n* at which there is a transition to a face centered orthorhombic structure. Using grazing incidence small angle X-ray scattering and transmission electron microscopy we show that that n* increases from 5 to 9 with increase in hPS from 0 to 12 vol%. For thicknesses just below n* the HCP and FCO structures coexist, but on long annealing HCP prevails. We hypothesize that the PS segregates to the interstices in the HCP structure reducing the stretching of the PS blocks and the free energy penalty of HCP versus BCC inner layers. Self consistent field theoretic simulations are being carried out to see if this idea is correct.

Phase transitions in blends functionalized thermoplastics

International Nuclear Information System (INIS)

Grigoryeva, O.; Sergeeva, L.; Starostenko, O.; Pissis, P.

2001-01-01

Phase transitions, morphology and structure-property relationships in polymer blends based on functionalized thermoplastics, i.e. widely used polyurethanes and styrene-acrylic acid copolymers, were investigated by means of inter-expletive non-destructive methods. Wide and small angle X-ray scattering (WAXS and SAXS), dynamic mechanical thermal analysis, thermally stimulated depolarization currents techniques, dielectric relaxation spectroscopy and several physico-mechanical characterization techniques were used. The results obtained by the various techniques were critically compared to each other. (author)

Preparation and characterization of amphiphilic copolymer PVDF-g-PMABS and its application in improving hydrophilicity and protein fouling resistance of PVDF membrane

Science.gov (United States)

Chen, Fengtao; Shi, Xingxing; Chen, Xiaobing; Chen, Wenxing

2018-01-01

A facile strategy to improve the hydrophilicity and the antifouling properties of poly(vinylidene fluoride) (PVDF) membranes, a functional monomer of 4-methacrylamidobenzenesulfonic acid (MABS), was designed and synthesized through the amidation reaction between 2-methylacryloyl chloride and sulfanilic acid. Utilizing PVDF and the obtained MABS as reaction monomers, a novel amphiphilic copolymer was firstly prepared by radical polymerization method. The resulting PVDF-g-PMABS was used as a hydrophilic additive in the fabrication of PVDF porous membranes via immersion precipitation process. The surface chemical compositions and structure morphologies of as-prepared blend membranes (PVDF-g-PMABS/PVDF) were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. Contact angle measurement and cross-flow permeation test were employed to evaluate the hydrophilicity and antifouling properties of the membranes. It was found that the blend membrane with 4 wt.% PVDF-g-PMABS exhibited a noticeable pure water flux (136.34 L m-2 h-1) and a remarkable flux recovery ratio (FRR) of 98.60% in comparison with the pristine PVDF membrane (63.37 L m-2 h-1 and 38.67%, respectively). The enhanced performance was attributed to the synergetic effects of the strong hydrogen bonding force and the electrostatic repulsion of sulfonic groups against the protein foulants.

PS-b-PMMA/PLA blends for nanoporous templates with hierarchical and tunable pore size

Science.gov (United States)

Nguyen, Thi-Hoa; Vayer, Marylène; Sinturel, Christophe

2018-01-01

Blends of poly(styrene)-block-poly(methyl methacrylate) (PS-b-PMMA) and poly(lactide) (PLA) were deposited in the form of thin films on the surface of modified silicon wafers and exposed to tetrahydrofuran (THF) vapor annealing. It was shown that in specific experimental conditions, a core-shell morphology consisting in cylinders with a PMMA shell and a PLA core, within a continuous matrix of PS, was formed. In this case, PLA naturally segregated in the core of the PMMA cylinders, minimizing the PS/PLA interaction, which constitutes the most incompatible pair (the interaction strength between the various components was confirmed in thin films of the corresponding polymer blends). Compared to other block copolymer/homopolymer blends described in the literature, this system exhibits unexpected high increase of the characteristic lengths of the system (center-to-center distance and diameter). This was attributed to a partial solubilization of the PLA in the PMMA corona (the two polymers are highly compatible), inducing an enhanced level of PS and PLA stretching caused by the strong repulsion between these two polymers. The selective extraction of the PLA yielded to porous domains with small dimensions (6 ± 2.5 nm), reaching the performances that are currently attained in highly incompatible block polymers with low molecular weight. Further PMMA removal revealed a second porosity level, with higher pores diameter and center-to-center distance compared to the neat PS-b-PMMA system. This work highlights how PS-b-PMMA, that currently represents one of the industrial standards nanoporous template precursors, can be modified in an easy and costless approach using PLA homopolymer addition.

Toughening mechanisms in interfacially modified HDPE/thermoplastic starch blends.

Science.gov (United States)

Taguet, Aurélie; Bureau, Martin N; Huneault, Michel A; Favis, Basil D

2014-12-19

The mechanical behavior of polymer blends containing 80 wt% of HDPE and 20 wt% of TPS and compatibilized with HDPE-g-MA grafted copolymer was investigated. Unmodified HDPE/TPS blends exhibit high fracture resistance, however, the interfacial modification of those blends by addition of HDPE-g-MA leads to a dramatic drop in fracture resistance. The compatibilization of HDPE/TPS blends increases the surface area of TPS particles by decreasing their size. It was postulated that the addition of HDPE-g-MA induces a reaction between maleic anhydride and hydroxyl groups of the glycerol leading to a decrease of the glycerol content in the TPS phase. This phenomenon increases the stiffness of the modified TPS particles and stiffer TPS particles leading to an important reduction in toughness and plastic deformation, as measured by the EWF method. It is shown that the main toughening mechanism in HDPE/TPS blends is shear-yielding. This article demonstrates that stiff, low diameter TPS particles reduce shear band formation and consequently decrease the resistance to crack propagation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Facile synthesis of main-chain degradable block copolymers for performance enhanced dismantlable adhesion.

Science.gov (United States)

Sato, Eriko; Hagihara, Takashi; Matsumoto, Akikazu

2012-04-01

Block copolymers consisting of readily degradable polyperoxides and non-degradable vinyl polymers as the block segments were successfully synthesized by reversible chain transfer catalyzed polymerization, which is one of living radical polymerization techniques. The block copolymers showed characteristic morphology and wettability being different from the polymer blends. When block copolymers containing polyperoxide and polymethacrylate blocks were heated below 150 °C, the polyperoxide blocks were completely degraded and the polymethacrylate blocks were recovered without degradation. Block copolymers containing a poly(2-ethylhexyl methacrylate) block were then investigated as a dismantlable adhesion material, which requires adequate bonding strength during use and easy debonding on demand. Among the several block copolymers, the one consisting of poly(2-ethylhexyl methacrylate) and polyperoxide from methyl sorbate (PPMS) (M(n) = 4900) exhibited good performance as a pressure-sensitive adhesive (PSA). After heating the test specimens in a temperature range from 60 to 100 °C, PSA performance, which was evaluated by 180° peel strength and shear holding power measurements, was significantly diminished. Especially, after heating at 100 °C for 1 h, spontaneous debonding of some test specimens was observed because of the evolution of volatile acetaldehyde from PPMS.

Electrochromatography on acrylate-based monolith in cyclic olefin copolymer microchip: an attractive technology.

Science.gov (United States)

Ladner, Y; Cretier, G; Faure, K

2015-01-01

Electrochromatography (EC) on a porous monolithic stationary phase prepared within the channels of a microsystem is an attractive alternative for on-chip separation. It combines the separation mechanisms of electrophoresis and liquid chromatography. Moreover, the porous polymer monolithic materials have become popular as stationary phase due to the ease and rapidity of fabrication via free radical photopolymerization. Here, we describe a hexyl acrylate (HA)-based porous monolith which is simultaneously in situ synthesized and anchored to the inner walls of the channel of a cyclic olefin copolymer (COC) device in only 2 min. The baseline separation of a mixture of neurotransmitters including six amino acids and two catecholamines is realized.

Responsive copolymers for enhanced petroleum recovery. Second annual report

Energy Technology Data Exchange (ETDEWEB)

McCormick, C.; Hester, R.

1995-05-01

The authors describe second year efforts in synthesis, characterization, and rheology to develop polymers with significantly improved efficiency in mobility control and conformance. These advanced polymer systems would maintain high viscosities or behave as virtual gels under low shear conditions and at elevated electrolyte concentrations. At high fluid shear rates, associates would deaggregate yielding low viscosity solutions, reducing problems of shear degradation or face plugging during injection. Polymeric surfactants were also developed with potential for use in higher salt, higher temperature reservoirs for mobilization of entrapped oil. Chapters include: Ampholytic terpolymers of acrylamide with sodium 3-acrylamido-3-methylbutanoate and 2-acrylamido-2-methylpropanetrimethylammonium chloride; Hydrophilic sulfobetaine copolymers of acrylamide and 3-(2-acrylamido-methylpropane-dimethylammonio)-1-propanesulfonate; Copolymerization of maleic anhydride and N-vinylformamide; Reactivity ratio of N-vinylformamide with acrylamide, sodium acrylate, and n-butyl acrylate; Effect of the distribution of the hydrophobic cationic monomer dimethyldodecyl(2-acrylamidoethyl)ammonium bromide on the solution behavior of associating acrylamide copolymers; Effect of surfactants on the solution properties of amphipathic copolymers of acrylamide and N,N-dimethyl-N-dodecyl-N-(2-acrylamidoethyl)ammonium bromide; Associative interactions and photophysical behavior of amphiphilic terpolymers prepared by modification of maleic anhydride/ethyl vinyl ether copolymers; Copolymer compositions of high-molecular-weight functional acrylamido water-soluble polymers using direct-polarization magic-angle spinning {sup 13}C NMR; Use of factorial experimental design in static and dynamic light scattering characterization of water soluble polymers; and Porous medium elongational rheometer studies of NaAMB/AM copolymer solutions.

Improved Mechanical Properties of Compatibilized Polypropylene/Polyamide-12 Blends

Directory of Open Access Journals (Sweden)

Nora Aranburu

2015-01-01

Full Text Available Compatibilized blends of polypropylene (PP and polyamide-12 (PA12 as a second component were obtained by direct injection molding having first added 20% maleic anhydride-modified copolymer (PP-g-MA to the PP, which produced partially grafted PP (gPP. A nucleating effect of the PA12 took place on the cooling crystallization of the gPP, and a second crystallization peak of the gPP appeared in the PA12-rich blends, indicating changes in the crystalline morphology. There was a slight drop in the PA12 crystallinity of the compatible blends, whereas the crystallinity of the gPP increased significantly in the PA12-rich blends. The overall reduction in the dispersed phase particle size together with the clear increase in ductility when gPP was used instead of PP proved that compatibilization occurred. Young’s modulus of the blends showed synergistic behavior. This is proposed to be both due to a change in the crystalline morphology of the blends on the one hand and, on the other, in the PA12-rich blends, to the clear increase in the crystallinity of the gPP phase, which may, in turn, have been responsible for the increase in its continuity and its contribution to the modulus.

Phase behavior of model ABC triblock copolymers

Science.gov (United States)

Chatterjee, Joon

The phase behavior of poly(isoprene-b-styrene- b-ethylene oxide) (ISO), a model ABC triblock copolymer has been studied. This class of materials exhibit self-assembly, forming a large array of ordered morphologies at length scales of 5-100 nm. The formation of stable three-dimensionally continuous network morphologies is of special interest in this study. Since these nanostructures considerably impact the material properties, fundamental knowledge for designing ABC systems have high technological importance for realizing applications in the areas of nanofabrication, nanoporous media, separation membranes, drug delivery and high surface area catalysts. A comprehensive framework was developed to describe the phase behavior of the ISO triblock copolymers at weak to intermediate segregation strengths spanning a wide range of composition. Phases were characterized through a combination of characterization techniques, including small angle x-ray scattering, dynamic mechanical spectroscopy, transmission electron microscopy, and birefringence measurements. Combined with previous investigations on ISO, six different stable ordered state symmetries have been identified: lamellae (LAM), Fddd orthorhombic network (O70), double gyroid (Q230), alternating gyroid (Q214), hexagonal (HEX), and body-centered cubic (BCC). The phase map was found to be somewhat asymmetric around the fI = fO isopleth. This work provides a guide for theoretical studies and gives insight into the intricate effects of various parameters on the self-assembly of ABC triblock copolymers. Experimental SAXS data evaluated with a simple scattering intensity model show that local mixing varies continuously across the phase map between states of two- and three-domain segregation. Strategies of blending homopolymers with ISO triblock copolymer were employed for studying the swelling properties of a lamellar state. Results demonstrate that lamellar domains swell or shrink depending upon the type of homopolymer that

Thermal Analysis, Mechanical and Rheological Behaviour of Melt Manufactured Polyethylene/Liquid Crystal Polymer Blends

Directory of Open Access Journals (Sweden)

Ilze ELKSNITE

2011-07-01

Full Text Available Modification of properties of conventional thermoplastics with thermotropic liquid crystal polymers, from one hand, allows decrease their viscosities, substantially facilitating processing conditions, and, from another hand, allows increase their exploitation properties. Orientation of the labile structure of liquid crystal polymer in extrusion or injection moulding causes specific reinforcement (so-called self-reinforcement to occur in the blends containing liquid crystal polymer. Up to now the effect of self-reinforcement is mostly investigated in the blends, containing considerable amount of liquid crystal polymer. In this research the effect of minor amounts of liquid crystalline co-polyester modifier on the properties of polyethylene is investigated. Various compositions of laboratory synthesized hydroxybenzoic acid /polyethylene terephtalate copolymer containing polyethylene composites have been manufactured by thermoplastic blending. It has been observed that 1 modulus of elasticity, yield strength and ultimate strength increase with raising the content of liquid crystalline modifier; 2 void content in the investigated polyethylene/liquid crystal copolymer composites is not greater that 1 %; 3 addition of liquid crystalline co-polyester modifier improves arrangement of PE crystalline phase.http://dx.doi.org/10.5755/j01.ms.17.2.483

Effect of gamma ray on poly(lactic acid)/poly(vinyl acetate-co-vinyl alcohol) blends as biodegradable food packaging films

Science.gov (United States)

Razavi, Seyed Mohammad; Dadbin, Susan; Frounchi, Masoud

2014-03-01

Poly(lactic acid) (PLA)/poly(vinyl acetate-co-vinyl alcohol) [P(VAc-co-VA)] blends as new transparent film packaging materials were prepared at various blend compositions and different vinyl alcohol contents. The blends and pure PLA were irradiated by gamma rays to investigate the extent of changes in the packaging material during gamma ray sterilization process. The miscibility of the blends was dependent on the blend composition and vinyl alcohol content; gamma irradiation had little effect on the extent of miscibility. The glass transition temperature of pure PLA and PLA/P(VAc-co-VA) miscible blends reduced after irradiation. On the other hand in PLA/P(VAc-co-VA) immiscible blends, while the glass transition temperature of the PLA phase decreased; that of the copolymer phase slightly increased. The reduction in the glass transition was about 10 percent for samples irradiated with 50 kGy indicating dominance of chain scission of PLA molecules at high irradiation dose. The latter was verified by drop in mechanical properties of pure PLA after exposing to gamma irradiation at 50 kGy. Blending of PLA with the copolymer P(VAc-co-VA) compensated greatly the adverse effects of irradiation on PLA. The oxygen-barrier property of the blend was superior to the neat PLA and remained almost intact with irradiation. The un-irradiated and irradiated blends had excellent transparency. Gamma ray doses used for sterilization purposes are usually less than 20 kGy. It was shown that gamma irradiation at 20 kGy had no or little adverse effects on PLA/P(VAc-co-VA) blends mechanical and gas barrier properties.

Thermoresponsive copolymer-grafted SBA-15 porous silica particles for temperature-triggered topical delivery systems

Directory of Open Access Journals (Sweden)

S. A. Jadhav

2017-02-01

Full Text Available A series of poly(N-isopropylacrylamide-co-acrylamide thermoresponsive random copolymers with different molecular weights and composition were synthesized and characterized by attenuated total reflectance Fourier-transform infrared (ATR-FTIR, differential scanning calorimetry (DSC, size exclusion chromatography (SEC and proton nuclear magnetic resonance (NMR spectroscopy. The lower critical solution temperatures (LCST of the copolymers were tuned by changing the mole ratios of monomers. Copolymer with highest molecular weight and LCST (41.2 °C was grafted on SBA-15 type mesoporous silica particles by a two-step polymer grafting procedure. Bare SBA-15 and the thermoresponsive copolymergrafted (hybrid SBA-15 particles were fully characterized by scanning electron microscope (SEM, ATR-FTIR, thermogravimetric analysis (TGA and Brunauer-Emmett-Teller (BET analyses. The hybrid particles were tested for their efficiency as temperature-sensitive systems for dermal delivery of the antioxidant rutin (quercetin-3-O-rutinoside. Improved control over rutin release by hybrid particles was obtained which makes them attractive hybrid materials for drug delivery.

Poly(Lactic Acid) Hemodialysis Membranes with Poly(Lactic Acid)-block-Poly(2-Hydroxyethyl Methacrylate) Copolymer As Additive: Preparation, Characterization, and Performance.

Science.gov (United States)

Zhu, Lijing; Liu, Fu; Yu, Xuemin; Xue, Lixin

2015-08-19

Poly(lactic acid) (PLA) hemodialysis membranes with enhanced antifouling capability and hemocompatibility were developed using poly(lactic acid)-block-poly(2-hydroxyethyl methacrylate) (PLA-PHEMA) copolymers as the blending additive. PLA-PHEMA block copolymers were synthesized via reversible addition-fragmentation (RAFT) polymerization from aminolyzed PLA. Gel permeation chromatography (GPC) and (1)H-nuclear magnetic resonance ((1)H NMR) were applied to characterize the synthesized products. By blending PLA with the amphiphilic block copolymer, PLA/PLA-PHEMA membranes were prepared by nonsolvent induced phase separation (NIPS) method. Their chemistry and structure were characterized with X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and atomic force microscopy (AFM). The results revealed that PLA/PLA-PHEMA membranes with high PLA-PHEMA contents exhibited enhanced hydrophilicity, water permeability, antifouling and hemocompatibility. Especially, when the PLA-PHEMA concentration was 15 wt %, the water flux of the modified membrane was about 236 L m(-2) h(-1). Its urea and creatinine clearance was more than 0.70 mL/min, lysozyme clearance was about 0.50 mL/min, BSA clearance was as less as 0.31 mL/min. All the results suggest that PLA-PHEMA copolymers had served as effective agents for optimizing the property of PLA-based membrane for hemodialysis applications.

Effect of Compatibilization on Interfacial Polarization and Intrinsic Length Scales in Biphasic Polymer Blends of PαMSAN and PMMA : A Combined Experimental and Modeling Dielectric Study

NARCIS (Netherlands)

Bharati, A.; Wübbenhorst, M.; Moldenaers, Paula; Cardinaels, Ruth

2016-01-01

We describe an approach to tailor the dielectric interfacial properties of polymer blends by the interplay of compatibilizer effects on blend morphology and on blocking of charge carriers. A systematic study of the effect of the concentration of the compatibilizer, a random copolymer of

Charge transfer complex in diketopyrrolopyrrole polymers and fullerene blends: Implication for organic solar cell efficiency

Science.gov (United States)

Moghe, D.; Yu, P.; Kanimozhi, C.; Patil, S.; Guha, S.

2012-02-01

Copolymers based on diketopyrrolopyrrole (DPP) have recently gained potential in organic photovoltaics. When blended with another acceptor such as PCBM, intermolecular charge transfer occurs which may result in the formation of charge transfer (CT) states. We present here the spectral photocurrent characteristics of two donor-acceptor DPP based copolymers, PDPP-BBT and TDPP-BBT, blended with PCBM to identify the CT states. The spectral photocurrent measured using Fourier-transform photocurrent spectroscopy (FTPS) and monochromatic photocurrent (PC) methods are compared with P3HT:PCBM, where the CT state is well known. PDPP-BBT:PCBM shows a stable CT state while TDPP-BBT does not. Our analysis shows that the larger singlet state energy difference between TDPP-BBT and PCBM along with the lower optical gap of TDPP-BBT obliterates the formation of a midgap CT state resulting in an enhanced photovoltaic efficiency over PDPP-BBT:PCBM.

Influence of copolymer architectures on adhesion and compatibilization of polymers at interfaces

Science.gov (United States)

Guo, Lantao

Adhesion and compatibilization of immiscible homopolymers by a variety of copolymer architectures were studied. The work is arranged into 5 chapters: In Chapter 1, an introduction to recent studies on improvement of adhesion and compatibilization of polymer blends using copolymers was made including the advantages and shortcomings of interfacial reinforcement by a diblock copolymer architecture. Emphasis is on the novel ways to improve adhesion at polymer interfaces by a variety of copolymer architectures, including physical entanglement and chemical modification and chemical bonding. In Chapter 2, a series of Polystyrene-Poly(methyl methacrylate) (PS-PMMA) graft copolymers were introduced to modify the PS and PMMA homopolymer interface and was found to increase the interfacial fracture toughness to a large extent, depending on the detailed architectural variables such as the graft number per chain, the lengths of the backbone and the grafts, and the total molecular weights of the graft copolymers. It was also found that there was an optimal number of grafts per chain which can be interpreted based on the graft length and inter-branch length of the backbone of the copolymer. Effect of in-situ grafting via a chemical reaction between Polystyrene-Poly(vinyl phenol) (PS-PSOH) and oxazoline containing Styrene-Acrylonitril (SAN) was also discussed compared with the physical grafting of a graft copolymer of different structural parameters. In Chapter 3, hydrogen bonding was utilized to toughen the interface between PS and PAA poly(acrylic acid)) or PMMA using a random copolymer architecture of Polystyrene-Poly(vinyl pyridine) (PS-PVP). It was shown that random copolymer architecture is not only economically feasible due to its low cost of producing but also very effective on adhesion because it not only overcomes the issue of micelle formation which is an unavoidable situation in the diblock and graft cases but the enhancement of adhesion is much higher utilizing a H

Synthesis of Inorganic Nanocomposites by Selective Introduction of Metal Complexes into a Self-Assembled Block Copolymer Template

Directory of Open Access Journals (Sweden)

Hiroaki Wakayama

2015-01-01

Full Text Available Inorganic nanocomposites have characteristic structures that feature expanded interfaces, quantum effects, and resistance to crack propagation. These structures are promising for the improvement of many materials including thermoelectric materials, photocatalysts, and structural materials. Precise control of the inorganic nanocomposites’ morphology, size, and chemical composition is very important for these applications. Here, we present a novel fabrication method to control the structures of inorganic nanocomposites by means of a self-assembled block copolymer template. Different metal complexes were selectively introduced into specific polymer blocks of the block copolymer, and subsequent removal of the block copolymer template by oxygen plasma treatment produced hexagonally packed porous structures. In contrast, calcination removal of the block copolymer template yielded nanocomposites consisting of metallic spheres in a matrix of a metal oxide. These results demonstrate that different nanostructures can be created by selective use of processes to remove the block copolymer templates. The simple process of first mixing block copolymers and magnetic nanomaterial precursors and then subsequently removing the block copolymer template enables structural control of magnetic nanomaterials, which will facilitate their applicability in patterned media, including next-generation perpendicular magnetic recording media.

Meso-scale Modeling of Block Copolymers Self-Assembly in Casting Solutions for Membrane Manufacture

KAUST Repository

Moreno Chaparro, Nicolas

2016-05-01

Isoporous membranes manufactured from diblock copolymer are successfully produced at laboratory scale under controlled conditions. Because of the complex phenomena involved, membrane preparation requires trial and error methodologies to find the optimal conditions, leading to a considerable demand of resources. Experimental insights demonstrate that the self-assembly of the block copolymers in solution has an effect on the final membrane structure. Nevertheless, the complete understanding of these multi-scale phenomena is elusive. Herein we use the coarse-grained method Dissipative Particle Dynamics to study the self-assembly of block copolymers that are used for the preparation of the membranes. To simulate representative time and length scales, we introduce a framework for model reduction of polymer chain representations for dissipative particle dynamics, which preserves the properties governing the phase equilibria. We reduce the number of degrees of freedom by accounting for the correlation between beads in fine-grained models via power laws and the consistent scaling of the simulation parameters. The coarse-graining models are consistent with the experimental evidence, showing a morphological transition of the aggregates as the polymer concentration and solvent affinity change. We show that hexagonal packing of the micelles can occur in solution within different windows of polymer concentration depending on the solvent affinity. However, the shape and size dispersion of the micelles determine the characteristic arrangement. We describe the order of crew-cut micelles using a rigid-sphere approximation and propose different phase parameters that characterize the emergence of monodisperse-spherical micelles in solution. Additionally, we investigate the effect of blending asymmetric diblock copolymers (AB/AC) over the properties of the membranes. We observe that the co-assembly mechanism localizes the AC molecules at the interface of A and B domains, and induces

Radiation polymerization and crosslinking: A viable alternative for synthesis of porous functional polymers

Energy Technology Data Exchange (ETDEWEB)

Safrany, Agnes, E-mail: a.safrany@iaea.or [Department of Nuclear Sciences and Applications, International Atomic Energy Agency, P.O. Box 100, A-1400 Vienna (Austria); Beiler, Barbara [Radiation Chemistry Department, Institute of Isotopes, Hungarian Academy of Sciences, P.O. Box 77, H1525 Budapest (Hungary); Vincze, Arpad [Miklos Zrinyi National Defence University, Department of NBC Defence, Budapest 146, P.O. Box 15, H-1581 Budapest (Hungary)

2010-04-15

We have earlier shown the possibility of preparation of crosslinked porous polymers by ionizing radiation-initiated reactions, and here we give an overview of the irradiation conditions-porous properties relationship for several methacrylate type copolymers. We illustrate the possible applications by an environment-friendly chromatographic column using water as eluent and a chemically stable scintillating polymer with excellent ion-binding capacity for possible continuous monitoring of radioactivity in natural waters.

Adsorption of copolymers at polymer/air and polymer/solid interfaces

Science.gov (United States)

Oslanec, Robert

Using mainly low-energy forward recoil spectrometry (LE-FRES) and neutron reflectivity (NR), copolymer behavior at polymer/air and polymer/solid interfaces is investigated. For a miscible blend of poly(styrene-ran-acrylonitrile) copolymers, the volume fraction profile of the copolymer with lower acrylonitrile content is flat near the surface in contrast to mean field predictions. Including copolymer polydispersity into a self consistent mean field (SCMF) model does not account for this profile shape. LE-FRES and NR is also used to study poly(deuterated styrene-block-methyl-methacrylate) (dPS-b-PMMA) adsorption from a polymer matrix to a silicon oxide substrate. The interfacial excess, zsp*, layer thickness, L, and layer-matrix width, w, depend strongly on the number of matrix segments, P, for P 2N, the matrix chains are repelled from the adsorbed layer and the layer characteristics become independent of P. An SCMF model of block copolymer adsorption is developed. SCMF predictions are in qualitative agreement with the experimental behavior of zsp*, L, and w as a function of P. Using this model, the interaction energy of the MMA block with the oxide substrate is found to be -8ksb{B}T. In a subsequent experiment, the matrix/dPS interaction is made increasingly unfavorable by increasing the 4-bromostyrene mole fraction, x, in a poly(styrene-ran-4-bromostyrene) (PBrsbxS) matrix. Whereas experiments show that zsp* slightly decreases as x increases, the SCMF model predicts that zsp* should increase as the matrix becomes more unfavorable. Upon including a small matrix attraction for the substrate, the SCMF model shows that zsp* decreases with x because of competition between PBrsbxS and dPS-b-PMMA for adsorbing sites. In thin film dewetting experiments on silicon oxide, the addition of dPS-b-PMMA to PS coatings acts to slow hole growth and prevent holes from impinging. Dewetting studies show that longer dPS-b-PMMA chains are more effective stabilizing agents than shorter

Effect of gamma ray on poly(lactic acid)/poly(vinyl acetate-co-vinyl alcohol) blends as biodegradable food packaging films

International Nuclear Information System (INIS)

Razavi, Seyed Mohammad; Dadbin, Susan; Frounchi, Masoud

2014-01-01

Poly(lactic acid) (PLA)/poly(vinyl acetate-co-vinyl alcohol) [P(VAc-co-VA)] blends as new transparent film packaging materials were prepared at various blend compositions and different vinyl alcohol contents. The blends and pure PLA were irradiated by gamma rays to investigate the extent of changes in the packaging material during gamma ray sterilization process. The miscibility of the blends was dependent on the blend composition and vinyl alcohol content; gamma irradiation had little effect on the extent of miscibility. The glass transition temperature of pure PLA and PLA/P(VAc-co-VA) miscible blends reduced after irradiation. On the other hand in PLA/P(VAc-co-VA) immiscible blends, while the glass transition temperature of the PLA phase decreased; that of the copolymer phase slightly increased. The reduction in the glass transition was about 10 percent for samples irradiated with 50 kGy indicating dominance of chain scission of PLA molecules at high irradiation dose. The latter was verified by drop in mechanical properties of pure PLA after exposing to gamma irradiation at 50 kGy. Blending of PLA with the copolymer P(VAc-co-VA) compensated greatly the adverse effects of irradiation on PLA. The oxygen-barrier property of the blend was superior to the neat PLA and remained almost intact with irradiation. The un-irradiated and irradiated blends had excellent transparency. Gamma ray doses used for sterilization purposes are usually less than 20 kGy. It was shown that gamma irradiation at 20 kGy had no or little adverse effects on PLA/P(VAc-co-VA) blends mechanical and gas barrier properties. - Highlights: • Poly(lactic acid)/poly(vinyl acetate-co-vinyl alcohol) blends were prepared as new packaging film. • The blends are superior to PLA in oxygen gas barrier property. • The blends are suitable for gamma ray sterilization and maintain useful mechanical properties. • The blends are perfectly transparent

Film-thickness dependence of structure formation in ultra-thin polymer blend films

CERN Document Server

Gutmann, J S; Stamm, M

2002-01-01

We investigated the film-thickness dependence of structure formation in ultra-thin polymer blend films prepared from solution. As a model system we used binary blends of statistical poly(styrene-co-p-bromostyrene) copolymers of different degrees of bromination. Ultra-thin-film samples differing in miscibility and film thickness were prepared via spin coating of common toluene solutions onto silicon (100) substrates. The resulting morphologies were investigated with scanning force microscopy, reflectometry and grazing-incidence scattering techniques using both X-rays and neutrons in order to obtain a picture of the sample structure at and below the sample surface. (orig.)

Preparation and Characterization of Keratin/Alginate Blend Microparticles

Directory of Open Access Journals (Sweden)

Yaowalak Srisuwan

2018-01-01

Full Text Available The water-in-oil (W/O emulsification-diffusion method was used for construction of keratin (Ker, alginate (Alg, and Ker/Alg blend microparticles. The Ker, Alg, and Ker/Alg blend solutions were used as the water phase, while ethyl acetate was used as the oil phase. Firstly, different concentrations of Ker solution was used to find suitable content. 1.6% w/v Ker solution was blended with the same concentration of the Alg solution for further microparticle construction. Results from scanning electron microscope analysis show that the microparticles have different shapes: spherical, bowl-like, porous, and hollow, with several sizes depending on the blend ratio. FTIR and TG analyses indicated that the secondary structure and thermal stability of the microparticles were influenced by the Ker/Alg blend ratio. The interaction between functional groups of keratin and alginate was the main factor for both β-sheet structure and Td,max values of the microparticles. The results suggested that Ker/Alg blend microparticles might be applied in many fields by varying the Ker/Alg ratio.

A theoretical and simulation study of the self-assembly of a binary blend of diblock copolymers

KAUST Repository

Padmanabhan, Poornima

2012-01-01

Pure diblock copolymer melts exhibit a narrow range of conditions at which bicontinuous and cocontinuous phases are stable; such conditions and the morphology of such phases can be tuned by the use of additives. In this work, we have studied a bidisperse system of diblock copolymers using theory and simulation. In particular, we elucidated how a short, lamellar-forming diblock copolymer modifies the phase behavior of a longer, cylinder-forming diblock copolymer. In a narrow range of intermediate compositions, self-consistent field theory predicts the formation of a gyroid phase although particle-based simulations show that three phases compete: the gyroid phase, a disordered cocontinuous phase, and the cylinder phase, all having free energies within error bars of each other. Former experimental studies of a similar system have yielded an unidentified, partially irregular bicontinuous phase, and our simulations suggest that at such conditions the formation of a partially transformed network phase is indeed plausible. Close examination of the spatial distribution of chains reveals that packing frustration (manifested by chain stretching and low density spots) occurs in the majority-block domains of the three competing phases simulated. In all cases, a double interface around the minority-block domains is also detected with the outer one formed by the short chains, and the inner one formed by the longer chains. © 2012 American Institute of Physics.

Copolymer-homopolymer blends : global energy minimisation and global energy bounds

NARCIS (Netherlands)

Gennip, van Y.; Peletier, M.A.

2008-01-01

Abstract We study a variational model for a diblock copolymer–homopolymer blend. The energy functional is a sharp-interface limit of a generalisation of the Ohta–Kawasaki energy. In one dimension, on the real line and on the torus, we prove existence of minimisers of this functional and we describe

Controlling sub-microdomain structure in microphase-ordered block copolymers and their nanocomposites

Science.gov (United States)

Bowman, Michelle Kathleen

Block copolymers exhibit a wealth of morphologies that continue to find ubiquitous use in a diverse variety of mature and emergent (nano)technologies, such as photonic crystals, integrated circuits, pharmaceutical encapsulents, fuel cells and separation membranes. While numerous studies have explored the effects of molecular confinement on such copolymers, relatively few have examined the sub-microdomain structure that develops upon modification of copolymer molecular architecture or physical incorporation of nanoscale objects. This work will address two relevant topics in this vein: (i) bidisperse brushes formed by single block copolymer molecules and (ii) copolymer nanocomposites formed by addition of molecular or nanoscale additives. In the first case, an isomorphic series of asymmetric poly(styrene-b -isoprene-b-styrene) (S1IS2) triblock copolymers of systematically varied chain length has been synthesized from a parent SI diblock copolymer. Small-angle x-ray scattering, coupled with dynamic rheology and self-consistent field theory (SCFT), reveals that the progressively grown S2 block initially resides in the I-rich matrix and effectively reduces the copolymer incompatibility until a critical length is reached. At this length, the S2 block co-locates with the S1 block so that the two blocks generate a bidisperse brush (insofar as the S1 and S2 lengths differ). This single-molecule analog to binary block copolymer blends affords unique opportunities for materials design at sub-microdomain length scales and provides insight into the transition from diblock to triblock copolymer (and thermoplastic elastomeric nature). In the second case, I explore the distribution of molecular and nanoscale additives in microphase-ordered block copolymers and demonstrate via SCFT that an interfacial excess, which depends strongly on additive concentration, selectivity and relative size, develops. These predictions are in agreement with experimental findings. Moreover, using a

Preparation of Thermoplastic Poly (vinyl Alcohol), Ethylene Vinyl Acetate and Vinyl Acetate Versatic Ester Blends for Exterior Masonry Coating

International Nuclear Information System (INIS)

EL-Nahas, H.H.; Gad, Y.H.; Magida, M.M.

2013-01-01

Blend systems including ethylene vinyl acetate (EVA), poly (vinyl alcohol) (PVA) and vinyl acetate versatic copolymer latex (VAcVe) were prepared and used as exterior coatings. Mechanical and thermal properties of the blends were investigated using a testo meter, shore hardness tester, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The water resistance of the samples was measured. Effect of ionizing irradiation on gel content, tensile strength and surface hardness were also followed. The blend offers binder base for exterior masonry coating systems having superior water resistant and mechanical properties

Compatibilization of acrylonitrile-butadiene-styrene terpolymer/poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) blend: effect on morphology, interface, mechanical properties and hydrophilicity

Science.gov (United States)

Chen, Tingting; Zhang, Jun

2018-04-01

The compatibilization of acrylonitrile-butadiene-styrene terpolymer (ABS) and poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) blends was first investigated. Styrene-acrylonitrile-glycidyl methacrylate terpolymer (SAG) and ABS grafted with maleic anhydride (ABS-g-MAH) were selected as reactive compatibilizers for the ABS/PETG blends. The compatibilization effect was assessed by scanning electron microscope (SEM), differential scanning calorimetry (DSC) and mechanical properties. And the effect of compatibilizers on the hydrophilicity of the blends was evaluated as well. SEM observation and DSC analysis confirmed that both SAG and ABS-g-MAH compatibilizers could improve the compatibility between ABS and PETG, leading to an improvement in toughness of the blend. The possible cause for the improvement of compatibility was the reaction between compatibilizers and PETG, which could in situ turn out compatibilizers that acted as interfacial agents to enhance the interfacial interaction in the blend. Especially, the addition of SAG significantly decreased the dispersion phase size and the interface voids almost disappeared. Since the in situ reactions between the epoxy groups of SAG and the end groups (sbnd COOH or sbnd OH) of PETG generated PETG-co-SAG copolymer at the blend interface, and the cross-linking reactions proposed to take place between SAG and the PETG-co-SAG copolymer, acting as compatibilizer, could significantly increase the interfacial interaction. The addition of SAG also enhanced the stiffness of the blends. Moreover, the addition of SAG made the blend more hydrophilic, whereas the addition of ABS-g-MAH made the blend more hydrophobic. Therefore, SAG was a good compatibilizer for the ABS/PETG blends and could simultaneously provide the blends with toughening, stiffening and hydrophilic effects.

Supertoughened renewable PLA reactive multiphase blends system: phase morphology and performance.

Science.gov (United States)

Zhang, Kunyu; Nagarajan, Vidhya; Misra, Manjusri; Mohanty, Amar K

2014-08-13

Multiphase blends of poly(lactic acid) (PLA), ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA) terpolymer, and a series of renewable poly(ether-b-amide) elastomeric copolymer (PEBA) were fabricated through reactive melt blending in an effort to improve the toughness of the PLA. Supertoughened PLA blend showing impact strength of ∼500 J/m with partial break impact behavior was achieved at an optimized blending ratio of 70 wt % PLA, 20 wt % EMA-GMA, and 10 wt % PEBA. Miscibility and thermal behavior of the binary blends PLA/PEBA and PLA/EMA-GMA, and the multiphase blends were also investigated through differential scanning calorimetric (DSC) and dynamic mechanical analysis (DMA). Phase morphology and fracture surface morphology of the blends were studied through scanning electron microscopy (SEM) and atomic force microscopy (AFM) to understand the strong corelation between the morphology and its significant effect on imparting tremendous improvement in toughness. A unique "multiple stacked structure" with partial encapsulation of EMA-GMA and PEBA minor phases was observed for the PLA/EMA-GMA/PEBA (70/20/10) revealing the importance of particular blend composition in enhancing the toughness. Toughening mechanism behind the supertoughened PLA blends have been established by studying the impact fractured surface morphology at different zones of fracture. Synergistic effect of good interfacial adhesion and interfacial cavitations followed by massive shear yielding of the matrix was believed to contribute to the enormous toughening effect observed in these multiphase blends.

Morphology Formation in PC/ABS Blends during Thermal Processing and the Effect of the Viscosity Ratio of Blend Partners

Directory of Open Access Journals (Sweden)

Stefanie Bärwinkel

2016-08-01

Full Text Available Morphology formation during compounding, as well as injection molding of blends containing 60 wt % polycarbonate (PC and 40 wt % polybutadiene rubber-modified styrene-acrylonitrile copolymers (ABS, has been investigated by transmission electron microscopy (TEM. Profiles of the blend morphology have been recorded in injection-molded specimens and significant morphology gradients observed between their skin and core. A <10 µm thick surface layer with strongly dispersed and elongated nano-scale (streak-like styrene acrylonitrile (SAN phases and well-dispersed, isolated SAN-grafted polybutadiene rubber particles is followed by a 50–150 µm thick skin layer in which polymer morphology is characterized by lamellar SAN/ABS phases. Thickness of these lamellae increases with the distance from the specimen’s surface. In the core of the specimens the SAN-grafted polybutadiene rubber particles are exclusively present within the SAN phases, which exhibit a much coarser and less oriented, dispersed morphology compared to the skin. The effects of the viscosity of the SAN in the PC/ABS blends on phase morphologies and correlations with fracture mechanics in tensile and impact tests were investigated, including scanning electron microscopy (SEM assessment of the fracture surfaces. A model explaining the mechanisms of morphology formation during injection molding of PC/ABS blends is discussed.

Coalescence in an interface-modified polymer blend as studied by light-scattering measurements

DEFF Research Database (Denmark)

Søndergaard, K.; Lyngaae-Jørgensen, Jørgen

1996-01-01

the requirement is the BC to reside at the interface. In the present study the block chain lengths were chosen shorter than the corresponding homopolymers as a starting point. For selected model systems it was found that symmetrical diblock copolymers with phi(bc) greater than or equal to 1% were most effective......The influence of B-B diblock copolymers on coalescence in A:B blends has been studied by rheo-optical measurements and electron microscopy. Divergent criteria and experimental evidence appear in the literature on the block copolymer (BC) molecular weight (M(W)) and volume fraction (phi(bc)) when...... is discussed based on various mechanisms: shear-induced mutual compatibility between components, squeeze-out/drainage of the interfacial layer, frictional pull-out of BC chains, collision-induced entrapment of BC between interfaces, encapsulation of the BC based on the concept of elastic interfacial curvature....

Phase behavior of binary polybutadiene copolymer mixtures as an example of weakly interacting polymers

CERN Document Server

Schwahn, D

2002-01-01

Binary blends of statistical polybutadiene copolymers of different vinyl content and molar volume were explored by small-angle neutron scattering. These samples represent the most simple class of statistical copolymer mixtures. In spite of this simplicity, changes in vinyl content, molar volume, and deuterium and hydrogen content of the chains give rise to strong effects; phase separation occurs from minus 230 C to more than plus 200 C and can even reverse from an enthalpically driven one at low temperatures to an entropically driven one at high temperatures. The entropic and enthalpic terms of the Flory-Huggins parameter as determined from the experiment are in excellent agreement with lattice cluster theory calculations. (orig.)

Electrospinning synthesis of porous Al{sub 2}O{sub 3} nanofibers by pluronic P123 triblock copolymer surfactant and properties of uranium (VI)-sorption

Energy Technology Data Exchange (ETDEWEB)

Ren, Bo [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Department of Applied Chemistry Engineering, Jilin Vocational College of Industry and Technology, Jilin 132013 (China); Institute of Petrochemistry Heilongjiang Academy of Sciences, Harbin 150001 (China); Fan, Meiqing [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Department of Applied Chemistry Engineering, Jilin Vocational College of Industry and Technology, Jilin 132013 (China); Tan, Lichao [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Li, Rumin, E-mail: lirumin@hrbeu.edu.cn [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Song, Dalei; Liu, Qi [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Wang, Jun, E-mail: zhqw1888@sohu.com [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Institute of Advanced Marine Materials, Harbin Engineering University, Harbin 150001 (China); Zhang, Bin [Institute of Petrochemistry Heilongjiang Academy of Sciences, Harbin 150001 (China); Jing, Xiaoyan [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China)

2016-07-01

Porous Alumina (Al{sub 2}O{sub 3}) nanofibers were prepared by electrospinning process using pluronic P123 triblock copolymer surfactant as template. The characterizations of the adsorbent were investigated by X-ray diffraction (XRD) fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption–desorption. The obtained nanofibers were used as adsorbents for the removal of Uranium (VI). The maximum adsorption occurred at pH 5, the equilibrium adsorption amount was about 87 mg/g, and the equilibrium time was 6.0 h. A pseudo-second order model could best describe adsorption kinetics. The adsorption equilibrium data fit Freundlich adsorption isotherm equation well. Thermodynamic parameters such as standard enthalpy (ΔH{sup 0}), standard entropy (ΔS{sup 0}), standard free energy (ΔG{sup 0}) and activation energy (E{sub a}) were calculated. The results predict an endothermic nature of adsorption and a spontaneous process. - Highlights: • The porous Al{sub 2}O{sub 3} nanofibers were used for U(VI)-sorption for the first time. • The adsorption process was endothermic and spontaneous. • The maximum adsorption capacity was 87 mg g{sup −1} at 25 °C.

Solid state double layer capacitor based on a polyether polymer electrolyte blend and nanostructured carbon black electrode composites

Energy Technology Data Exchange (ETDEWEB)

Lavall, Rodrigo L.; Borges, Raquel S.; Calado, Hallen D.R.; Welter, Cezar; Trigueiro, Joao P.C.; Silva, Glaura G. [Departamento de Quimica, Instituto de Ciencias Exatas, Universidade Federal de Minas Gerais, CEP 31270-901, Belo Horizonte (Brazil); Rieumont, Jacques [Departamento de Quimica, Instituto de Ciencias Exatas, Universidade Federal de Minas Gerais, CEP 31270-901, Belo Horizonte (Brazil); Facultad de Quimica, Universidad de La Habana, Habana 10400 (Cuba); Neves, Bernardo R.A. [Departamento de Fisica, Instituto de Ciencias Exatas, Universidade Federal de Minas Gerais, CEP 31270-901, Belo Horizonte (Brazil)

2008-03-01

An all solid double layer capacitor was assembled by using poly(ethylene oxide)/poly(propylene glycol)-b-poly(ethylene glycol)-b-poly(propylene glycol)-bis(2-aminopropyl ether) blend (PEO-NPPP) and LiClO{sub 4} as polymer electrolyte layer and PEO-NPPP-carbon black (CB) as electrode film. High molecular weight PEO and the block copolymer NPPP with molecular mass of 2000 Da were employed, which means that the design is safe from the point of view of solvent or plasticizer leakage and thus, a separator is not necessary. Highly conductive with large surface area nanostructured carbon black was dispersed in the polymer blend to produce the electrode composite. The electrolyte and electrode multilayers prepared by spray were studied by differential scanning calorimetry, atomic force microscopy (AFM) and impedance spectroscopy. The ionic conductivity as a function of temperature was fitted with the Williams-Landel-Ferry equation, which indicates a conductivity mechanism typical of solid polymer electrolyte. AFM images of the nanocomposite electrode showed carbon black particles of approximately 60 nm in size well distributed in a semicrystalline and porous polymer blend coating. The solid double layer capacitor with 10 wt.% CB was designed with final thickness of approximately 130 {mu}m and delivered a capacitance of 17 F g{sup -1} with a cyclability of more than 1000 cycles. These characteristics make possible the construction of a miniature device in complete solid state which will avoid electrolyte leakage and present a performance superior to other similar electric double layer capacitors (EDLCs) presented in literature, as assessed in specific capacitance by total carbon mass. (author)

Photostabilizing of bisphenol A polycarbonate by using UV-absorbers and self protective block copolymers based on resorcinol polyarylate blocks

NARCIS (Netherlands)

Diepens, M.; Gijsman, P.

2009-01-01

Bisphenol A polycarbonate degrades due to sunlight, humidity and oxygen. In this study two possible techniques to stabilize the polymer were compared, i.e. blending of UV-absorbers (UVAs) into the polymer or using block copolymers based on resorcinol polyarylates. Combination of different analysis

Studies on microphase-separated structures of block copolymers by neutron reflectivity measurement

International Nuclear Information System (INIS)

Torikai, Naoya; Noda, Ichiro; Matsushita, Yushu; Karim, A.; Satija, S.K.; Han, C.C.; Ebisawa, Toru.

1996-01-01

Segmental distributions of block copolymer chains in lamellar microphase-separated structure and those of homopolymers in block copolymer/homopolymer blends also with lamellar structures were studied by neutron reflectivity measurements. It was revealed that polystyrene and poly(2-vinylpyridine) lamellae were alternately stacked within the thin films of pure block copolymers spin-coated on silicon wafers, and they were preferentially oriented along the direction parallel to film surface. Polystyrene lamella appeared at air surfaces of the films, while poly(2-vinylpyridine) lamella did on silicon surfaces. Segment distribution at lamellar interface was well described by an error function, and the width of the lamellar interface, defined by a full-width half-maximum value of interfacial profile, was estimated to be about 4.5 nm. Segments of block chains adjacent to the chemical junction points connecting different block chains were strongly localized near the lamellar interfaces, while those on the free ends of block chains were distributed all over the lamellar microdomains with their distribution maxima at the centers of lamellae. On the other hand, it was clarified that homopolymers dissolved in the corresponding lamellar microdomains of block copolymers were also distributed throughout the microdomains with their concentration maxima at the centers of the lamellae. (author)

Surface treatment of poly(ethylene terephthalate) by gamma-ray induced graft copolymerization of methyl acrylate and its toughening effect on poly(ethylene terephthalate)/elastomer blend

International Nuclear Information System (INIS)

Ma, Liang; Wang, Mozhen; Ge, Xuewu

2013-01-01

To improve the compatibility between ethylene-methyl acrylate-glycidyl methacrylate random terpolymer (E-MA-GMA) elastomer and poly(ethylene terephthalate) (PET), thereby enhance the toughening effect of E-MA-GMA on PET, γ-radiation-induced graft copolymerization technique was used to graft methyl acrylate (MA) monomer onto PET. The produced PET-g-PMA copolymer can be used as a self-compatibilizer in PET/E-MA-GMA blend since the copolymer contains the same segments, respectively, with PET and E-MA-GMA. The impact strength of PET/E-MA-GMA blend increased nearly by 30% in the presence of less than 0.1 wt% PET-g-PMA compared with that of the neat PET/elastomer blend, without loss of the tensile strength of the blends. This work proposed a potential application of radiation-induced grafting copolymerization technique on the in-situ compatibilization of PET/elastomer blends so as to improve the integral mechanical properties of PET based engineering plastic. - Highlights: • PMA was grafted onto PET resins by γ-ray radiation-induced copolymerization. • The obtained PET-g-PMA can improve the compatibility between PET and E-MA-GMA. • A small amount of PET-g-PMA can enhance the impact strength of PET/E-MA-GMA blend

Synthesis and Characterization of a Novel Ammonia Gas Sensor Based on PANI-PVA Blend Thin Films

Directory of Open Access Journals (Sweden)

D. B. DUPARE

2008-06-01

Full Text Available The polyaniline - polyvinyl alcohol blend films were synthesized by oxidative polymerization using chemical synthesis route. The polyaniline films were synthesized using optimized concentration of monomer aniline, hydrochloric acid as a dopant using ammonium peroxy-disulphate as a oxidant and insulating addative matrix polyvinyl alcohol on glass substrate for development of ammonia sensor. The formation of PANI- PVA blend films show good uniform surface morphology at 10ºc temperature, maintained at constant temperature bath. The synthesized PANI-PVA blend thin films were characterized by analyzing UV-Visible and FTIR spectra. The SEM study ensures that the thin films are uniform and porous in nature. The I-V characterization shows ohmic behaviour and also determines conductivity of the films. The response time of PANI-PVA blend thin films show that excellent behavior for 50-800 ppm and higher range of ammonia gas. This study reveals that PANI-PVA blend thin films provide a polymer matrix with very good mechanical strength, environmental stability, uniformity in surface, porous morphology and high conductivity, which are suitable for ammonia gas sensing.

Block copolymers of poly(l-lactide) and poly(e-caprolactone) or poly(ethylene glycol) prepared by reactive extrusion

NARCIS (Netherlands)

Stevels, W.M.; Bernard, A.; van de Witte, P.; van de Witte, P.; Dijkstra, Pieter J.; Feijen, Jan

1996-01-01

Blends of poly(L-lactide) (PLLA) and poly(-caprolactone) (PCL) were prepared in a co-rotating twin screw miniextruder (40 rpm, 200°). It was attempted to prepare multiblock copolymers by allowing a controlled number of transesterification reactions. Various cat-alysts (n-Bu3SnOMe, Sn(Oct)2,

Utilization of waste expanded polystyrene: Blends with silica-filled natural rubber

International Nuclear Information System (INIS)

Sekharan, Renju Vaikathusseril; Abraham, Beena Thattekatt; Thachil, Eby Thomas

2012-01-01

Highlights: ► Tensile strength of the silica filled blend is comparable with silica filled NR. ► Modulus and compression set were the best for compatibilized NR/EPS blends. ► Tear strength has increased by 25% for compatibilized blends. ► A 5% waste EPS can be incorporated into NR compounds as a waste management measure. -- Abstract: Expanded polystyrene (EPS) constitutes a considerable part of thermoplastic waste in the environment in terms of volume. In this study, this waste material has been utilized for blending with silica-reinforced natural rubber (NR). The NR/EPS (35/5) blends were prepared by melt mixing in a Brabender Plasticorder. Since NR and EPS are incompatible and immiscible a method has been devised to improve compatibility. For this, EPS and NR were initially grafted with maleic anhydride (MA) using dicumyl peroxide (DCP) to give a graft copolymer. Grafting was confirmed by Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy. This grafted blend was subsequently blended with more of NR during mill compounding. Morphological studies using Scanning Electron Microscopy (SEM) showed better dispersion of EPS in the compatibilized blend compared to the noncompatibilized blend. By this technique, the tensile strength, elongation at break, modulus, tear strength, compression set and hardness of the blend were found to be either at par with or better than that of virgin silica filled NR compound. It is also noted that the thermal properties of the blends are equivalent with that of virgin NR. The study establishes the potential of this method for utilising waste EPS.

Synthesis, characterizations and biocompatibility of novel biodegradable star block copolymers based on poly[(R)-3-hydroxybutyrate] and poly(epsilon-caprolactone)

DEFF Research Database (Denmark)

Wu, Linping; Wang, Liang; Wang, Xiaojuan

2010-01-01

Star block copolymers based on poly[(R)-3-hydroxybutyrate] (PHB) and poly(epsilon-caprolactone) (PCL), termed SPHBCL, were successfully synthesized with structural variation on arm numbers and lengths via coupling reactions and ring opening polymerizations. Arm numbers 3, 4 and 6 of SPHBCL were...... weights of the SPHBCL due to the discrepancy of star copolymer structures. The melting temperature of SPHBCL decreased with increasing degree of branching. Thermal decomposition temperature was revealed to be lower than that of linear block copolymer LPHBCL counterparts based on PHB and PCL. Films made...... from various SPHBCL copolymers had different porous or networking surface morphology, and all possessed improved biocompatibility in terms of less blood clotting and more osteoblast cell growth compared with their corresponding homopolymers PHB and PCL. Among them, it was found, however, that the 4-arm...

[Phase transition in polymer blends and structure of ionomers and copolymers

Energy Technology Data Exchange (ETDEWEB)

1993-01-01

The main thrust of the program in the past 3 years are summarized: SAXS instrumentation development; structure and dynamics of macro- and supra-molecules, phase transitions in polymer blends and solutions, structure of ionomers, and fractals and anisotropic systems.

Thermosetting materials of the radiation-modified polymer compositions. 3. Development of thermoplastic thermosetting materials from polymeric blends

International Nuclear Information System (INIS)

Kalkis, V.; Zicans, J.; Bocoka, T.; Ivanova, T.

2000-01-01

Experimental studies of blends consisting of chemically and radiation modified polyethylene and ethylene-propylene-diene copolymers have been carried out. Measurements of crystallinity, toughness, viscoelastic, adhesion and thermorelaxation properties as well as scanning electron-microscopic studies have shown that the blends chemically vulcanized by elastomer phase crosslinking system possess a typical double-phase structure within the whole composition range and characteristics specific for rubber, whereas, in radiation-vulcanized blends where crosslinking of both disperse phases takes part, formation of chemical bonds between these phases was observed. Consequently, the radiation treatment improves the properties of the blends, and materials formed by such a system can be successfully used, e.g., as elastic and adhesion active thermosetting materials if the polymer is previously oriented. (author)

Meniscal tissue regeneration in porous 50/50 copoly(L-lactide/epsilon-caprolactone) implants

NARCIS (Netherlands)

de Groot, J. H.; Zijlstra, F. M.; Kuipers, HW; Pennings, A. J.; Veth, RPH; Jansen, HWB

Porous materials of a high-molecular-weight 50/50 copolymer of L-lactide and epsilon-caprolactone with different compression moduli were used for meniscal repair. In contrast to the previously used 4,4'-diphenylmethane and 1,6-trans-cyclohexane diisocyanates containing polyurethanes, degradation

Toughening modification of poly(butylene terephthalate)/poly(ethylene terephthalate) blends by an epoxy-functionalized elastomer

Science.gov (United States)

Zhang, Weizhou; Wang, Kai; Yan, Wei; Guo, Weihong

2017-10-01

New toughened poly(butylene terephthalate) (PBT)/poly(ethylene terephthalate) (PET) (40/60 wt%) blends were obtained by melting with Glycidyl methacrylate grafted poly(ethylene octane) copolymer (POE-g-GMA), varying the POE-g-GMA content up to 20 wt%, in a twin-screw extruder, followed by injection molding. The influence of POE-g-GMA on the properties of the PBT/PET blends was investigated by mechanical testing, Fourier transform infrared (FT-IR) analysis, gel fractions analysis, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and scanning electronic microscopy (SEM). The mechanical testing results indicated that the incorporation of POE-g-GMA led to increases in the notched impact strength and decreases in the tensile strength, flexural strength, and flexural modulus. When POE-g-GMA content reached 20 wt%, the notched impact strength (8.0 kJ m-2) was achieved for the PBT/PET/POE-g-GMA blends. FT-IR results proved that some PBT/PET/POE-g-GMA copolymers were produced, which improved the compatibility between POE-g-GMA and the PBT/PET matrix. The extent of crosslinking was observed by gel fraction measurements. DMA results further testified chain-extending and micro-crosslink reactions occurred between POE-g-GMA and PBT/PET blends. In addition, the reactions induced by POE-g-GMA affected the crystallization behavior of PBT/PET blends obviously, as observed from DSC results. By means of SEM observation of the impact fracture surface morphology, and the discussion of the micro-crosslink reaction process between the epoxide-containing elastomers and PBT/PET matrix, the toughening mechanism was proposed to be taken into account the shear yielding of PBT/PET matrix and cavitation of elastomer particles.

PVDF-based copolymers, terpolymers and their multi-component material systems for capacitor applications

Science.gov (United States)

Chu, Baojin

at 1 kHz at room temperature), were further investigated for dielectric materials of high energy density. Due to the lower dielectric constant, the early polarization saturation was avoided and these polymers showed a very high breakdown field and energy density. For the P(VDF-CTFE) copolymer with 15 wt% CTFE, an energy density of higher than 24 J/cm 3 at an electric field higher than 650 MV/m could be obtained. Based on thermal and microstructure studies, the high energy density was found to be caused by the structural modification of PVDF by bulky CTFE or HFP, which also act as defects, similar to the terpolymers. The discharge behavior of the copolymers mainly relies on the load resistors, suggesting that the copolymers have lower equivalent series resistance. Multi-component material system based on current available materials was found to be a useful strategy to tailor and improve the performance of dielectric materials. Nanocomposites composed of the P(VDF-TrFE-CFE) terpolymers and ZrO2 or TiO2 nanoparticles were found to greatly enhance the polarization response and energy density of terpolymers (from 9 J/cm3 to 10.5 J/cm3). Based on comprehensive thermal, dielectric and microstructure studies, the enhancement was believed to be related to the large amount of interfaces in the nanocomposites. In the interfaces, the chain mobility is increased and the energy barrier between the polar and nonpolar phases is reduced, resulting in higher polarization response and energy density at a reduced electric field. The P(VDF-TrFE-CFE) terpolymer/P(VDF-CTFE) copolymer and the P(VDFTrFE-CFE) terpolymer/PMMA blends were also studied. It was found that the P(VDFTrFE-CFE) terpolymers could not be completely miscible with the P(VDF-CTFE) copolymer. In the P(VDF-TrFE-CFE) terpolymer/P(VDF-CTFE) copolymer blends, with a small amount of the copolymer (5 and 10 wt%) in the terpolymer, enhancement of the polarization response similar to that observed in the terpolymer/ZrO 2

Multi-template synthesis of hierarchically porous carbon spheres with potential application in supercapacitors

NARCIS (Netherlands)

Zhou, Weizheng; Lin, Zhixing; Tong, Gangsheng; Stoyanov, Simeon D.; Yan, Deyue; Mai, Yiyong; Zhu, Xinyuan

2016-01-01

A new and simple multi-template approach towards hierarchical porous carbon (HPC) materials was reported. HPC spheres were prepared by using hierarchical silica capsules (HSCs) as the hard template and triblock copolymer Pluronic P123 as the soft template. Three types of pores were tunably

Morphology and properties of SEBS block copolymer compatibilized PS/HDPE blends

Czech Academy of Sciences Publication Activity Database

Rek, V.; Vranješ, N.; Šlouf, Miroslav; Fortelný, Ivan; Jelčic, Ž.

2008-01-01

Roč. 40, č. 3 (2008), s. 237-251 ISSN 0095-2443 Grant - others:Ministry of Science, Education and Sport (HR) 0125059 Institutional research plan: CEZ:AV0Z40500505 Keywords : aPS/HDPE/SEBS blends * morphology * processing * rheological Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.658, year: 2008

Enhancement of conductivity in polyaniline-[poly(vinylidene chloride)-co-(vinyl acetate)] blends by irradiation

International Nuclear Information System (INIS)

Bodugoez-Sentuerk, Hatice; Gueven, Olgun

2011-01-01

In this study we have prepared conductive poly(aniline), (PANI) blends with poly(vinylidene chloride-co-vinyl acetate), [P(VDC-co-VAc)] copolymer with varying compositions using gamma radiation to induce conductivity. A number of blends with different compositions were prepared by solution casting followed by irradiation in a 60 Co gamma cell to different doses up to 800 kGy. Electrical conductivity of the blends was measured before and after irradiation using a four-probe technique. Increasing radiation dose resulted in an increase of 9 orders of magnitude in the conductivity of P(VDC-co-VAc)/(PANI) films reaching 0.1 S/cm at 500 kGy and beyond this dose a decrease was observed. Effect of film thickness on conductivity of the blends was investigated and a slight increase of an order of magnitude was observed on increasing the film thickness from 50 to 200 μm. It was also observed that PANI blends exhibited a stretch dependent small increase in conductivity. The conductivity of the irradiated films was found to be stable for up to 12 months under ambient conditions.

Development of Radiation Processed Nano-Composite Blends and Nano-Coatings for Industrial Applications

International Nuclear Information System (INIS)

Dubey, K.A.; Kumar, Virendra; Bhardwaj, Yatender; Chaudhari, Chandrasekhar; Sarma, K.S.S.; Khader, Sheikh Abdul; Acharya, Satyanarayan

2011-01-01

Radiation processing of nanoparticle-filled polymer blends and coatings is expected to synergize the benefits of radiation processing and the flexibility of achieving various property combinations. High energy radiation can be utilized in a variety of ways to modify these systems. It can be used to crosslink the matrix, to compatibilize the blend components, to synthesize graft copolymer based compatibilizers, to improve interfacial bonding between the nanofiller/polymers or to freeze the morphology. Properties like flame retardency, permeability, abrasion resistance, biocompatibility and antibacterial activity can also be significantly affected by this composite approach. Due to the variety and quality of the product it promises, radiation processing of these mixed systems has been our core interest in the last few years. In the report, some of results on the radiation processing of SBR/EPDM blends and SBR/EPDM/MWNT nanocomposites are presented. (author)

Development and characterization of biodegradable polymer blends - PHBV/PCL irradiated with gamma rays

International Nuclear Information System (INIS)

Rosario, F.; Casarin, S.A.; Agnelli, J.A.M.; Souza Junior, O.F. de

2010-01-01

This paper presents the results of a study that aimed to develop PHBV biodegradable polymer blends, in a major concentration with PCL, irradiate the pure polymers and blends in two doses of gamma radiation and to analyze the changes in chemical and mechanical properties. The blends used in this study were from natural biodegradable copolymer poly (hydroxybutyrate-valerate) (PHBV) and synthetic biodegradable polymer poly (caprolactone) (PCL 2201) with low molar mass (2,000 g/mol). Several samples were prepared in a co-rotating twin-screw extruder and afterwards, the tensile specimens were injected for the irradiation treatment with 50 kGy to 100 kGy doses and for the mechanical tests. The characterization of the samples before and after the irradiation treatments was performed through scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC) and mechanical tensile tests. (author)

Development of Radiation Processed Nano-Composite Blends and Nano-Coatings for Industrial Applications

Energy Technology Data Exchange (ETDEWEB)

Dubey, K. A.; Kumar, Virendra; Bhardwaj, Yatender; Chaudhari, Chandrasekhar; Sarma, K. S.S.; Khader, Sheikh Abdul; Acharya, Satyanarayan [Bhabha Atomic Research Centre, Trombay, Mumbai (India)

2011-07-01

Radiation processing of nanoparticle-filled polymer blends and coatings is expected to synergize the benefits of radiation processing and the flexibility of achieving various property combinations. High energy radiation can be utilized in a variety of ways to modify these systems. It can be used to crosslink the matrix, to compatibilize the blend components, to synthesize graft copolymer based compatibilizers, to improve interfacial bonding between the nanofiller/polymers or to freeze the morphology. Properties like flame retardency, permeability, abrasion resistance, biocompatibility and antibacterial activity can also be significantly affected by this composite approach. Due to the variety and quality of the product it promises, radiation processing of these mixed systems has been our core interest in the last few years. In the report, some of results on the radiation processing of SBR/EPDM blends and SBR/EPDM/MWNT nanocomposites are presented. (author)

Preparation and characterization of composites based on the blends of collagen, chitosan and hyaluronic acid with nano-hydroxyapatite.

Science.gov (United States)

Sionkowska, Alina; Kaczmarek, Beata

2017-09-01

3D porous composites based on the blend of chitosan, collagen and hyaluronic acid with the addition of nano-hydroxyapatite were prepared. SEM images for the composites were made and the structure was assessed. Mechanical properties were studied using a Zwick&Roell Testing Mashine. In addition, the porosity and density of composites were measured. The concentration of calcium ions released from the material was detected by the complexometric titration method. The results showed that in 3D porous sponge based on the blend of chitosan, collagen and hyaluronic acid, inorganic particles of nanohydroxyapatite can be incorporated, as well as that the properties of 3D composites depend on the material composition. Mechanical parameters and thermal stability of ternary biopolymeric blends were improved by the addition of hydroxyapatite. Moreover, the porosity of ternary materials was higher than in materials based on pure chitosan or collagen. All composites were characterized by a porous structure with interconnected pores. Calcium ions can be released from the composite during its degradation in water. Copyright © 2017 Elsevier B.V. All rights reserved.

Funding initiates production of tunable nano-porous block copolymer membranes

KAUST Repository

Peinemann, Klaus-Viktor

2013-06-01

Researchers in Saudi Arabia at King Abdullah University of Science & Technology have created a membrane comprising a thin layer of densely packed, highly ordered cylindrical channels with uniform pore sizes - oriented perpendicular to its surface - on top of a non-ordered sponge-like layer. It is fabricated in a fast, one-step process by combining the self-assembly of an amphiphilic block copolymer (PS- b-P4VP) with non-solvent-induced phase separation. The university\\'s "Seed Fund" has helped the researchers to start manufacturing this membrane, which is particularly suited to size-selective and charge-based separation of bio-molecules. © 2013 Elsevier Ltd.

Synthesis and characterization of biocompatible multicomponent polymer systems as supports for cell cultures

International Nuclear Information System (INIS)

Porjazoska, Aleksandra; Cvetkovska, Maja; Yylmaz, Oksan Karal; Baysal, Kemal; Apohan, Nilhan Kayaman; Baysal, Bahattin M.

2004-01-01

Engineering living tissue for reconstructive surgery requires an appropriate cell source and optimal culture conditions, but also a suitable biodegradable scaffold as the basic elements. On the basis of the well known facts that scaffold chemistry and architecture can influence the fate and function of engrafted cells, a large number of polymers, as cell cultures supports, have been proposed. In this study, we report a synthesis, characterization and cell interactions with the following polymer systems: I. Poly[L- lactic acid / glycolic acid / poly(dimethylsiloxane)], copolymers; II. Poly(DL - lactic acid) / triblock PCL - PDMS - PCL copolymers; III. Blends of poly(DL - lactic - co - glycolic acid) and triblock PCL - PDMS - PCL copolymers. For the cell seeding experiments, Swiss 3T3 and/or L929 mouse fibroblasts were grown in RPMI 1640 and/or DMEM / F12 medium, and placed onto the bio polymer non porous or porous films, prepared using a particulate leaching technique. The amount of cells present on the surfaces of the scaffolds was quantified using a neutral red uptake assay. (Author)

Characterization and some properties of cellulose acetate-co-polyethylene oxide blends prepared by the use of gamma irradiation

Directory of Open Access Journals (Sweden)

H. Kamal

2014-04-01

Full Text Available Cellulose acetate (CA, polyethylene oxide (PEO copolymer blend was prepared using γ-rays as initiator. PEO as an additive was added with different concentrations (0 – 5% based on cellulose acetate. As the PEO is water soluble, some portions of them were extracted into aqueous solution. To overcome this, the PEO additives were crosslinked with N,N′Methylene bis-acrylamide (MBAAm to be stably entrapped in the CA matrix. The efficiency was calculated to be 100%. Morphological changes using scanning electron microscope (SEM and the bulk properties such as water sorption, electrical conductivity, and chemical stability were investigated. The thermal stability of the developed copolymer blend has also been studied using thermogravimetric analysis (TGA, and differential scanning calorimeter (DSC. Different variations of the copolymerization were studied such as crosslinker concentration and ratio of PEO to cellulose acetate. It was observed that the addition of small amounts of PEO 3 weight % as an additive resulted in a considerable change of the thermal characteristics.

Gradient Architecture as Means of Phase Diagram Manipulation in Copolymers: Accessing Both LCOT and UCOT in High Molecular Weight Styrene/n-Butyl Acrylate Systems

Science.gov (United States)

Mok, Michelle; Burghardt, Wesley; Ellison, Christopher; Torkelson, John

2009-03-01

Traditionally, phase transitions of block copolymers could only be tuned through molecular weight and relative block length. Here, we introduce comonomer sequence design through gradient compositions as a means of further manipulating phase diagram boundaries. In such gradient copolymers, the reduced repulsion between chain segments allows access to phase transitions even at high molecular weights (MW). Rheological and x-ray scattering studies were performed to study the impact of comonomer sequence on phase behavior in styrene/n-butyl acrylate (S/nBA) systems. In S/nBA block copolymers, only upper critical ordering behavior was observed. In contrast, by using a gradient architecture of higher MW we observed both upper and lower ordering transitions similar to those seen in very weakly segregating S/n-butyl methacrylate block copolymers, where such dual ordering transitions were first detected by Russell et al. This is the first study to access a miscibility gap in gradient copolymers. Access to such behavior is very rare in blends and block copolymers, limited to low MW and/or very weakly segregating systems.

Preparation of PVDF porous membranes by using PVDF-g-PVP powder as an additive and their antifouling property

International Nuclear Information System (INIS)

Xu, Chenqi; Huang, Wei; Lu, Xin; Yan, Deyue; Chen, Shutao; Huang, Hua

2012-01-01

The hydrophilic PVDF-g-PVP powder was used as additive to prepare a series of PVDF/PVDF-g-PVP blend porous membranes via an immersion precipitation phase inversion process. FTIR-ATR measurements confirmed that the hydrophilic PVP preferentially segregated to the interface between membrane and coagulant. SEM images showed that there was no big change in the membrane cross-section with the amount of PVDF-g-PVP increased. However, the membrane surface roughness increased with the amount of PVDF-g-PVP increased according to AFM data. The mean pore size of membranes reached max when the amount of PVDF-g-PVP was 10 wt%. The water contact angle and filtration experiments revealed that the surface enrichment of PVP endowed the membranes with significantly enhanced surface hydrophilicity and protein-adsorption resistance. The flux recovery of the porous membranes was increased from 37.50% to 77.23% with the amount of PVDF-g-PVP increased from 0 to 50 wt%, also indicating that the antifouling property of the porous membranes was improved. - Highlights: ► The hydrophilic PVDF-g-PVP powder is used as additive to prepare PVDF/PVDF-g-PVP blend porous membranes. ► The immersion precipitation phase inversion process is adopted to prepare the blend membranes. ► The hydrophilicity of the porous membranes surface is enhanced with increasing the amount of PVDF-g-PVP. ► The pure water flux of the porous membranes depends on the amount of PVDF-g-PVP in the porous membranes. ► Antifouling property of the porous membranes is improved obviously comparing with a pristine PVDF membrane.

A Self-Propagating Foaming Process of Porous Al-Ni Intermetallics Assisted by Combustion Reactions

Directory of Open Access Journals (Sweden)

Makoto Kobashi

2009-12-01

Full Text Available The self-propagating foaming process of porous Al-Ni intermetallics was investigated. Aluminum and nickel powders were blended, and titanium and boron carbide powders were added as reactive exothermic agents. The blended powder was extruded to make a rod-shape precursor. Only one end of the rod precursor was heated to ignite the reaction. The reaction propagated spontaneously throughout the precursor. Pore formation took place at the same time as the reaction occurred. Adding the exothermic agent was effective to increase the porosity. Preheating the precursor before the ignition was also very effective to produce porous Al-Ni intermetallics with high porosity.

Degradable polyphosphazene/poly(alpha-hydroxyester) blends: degradation studies.

Science.gov (United States)

Ambrosio, Archel M A; Allcock, Harry R; Katti, Dhirendra S; Laurencin, Cato T

2002-04-01

Biomaterials based on the polymers of lactic acid and glycolic acid and their copolymers are used or studied extensively as implantable devices for drug delivery, tissue engineering and other biomedical applications. Although these polymers have shown good biocompatibility, concerns have been raised regarding their acidic degradation products, which have important implications for long-term implantable systems. Therefore, we have designed a novel biodegradable polyphosphazene/poly(alpha-hydroxyester) blend whose degradation products are less acidic than those of the poly(alpha-hydroxyester) alone. In this study, the degradation characteristics of a blend of poly(lactide-co-glycolide) (50:50 PLAGA) and poly[(50% ethyl glycinato)(50% p-methylphenoxy) phosphazene] (PPHOS-EG50) were qualitatively and quantitatively determined with comparisons made to the parent polymers. Circular matrices (14mm diameter) of the PLAGA, PPHOS-EG50 and PLAGA-PPHOS-EG50 blend were degraded in non-buffered solutions (pH 7.4). The degraded polymers were characterized for percentage mass loss and molecular weight and the degradation medium was characterized for acid released in non-buffered solutions. The amounts of neutralizing base necessary to bring about neutral pH were measured for each polymer or polymer blend during degradation. The poly(phosphazene)/poly(lactide-co-glycolide) blend required significantly less neutralizing base in order to bring about neutral solution pH during the degradation period studied. The results indicated that the blend degraded at a rate intermediate to that of the parent polymers and that the degradation products of the polyphosphazene neutralized the acidic degradation products of PLAGA. Thus, results from these in vitro degradation studies suggest that the PLAGA-PPHOS-EG50 blend may provide a viable improvement to biomaterials based on acid-releasing organic polymers.

Tunable Surface Properties of a Conductive PEDOT/EVAL blend

DEFF Research Database (Denmark)

Pizzi, Elisa; Martinelli, Andrea; D'Ilario, Lucio

Conductive polymers have been studied extensively during recent years. Especially,poly(3,4-ethylenedioxythiophene) (PEDOT) have found many application areas and arebroadly considered one of the most promising conductive polymers. In order to broadenthe application field of PEDOT we have developed...... an azide functional poly(3,4-ethylenedioxythiophene) (PEDOT-N3)1. The azide functional conductive polymer canbe postpolymerization functionalized to introduce a large range of molecules onto theconductive backbone through click chemistry2.Here we present a study of the incorporation of poly......(ethylene-co-vinyl alcohol) (EVAL)into a copolymer of EDOT and EDOT-N3 (poly(EDOT-co-EDOT-N3)). Poly(ethyleneco-vinyl alcohol) (EVAL) is known to swell in polar solvents, which was exploited inthis study to permit a good blending of the two polymers. Since both polymers haveresidual functional groups the polymer blend...

Flash nano-precipitation of polymer blends: a role for fluid flow?

Science.gov (United States)

Grundy, Lorena; Mason, Lachlan; Chergui, Jalel; Juric, Damir; Craster, Richard V.; Lee, Victoria; Prudhomme, Robert; Priestley, Rodney; Matar, Omar K.

2017-11-01

Porous structures can be formed by the controlled precipitation of polymer blends; ranging from porous matrices, with applications in membrane filtration, to porous nano-particles, with applications in catalysis, targeted drug delivery and emulsion stabilisation. Under a diffusive exchange of solvent for non-solvent, prevailing conditions favour the decomposition of polymer blends into multiple phases. Interestingly, dynamic structures can be `trapped' via vitrification prior to thermodynamic equilibrium. A promising mechanism for large-scale polymer processing is flash nano-precipitation (FNP). FNP particle formation has recently been modelled using spinodal decomposition theory, however the influence of fluid flow on structure formation is yet to be clarified. In this study, we couple a Navier-Stokes equation to a Cahn-Hilliard model of spinodal decomposition. The framework is implemented using Code BLUE, a massively scalable fluid dynamics solver, and applied to flows within confined impinging jet mixers. The present method is valid for a wide range of mixing timescales spanning FNP and conventional immersion precipitation processes. Results aid in the fabrication of nano-scale polymer particles with tuneable internal porosities. EPSRC, UK, MEMPHIS program Grant (EP/K003976/1), RAEng Research Chair (OKM), PETRONAS.

Thermally stable sintered porous metal articles

International Nuclear Information System (INIS)

Gombach, A.L.; Thellmann, E.L.

1980-01-01

A sintered porous metal article is provided which is essentially thermally stable at elevated temperatures. In addition, a method for producing such an article is also provided which method comprises preparing a blend of base metal particles and active dispersoid particles, forming the mixture into an article of the desired shape, and heating the so-formed article at sintering temperatures

Melting and crystallization behavior of partially miscible high density polyethylene/ethylene vinyl acetate copolymer (HDPE/EVA) blends

Energy Technology Data Exchange (ETDEWEB)

Chen, Yang; Zou, Huawei, E-mail: hwzou@163.com; Liang, Mei, E-mail: liangmeiww@163.com; Cao, Ya

2014-06-01

Highlights: • HDPE/EVA blends undergo phase separation, making it an interesting topic to investigate the relationships between miscibility and crystallization. • Influences from blending on the crystallization kinetics were successfully evaluated by Friedman's and Khanna's method. • X-ray diffraction studies revealed that blending with EVA the unit length of the unit cell of the HDPE increases. • Thermal fractionation method was successfully used to characterize the co-crystallization in HDPE/EVA blends. - Abstract: Crystallization studies on HDPE/EVA blends and the individual components were performed with differential scanning calorimetry (DSC) technique and wide angle X-ray scattering (WAXS). Influences of blending on the crystallization kinetics of each component in HDPE/EVA mixture were evaluated by Friedman's activation energy and Khanna's crystallization rate coefficient (CRC). The addition of more HDPE into the EVA matrix causes more heterogeneous nucleation while the addition of EVA would hinder the nucleation of HDPE at the beginning of cooling process. Inter-molecular interaction in the melt facilitated the crystallization of both EVA and HDPE components. X-ray diffraction studies revealed that HDPE and EVA have orthorhombic unit cell. Blending with EVA did not affect the crystalline structure of HDPE. In addition, a little shift of (1 1 0), (2 0 0) and (0 2 0) crystalline peaks toward lower 2θ values of samples indicating a little increase of unit cell parameters of the orthorhombic unit cell of polyethylene. Thermal fractionation results showed that co-crystallization took place in the HDPE/EVA blend. All those results indicated that the polymer pair we choose was partially miscible.

Radiation effect of ethylene/vinyl alcohol copolymer

International Nuclear Information System (INIS)

Liu Meihua; Jilin Univ., Changchun; Deng Pengyang; Sun Jiazhen; Dong Lisong; Sun Guoen; Zhang Wanxi

2006-01-01

The radiation effect of ethylene-vinyl alcohol copolymer (EVOH), EVOH/glycerin blend was studied by solvent extraction, gel permeation chromatography (GPC) and Fourier transform infrared spectrum (FTIR) methods. Samples were irradiated up to 1800 kGy at room temperature under N 2 . The results show that degradation is the main reaction in pure EVOH. Trace gel content could be found in E151 irradiated to at least 800 kGy, and only 5.9% gel content was found in the sample irradiated to 1200 kGy. While trace gel content could be found in F101 irradiated to at least 1800 kGy, the different gelation doses of E151 and F101 are due to different contents of vinyl alcohol units. Unsaturation structure can be found in the irradiated EVOH. The content increased at first, and then decreased, with the dose. The existence of double bond enhances the radiation efficiency of EVOH. For EVOH/glycerin blend, the gel content was higher than that of pure EVOH when the absorbed dose exceeds 800 kGy, and the gel content increased with the absorbed dose. But it cannot enhance radiation efficiency of EVOH as water. (authors)

Effect of annealing and UV-radiation time over micropore architecture of self-assembled block copolymer thin film

Directory of Open Access Journals (Sweden)

G. del C. Pizarro

2015-06-01

Full Text Available Block copolymers have been recognized as versatile materials to prepare nanoporous polymer films or membranes, but their potential has not been completely explored. This study focuses on the formation and characterization of nanoporous polymer films based on poly(styrene-block-(methylmethacrylate/methacrylic acid; (PS-b-MMA/MAA were obtained through atom transfer radical polymerization (ATRP, by using two different protocols: annealing and annealingirradiation; for improving the formation of microporous surface. The composition, crystallinity and structural order of the films were studied by Raman spectroscopy. The film polymer thickness was obtained through very high resolution ellipsometry (VHRE. Finally, atomic force microcopy (AFM and scanning electron microscopy (SEM techniques were used to detect changes in the porous-structure. These results show that the morphological properties of the block copolymer were affected via the modification of two variables, UV-radiation time and annealing. SEM and AFM micrographs showed that the morphology exhibit a porous ordered structure. Contact angle measurement suggests additional interactions between hydrophilic functional groups that influence the film wettability.

Copolymers of various architectures containing ethylene and 5-norbornen-2-yl derivatives

Science.gov (United States)

Diamanti, Steve Jon

Polyolefins are a class of materials with enormous economic impact. Tailoring of polyolefin bulk properties by synthetic control is a major focus of many industrial and academic research groups. Polar functionalities within the hydrophobic polyolefin backbone can change important properties, such as, toughness, adhesion, solvent resistance, blend compatibility with other functional polymers, and rheological properties. Functional polyolefin materials with block or graft architectures are the most desirable structures as the pure polyolefin block maintains its intrinsic properties. Our initial work elucidated a neutral nickel based catalyst system capable of catalyzing the "quasi-living" homopolymerization of ethylene and the "quasi-living" copolymerization of ethylene with 5-norbornen-2-yl acetate (NBA), a polar comonomer. Through testing the effect of several reaction variables on the copolymerization of ethylene with NBA it was found that changing ethylene pressure causes a large change in the content of NBA in the copolymer chain. This change in NBA content, in turn, drastically affects the physical and thermal properties of these polymers. Understanding the impact of such reaction variables on copolymer properties made it possible to design more sophisticated architectures. This catalytic system has since been used to synthesize block copolymers and tapered block copolymers of ethylene and NBA. Block copolymers of ethylene and NBA have been synthesized by a method utilizing ethylene pressure variation to create two distinct copolymeric blocks that are able to order into microphase-separated structures. The block structure of these materials has been proven by 1H-NMR spectroscopy, thermal analysis, GPC, AFM, and TEM. The synthesis, characterization, and bulk and thermal properties of tapered block copolymers containing ethylene and NBA, has also been performed. The final structure of the tapered block polymer is a polar amorphous chain (rich in NBA) on one

Fabrication of tissue engineering scaffolds through solid-state foaming of immiscible polymer blends

International Nuclear Information System (INIS)

Zhou Changchun; Li Wei; Ma Liang; Yao Donggang

2011-01-01

In scaffold-based tissue engineering, the fabrication process is important for producing suitable microstructures for seeded cells to grow and reformulate. In this paper, we present a new approach to scaffold fabrication by combining the solid-state foaming and the immiscible polymer-blending method. The proposed approach has the advantage of being versatile and able to create a wide range of pore size and porosity. The proposed method is studied with polylactic acid (PLA) and polystyrene (PS) blends. The interconnected porous structure was created by first foaming the PLA/PS blend and then extracting the PS phase. The solid-state foaming experiments were conducted under various conditions to achieve the desired pore sizes. It is shown that the PS phase of the PLA/PS blend can be extracted much faster in the foamed samples and the pore size of the scaffolds can be easily controlled with proper gas foaming parameters. The average pore size achieved in the foaming process ranged from 20 to 70 μm. After PS extraction, both pore size and porosity can be further improved. For example, the pore size and porosity increased from 48 μm and 49% to 59 μm and 67%, respectively, after the PS extraction process. The fabricated porous scaffolds were used to culture human osteoblast cells. Cells grew well and gradually formed a fibrous structure. The combined solid-state foaming and immiscible polymer blending method provides a new technique for fabricating tissue-engineering scaffolds.

Enchansing the Ionic Purity of Hydrophilic Channels by Blending Fully Sulfonated Graft Copolymers with PVDF Homopolymer

DEFF Research Database (Denmark)

Nielsen, Mads Møller; Ching-Ching Yang, Ami; Jankova Atanasova, Katja

2013-01-01

The influence of tuning the ionic content of membranes by blending, as opposed to varying the degree of sulfonation, is evaluated. Membranes of fully sulfonated poly(vinylidene fluoride-co-chlorotrifluoroethylene)-g-poly(styrene sulfonic acid) blended with PVDF were prepared and investigated...

Preparation and performances of porous polyacrylonitrile-methyl methacrylate membrane for lithium-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Zhou, D.Y.; Wang, G.Z.; Tan, C.L.; Rao, M.M.; Liao, Y.H. [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Li, W.S.; Li, G.L. [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Key Lab of Technology on Electrochemical Energy Storage and Power Generation in Guangdong Universities, Guangzhou 510006 (China)

2008-10-01

A copolymer, polyacrylonitrile-methyl methacrylate P(AN-MMA), was synthesized by suspension polymerization with acrylonitrile (AN) and methyl methacrylate (MMA) as monomers. With this copolymer, polymer membrane was prepared by phase inversion. The performances of the polymer were characterized by FTIR, SEM, DSC/TG, EIS and LSV. The copolymer contains CH{sub 2}, CN and CO bonds, and shows its thermal stability up to 300 C. The polymer membrane has a porous structure with an average pore diameter of 0.5 {mu}m. The conductivity of the polymer electrolyte is 1.25 mS cm{sup -1} at room temperature, and it is electrochemically stable up to 5 V (vs. Li). Using the polymer electrolyte as the gel polymer electrolyte (GPE), the cell Li/GPE/LiCoO{sub 2} shows its cyclic stability as good as the cell with liquid electrolyte. (author)

Fabrication of gold nanoparticle arrays by block copolymer

Energy Technology Data Exchange (ETDEWEB)

Chen, Xiao Ling

2011-02-15

Gold nanoparticle is one of the widely research objects in various fields including catalysis and biotechnology. Precise control of gold nanoparticles placement and their integration is essential to take full advantage of these unique properties for applications. An approach to self-assembling of gold nanoparticles (AuNPs) from reconstructed block copolymer was introduced. Highly ordered polystyrene-block-poly(2-vinylpyridine)(PS-b-P2VP) micellar arrays were obtained by solvent annealing. Subsequent immersion of the films in a preferential solvent for P2VP caused a reorganization of the film to generate a porous structure upon drying. PEG-coated AuNPs were spin-coated onto this reconstruction PS-b-P2VP template. When such films were exposed to toluene vapor-which is non-selective solvent for PEO and P2VP, AuNPs were drawn into those porous to form ordered arrays. Gold nanospheres with size 12±1.8 nm were synthesized by reducing HAuCl{sub 4} via sodium citrate. Gold nanorods (aspect ratio about 6) were prepared from seed-mediated surfactant capping wet chemical method and the aspect ratio is tunable by changing surfactant amount. PEG ligand is used to modify gold nanoparticle surface by removing the original surfactant (sodium citrate -gold nanospheres: CTAB-gold nanorods), which have affinity with certain block copolymer component. Once gold nanoparticle is modified with PEG thiol, they were spin coated onto PS-b-P2VP template, which was prepared by solvent annealing and surface reconstruction process. So gold nanoparticle array was fabricated by this self-assembling process. The same idea can be applied on other nanoparticles.

Fabrication of gold nanoparticle arrays by block copolymer

International Nuclear Information System (INIS)

Chen, Xiao Ling

2011-02-01

Gold nanoparticle is one of the widely research objects in various fields including catalysis and biotechnology. Precise control of gold nanoparticles placement and their integration is essential to take full advantage of these unique properties for applications. An approach to self-assembling of gold nanoparticles (AuNPs) from reconstructed block copolymer was introduced. Highly ordered polystyrene-block-poly(2-vinylpyridine)(PS-b-P2VP) micellar arrays were obtained by solvent annealing. Subsequent immersion of the films in a preferential solvent for P2VP caused a reorganization of the film to generate a porous structure upon drying. PEG-coated AuNPs were spin-coated onto this reconstruction PS-b-P2VP template. When such films were exposed to toluene vapor-which is non-selective solvent for PEO and P2VP, AuNPs were drawn into those porous to form ordered arrays. Gold nanospheres with size 12±1.8 nm were synthesized by reducing HAuCl 4 via sodium citrate. Gold nanorods (aspect ratio about 6) were prepared from seed-mediated surfactant capping wet chemical method and the aspect ratio is tunable by changing surfactant amount. PEG ligand is used to modify gold nanoparticle surface by removing the original surfactant (sodium citrate -gold nanospheres: CTAB-gold nanorods), which have affinity with certain block copolymer component. Once gold nanoparticle is modified with PEG thiol, they were spin coated onto PS-b-P2VP template, which was prepared by solvent annealing and surface reconstruction process. So gold nanoparticle array was fabricated by this self-assembling process. The same idea can be applied on other nanoparticles

Elucidation of the Structure Formation of Polymer-Conjugated Proteins in Solution and Block Copolymer Templates

Science.gov (United States)

Ferebee, Rachel L.

The broader technical objective of this work is to contribute to the development of enzyme-functionalized nanoporous membranes that can function as autonomous and target selective dynamic separators. The scientific objective of the research performed within this thesis is to elucidate the parameters that control the mixing of proteins in organic host materials and in block copolymers templates in particular. A "biomimetic" membrane system that uses enzymes to selectively neutralize targets and trigger a change in permeability of nanopores lined with a pH-responsive polymer has been fabricated and characterized. Mechanical and functional stability, as well as scalability, have been demonstrated for this system. Additional research has focused on the role of polymeric ligands on the solubility characteristics of the model protein, Bovine Serum Albumin (BSA). For this purpose BSA was conjugated with poly(ethylene glycol) (PEG) ligands of varied degree of polymerization and grafting density. Combined static and dynamic light scattering was used (in conjunction with MALDI-TOF) to determine the second virial coefficient in PBS solutions. At a given mass fraction PEG or average number of grafts, the solubility of BSA-PEG conjugates is found to increase with the degree of polymerization of conjugated PEG. This result informs the synthesis of protein-conjugate systems that are optimized for the fabrication of block copolymer blend materials with maximum protein loading. Blends of BSA-PEG conjugates and block copolymer (BCP) matrices were fabricated to evaluate the dispersion morphology and solubility limits in a model system. Electron microscopy was used to evaluate the changes in lamellar spacing with increased filling fraction of BSA-PEG conjugates.

Comprehensive Study on Thermal and Dynamic Mechanical Behavior of PET/PEN Blends

Directory of Open Access Journals (Sweden)

Hossien Ali Khonakdar

2013-10-01

Full Text Available The effects of interchange reactions on the crystallization, melting, and dynamic mechanical thermal behavior of poly(ethylene terephthalate/poly(ethylene naphthalate (PET/PEN blends prepared by melt mixing have been investigated. The occurrence of interchange reactions has been verified by proton nuclear magnetic resonance (1H NMR. Differential scanning calorimetry (DSC and dynamic mechanical analysis (DMA were used to study the effect of transesterification reaction on crystallinity, melting and dynamic mechanical properties of the blends. It was found that by extension of transesterification, the miscibility of the blend increased. Time and temperature of mixing were most important parameters affecting the transesterification level. On blending, the melt crystallinity of poly(ethylene terephthalate was reduced and in contrast that of poly(ethylene naphthalate was increased; where melt crystallization temperatures of both phases were depressed. A single composition-dependent glass transition peak, which was indicative of miscibility, was detected in second heating thermograms of the blends. It was observed that cold crystallization of poly(ethylene terephthalate phase decreases while that of poly(ethylene naphthalate was suppressed on blending. It was found that each phase crystallized individually and a melting point depression which was an indication of compatibility was evident at the same time. Dynamic mechanical analysis confirmed the proton nuclear magnetic resonance and differential scanning calorimetry results. The secondary viscoelastic transitions of each phase in blend samples were also probed. Increment of peak area in the loss factor has implied the miscibility of blend due to formation of poly(ethylene terephthalate/poly(ethylene naphthalate random copolymer.

In-situ polymerized PLOT columns III: divinylbenzene copolymers and dimethacrylate homopolymers

Science.gov (United States)

Shen, T. C.; Fong, M. M.

1994-01-01

Studies of divinylbenzene copolymers and dimethacrylate homopolymers indicate that the polymer pore size controls the separation of water and ammonia on porous-layer-open-tubular (PLOT) columns. To a lesser degree, the polarity of the polymers also affects the separation of a water-ammonia gas mixture. Our results demonstrate that the pore size can be regulated by controlling the cross-linking density or the chain length between the cross-linking functional groups. An optimum pore size will provide the best separation of water and ammonia.

Tensile and morphology properties of PLA/LNR blends modified with maleic anhydride grafted-polylactic acid and -natural rubber

Science.gov (United States)

Ruf, Mohd Farid Hakim Mohd; Ahmad, Sahrim; Chen, Ruey Shan; Shahdan, Dalila; Zailan, Farrah Diyana

2018-04-01

This research was carried out to investigate the addition of grafted copolymers of maleic anhydride grafted-polylactic acid(PLA-g-MA) and maleic anhydride grafted-natural rubber (NR-g-MA) on the tensile and morphology properties of polylactic acid/ liquid natural rubber (PLA/LNR) blends. Prior to blend preparation, the PLA-g-MA and NR-g-MA was first self-synthesized using maleic anhydride (MA) and dicumyl peroxide (DCP) as initiator together with the PLA and NR respectively. The PLA/LNR, PLA/LNR/PLA-g-MA and PLA/LNR/NR-g-MA blends were prepared via melt-blending method. The loading of PLA-g-MA and NR-g-MA was varied by 5, 10 and 15 wt% respectively. The addition of PLA-g-MA led to increment in tensile strength with 5 and 10 wt% while NR-g-MA gives lower than controlled sample (PLA/LNR blend). Scanning electron microscope (SEM) showed the interaction of the components in the blends. The PLA/LNR compatibilized with PLA-g-MA and NR-g-MA shows greater dispersion and adhesion.

Efficient polymer white-light-emitting diodes with a single-emission layer of fluorescent polymer blend

International Nuclear Information System (INIS)

Niu Qiaoli; Xu Yunhua; Jiang Jiaxing; Peng Junbiao; Cao Yong

2007-01-01

Efficient polymer white-light-emitting diodes (WPLEDs) have been fabricated with a single layer of fluorescent polymer blend. The device structure consists of ITO/PEDOT/PVK/emissive layer/Ba/Al. The emissive layer is a blend of poly(9,9-dioctylfluorene) (PFO), phenyl-substituted PPV derivative (P-PPV) and a copolymer of 9,9-dioctylfluorene and 4,7-di(4-hexylthien-2-yl)-2,1,3-benzothiadiazole (PFO-DHTBT), which, respectively, emits blue, green and red light. The emission of pure and efficient white light was implemented by tuning the blend weight ratio of PFO: P-PPV: PFO-DHTBT to 96:4:0.4. The maximum current efficiency and luminance are, respectively, 7.6 cd/A at 6.7 V and 11930 cd/m 2 at 11.2 V. The CIE coordinates of white-light emission were stable with the drive voltages

Review on PCL, PBS, and PCL/PBS blends containing carbon nanotubes

Directory of Open Access Journals (Sweden)

T. P. Gumede

2018-06-01

Full Text Available Biodegradable polymers received considerable attention due to their contribution in the reduction of environmental concerns and the realization that global petroleum resources are finite. The development of double crystalline biobased blends such as poly(ε-caprolactone (PCL and poly(butylene succinate (PBS are particularly interesting because each component has an influence on the crystallization behaviour of the other component, and thus influences the strength and mechanical properties of a polymer blend. The lack of miscibility between PCL and PBS constitutes a bottleneck, and efforts have been made to improve the miscibility through the inclusion of copolymers. Having realized that incorporating conductive nanofillers such as carbon nanotubes (CNTs, (especially when the CNTs are functionalized or used as a masterbatch i.e., polycarbonate/MWCNTs masterbatch, into biopolymer matrices, can enhance the thermal and mechanical properties, as well as electrical and thermal conductivity, a lot of research was aimed at the production of bionanocomposites. This review paper discusses the properties of PCL, PBS, their blends, and their CNTs containing nanocomposites.

Mechanical, thermal and morphological properties of poly(lactic acid)/ethylene-butyl acrylate copolymer nanocomposites

Science.gov (United States)

Wacharawichanant, S.; Hoysang, P.; Ratchawong, S.

2017-07-01

This paper reports a melt blend of poly(lactic acid) (PLA)/ethylene-butyl acrylate copolymer (EBAC) with organoclay content at 3 phr. The mechanical, thermal and morphological properties of PLA/EBAC blends and nanocomposites were investigated. The morphological analysis revealed EBAC phase dispersed as a spherical domain in PLA matrix and the domain size of EBAC dispersed phase increased with increasing EBAC content. The addition of organoclay could improve the miscibility of PLA/EBAC blends due to the decrease of domain size of EBAC dispersed phase. The mechanical properties indicated that the strain at break and impact strength of PLA increased when added EBAC, but Young’s modulus and tensile strength decreased. Storage modulus increased with the addition of organoclay to the PLA/EBAC blends. The thermal properties found that the incorporation of organoclay in the PLA/EBAC blends did not effect on the glass transition temperature and melting temperature values relative to PLA. The degradation temperature of PLA improved with the addition of EBAC. This indicated that EBAC has more thermal stability and degradation temperature than PLA. From X-ray diffraction patterns displayed the characteristic peak in PLA/EBAC/organoclay nanocomposites appeared at the lower angle, which indicated the dispersed clay is intercalated in the polymer matrix. However, second-order diffraction peak appeared at the higher angle indicated that there was partially the conventional composite.

Ultrafine-grained porous titanium and porous titanium/magnesium composites fabricated by space holder-enabled severe plastic deformation

Energy Technology Data Exchange (ETDEWEB)

Qi, Yuanshen, E-mail: yuanshen.qi@monash.edu [Centre for Advanced Hybrid Materials, Department of Materials Engineering, Monash University, Clayton, Victoria 3800 (Australia); Contreras, Karla G. [Monash Institute of Medical Engineering, Faculty of Engineering, Monash University, Clayton, Victoria 3800 (Australia); Jung, Hyun-Do [Liquid Processing & Casting Technology R& D Group, Korea Institute of Industrial Technology, Incheon 406-840 (Korea, Republic of); Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Kim, Hyoun-Ee [Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Advanced Institutes of Convergence Technology, Seoul National University, Gwanggyo, Yeongtong-gu, Suwon-si, Gyeonggi-do 443-270 (Korea, Republic of); Lapovok, Rimma [Centre for Advanced Hybrid Materials, Department of Materials Engineering, Monash University, Clayton, Victoria 3800 (Australia); Estrin, Yuri, E-mail: yuri.estrin@monash.edu [Centre for Advanced Hybrid Materials, Department of Materials Engineering, Monash University, Clayton, Victoria 3800 (Australia); Laboratory of Hybrid Nanostructured Materials, NUST MISiS, Moscow 119490 (Russian Federation)

2016-02-01

Compaction of powders by equal channel angular pressing (ECAP) using a novel space holder method was employed to fabricate metallic scaffolds with tuneable porosity. Porous Ti and Ti/Mg composites with 60% and 50% percolating porosity were fabricated using powder blends with two kinds of sacrificial space holders. The high compressive strength and good ductility of porous Ti and porous Ti/Mg obtained in this way are believed to be associated with the ultrafine grain structure of the pore walls. To understand this, a detailed electron microscopy investigation was employed to analyse the interface between Ti/Ti and Ti/Mg particles, the grain structures in Ti particles and the topography of pore surfaces. It was found that using the proposed compaction method, high quality bonding between particles was obtained. Comparing with other powder metallurgy methods to fabricate Ti with an open porous structure, where thermal energy supplied by a laser beam or high temperature sintering is essential, the ECAP process conducted at a relatively low temperature of 400 °C was shown to produce unique properties. - Highlights: • Porous Ti and porous Ti/Mg composite scaffolds were fabricated successfully. • Space holder-enabled severe plastic deformation was first used in this application. • Silicon particles as sacrificial space holders were used for the first time. • Ultrafine-grained microstructure and good bonding between particles were obtained. • Good preosteoblast cell response to as-manufactured porous Ti was achieved.

Silicon containing copolymers

CERN Document Server

Amiri, Sahar; Amiri, Sanam

2014-01-01

Silicones have unique properties including thermal oxidative stability, low temperature flow, high compressibility, low surface tension, hydrophobicity and electric properties. These special properties have encouraged the exploration of alternative synthetic routes of well defined controlled microstructures of silicone copolymers, the subject of this Springer Brief. The authors explore the synthesis and characterization of notable block copolymers. Recent advances in controlled radical polymerization techniques leading to the facile synthesis of well-defined silicon based thermo reversible block copolymers?are described along with atom transfer radical polymerization (ATRP), a technique utilized to develop well-defined functional thermo reversible block copolymers. The brief also focuses on Polyrotaxanes and their great potential as stimulus-responsive materials which produce poly (dimethyl siloxane) (PDMS) based thermo reversible block copolymers.

Fabrication of an open Au/nanoporous film by water-in-oil emulsion-induced block copolymer micelles.

Science.gov (United States)

Koh, Haeng-Deog; Kang, Nam-Goo; Lee, Jae-Suk

2007-12-18

Water-in-oil (W/O) emulsion-induced micelles with narrow size distributions of approximately 140 nm were prepared by sonicating the polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer in the toluene/water (50:1 vol %). The ordered nanoporous block copolymer films with the hydrophilic P2VP interior and the PS matrix were distinctly fabricated by casting the resultant solution on substrates, followed by evaporating the organic solvent and water. The porous diameter was estimated to be about 70 nm. Here, we successfully prepared the open nanoporous nanocomposites, the P2VP domain decorated by Au (5+/-0.4 nm) nanoparticles based on the methodology mentioned. We anticipate that this novelty enhances the specific function of nanoporous films.

Phase behavior of diblock copolymer/star-shaped polymer thin film mixtures.

Science.gov (United States)

Zhao, Junnan; Sakellariou, Georgios; Green, Peter F

2016-05-07

We investigated the phase behavior of thin film, thickness h≈ 100 nm, mixtures of a polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer with star-shaped polystyrene (SPS) molecules of varying functionalities f, where 4 ≤f≤ 64, and molecular weights per arm Marm. The miscibility of the system and the surface composition varied appreciably with Marm and f. For large values of Marm, regardless of f, the miscibility of the system was qualitatively similar to that of linear chain PS/PS-b-P2VP mixtures - the copolymer chains aggregate to form micelles, each composed of an inner P2VP core and PS corona, which preferentially segregate to the free surface. On the other hand, for large f and small Marm, SPS molecules preferentially resided at the free surface. Moreover, blends containing SPS molecules with the highest values of f and lowest values of Marm were phase separated. These observations are rationalized in terms of competing entropic interactions and the dependence of the surface tension of the star-shaped molecules on Marm and f.

Modification of Carboxymethyl Chitosan Film by Blending with Poly(benzyl L-glutamate)-block-poly(ethylene glycol) Copolymer

International Nuclear Information System (INIS)

Zhu, G.Z.; Gao, Q.C.; Liu, Y.Y.

2013-01-01

A series of water-soluble carboxymethyl chitosan (CMCS)/poly(benzyl L-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) blend films with various CMCS/PBLG-b-PEG mol ratios were prepared by pervaporation method. Morphologies of CMCS/PBLG-b-PEG blend films were researched by scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of CMCS/PBLG-b-PEG blend films were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile tests, and contact angle tests. It was revealed that the introduction of PBLG-b-PEG segments could greatly affect the morphology and the properties of CMCS films. (author)

Voltage-stabilised elastomers with increased relative permittivity and high electrical breakdown strength by means of phase separating binary copolymer blends of silicone elastomers

DEFF Research Database (Denmark)

A Razak, Aliff Hisyam; Yu, Liyun; Skov, Anne Ladegaard

2017-01-01

Increased electrical breakdown strength and increased dielectric permittivity of silicone-based dielectric elastomers are achieved by means of the addition of so-called voltage-stabilisers prepared from PDMS–PPMS copolymers as well as PDMS–PEG copolymers in order to compensate for the negative...... effect of softness on electrical stability of silicone elastomers. The voltage-stabilised elastomer, incorporating a high-permittivity PDMS–PEG copolymer, possesses increased relative permittivity, high electrical breakdown strength, excellent network integrity and low dielectric loss and paves the way...

Phase boundary in compatible and incompatible polymer blends studied by micro indentation test and microscopic observations

International Nuclear Information System (INIS)

Mina, M. F.; Akhtar, F.; Haque, M.E.

2003-10-01

The phase boundary of incompatible polymer blends such as poly (methyl methacrylate) (PMMA)/natural rubber (NR) and polyestyrene (PS)/NR as well as compatible blends such as PMMA/NR/epoxidizer NR (compatibilizer) and PS/NR/styrene-butadiene-styrene (SBS) block copolymer (compatibilizer) was studied by means of microhardness (H) technique and microscopy. Solution grown films of neat PMMA, PS and blended films of PMMA/NR, PS/NR, PMMA/NR/ENR and PS/NR/SBS were cast using a common solvent (toluene). While the neat PMMA and PS provide constant hardness values of 178 and 173 MPa, respectively, the binary (incompatible) and the ternary (compatible) blends show a conspicuous H-decrease (PMMA/NR=140 MPa, PS/NR=167 MPa, PMMA/NR/ENR=109 MPa and PS/NR/SBS=127 MPa). Scanning electron microscopy and optical microscopy reveal clear difference of the phase boundary of compatible (smooth boundary) and incompatible (sharp boundary) blends. Besides, the compatibilizer blends are characterised by the thinnest phase boundary (30 μm), which is found about 60 μm in the incompatible blends, showing a final hardness value that demonstrates the compatibilizer to be smoothly distributed in the interface between the two blend components. Results highlight that microindentation technique, in combination with microscopic observations, is a sensitive tool for studying the breadth and quality of the interphase boundary in non- or compatibilized polymer blends and other inhomogeneous materials. (author)

Morphology and mechanical properties of PA12/plasticized starch blends prepared by high-shear extrusion

International Nuclear Information System (INIS)

Teyssandier, F.; Cassagnau, P.; Gérard, J.F.; Mignard, N.; Mélis, F.

2012-01-01

Highlights: ► High shear rate processing was found to greatly impact PA12/starch blend morphologies. ► The morphology was observed to be stable under subsequent processing conditions. ► The mechanical properties of the blends under high-shear rate were greatly improved. ► Polymer blend preparation via high-shear processing has proved to be very effective. ► Finally, polymer blends with improved mechanical properties were obtained. - Abstract: PA12/plasticized starch blends (PA12/TPS) were prepared by high-shear twin screw extruder. The morphology development and the mechanical properties of the blends were investigated as a function of the apparent shear rate. High-shear processing has proved to be an efficient method to finely disperse thermoplastic starch in polyamide 12 matrix. Blends containing TPS domains with a size at the nano-scale (R n ∼ 150 nm) homogeneously dispersed in PA12 matrix were obtained. From a modeling point of view, the variation of the droplet radius is closer to the Wu's predictions compared to the Serpe's predictions. From the basic hypothesis of these models, it can be then assumed that compatibilization between both phases occurs during the blend processing. Furthermore, this morphology of the blends has been proved to be stable after a reprocessing step in an internal mixer most likely due to either strong hydrogen bonds between the hydroxyl groups of starch and amide groups of polyamide 12 or to potentially cross reactions between macroradicals accounting for in situ formation of graft copolymers with the potential function of compatibilizers. Mechanical properties of the blends were found to be strongly dependent on the shear rate parameter of blend processing as the mechanical properties increase with shear rate. In agreement to the blend morphology, the elongation at break of the blends was greatly improved attesting of a good adhesion between both phases.

Potential Application of ENR/EPDM Blends

Directory of Open Access Journals (Sweden)

B.L. Chan

2017-06-01

Full Text Available Since the process and conversion of natural rubber into epoxidized natural rubber (ENR was discovered and patented by I. R. Gelling of the Malaysian Rubber Product Research Association  (or now known as the Tun Razak laboratory, Brickendonbury, Hertford, in the United Kingdom, there are more than 10 000 technical and technological papers cited in the internet. Information on ENR is available, not only in the the English language but also other languages like Chinese, Malay, French, Thai and even German languages are used. NR is the most versatile and reactive rubber/elastomer. It is an advanced natural rubber which could be potentially used as a starting material for the development of other rubbers, modifie elastomers, for grafting, plastic-based materials and also thermoplastic rubbers. Its reactivity is dependent on its epoxy groups, the opening of its ring structure, and also the subsequent structures of carboxylic groups and the in-situ side-chains “carbon – carbon” double bonds (> C = C <. In some instances, up to 65% epoxidation of NR is possible and achieved for more oil resistance. For these reasons, there are many new and advanced materials which have been formed and developed in the last two decades. Among them, some of the recent research work is listed here. Apart from studies of compounding the ENR itself and its potential uses, there are many rubber-rubber blends and ENR rubber-plastics blends, some of the studies cited are “uses of new and advanced chemicals”  and synthetic rubbers:  ENR/NBR, ENR/PVC, ENR/polylactic acid blends, ENR/copolyester blends, ENR/Copolyamide Blends, ENR/poly (vinylidene fluorideblends, ENR/Carbon Nanotubes with co-agent Trimethylol Propane Triacrylate, ENR /recycled silicon materials, and ENR/copolymer of n-butyl acrylate/butyl methacrylate “grafted”. Each of these blends has its own characteristics in terms of processing, enhancement of processing like safety, scorch, oil and water

Merging Bottom-Up with Top-Down: Continuous Lamellar Networks and Block Copolymer Lithography

Science.gov (United States)

Campbell, Ian Patrick

Block copolymer lithography is an emerging nanopatterning technology with capabilities that may complement and eventually replace those provided by existing optical lithography techniques. This bottom-up process relies on the parallel self-assembly of macromolecules composed of covalently linked, chemically distinct blocks to generate periodic nanostructures. Among the myriad potential morphologies, lamellar structures formed by diblock copolymers with symmetric volume fractions have attracted the most interest as a patterning tool. When confined to thin films and directed to assemble with interfaces perpendicular to the substrate, two-dimensional domains are formed between the free surface and the substrate, and selective removal of a single block creates a nanostructured polymeric template. The substrate exposed between the polymeric features can subsequently be modified through standard top-down microfabrication processes to generate novel nanostructured materials. Despite tremendous progress in our understanding of block copolymer self-assembly, continuous two-dimensional materials have not yet been fabricated via this robust technique, which may enable nanostructured material combinations that cannot be fabricated through bottom-up methods. This thesis aims to study the effects of block copolymer composition and processing on the lamellar network morphology of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) and utilize this knowledge to fabricate continuous two-dimensional materials through top-down methods. First, block copolymer composition was varied through homopolymer blending to explore the physical phenomena surrounding lamellar network continuity. After establishing a framework for tuning the continuity, the effects of various processing parameters were explored to engineer the network connectivity via defect annihilation processes. Precisely controlling the connectivity and continuity of lamellar networks through defect engineering and

Peel strength of LDPE/ethylene-1-butene copolymer film crosslinked by radiation

International Nuclear Information System (INIS)

Nho, Young Chang; Kim, Jeong Il; Kang, Phil Hyun

2003-01-01

In this study, ethylene-1-butene copolymer(EBP) was blended with LDPE to improve the mechanical properties as the packaging materials. After they were irradiated by an electron beam, their physical properties such as tensile strength, elongation, modulus, peel strength, DSC, and DMA were examined. The results showed that the addition of EBP to LDPE exerted significant effects on the mechanical properties such as the tensile strength and peel strength. The addition of EBP led to a maximum increase in peel strength of ∼ 430%. The addition of 10-25w% EBP in LDPE was sufficient to enhance the peel strength significantly

Preparation of porous PLLA/PCL blend by a combination of PEO phase and NaCl particulate leaching in PLLA/PCL/PEO/NaCl blend

Czech Academy of Sciences Publication Activity Database

Ezzati, P.; Ghasemi, I.; Karrabi, M.; Azizi, H.; Fortelný, Ivan

2014-01-01

Roč. 23, č. 10 (2014), s. 757-766 ISSN 1026-1265 Institutional support: RVO:61389013 Keywords : PLLA/PCL/PEO ternary blend * bio -scaffold * melts blending Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.806, year: 2014

Optimization of disintegration behavior of biodegradable poly (hydroxy butanoic acid) copolymer mulch films in soil environment

Science.gov (United States)

Mahajan, Viabhav

Biodegradation of polymeric films used for mulch film applications in agriculture not only eliminates problems of sorting out and disposal of plastics films, but also ensures increased yields in crop growth and cost reduction. One such polymer which is completely biodegradable in the soil is poly 3-hydroxy butanoic acid copolymer, which is a promising alternative to non-biodegradable incumbent polyethylene mulch films. The purpose of mulch film made of poly 3-hydroxy butanoic acid copolymers is to sustain itself during the crop growth and disintegrate and eventually biodegrade back to nature after the crop cycle is over. The disintegration phase of the biodegradation process was evaluated for poly 3-hydroxy butanoic acid copolymer incorporated with no additive, antimicrobial additives, varying amount of crystallinities, another biodegradable polymer, and in different soils, with or without varying soil moisture content. The tools used for quantification were weight loss and visual observation. The test method was standardized using repeatability tests. The onset of disintegration was optimized with addition of right anti-microbial additives, higher crystallinity of film, blending with other biodegradable polymers, compared to virgin poly 3-hydroxy butanoic acid copolymer film. The onset of disintegration time was reduced when soil moisture content was reduced. After the onset of disintegration, the polymer film was physically and mechanically deteriorated, withering away in soil, which is possible to tailor with the crop growth cycle.

Hollow fibers made from a poly(3-hydroxybutyrate/poly-ε-caprolactone blend

Directory of Open Access Journals (Sweden)

2011-07-01

Full Text Available Since poly(3-hydroxybutyrate (PHB is inherently brittle and possesses poor elastic properties, hollow fibers produced by melt spinning from pure PHB, as described in our earlier study [Macromolecular Materials and Engineering, 2010, 295/6, 585–594], do not meet the required needs regarding the mechanical performance. Besides hardly available PHB copolymers, also blend systems are known to enhance material properties and have thus been considered to be eligible to fabricate flexible or rather pliable hollow fibers based on PHB. Blends of PHB and poly-!-caprolactone (PCL are promising for the application in tissue engineering due to the inherent biocompatibility and biodegradability. A wide range of PHB/PCL compositions have been prepared by melt extrusion. Thermal and mechanical properties of the obtained specimens were analyzed in order to identify miscibility and degree of dispersion as well as to determine the influence on the overall mechanical performance. Even though these constituents are known to be immiscible, PHB/PCL 70/30 was proven to be an adequate composition. This blend showed a highly increased elongation and was found to be easily processable by melt spinning compared to pure PHB. From this blend well defined dimensionally stable bendable hollow fibers were fabricated.

Porous silicon based anode material formed using metal reduction

Science.gov (United States)

Anguchamy, Yogesh Kumar; Masarapu, Charan; Deng, Haixia; Han, Yongbong; Venkatachalam, Subramanian; Kumar, Sujeet; Lopez, Herman A.

2015-09-22

A porous silicon based material comprising porous crystalline elemental silicon formed by reducing silicon dioxide with a reducing metal in a heating process followed by acid etching is used to construct negative electrode used in lithium ion batteries. Gradual temperature heating ramp(s) with optional temperature steps can be used to perform the heating process. The porous silicon formed has a high surface area from about 10 m.sup.2/g to about 200 m.sup.2/g and is substantially free of carbon. The negative electrode formed can have a discharge specific capacity of at least 1800 mAh/g at rate of C/3 discharged from 1.5V to 0.005V against lithium with in some embodiments loading levels ranging from about 1.4 mg/cm.sup.2 to about 3.5 mg/cm.sup.2. In some embodiments, the porous silicon can be coated with a carbon coating or blended with carbon nanofibers or other conductive carbon material.

Block Copolymer Modified Epoxy Amine System for Reactive Rotational Molding: Structures, Properties and Processability

Science.gov (United States)

Lecocq, Eva; Nony, Fabien; Tcharkhtchi, Abbas; Gérard, Jean-François

2011-05-01

Poly(styrene-butadiene-methylmethacrylate) (SBM) and poly(methylmethacrylate-butyle-acrylate-methylmethacrylate) (MAM) triblock copolymers have been dissolved in liquid DGEBA epoxy resin which is subsequently polymerized by meta-xylene diamine (MXDA) or Jeffamine EDR-148. A chemorheology study of these formulations by plate-plate rheology and by thermal analysis has allowed to conclude that the addition of these copolymer blocks improve the reactive rotational moulding processability without affecting the processing time. Indeed, it prevents the pooling of the formulation at the bottom of the mould and a too rapid build up of resin viscosity of these thermosetting systems. The morphology of the cured blends examined by scanning electron microscopy (SEM) shows an increase of fracture surface area and thereby a potential increase of the toughness with the modification of epoxy system. Dynamic mechanical spectroscopy (DMA) and opalescence of final material show that the block PMMA, initially miscible, is likely to induce phase separation from the epoxy-amine matrix. Thereby, the poor compatibilisation between the toughener and the matrix has a detrimental effect on the tensile mechanical properties. The compatibilisation has to be increased to improve in synergy the processability and the final properties of these block copolymer modified formulations. First attempts could be by adapting the length and ratio of each block.

Porous TiNb2O7 Nanospheres as ultra Long-life and High-power Anodes for Lithium-ion Batteries

International Nuclear Information System (INIS)

Cheng, Qiushi; Liang, Jianwen; Lin, Ning; Guo, Cong; Zhu, Yongchun; Qian, Yitai

2015-01-01

Graphical abstract: Due to the combinative merits of porosity and nanostructure, porous TiNb 2 O 7 nanospheres exhibit ultra long cyclic life and excellent rate performance for lithium ion batteries. - Highlights: • Porous TiNb 2 O 7 nanospheres have been fabricated with the assistance of block copolymer P123. • The as-prepared TiNb 2 O 7 anodes present a reversible capacity of 160 mA h/g after 10000 cycles at 5 C with a capacity loss of only 0.0033% per cycle. • The TiNb 2 O 7 anodes show good rate performance of 167 mA h/g at 50C. • The TiNb 2 O 7 materials maintain the morphology of nanospheres and the porous structure even after 10000 cycles. - Abstract: Porous TiNb 2 O 7 nanospheres comprised of nanoparticles have been synthesized with the assistance of block copolymer P123 (EO 20 PO 70 EO 20 ). Such porous TiNb 2 O 7 nanospheres, with diameter of 500 nm, exhibit a BET surface area of 23.4 m 2 /g and pore volume of 0.155 cm 3 /g. As the anodes for lithium-ion batteries, the TiNb 2 O 7 nanospheres present a reversible capacity of 160 mA h/g after 10000 cycles at 5 C with a capacity loss of only 0.0033% per cycle, and good rate performance of 167 mA h/g at 50 C. Furthermore, the TiNb 2 O 7 materials still maintain the morphology of nanospheres and the porous structure even after 10000 cycles

Nano-porous Material with Spherical or Gyroid Cavities Created by Quantitative Etching of Polydimethylsiloxane in Polystyrene-Polydimethylsiloxane Block Copolymers

DEFF Research Database (Denmark)

Ndoni, Sokol; Vigild, Martin Etchells; Berg, Rolf H.

2003-01-01

A new method for quantitative etching of the poly(dimethylsiloxane) block in polystyrene-poly(dimethylsiloxane) (PS-PDMS) block copolymers is reported. Reacting the block copolymer with anhydrous hydrogen fluoride renders a nanoporous material (NPM) with the remaining glassy PS maintaining...... the original bulk morphology. 1H NMR, mass difference, size exclusion chromatography, and X-ray photoelectron spectroscopy were used to characterize the materials before and after etching. NPMs containing spherical and gyroid cavities were prepared, as ascertained by small-angle X-ray scattering...

Preparation of Starch/Gelatin Blend Microparticles by a Water-in-Oil Emulsion Method for Controlled Release Drug Delivery.

Science.gov (United States)

Phromsopha, Theeraphol; Baimark, Yodthong

2014-01-01

Information on the preparation and properties of starch/gelatin blend microparticles with and without crosslinking for drug delivery is presented. The blend microparticles were prepared by the water-in-oil emulsion solvent diffusion method. Glutaraldehyde and methylene blue were used as the crosslinker and the water-soluble drug model, respectively. The blend microparticles were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and UV-Vis spectroscopy. The functional groups of the starch and gelatin blend matrices were determined from the FTIR spectra. Blend microparticles with a nearly spherical shape and internal porous structure were observed from SEM images. The average particle size of the gelatin microparticles depended on the crosslinker ratio but not on the starch/gelatin blend ratio. The in vitro drug release content significantly decreased as the crosslinker ratio increased and the starch blend ratio decreased. The results demonstrated that the starch/gelatin blend microparticles should be a useful controlled release delivery carrier for water-soluble drugs.

Synthesis of Diblock copolymer poly-3-hydroxybutyrate -block-poly-3-hydroxyhexanoate [PHB-b-PHHx] by a β-oxidation weakened Pseudomonas putida KT2442.

Science.gov (United States)

Tripathi, Lakshmi; Wu, Lin-Ping; Chen, Jinchun; Chen, Guo-Qiang

2012-04-05

Block polyhydroxyalkanoates (PHA) were reported to be resistant against polymer aging that negatively affects polymer properties. Recently, more and more attempts have been directed to make PHA block copolymers. Diblock copolymers PHB-b-PHHx consisting of poly-3-hydroxybutyrate (PHB) block covalently bonded with poly-3-hydroxyhexanoate (PHHx) block were for the first time produced successfully by a recombinant Pseudomonas putida KT2442 with its β-oxidation cycle deleted to its maximum. The chloroform extracted polymers were characterized by nuclear magnetic resonance (NMR), thermo- and mechanical analysis. NMR confirmed the existence of diblock copolymers consisting of 58 mol% PHB as the short chain length block with 42 mol% PHHx as the medium chain length block. The block copolymers had two glass transition temperatures (Tg) at 2.7°C and -16.4°C, one melting temperature (Tm) at 172.1°C and one cool crystallization temperature (Tc) at 69.1°C as revealed by differential scanning calorimetry (DSC), respectively. This is the first microbial short-chain-length (scl) and medium-chain-length (mcl) PHA block copolymer reported. It is possible to produce PHA block copolymers of various kinds using the recombinant Pseudomonas putida KT2442 with its β-oxidation cycle deleted to its maximum. In comparison to a random copolymer poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (P(HB-co-HHx)) and a blend sample of PHB and PHHx, the PHB-b-PHHx showed improved structural related mechanical properties.

Synthesis and characterization of novel curing agents for surface coatings based on acrylamide copolymers

International Nuclear Information System (INIS)

Patel, N. V.; Parmar, R. J.; Parmar, J. S.

2003-01-01

The acrylamide based curing agents were prepared form methyl methacrylate-acrylamide copolymers by further methylolation and subsequent etherification with butanol. These were characterized for their various physico-chemical characteristics. Various sets of these ACAs were blended with hydroxyl functional acrylic resin to prepare the staving compared with the conventional melamine-formaldehyde based curing agent containing compositions. The films were also characterized thermogravimetric analysis and IR-spectra. The result reveals that the properties of certain compositions based on ACAs were remarkably better than those of conventional melamine-formaldehyde based curing agent based coatings

Porous electrode preparation method

Science.gov (United States)

Arons, R.M.; Dusek, J.T.

1983-10-18

A porous sintered plaque is provided with a bimodal porosity that is especially well suited for use as an electrode within a molten carbonate fuel cell. The coarse porosity is sufficient for admitting gases into contact with the reaction surfaces while the fine porosity is wetted with and retains molten electrolyte on the reaction sites. The electrode structure is prepared by providing a very fine powder of such as nickel oxide and blending the powder with a suitable decomposable binder to form a solid mass. The mass is comminuted into agglomerate size particles substantially larger than the fine oxide particles and formed into a cohesive compact for subsequent sintering. Sintering is carried out at sufficient conditions to bind the agglomerates together into a porous structure having both coarse and fine porosity. Where lithiated nickel oxide cathodes are prepared, the sintering conditions can be moderate enough to retain substantial quantities of lithium within the electrode for adequate conductivity. 2 figs.

Unimpeded permeation of water through biocidal graphene oxide sheets anchored on to 3D porous polyolefinic membranes

Science.gov (United States)

Mural, Prasanna Kumar S.; Jain, Shubham; Kumar, Sachin; Madras, Giridhar; Bose, Suryasarathi

2016-04-01

3D porous membranes were developed by etching one of the phases (here PEO, polyethylene oxide) from melt-mixed PE/PEO binary blends. Herein, we have systematically discussed the development of these membranes using X-ray micro-computed tomography. The 3D tomograms of the extruded strands and hot-pressed samples revealed a clear picture as to how the morphology develops and coarsens over a function of time during post-processing operations like compression molding. The coarsening of PE/PEO blends was traced using X-ray micro-computed tomography and scanning electron microscopy (SEM) of annealed blends at different times. It is now understood from X-ray micro-computed tomography that by the addition of a compatibilizer (here lightly maleated PE), a stable morphology can be visualized in 3D. In order to anchor biocidal graphene oxide sheets onto these 3D porous membranes, the PE membranes were chemically modified with acid/ethylene diamine treatment to anchor the GO sheets which were further confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and surface Raman mapping. The transport properties through the membrane clearly reveal unimpeded permeation of water which suggests that anchoring GO on to the membranes does not clog the pores. Antibacterial studies through the direct contact of bacteria with GO anchored PE membranes resulted in 99% of bacterial inactivation. The possible bacterial inactivation through physical disruption of the bacterial cell wall and/or reactive oxygen species (ROS) is discussed herein. Thus this study opens new avenues in designing polyolefin based antibacterial 3D porous membranes for water purification.3D porous membranes were developed by etching one of the phases (here PEO, polyethylene oxide) from melt-mixed PE/PEO binary blends. Herein, we have systematically discussed the development of these membranes using X-ray micro-computed tomography. The 3D tomograms of the extruded strands and

Olefin–Styrene Copolymers

OpenAIRE

Nunzia Galdi; Antonio Buonerba; Leone Oliva

2016-01-01

In this review are reported some of the most relevant achievements in the chemistry of the ethylene–styrene copolymerization and in the characterization of the copolymer materials. Focus is put on the relationship between the structure of the catalyst and that of the obtained copolymer. On the other hand, the wide variety of copolymer architecture is related to the properties of the material and to the potential utility.

Preparation and performance of porous phase change polyethylene glycol/polyurethane membrane

International Nuclear Information System (INIS)

Ke Guizhen; Xie Huifang; Ruan Ruping; Yu Weidong

2010-01-01

Based on the theory of clotty porous phase change materials, the porous membrane was prepared with the blend of polyurethane (PU) and two polyethylene glycol (PEG) systems. Studied by scanning electron microscope (SEM), Fourier transform infrared (FT-IR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and thermo-gravimetric (TG) tests, the morphology structure, chemical composition, crystalline morphology, phase change behaviors and thermal stability of porous phase change membrane were investigated. The results showed that the PU/PEG membrane had obvious porous structural feature, suitable transition temperature and high transition enthalpy. It is a flexible membrane with good energy storage function. When it is between solid and liquid transfer state in microcosms, the membrane can still keep solid shape in macroscopic state at high temperature during phase transition processing. It means that porous membrane PCM can be regarded as functional polymer. This method solved the problem of low working materials content in phase change textile. It succeeded in introducing the porous technology into functional textile's formation, and developed a new way to improve the phase change enthalpy largely for adjustable textile.

Volume holographic storage and multiplexing in blends of PMMA and a block methacrylic azopolymer, using 488 nm light pulses in the range of 100 ms to 1 s

DEFF Research Database (Denmark)

Forcen, Patricia; Oriol, Luis; Sanchez, Carlos

2008-01-01

Blends of polymethylmethacrylate (PMMA) and diblock methacrylic azopolymers have been investigated for holographic storage with short light pulses. Transmission electron microscopy measurements show that the dilution of the block copolymer in PMMA changes the microstructure from a lamellar to a s...

Responsive Block Copolymer and Gold Nanoparticle Hybrid Nanotubes.

Science.gov (United States)

Chang, Sehoon; Singamaneni, Srikanth; Young, Seth; Tsukruk, Vladimir

2009-03-01

We demonstrate the facile fabrication of responsive polymer and metal nanoparticle composite nanotube structures. The nanotubes are comprised of responsive block copolymer, polystyrene-block-poly (2-vinylpyridine) (PS-b-P2VP), and gold nanoparticles. PS-b-P2VP nanotubes were fabricated using porous alumina template and in situ reduction of the gold nanoparticles in P2VP domains. Owing to the pH sensitive nature of P2VP (anionic polymer with a pKa of 3.8), the nanotubes exhibit a dramatic change in topology in response to the changes in the external pH. Furthermore, the gold nanoparticles in the responsive block exhibit a reversible aggregation, causing a reversible change in optical properties such as absorption.

A New Supramolecular Route for Using Rod-Coil Block Copolymers in Photovoltaic Applications

Science.gov (United States)

Mezzenga, Raffaele; Sary, Nicolas; Richard, Fanny; Brochon, Cyril; Leclerc, Nicolas; Leveque, Patrick; Audinot, Jean Nicolas; Heiser, Thomas; Hadziioannou, Georges; Berson, Solenn

2010-03-01

We propose a new supramolecular strategy to blend together rod-coil poly(3-hexylthiophene)-poly(4-vinylpyridine) (P3HTP4VP) block copolymers and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The P4VP and PCBM are mixed together by weak supramolecular interactions, and the resulting materials exhibit microphase separated morphologies of electron-donor and electron-acceptor rich domains. The microphase segregated P3HT-rod domains act as electron-donating species and the homogeneous P4VP block:PCBM blend acts as the electron-acceptor domain. We describe the photovoltaic performance of standard and inverted devices whose active layer is composed thereof and show the effect of finely engineering the interfacial properties of the active layer to obtain competitive photovoltaic performance with superior thermal stability. (1) N. Sary, F. Richard, C. Brochon, N. Leclerc, P. Leveque, JN Audinot, S. Berson, T. Heiser, G. Hadziioannou, R. Mezzenga, Adv. Mater. in Press (2010)

Nanowire and Mesh Conformations of Diblock Copolymer Blends at the Air/Water Interface

NARCIS (Netherlands)

Seo, Young-Soo; Kim, K.S.; Galambos, Arielle; Lammertink, Rob G.H.; Vancso, Gyula J.; Sokolov, J.; Rafailovich, M.

2004-01-01

We investigated the structures formed when blends of poly(styrene-b-ferrocenyl silane) (PS-b-FS) and poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) were spread at the air/water interface. The results demonstrated that new structures were formed which were distinct from those formed when either of the

Physical properties of LDPE/ethylene-1-butene copolymer film irradiated by electron beam

International Nuclear Information System (INIS)

Kim, Jeong Il; Nho, Young Chang

2004-01-01

In this study, ethylene-1-butene copolymer (EBP) was blended with LDPE to improve the mechanical properties as the packaging materials. After they were irradiated by electron beam, their physical properties such as tensile strength, elongation, modulus, peel strength, DSC, DMA were examined. The results showed that the addition of EBP to LDPE exerted significant effects on the mechanical properties such as the tensile strength and peel strength. The addition of EBP led to a maximum increase in peel strength of ∼430%. The addition of 10 - 25 w% EBP in LDPE was sufficient to enhance the peel strength significantly. (author)

Hierarchical porous TiO{sub 2} thin films by soft and dual templating

Energy Technology Data Exchange (ETDEWEB)

Henrist, Catherine, E-mail: catherine.henrist@ulg.ac.be [University of Liege, Department of Chemistry, GREENMAT-LCIS, B6 Sart Tilman, Liege 4000 (Belgium); University of Liege, Center for Applied Technology in Microscopy (CATmu), B6 Sart Tilman, Liege 4000 (Belgium); Dewalque, Jennifer [University of Liege, Department of Chemistry, GREENMAT-LCIS, B6 Sart Tilman, Liege 4000 (Belgium); Cloots, Rudi [University of Liege, Department of Chemistry, GREENMAT-LCIS, B6 Sart Tilman, Liege 4000 (Belgium); University of Liege, Center for Applied Technology in Microscopy (CATmu), B6 Sart Tilman, Liege 4000 (Belgium); Vertruyen, Bénédicte; Jonlet, Jonathan; Colson, Pierre [University of Liege, Department of Chemistry, GREENMAT-LCIS, B6 Sart Tilman, Liege 4000 (Belgium)

2013-07-31

Hierarchical porous structures, with different pore sizes, including pores larger than 10 nm, constitute an important field of research for many applications such as selective molecule detection, catalysis, dye-sensitized solar cells, nanobiotechnology and nanomedecine. However, increasing the pore size logically results in the decrease of specific surface. There is a need to quantify and predict the resulting porosity and specific surface. We have prepared hierarchical porous TiO{sub 2} thin films either by surfactant templating (soft) or dual surfactant/nanospheres templating (soft/hard). They all show narrow, bimodal distribution of pores. Soft templating route uses a modified sol–gel procedure by adding a swelling agent (polypropylene glycol) to a precursor solution containing Ti alkoxide and block-copolymer surfactant. This scheme leads to very thin films showing high specific surface and bimodal porosity with diameters of 10 nm and 54 nm. Dual templating route combines a precursor solution made of Ti alkoxide and block-copolymer surfactant with polystyrene (PS) nanospheres (diam. 250 nm) in a one-pot simple process. This gives thicker films with a bimodal distribution of pores (8 nm and 165-200 nm). The introduction of PS nanospheres in the surfactant–Ti system does not interfere with the soft templating process and results in a macroporosity with a pore diameter 20–30% smaller than the original beads diameter. The dye loading of hierarchical films is compared to pure surfactant-templated TiO{sub 2} films and shows a relative decrease of 29% for soft templating and 43% for dual templating. The microstructure of bimodal porous films is characterized by several techniques such as transmission and scanning electron microscopy, X-ray diffraction, profilometry and ellipsometry. Finally, a geometrical model is proposed and validated for each system, based on the agreement between calculated specific surfaces and experimental dye loading with N719 dye

3D composites based on the blends of chitosan and collagen with the addition of hyaluronic acid.

Science.gov (United States)

Sionkowska, Alina; Kaczmarek, Beata; Lewandowska, Katarzyna; Grabska, Sylwia; Pokrywczyńska, Marta; Kloskowski, Tomasz; Drewa, Tomasz

2016-08-01

3D porous composites based on blends of chitosan, collagen and hyaluronic acid were obtained through the lyophilization process. Mechanical properties, swelling behavior and thermal stability of the blends were studied. Moreover, SEM images were taken and the structure of the blends was studied. Biological properties of the materials obtained were investigated by analyzing of proliferation rate of fibroblast cells incubated with biomaterial extract using MTT assay (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide). The results showed that the properties of 3D composites based on the blends of chitosan and collagen were altered after the addition 1%, 2% and 5% of hyaluronic acid. Mechanical properties and thermal stability of chitosan/collagen blends were improved in the presence of hyaluronic acid in the composite. New 3D materials based on the blends of chitosan, collagen and hyaluronic acid were non-toxic and did not significantly affect cell morphology. Copyright © 2016 Elsevier B.V. All rights reserved.

The effect of film thickness and molecular structure on order and disorder in thin films of compositionally asymmetric block copolymers

Science.gov (United States)

Mishra, Vindhya

Directed self-assembly of thin film block copolymers offer a high throughput-low cost route to produce next generation lithographic devices, if one can bring the defect densities in the self assembled patterns below tolerance limits. However, the ability to control the nanoscale structure or morphology in thin film block copolymers presents challenges due to confinement effects on equilibrium behavior. Using structure characterization techniques such as grazing incidence small angle X-ray scattering (GISAXS), transmission electron and atomic force microscopy as well as self-consistent field theory, we have investigated how film thickness, annealing temperature and block copolymer structure affects the equilibrium behavior of asymmetric block copolymer films. Our studies have revealed the complicated dependence of order-disorder transitions, order-order transitions and symmetry transitions on film thickness. We found that the thickness dependent transition in the packing symmetry of spherical morphology diblock copolymers can be suppressed by blending with a small amount of majority block homopolymer, which allowed us to resolve the driving force behind this transition. Defect densities in, and the order-disorder transition temperature of, thin films of graphoepitaxially aligned diblock copolymer cylinders showed surprising sensitivity to the microdomain spacing. Methods to mitigate defect formation in thin films have been identified. The challenge of quantification of structural order in these systems was overcome using GISAXS, which allowed us to study the phenomena of disordering in two and three dimensions. Through studies on block copolymers which exhibit an order-order transition in bulk, we found that that subtle differences in the packing frustration of the spherical and cylindrical phases as well as the higher configurational entropy of free chain ends at the surface can drive the equilibrium configuration in thin films away from the stable bulk structure

Template-assisted electrostatic spray deposition as a new route to mesoporous, macroporous, and hierarchically porous oxide films.

Science.gov (United States)

Sokolov, S; Paul, B; Ortel, E; Fischer, A; Kraehnert, R

2011-03-01

A novel film coating technique, template-assisted electrostatic spray deposition (TAESD), was developed for the synthesis of porous metal oxide films and tested on TiO(2). Organic templates are codeposited with the titania precursor by electrostatic spray deposition and then removed during calcination. Resultant films are highly porous with pores casted by uniformly sized templates, which introduced a new level of control over the pore morphology for the ESD method. Employing the amphiphilic block copolymer Pluronic P123, PMMA latex spheres, or a combination of the two, mesoporous, macroporous, and hierarchically porous TiO(2) films are obtained. Decoupled from other coating parameters, film thickness can be controlled by deposition time or depositing multiple layers while maintaining the coating's structure and integrity.

Fabrication and Intermolecular Interactions of Silk Fibroin/Hydroxybutyl Chitosan Blended Nanofibers

Directory of Open Access Journals (Sweden)

Xiu-Mei Mo

2011-03-01

Full Text Available The native extracellular matrix (ECM is composed of a cross-linked porous network of multifibril collagens and glycosaminoglycans. Nanofibrous scaffolds of silk fibroin (SF and hydroxybutyl chitosan (HBC blends were fabricated using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP and trifluoroacetic acid (TFA as solvents to biomimic the native ECM via electrospinning. Scanning electronic microscope (SEM showed that relatively uniform nanofibers could be obtained when 12% SF was blended with 6% HBC at the weight ratio of 50:50. Meanwhile, the average nanofibrous diameter increased when the content of HBC in SF/HBC blends was raised from 20% to 100%. Fourier transform infrared spectra (FTIR and 13C nuclear magnetic resonance (NMR showed SF and HBC molecules existed in hydrogen bonding interactions but HBC did not induce conformation of SF transforming from random coil form to β-sheet structure. X-ray diffraction (XRD confirmed the different structure of SF/HBC blended nanofibers from both SF and HBC. Thermogravimetry-Differential thermogravimetry (TG-DTG results demonstrated that the thermal stability of SF/HBC blend nanofibrous scaffolds was improved. The results indicated that the rearrangement of HBC and SF molecular chain formed a new structure due to stronger hydrogen bonding between SF and HBC. These electrospun SF/HBC blended nanofibers may provide an ideal tissue engineering scaffold and wound dressing.

Hierarchical porous nitrogen-doped partial graphitized carbon monoliths for supercapacitor

Energy Technology Data Exchange (ETDEWEB)

Yu, Yifeng; Du, Juan; Liu, Lei; Wang, Guoxu; Zhang, Hongliang; Chen, Aibing, E-mail: chen-ab@163.com [Hebei University of Science and Technology, College of Chemical and Pharmaceutical Engineering (China)

2017-03-15

Porous carbon monoliths have attracted great interest in many fields due to their easy availability, large specific surface area, desirable electronic conductivity, and tunable pore structure. In this work, hierarchical porous nitrogen-doped partial graphitized carbon monoliths (N–MC–Fe) with ordered mesoporous have been successfully synthesized by using resorcinol-formaldehyde as precursors, iron salts as catalyst, and mixed triblock copolymers as templates via a one-step hydrothermal method. In the reactant system, hexamethylenetetramine (HMT) is used as nitrogen source and one of the carbon precursors under hydrothermal conditions instead of using toxic formaldehyde. The N–MC–Fe show hierarchically porous structures, with interconnected macroporous and ordered hexagonally arranged mesoporous. Nitrogen element is in situ doped into carbon through decomposition of HMT. Iron catalyst is helpful to improve the graphitization degree and pore volume of N–MC–Fe. The synthesis strategy is user-friendly, cost-effective, and can be easily scaled up for production. As supercapacitors, the N–MC–Fe show good capacity with high specific capacitance and good electrochemical stability.

Engineering new polypropylene copolymer for asphalt modification. Progettazione di un polimero a base polipropilenica adatto per la modifica dei bitumi

Energy Technology Data Exchange (ETDEWEB)

Giavarini, C.; Santarelli, M.L. (Rome Univ. (Italy). Dipt. di Ingegneria Chimica); Braga, V. (Himont Centro Ricerche ' G. Natta' , Ferrara (Italy))

1993-04-01

Polypropylene polymers: isotactic PP, random, heterophasic copolymer, ethylene-propylene rubber, are suitable as modifiers for road bitumens. Among the advantages of PP polymers, such as heterophasic polymers, prepared via synthesis, are good thermal and ageing resistance, and the fact that they can be easily tailored to the specific application. Various types of PP and EPR polymers, possibly blended, prepared or modified for this purpose, were mixed with bitumens to study the dispersion of the polymer, segregation characteristics, ageing and viscoelastic properties. The experimental results gave indications on the characteristics of a polyolefinic copolymer for bitumen modification. The PP based products applicable as bitumen modifiers are the heterophasic copolymers containing a substantial amounts of EPR, possibly modified to increase branching. For road bitumens with a penetration between 100 and 200 dmm, the average molecular weight of the polymer should be arranged to reach an intrinsic viscosity between about 1.5 and 2.0 dl/g. Partial branching (or partial crosslinking) of the chains in the PP-phase is helpful when not followed by EPR-phase crosslinking.

Main-chain supramolecular block copolymers.

Science.gov (United States)

Yang, Si Kyung; Ambade, Ashootosh V; Weck, Marcus

2011-01-01

Block copolymers are key building blocks for a variety of applications ranging from electronic devices to drug delivery. The material properties of block copolymers can be tuned and potentially improved by introducing noncovalent interactions in place of covalent linkages between polymeric blocks resulting in the formation of supramolecular block copolymers. Such materials combine the microphase separation behavior inherent to block copolymers with the responsiveness of supramolecular materials thereby affording dynamic and reversible materials. This tutorial review covers recent advances in main-chain supramolecular block copolymers and describes the design principles, synthetic approaches, advantages, and potential applications.

Reactive modification of polyesters and their blends

Science.gov (United States)

Wan, Chen

2004-12-01

As part of a broader research effort to investigate the chemical modification of polyesters by reactive processing a low molecular weight (MW) unsaturated polyester (UP) and a higher MW saturated polyester, polyethylene terephthalate (PET), alone or blended with polypropylene (PP) were melt processed in a batch mixer and continuous twin screw extruders. Modification was monitored by on-line rheology and the products were characterized primarily by off-line rheology, morphology and thermal analysis. Efforts were made to establish processing/property relationships and provide an insight of the accompanying structural changes. The overall response of the reactively modified systems was found to be strongly dependent on the component characteristics, blend composition, type and concentrations of reactive additives and processing conditions. The work concluded that UP can be effectively modified through reactive melt processing. Its melt viscosity and MW can be increased through chemical reactions between organic peroxides (POX) and chain unsaturation or between MgO and carboxyl/hydroxyl end groups. Reactive blending of PP/UP blends through peroxide modification gave finer and more uniform morphology than unreacted blends and at a given PP/UP weight ratio more thermoplastic elastomers-like rheological behavior. This is due to the continuously decreasing viscosity ratio of PP/UP towards unity by the competing reactions between POX and the blend components and formation of PP-UP copolymers which serve as in-situ compatibilizers to promote better interfacial adhesion. Kinetics of the competing reactions were analyzed through a developed model. In addition to POX concentration and mixing efficiency, rheology and morphology of UP/PP bends were significantly affected by the addition of inorganic and organic coagents. Addition of coagents such as a difunctional maleimide, MgO and/or an anhydride functionalized PP during reactive blending offers effective means for tailoring

Interstitial micelles in binary blends of A B A triblock copolymers and homopolymers

Science.gov (United States)

Wołoszczuk, S.; Banaszak, M.

2018-01-01

We investigate triblock-homopolymer blends of types A1BA2/A and A1BA2/B, using a lattice Monte Carlo method. While the simulated triblock chains are compositionally symmetric in terms of the A-to-B volume ratio, the A1 block is significantly shorter than the A2 block. For the pure A1BA2 melt and the A1BA2 solutions in selective solvent the phase behavior is relatively well known, including existence and stability of the interstitial micelles which were discovered in previous Monte Carlo simulations. In this paper we study the stability of the interstitial micelles as a function of triblock volume fraction in selective homopolymers of either type A or type B, using two significantly different homopolymer chain lengths. We found that adding selective homopolymer of type A shifts the stability of the interstitial micelles into significantly higher temperatures. We also obtained, via self-assembly, intriguing new nanostructures which can be identified as ordered truncated octahedra. Finally, we established that the phase behavior of the triblock-homopolymer blends depends relatively weakly on the chain length of the added homopolymer.

Super toughened biodegradable polylactide blends with non-linear copolymer interfacial architecture obtained via facile in-situ reactive compatibilization

CSIR Research Space (South Africa)

Ojijo, Vincent O

2015-12-01

Full Text Available to the formation of non-linear copolymer architecture at the interface. Scanning electron microscopy showed a drastic reduction of the dispersed phase size upon compatibilization, even at very low quantities of the chain extender. Rheological probing...

Utilização de NBR modificada com grupos 2-oxazolina em misturas de NBR/EVA Utilization of 2-oxazoline modified NBR in NBR/EVA blends

Directory of Open Access Journals (Sweden)

Mauricio S. M. Almeida

2003-06-01

Full Text Available Misturas envolvendo borracha nitrílica e copolímeros de etileno-acetato de vinila na proporção 70:30 % em peso, foram preparadas na presença de borracha nitrílica funcionalizada com 2-oxazolina isoladamente ou combinada com EVA funcionalizado com grupos hidroxila, carboxila ou mercaptana. A reação entre os grupos funcionais foi verificada por análise de FTIR da fração insolúvel de amostras não vulcanizadas e pelo decréscimo nos valores de tan delta nos ensaios dinâmico-mecânicos. A utilização desses copolímeros funcionalizados não influenciou significativamente as propriedades mecânicas, provavelmente devido à proporção da mistura utilizada (rica em NBR o que facilita a localização da NBR funcionalizada no interior da fase elastomérica.Nitrile rubber/ethylene-vinyl acetate copolymer (NBR/EVA blends with ratio of 70/30 wt% were prepared in the presence of functionalized NBR with 2-oxazoline groups. This functionalized copolymer was employed alone or in combination with EVA copolymer functionalized with hydroxyl, carboxyl or mercaptan groups. The reaction between the functional groups was confirmed by FTIR analysis of the unvulcanized samples insoluble fraction, and by the decrease in the tan delta values. The mechanical properties were not substantially affected by the presence of these functionalized copolymers, probably due to the proportion of blend composition (with high amount of NBR, thus forcing the location of functionalized NBR inside the elastomer phase.

Metallo-supramolecular block copolymer micelles

NARCIS (Netherlands)

Gohy, J.M.W.

2009-01-01

Supramolecular copolymers have become of increasing interest in recent years in the search for new materials with tunable properties. In particular, metallo-supramolecular block copolymers in which metal-ligand complexes are introduced in block copolymer architectures, have known important progress,

Thermal Conductivity of Ethylene Vinyl Acetate Copolymer/Nanofiller Blends

Science.gov (United States)

Ghose, S.; Watson, K. A.; Working, D. C.; Connell, J. W.; Smith, J. G., Jr.; Lin, Y.; Sun, Y. P.

2007-01-01

To reduce weight and increase the mobility, comfort, and performance of future spacesuits, flexible, thermally conductive fabrics and plastic tubes are needed for the Liquid Cooling and Ventilation Garment. Such improvements would allow astronauts to operate more efficiently and safely for extended extravehicular activities. As an approach to raise the thermal conductivity (TC) of an ethylene vinyl acetate copolymer (Elvax 260), it was compounded with three types of carbon based nanofillers: multi-walled carbon nanotubes (MWCNTs), vapor grown carbon nanofibers (CNFs), and expanded graphite (EG). In addition, other nanofillers including metallized CNFs, nickel nanostrands, boron nitride, and powdered aluminum were also compounded with Elvax 260 in the melt at various loading levels. In an attempt to improve compatibility between Elvax 260 and the nanofillers, MWCNTs and EG were modified by surface coating and through noncovalent and covalent attachment of organic molecules containing alkyl groups. Ribbons of the nanocomposites were extruded to form samples in which the nanofillers were aligned in the direction of flow. Samples were also fabricated by compression molding to yield nanocomposites in which the nanofillers were randomly oriented. Mechanical properties of the aligned samples were determined by tensile testing while the degree of dispersion and alignment of nanoparticles were investigated using high-resolution scanning electron microscopy. TC measurements were performed using a laser flash (Nanoflash ) technique. TC of the samples was measured in the direction of, and perpendicular to, the alignment direction. Additionally, tubing was also extruded from select nanocomposite compositions and the TC and mechanical flexibility measured.

Poly(NIPAM-co-MPS-grafted multimodal porous silica nanoparticles as reverse thermoresponsive drug delivery system

Directory of Open Access Journals (Sweden)

Sushilkumar A. Jadhav

2017-05-01

Full Text Available Hybrid drug delivery systems (DDS have been prepared by grafting poly(NIPAM-co-MPS chains on multimodal porous silica nanoparticles having an inner mesoporous structure and an outer thin layer of micropores. The hybrid thermoresponsive DDS were fully characterized and loaded with a model drug. The in vitro drug release tests are carried out at below and above the lower critical solution temperature (LCST of the copolymer. The results have revealed that due to the presence of small diameter (~1.3 nm micropores at the periphery of the particles, the collapsed globules of the thermoresponsive copolymer above its LCST hinders the complete release of the drug which resulted in a reverse thermoresponsive drug release profile by the hybrid DDS.

Phase behavior of UCST blends: Effects of pristine nanoclay as an effective or ineffective compatibilizer

Directory of Open Access Journals (Sweden)

F. Hemmati

2013-12-01

Full Text Available The effects of unmodified nanoclay (natural montmorillonite on the miscibility, phase behavior and phase separation kinetics of polyethylene (PE/ethylene vinyl acetate copolymer (EVA blends have been investigated. Depending on the blend composition, it was observed that the intercalated pristine nanoclay influences the biphasic morphology either as an effective compatibilizer or just as an ineffectual modifier. In spite of the presence of micrometer-sized agglomerated tactoids, natural nanoclay can play a thermodynamic role in reducing the interfacial tension of polymer components. The addition of clay nanoparticles was found to change the phase diagram slightly and diminishes the composition dependency of the binodal temperatures. Moreover, it was observed that a small amount of unmodified layered silicate slows down the phase separation process considerably and enhances the solubility of each polymer in the domains of its counterpart. The findings of this study verify that even poorly dispersed nanoclay with high surface tension can act as a conventional compatibilizer and change the immiscible PE/EVA blends to the partially miscible ones.

Porous carbonaceous electrode structure and method for secondary electrochemical cell

Science.gov (United States)

Kaun, Thomas D.

1977-03-08

Positive and negative electrodes are provided as rigid, porous carbonaceous matrices with particulate active material fixedly embedded. Active material such as metal chalcogenides, solid alloys of alkali metal or alkaline earth metals along with other metals and their oxides in particulate form are blended with a thermosetting resin and a solid volatile to form a paste mixture. Various electrically conductive powders or current collector structures can be blended or embedded into the paste mixture which can be molded to the desired electrode shape. The molded paste is heated to a temperature at which the volatile transforms into vapor to impart porosity as the resin begins to cure into a rigid solid structure.

Morphology and mechanical properties of polypropylene/polystyrene blends compatibilized with styrene-butadiene block copolymers

Czech Academy of Sciences Publication Activity Database

Fortelný, Ivan; Minkova, L. I.; Kotek, Jiří; Lapčíková, Monika; Michálková, Danuše

2012-01-01

Roč. 52, č. 1 (2012), s. 191-204 ISSN 0032-3888 R&D Projects: GA ČR GA106/06/0729; GA AV ČR IAA200500903 Institutional research plan: CEZ:AV0Z40500505 Keywords : polymer blends * compatibilization * morphology Subject RIV: JI - Composite Materials Impact factor: 1.243, year: 2012

Effect of dynamic crosslinking on phase morphology and mechanical properties of polyamide 6,12/ethylene vinyl acetate copolymer blends

Directory of Open Access Journals (Sweden)

Fabrício Bondan

2015-03-01

Full Text Available The dynamic crosslinking of polyamide 6,12 and ethylene vinyl acetate (PA6,12/EVA blends in the mixing chamber of a torque rheometer was investigated. EVA was selectively crosslinked within the PA6,12 phase through free radical reactions using dycumil peroxide. The degree of EVA crosslinking in the PA12,6/EVA materials was estimated based on the gel content (insoluble EVA fraction. The PA6,12/EVA phase morphology was investigated by scanning electron microscopy. The mechanical properties were investigated by determining the tensile strength and hardness. The half-life time ( for homolytic scission of the dcumil peroxide (DCP was ~6s, and this time is longer than the dispersion time of the DCP in the blends. The addition of DCP resulted in increased torque values due to specific crosslinking in the EVA phase. For the pure EVA and its blends with PA6,12 the stabilized torque values increased proportionally with the amount of DCP in the system, due to a higher degree of crosslinking of the elastomeric phase. The gel content of the dynamically crosslinked blends increased with the amount of DCP incorporated until 4 phr. At 1 phr the gel content value was 2.6wt.%, while at 4 phr it was 17wt.%. For the polymer blend with 8 phr of DCP a lubricating effect contributed to reducing the gel content. The dynamically crosslinked blends, regardless of the amount of DCP added, showed a reduction in the mechanical properties, which is related to the morphological features of the system due to the low mechanical fragmentation during melt processing.

Complexing blends of polyacrylic acid-polyethylene glycol and poly(ethylene-co-acrylic acid)-polyethylene glycol as shape stabilized phase change materials

International Nuclear Information System (INIS)

Alkan, Cemil; Günther, Eva; Hiebler, Stefan; Himpel, Michael

2012-01-01

Highlights: ► Complexing groups to PEGs in a polymer could stabilize PEG at different molecular weights. ► Shape stabilized PEGs for thermal energy storage are prepared using compounds with interacting groups. ► Phase change temperature of PEGs could be changed using a complexing copolymer with acid groups. - Abstract: Blends of poly(ethylene glycol) (PEG) at 1000, 6000, and 10,000 g/mole average molecular weights and poly(acrylic acid) (PAA) or poly(ethylene-co-acrylic acid) (EcoA) have been prepared by solution blending and accounted for thermal energy storage properties as shape stabilized polymer blends. The blends have been analyzed using Fourier transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC) techniques. Total thermal energy values of the complexes have been determined by the method of Mehling et al. As a result of the investigation it is found that polymers with acid groups form interpolymer complexes (IPCs) and miscible and immiscible IPC–PEG blends when blended with PEGs. PEGs formed IPCs with PAA and EcoA polymers in solutions and reach to saturation and turns to be blends of IPC and PEG polymer. PEGs in this work bleed out of the blends when its compositions reach to a degree of immiscibility. In the first range where blends are IPCs and in the third range where bleeding of PEG occurs, blends are not feasible for thermal energy storage applications. However, in the second range, the blends are potential materials for passive thermal energy storage applications.

Rheological, mechanical and morphological properties of poly(methyl methacrylate/poly(ethylene terephthalate blend with dual reactive interfacial compatibilization

Directory of Open Access Journals (Sweden)

Juciklécia da Silva Reinaldo

2015-10-01

Full Text Available Abstract In this work, the rheological, mechanical and morphological behavior of immiscible blend poly (methyl methacrylate with elastomeric particles (PMMAelast and post-consumer poly (ethylene terephthalate (PET with and without the use of the interfacial compatibilizer poly (methyl methacrylate-co-glycidyl methacrylate-co-ethyl acrylate (MGE was studied. The significant increase in torque presented in rheological analyses has shown a indication of chemical reactions between the epoxy group of MGE with end groups of PET chains and also with the elastomeric phase of PMMAelast. The increased concentration of PET yielded an increase in maximum strength and elasticity modulus and a decrease in elongation at break. The PMMAelast/PET binary blend (50/50 wt% and PMMAelast/PET/MGE compatibilized blend (65/30/5 wt% showed pronounced results in elongation at break compared to PMMAelast, whereas, in the first results were due to the evidence of a co-continuous morphological structure and in the second, due to the efficiency of the dual reactive interfacial compatibilization of PMMAelast/PET blends. Scanning electron microscopy (SEM and transmission electron microscopy (TEM analyses showed that PMMAelast/PET/MGE blends exhibit complex phase morphology due to the presence of elastomeric particles in the PMMAelast copolymer and in the use of MGE terpolymer.

Ink-jet printed porous composite LiFePO4 electrode from aqueous suspension for microbatteries

Science.gov (United States)

Delannoy, P.-E.; Riou, B.; Brousse, T.; Le Bideau, J.; Guyomard, D.; Lestriez, B.

2015-08-01

This work demonstrates ink-jet printed LiFePO4-based composite porous electrodes for microbattery application. As binder and dispersant, we found that aqueous inks with more suitable rheological properties with respect to ink-jet printing are prepared with the low molecular weight poly-acrylic-co-maleic acid copolymer, rather than with the carboxymethyl cellulose standard binder of the lithium-ion technology. The ink-jet printed thin and porous electrode shows very high rate charge/discharge behavior, both in LiPF6/ethylene carbonate-dimethyl carbonate (LP30) and lithium bis(trifluoromethane)sulfonylimide salt (Li-TFSI) in N-methyl-N-propylpyrrolidinium bis(trifluoromethane)suflonylimide ionic liquid (PYR13-TFSI) electrolytes, as well as good cyclability.

Artificial 3D hierarchical and isotropic porous polymeric materials

KAUST Repository

Chisca, Stefan; Musteata, Valentina-Elena; Sougrat, Rachid; Behzad, Ali Reza; Nunes, Suzana Pereira

2018-01-01

Hierarchical porous materials that replicate complex living structures are attractive for a wide variety of applications, ranging from storage and catalysis to biological and artificial systems. However, the preparation of structures with a high level of complexity and long-range order at the mesoscale and microscale is challenging. We report a simple, nonextractive, and nonreactive method used to prepare three-dimensional porous materials that mimic biological systems such as marine skeletons and honeycombs. This method exploits the concurrent occurrence of the self-assembly of block copolymers in solution and macrophase separation by nucleation and growth. We obtained a long-range order of micrometer-sized compartments. These compartments are interconnected by ordered cylindrical nanochannels. The new approach is demonstrated using polystyrene-b-poly(t-butyl acrylate), which can be further explored for a broad range of applications, such as air purification filters for viruses and pollution particle removal or growth of bioinspired materials for bone regeneration.

Artificial 3D hierarchical and isotropic porous polymeric materials

KAUST Repository

Chisca, Stefan

2018-05-11

Hierarchical porous materials that replicate complex living structures are attractive for a wide variety of applications, ranging from storage and catalysis to biological and artificial systems. However, the preparation of structures with a high level of complexity and long-range order at the mesoscale and microscale is challenging. We report a simple, nonextractive, and nonreactive method used to prepare three-dimensional porous materials that mimic biological systems such as marine skeletons and honeycombs. This method exploits the concurrent occurrence of the self-assembly of block copolymers in solution and macrophase separation by nucleation and growth. We obtained a long-range order of micrometer-sized compartments. These compartments are interconnected by ordered cylindrical nanochannels. The new approach is demonstrated using polystyrene-b-poly(t-butyl acrylate), which can be further explored for a broad range of applications, such as air purification filters for viruses and pollution particle removal or growth of bioinspired materials for bone regeneration.

Artificial 3D hierarchical and isotropic porous polymeric materials.

Science.gov (United States)

Chisca, Stefan; Musteata, Valentina-Elena; Sougrat, Rachid; Behzad, Ali Reza; Nunes, Suzana P

2018-05-01

Hierarchical porous materials that replicate complex living structures are attractive for a wide variety of applications, ranging from storage and catalysis to biological and artificial systems. However, the preparation of structures with a high level of complexity and long-range order at the mesoscale and microscale is challenging. We report a simple, nonextractive, and nonreactive method used to prepare three-dimensional porous materials that mimic biological systems such as marine skeletons and honeycombs. This method exploits the concurrent occurrence of the self-assembly of block copolymers in solution and macrophase separation by nucleation and growth. We obtained a long-range order of micrometer-sized compartments. These compartments are interconnected by ordered cylindrical nanochannels. The new approach is demonstrated using polystyrene- b -poly( t -butyl acrylate), which can be further explored for a broad range of applications, such as air purification filters for viruses and pollution particle removal or growth of bioinspired materials for bone regeneration.

Formation of nanoscale networks: selectively swelling amphiphilic block copolymers with CO2-expanded liquids.

Science.gov (United States)

Gong, Jianliang; Zhang, Aijuan; Bai, Hua; Zhang, Qingkun; Du, Can; Li, Lei; Hong, Yanzhen; Li, Jun

2013-02-07

Polymeric films with nanoscale networks were prepared by selectively swelling an amphiphilic diblock copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), with the CO(2)-expanded liquid (CXL), CO(2)-methanol. The phase behavior of the CO(2)-methanol system was investigated by both theoretical calculation and experiments, revealing that methanol can be expanded by CO(2), forming homogeneous CXL under the experimental conditions. When treated with the CO(2)-methanol system, the spin cast compact PS-b-P4VP film was transformed into a network with interconnected pores, in a pressure range of 12-20 MPa and a temperature range of 45-60 °C. The formation mechanism of the network, involving plasticization of PS and selective swelling of P4VP, was proposed. Because the diblock copolymer diffusion process is controlled by the activated hopping of individual block copolymer chains with the thermodynamic barrier for moving PVP segments from one to another, the formation of the network structures is achieved in a short time scale and shows "thermodynamically restricted" character. Furthermore, the resulting polymer networks were employed as templates, for the preparation of polypyrrole networks, by an electrochemical polymerization process. The prepared porous polypyrrole film was used to fabricate a chemoresistor-type gas sensor which showed high sensitivity towards ammonia.

The radiation crosslinking of ethylene copolymers

International Nuclear Information System (INIS)

Burns, N.M.

1979-01-01

The enhanced radiation crosslinking tendency of ethylene-vinyl acetate and ethylene-ethyl acrylate copolymers over ethylene homopolymer is proportional to the comonomer content. This is caused by an increase in the amorphous polymer content and by structure-related factors. The copolymers crosslink by a random process that for ethylene-vinyl acetate copolymer involves some crosslinking through the acetoxy group of the comonomer. While knowledge of the process for the crosslinking of ethylene-ethyl acrylate copolymer is less certain, it is currently believed to occur primarily at the branch point on the polymer backbone. Data relating comonomer content and the molecular weight of the copolymers to the radiation crosslinking levels realized were developed to aid in resin selection by the formulator. Triallyl cyanurate cure accelerator was found to be less effective in ethylene-vinyl acetate copolymer than in homopolymer and to have no effect on gel development in ethylene-ethyl acrylate copolymer. (author)

Cellulose/poly-(m-phenylene isophthalamide) porous film as a tissue-engineered skin bioconstruct

Science.gov (United States)

Lee, Jae Woong; Han, Sung Soo; Zo, Sum Mi; Choi, Soon Mo

2018-06-01

Regarding the porous structure, coagulated cellulose may not provide sufficient voids for cell proliferation, resulting in tissue growth. For this reason, it was blended with poly(m-phenylene isophthalamide) (PMIA), which could produce a porous structure in the resulting construct. The aim of this study was to confirm the potential of a novel cellulose/PMIA porous film as a tissue-engineered bioconstruct for impaired skin. The films were fabricated by a coagulation process added with a peel-off method, and the structural, mechanical properties were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and capillary flow porometry. CRL-2310 human keratinocytes were used to determine the biocompatibility of the prepared films. The attachment and proliferation of cells were investigated by scanning electron microscopy, DAPI staining, and a cell viability assay. The results show that cellulose/PMIA porous films have potential use as wound matrices for skin tissue genesis.

Effect of Chain-Extenders on the Properties and Hydrolytic Degradation Behavior of the Poly(lactide/ Poly(butylene adipate-co-terephthalate Blends

Directory of Open Access Journals (Sweden)

Mingqing Chen

2013-10-01

Full Text Available Biodegradable poly(lactide/poly(butylene adipate-co-terephthalate (PLA/PBAT blends were prepared by reactive blending in the presence of chain-extenders. Two chain-extenders with multi-epoxy groups were studied. The effect of chain-extenders on the morphology, mechanical properties, thermal behavior, and hydrolytic degradation of the blends was investigated. The compatibility between the PLA and PBAT was significantly improved by in situ formation of PLA-co-PBAT copolymers in the presence of the chain-extenders, results in an enhanced ductility of the blends, e.g., the elongation at break was increased to 500% without any decrease in the tensile strength. The differential scanning calorimeter (DSC results reveal that cold crystallization of PLA was enhanced due to heterogeneous nucleation effect of the in situ compatibilized PBAT domains. As known before, PLA is sensitive to hydrolysis and in the presence of PBAT and the chain-extenders, the hydrolytic degradation of the blend was evident. A three-stage hydrolysis mechanism for the system is proposed based on a study of weight loss and molecular weight reduction of the samples and the pH variation of the degradation medium.

Wettability modification of rock cores by fluorinated copolymer emulsion for the enhancement of gas and oil recovery

Energy Technology Data Exchange (ETDEWEB)

Feng Chunyan [State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266555 (China); Kong Ying, E-mail: yingkong1967@yahoo.com.cn [State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266555 (China); Jiang Guancheng [MOE Key Laboratory of Petroleum Engineering, China University of Petroleum, Beijing 102249 (China); Yang Jinrong; Pu Chunsheng [State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266555 (China); Zhang Yuzhong [Key Lab of Hollow Fibre Membrane Materials and Membrane Process, Tianjin Polytechnic University, Tianjin 300160 (China)

2012-07-01

The fluorine-containing acrylate copolymer emulsion was prepared with butyl acrylate, methacrylic acid and 1H, 1H, 2H, 2H-perfluorooctyl acrylate as monomers. Moreover, the structure of the copolymer was verified by Fourier transform infrared (FTIR), nuclear magnetic resonance ({sup 1}H NMR and {sup 19}F NMR) and X-ray photoelectron spectroscopy (XPS) analyses. The results showed that all the monomers had been copolymerized and the presence of fluorine moieties. The contact angle (CA) analyses, capillary rise and imbibition spontaneous tests were used to estimate the influence of the copolymer emulsion on the wettability of gas reservoirs. It was observed that the rock surface was of large contact angles of water, oilfield sewage, hexadecane and crude oil after treatment with the emulsion. The capillary rise results indicated that the contact angles of water/air and oil/air systems increased from 60 Degree-Sign and 32 Degree-Sign to 121 Degree-Sign and 80 Degree-Sign , respectively, due to the emulsion treatment. Similarly, because of wettability alteration by the fluoropolymer, the imbibition of water and oil in rock core decreased significantly. Experimental results demonstrated that the copolymer emulsion can alter the wettability of porous media from strong liquid-wetting to gas-wetting. This work provides a cost-effective method to prepare the fluoropolymer which can increase gas deliverability by altering the wettability of gas-condensate reservoirs and mitigating the water block effect.

Study the Possibility of Using an Elastomeric Blend as a Plastic Interfacial media in Ultrasonic Transducers

Directory of Open Access Journals (Sweden)

Auda Jabbar Braihi

2017-03-01

Full Text Available This work tries to study the using of bromobutyle / butyle elasomeric blends in ultrasonic transducers as a dry plastic interfacial media to inspect porous materials such as concrete and refractory materials which can absorb liquid medias , through the study of acoustic impedance characteristics at interfaces . These characteristics include acoustic impedance , the percentage of energy reflected, dB loss, Power ratios expressions , and Pressure ratios expressions (Reflection Coefficient & Transmission Coefficient . They are studied by using ultrasonic instrument named CSI (type CCT- 4 with 26 KHz frequency . Also, this research try to specify the suitable bromobutyle / butyle blend for immersion inspect through the matching between the acoustic impedance of the blend and that of water. Samples preparation achieved in Babylon Tiers Factory. Results showed that by increasing bromobutyle ratio in the blend both reflection coefficient and the percentage of energy reflected increased while acoustic impedance and Transmission Coefficient have been decreased. Also, the results show that 20 bromobutyle / 80 butyle is the suitable blend for immersion tests.

Effect of Ethyl Ester L-Lysine Triisocyanate addition to produce reactive PLA/PCL bio-polyester blends for biomedical applications.

Science.gov (United States)

Visco, Annamaria; Nocita, Davide; Giamporcaro, Alberto; Ronca, Sara; Forte, Giuseppe; Pistone, Alessandro; Espro, Claudia

2017-04-01

We report in this paper the effects of Ethyl Ester L-Lysine Triisocyanate (LTI) on the physical-mechanical properties of Poly(lactide)/Poly(ε-caprolactone) (PLA/PCL) polyesters blends. The PLA/PCL ratios considered were 20/80, 50/50 and 80/20 (wt/wt %) and LTI was added in amounts of 0.0-0.5-1.0 phr. PLA and PCL reacted with LTI during processing in a Brabender twin screw internal mixer to produce block copolymers in-situ. The resulting blends have been characterized by torque measurements, uniaxial tensile tests, Differential Scanning Calorimeter, contact angle measurements with a Phosphate Buffered Saline (PBS) solution, ATR analysis and morphological SEM observations. Experimental results highlighted how LTI enhanced interaction and dispersion of the two components, resulting into a synergic effect in mechanical properties. Mechanical and physical properties can be tailored by changing the blend composition. The most noticeable trend was an increase in ductility of the mixed polymers. Besides, LTI decreased blend's wet ability in PBS and lowered the starting of crystalline phase formation for both polymers, confirming an interaction among them. These reactive blends could find use as biomedical materials, e.g. absorbable suture threads or scaffolds for cellular growth. Copyright © 2017 Elsevier Ltd. All rights reserved.

Poly(hydroxybutyrate)/cellulose acetate blend nanofiber scaffolds: Preparation, characterization and cytocompatibility

Energy Technology Data Exchange (ETDEWEB)

Zhijiang, Cai, E-mail: caizhijiang@hotmail.com [School of Textiles, Tianjin Polytechnic University, Tianjin 300387 (China); State Key Laboratory of Hollow Fiber Membrane Material and Processes, No 399 BingShuiXi Street, XiQing District, Tianjin, China, 300387 (China); Yi, Xu; Haizheng, Yang; Jia, Jianru; Liu, Yuanpei [School of Textiles, Tianjin Polytechnic University, Tianjin 300387 (China)

2016-01-01

Poly(hydroxybutyrate) (PHB)/cellulose acetate (CA) blend nanofiber scaffolds were fabricated by electrospinning using the blends of chloroform and DMF as solvent. The blend nanofiber scaffolds were characterized by SEM, FTIR, XRD, DSC, contact angle and tensile test. The blend nanofibers exhibited cylindrical, uniform, bead-free and random orientation with the diameter ranged from 80–680 nm. The scaffolds had very well interconnected porous fibrous network structure and large aspect surface areas. It was found that the presence of CA affected the crystallization of PHB due to formation of intermolecular hydrogen bonds, which restricted the preferential orientation of PHB molecules. The DSC result showed that the PHB and CA were miscible in the blend nanofiber. An increase in the glass transition temperature was observed with increasing CA content. Additionally, the mechanical properties of blend nanofiber scaffolds were largely influenced by the weight ratio of PHB/CA. The tensile strength, yield strength and elongation at break of the blend nanofiber scaffolds increased from 3.3 ± 0.35 MPa, 2.8 ± 0.26 MPa, and 8 ± 0.77% to 5.05 ± 0.52 MPa, 4.6 ± 0.82 MPa, and 17.6 ± 1.24% by increasing PHB content from 60% to 90%, respectively. The water contact angle of blend nanofiber scaffolds decreased about 50% from 112 ± 2.1° to 60 ± 0.75°. The biodegradability was evaluated by in vitro degradation test and the results revealed that the blend nanofiber scaffolds showed much higher degradation rates than the neat PHB. The cytocompatibility of the blend nanofiber scaffolds was preliminarily evaluated by cell adhesion studies. The cells incubated with PHB/CA blend nanofiber scaffold for 48 h were capable of forming cell adhesion and proliferation. It showed much better biocompatibility than pure PHB film. Thus, the prepared PHB/CA blend nanofiber scaffolds are bioactive and may be more suitable for cell proliferation suggesting that these scaffolds can be used for

Fabrication of metallized nanoporous films from the self-assembly of a block copolymer and homopolymer mixture.

Science.gov (United States)

Li, Xue; Zhao, Shuying; Zhang, Shuxiang; Kim, Dong Ha; Knoll, Wolfgang

2007-06-19

Inorganic compound HAuCl4, which can form a complex with pyridine, is introduced into a poly(styrene-block-2-vinylpyridine) (PS-b-P2VP) block copolymer/poly(methyl methacrylate) (PMMA) homopolymer mixture. The orientation of the cylindrical microdomains formed by the P2VP block, PMMA, and HAuCl4 normal to the substrate surface can be generated via cooperative self-assembly of the mixture. Selective removal of the homopolymer can lead to porous nanostructures containing metal components in P2VP domains, which have a novel photoluminescence property.

Effect of thermal-treatment sequence on sound absorbing and mechanical properties of porous sound-absorbing/thermal-insulating composites

Directory of Open Access Journals (Sweden)

Huang Chen-Hung

2016-01-01

Full Text Available Due to recent rapid commercial and industrial development, mechanical equipment is supplemented massively in the factory and thus mechanical operation causes noise which distresses living at home. In livelihood, neighborhood, transportation equipment, jobsite construction noises impact on quality of life not only factory noise. This study aims to preparation technique and property evaluation of porous sound-absorbing/thermal-insulating composites. Hollow three-dimensional crimp PET fibers blended with low-melting PET fibers were fabricated into hollow PET/low-melting PET nonwoven after opening, blending, carding, lapping and needle-bonding process. Then, hollow PET/low-melting PET nonwovens were laminated into sound-absorbing/thermal-insulating composites by changing sequence of needle-bonding and thermal-treatment. The optimal thermal-treated sequence was found by tensile strength, tearing strength, sound-absorbing coefficient and thermal conductivity coefficient tests of porous composites.

Tailoring of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymers for bone tissue applications

Science.gov (United States)

Liu, Hui

is mineralized. The phenotypic character of the cells grown on modified PHBV matrix was compared against TCPS (a positive control). RNA was extracted from the UMR-106 cells, and reverse transcriptase-polymerase chain reaction (RT-PCR) was applied to detect expression of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) (a house keeping gene) and bone sialoprotein (BSP) (marker of the osteoblastic phenotype) on both matrices. Cells grown on both modified porous and nonporous PHBV were found to retain their original phenotypic character. In addition to evaluating the biocompatibility of modified PHBV, an attempt was made to investigate the degradability of PHBV in physiological medium (phosphate buffer medium at 37°C). The degradation was followed by monitoring the time dependent changes in chemical composition and mass loss of the macroporous films. FT-1R data of the bulk film showed ester hydrolysis upon long immersion of PHBV film in buffer medium. The mass loss of PHBV film after 19 weeks of exposure to buffer medium was found to range from 2.8 % to 9.2 % with a strong dependence on the HV content of the original copolyester. Like mass loss data, the NMR results showed a big drop in the mol% of HV content for degraded copolymer with high HV content of the copolymer. Information generated from this study can be useful in the selection of appropriate PHBV copolymer for clinical applications where the biopolymer needs to remain intact during the period of short term use.

Radiation resistance of ethylene-styrene copolymers

International Nuclear Information System (INIS)

Matsumoto, Kaoru; Ikeda, Masaaki; Ohki, Yoshimichi; Kusama, Yasuo; Harashige, Masahiro; Yazaki, Fumihiko.

1988-01-01

In this paper, the radiation resistance of ethylene-styrene copolymer, a polymeric resin developed newly by the authors, is reported. Resin examined were five kinds of ethylene-styrene copolymers: three random and two graft copolymers with different styrene contents. Low-density polyethylene was used as a reference. The samples were irradiated by 60 Co γ-rays to total absorbed doses up to 10 MGy. The mechanical properties of the smaples were examined. Infrared spectroscopy, differential scanning calorimetry and X-ray scattering techniques were used to examine the morphology of the samples. The random copolymers are soft and easy to extend, because benzene rings which exisist highly at random hinder the crystallization. As for the radiation resistance, they are highly resistant to γ-rays in the aspects of carbonyl group formation, gel formation, and elongation. Further, they show even better radiation resistance when proper additives were compounded in. The graft copolymers are hard to extend, because they consist of segregated polystyrene and polyethylene regions which are connected with each other. The tensile strength of irradiated graft copolymers does not decrease below that of unirradiated copolymers, up to a total dose of 10 MGy. As a consequence, it can be said that ethylene-styrene copolymers have good radiation resistance owing to the so-called 'sponge' effect of benzene rings. (author)

Fabrication of honeycomb-structured poly(ethylene glycol)-block-poly(lactic acid) porous films and biomedical applications for cell growth

Energy Technology Data Exchange (ETDEWEB)

Yao, Bingjian [Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250199 (China); College of chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Normal University, Jinan 250014 (China); Zhu, Qingzeng, E-mail: qzzhu@sdu.edu.cn [Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250199 (China); Yao, Linli [Key Laboratory of the Ministry of Education for Experimental Teratology, Department of Histology and Embryology, Shandong University School of Medicine, 250012 Jinan (China); Hao, Jingcheng [Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250199 (China)

2015-03-30

Graphical abstract: - Highlights: • Honeycomb-structured PEG-PLA porous films were fabricated. • The organization of pores depends on molecular weight ratio of PEG-to-PLA block. • The pores in the film were internally decorated with a layer of PEG. • The honeycomb-structured PEG-PLA film was suitable as a substrate for cell growth. - Abstract: A series of poly(ethylene glycol)-block-poly(lactic acid) (PEG-PLA) copolymers with a hydrophobic PLA block of different molecular weights and a fixed length hydrophilic PEG were synthesized successfully and characterized. These amphiphilic block copolymers were used to fabricate honeycomb-structured porous films using the breath figure (BF) templating technique. The surface topology and composition of the highly ordered pattern film were further characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and fluorescence microscopy. The results indicated that the PEG-to-PLA block molecular weight ratio influenced the BF film surface topology. The film with the best ordered pores was obtained with a PEG-to-PLA ratio of 2.0 × 10{sup 3}:3.0 × 10{sup 4}. The self-organization of the hydrophilic PEG chains within the pores was confirmed by XPS and fluorescence labeled PEG. A model is proposed to elucidate the stabilization process of the amphiphilic PEG-PLA aggregated architecture on the water droplet-based templates. In addition, GFP-U87 cell viability has been investigated by MTS test and the cell morphology on the honeycomb-structured PEG-PLA porous film has been evaluated using phase-contrast microscope. This porous film is shown to be suitable as a matrix for cell growth.

Fabrication of honeycomb-structured poly(ethylene glycol)-block-poly(lactic acid) porous films and biomedical applications for cell growth

International Nuclear Information System (INIS)

Yao, Bingjian; Zhu, Qingzeng; Yao, Linli; Hao, Jingcheng

2015-01-01

Graphical abstract: - Highlights: • Honeycomb-structured PEG-PLA porous films were fabricated. • The organization of pores depends on molecular weight ratio of PEG-to-PLA block. • The pores in the film were internally decorated with a layer of PEG. • The honeycomb-structured PEG-PLA film was suitable as a substrate for cell growth. - Abstract: A series of poly(ethylene glycol)-block-poly(lactic acid) (PEG-PLA) copolymers with a hydrophobic PLA block of different molecular weights and a fixed length hydrophilic PEG were synthesized successfully and characterized. These amphiphilic block copolymers were used to fabricate honeycomb-structured porous films using the breath figure (BF) templating technique. The surface topology and composition of the highly ordered pattern film were further characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and fluorescence microscopy. The results indicated that the PEG-to-PLA block molecular weight ratio influenced the BF film surface topology. The film with the best ordered pores was obtained with a PEG-to-PLA ratio of 2.0 × 10 3 :3.0 × 10 4 . The self-organization of the hydrophilic PEG chains within the pores was confirmed by XPS and fluorescence labeled PEG. A model is proposed to elucidate the stabilization process of the amphiphilic PEG-PLA aggregated architecture on the water droplet-based templates. In addition, GFP-U87 cell viability has been investigated by MTS test and the cell morphology on the honeycomb-structured PEG-PLA porous film has been evaluated using phase-contrast microscope. This porous film is shown to be suitable as a matrix for cell growth

Electronic Properties and Photovoltaic Performances of a Series of Oligothiophene Copolymers Incorporating Both Thieno[3,2-b]thiophene and 2,1,3-Benzothiadiazole Moieties.

Science.gov (United States)

Biniek, Laure; Chochos, Christos L; Hadziioannou, Georges; Leclerc, Nicolas; Lévêque, Patrick; Heiser, Thomas

2010-04-06

A series of donor-acceptor alternated conjugated copolymers, composed of thiophene, bithiophene, thieno[3,2-b]thiophene, and 2,1,3-benzothiadiazole units and differing from each other by the nature and the number of 3-alkylthiophene in the backbone, have been synthesized by Stille cross-coupling polymerization. The material's optical and electrochemical properties, in solution and in thin films, have been investigated using UV-Visible absorption and cyclic voltammetry. Bulk heterojunction solar cells using blends of the newly synthesized copolymers, as electron donor, and C60-PCBM or C70-PCBM, as electron transporting material, have been elaborated. A maximum power conversion efficiency of 1.8% is achieved with a 1:4 PPBzT(2) -C12:C70-PCBM weight ratio. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of porous carbon/silica nanostructured microfiber with ultrahigh surface area

Science.gov (United States)

Zhou, Dan; Dong, Yan; Cui, Liru; Lin, Huiming; Qu, Fengyu

2014-12-01

Carbon/silica-nanostructured microfibers were synthesized via electrospinning method using phenol-formaldehyde resin and tetraethyl orthosilicate as carbon and silica precursor with triblock copolymer Pluronic P123 as soft template. The prepared samples show uniform microfiber structure with 1 μm in diameter and dozens of microns in length. Additionally, the mesopores in the material is about 2-6 nm. When the silica component was removed by HF, the porous carbon microfibers (PCMFs) were obtained. In addition, after the carbon/silica composites were calcined in air, the porous silica microfibers (PSiMFs) were obtained, revealing the converse porous nanostructure as PCMFs. It is a simple way to prepare PCMFs and PSiMFs with silica and carbon as the template to each other. Additionally, PCMFs possess an ultrahigh specific surface area (2,092 m2 g-1) and large pore volume. The electrochemical performance of the prepared PCMF material was investigated in 6.0 M KOH electrolyte. The PCMF electrode exhibits a high specific capacitance (252 F g-1 at 0.5 A g-1). Then, superior cycling stability (97 % retention after 4,000 cycles) mainly is due to its unique nanostructure.

From charge-mosaic to micelle self-assembly: Block copolymer membranes in the last 40 years

KAUST Repository

Nunes, Suzana Pereira; Car, Anja

2013-01-01

Different strategies for membrane preparation based on block copolymers are reviewed in this paper, starting from early papers on charge-mosaic membranes and following with dense membranes for gas separation for applications like CO2 separation, pervaporation of aqueous solutions containing organic pollutants, low-fouling surfaces and finally tailoring porous membranes with very sharp pore size distribution. The approaches for manufacture of nanoporous films are summarized, including etching and preferential dissolution. The advantages of a new process based on micelle assembly and phase inversion are emphasized, confirming its perspective of up-scale and application at large scale. © 2012 American Chemical Society.

From charge-mosaic to micelle self-assembly: Block copolymer membranes in the last 40 years

KAUST Repository

Nunes, Suzana Pereira

2013-01-23

Different strategies for membrane preparation based on block copolymers are reviewed in this paper, starting from early papers on charge-mosaic membranes and following with dense membranes for gas separation for applications like CO2 separation, pervaporation of aqueous solutions containing organic pollutants, low-fouling surfaces and finally tailoring porous membranes with very sharp pore size distribution. The approaches for manufacture of nanoporous films are summarized, including etching and preferential dissolution. The advantages of a new process based on micelle assembly and phase inversion are emphasized, confirming its perspective of up-scale and application at large scale. © 2012 American Chemical Society.

Thermal Conductivity of Ethylene Vinyl Acetate Copolymer/Carbon Nanofiller Blends

Science.gov (United States)

Ghose, S.; Watson, K. A.; Working, D. C.; Connell, J. W.; Smith, J. G., Jr.; Lin, Y.; Sun, Y. P.

2007-01-01

To reduce weight and increase the mobility, comfort, and performance of future spacesuits, flexible, thermally conductive fabrics and plastic tubes are needed for the Liquid Cooling and Ventilation Garment. Such improvements would allow astronauts to operate more efficiently and safely for extended extravehicular activities. As an approach to raise the thermal conductivity (TC) of an ethylene vinyl acetate copolymer (Elvax 260), it was compounded with three types of carbon based nanofillers: multi-walled carbon nanotubes (MWCNTs), vapor grown carbon nanofibers (CNFs), and expanded graphite (EG). In addition, other nanofillers including metallized CNFs, nickel nanostrands, boron nitride, and powdered aluminum were also compounded with Elvax 260 in the melt at various loading levels. In an attempt to improve compatibility between Elvax 260 and the nanofillers, MWCNTs and EG were modified by surface coating and through noncovalent and covalent attachment of organic molecules containing alkyl groups. Ribbons of the nanocomposites were extruded to form samples in which the nanofillers were aligned in the direction of flow. Samples were also fabricated by compression molding to yield nanocomposites in which the nanofillers were randomly oriented. Mechanical properties of the aligned samples were determined by tensile testing while the degree of dispersion and alignment of nanoparticles were investigated using high-resolution scanning electron microscopy. TC measurements were performed using a laser flash (Nanoflash ) technique. TC of the samples was measured in the direction of, and perpendicular to, the alignment direction. Additionally, tubing was also extruded from select nanocomposite compositions and the TC and mechanical flexibility measured.

Influence of compatibilizer and/or montmorillonite addition on the mechanical properties and morphology of PP/recycled PET blends

International Nuclear Information System (INIS)

Silva, Murilo S.; Souza, Adriana M.C.

2011-01-01

In this work, the mechanical properties and morphology PP/recycled PET blends with addition of P(E-co-MA-co-GMA) copolymer and/or montmorillonite clay (MMT) was investigated. The blends were obtained by extrusion and their morphology was observed by scanning electron microscopy. The mechanical properties were evaluated by tensile and impact tests. Thin films of nanocomposites were characterized by x-ray diffraction (XRD). The addition of P (E-co-MA-co-GMA) or MMT clay separately promoted a decrease of the dispersed phase size. XRD analysis indicated that there was incorporation of polymer in clay galleries. The addition of clay in PP / PET blend resulted in an increase of apparent elastic modulus, impact resistance and HDT and a decrease of tensile strength and elongation at break. The addition of P (E-co-MA-co-GMA) resulted in an increased impact strength and reduction of other properties. There were no significant changes on mechanical properties when the clay and P (E-co-MA-co-GMA) are added simultaneously. (author)

Study of lamellar structure and crystallization behavior of poly(butylene terephthalate (PBT) in PBT/ABS and PBT/ABS/MMA-GMA blends using DSC, SAXS and DMTA

International Nuclear Information System (INIS)

Mantovani, Gerson L.; Pessan, Luiz A.; Hage, Elias; Torriani, Iris L.

2001-01-01

The effects of processing conditions and blend composition in the crystallization behaviour and lamellar structure of poly(butylene terephthalate) (PBT) in blends with acrylonitrile-butadiene-styrene copolymer (ABS) were studied. Differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS) and dynamic mechanical thermal analysis (DMTA) were used to observe those effects. Addition of reactive acrylic compatibilizer to the PBT/ABS blends has promoted an increase in the heat of crystallization of the related blends. The Long Period (L), obtained from the peak in the Lorentz-corrected SAXS pattern, was used to observe the effect in the lamellar structure of PBT phase in the blends. The results were in good agreement with the calculated values from de correlation function and the values of L do not show a significant dependence with the PBT mass fraction, either in the binary blends (PBT/ABS) or in the compatibilized blends. A slight but clear increase of the long period (from 3 to 5 angstrom) is noted for the systems injection molded at 240 deg C when compared to the ones molded at 260 deg C, although PBT crystallinity in the blends does not change significantly with blend composition or processing conditions. DMTA curves show a slight shift in the temperature of the tan δ main peaks for both PBT and ABS phases in the compatibilized blends, thereby indicating changes in the degree of miscibility or interaction between phases of those blends. Changes in the compatibilized blends miscibility may be responsible by the effects in the crystallization behaviour and lamellar structure of the PBT/ABS blends. (author)

Study of lamellar structure and crystallization behavior of poly(butylene terephthalate (PBT) in PBT/ABS and PBT/ABS/MMA-GMA blends using DSC, SAXS and DMTA

Energy Technology Data Exchange (ETDEWEB)

Mantovani, Gerson L.; Pessan, Luiz A.; Hage, Elias [Sao Carlos Univ., SP (Brazil). Dept. de Engenharia de Materiais]. E-mail: elias@power.ufscar.br; Plivelic, Tomas S. [Laboratorio Nacional de Luz Sincrotron (LNLS), Campinas, SP (Brazil); Torriani, Iris L. [Universidade Estadual de Campinas, SP (Brazil). Inst. de Fisica Gleb Wataghin

2001-07-01

The effects of processing conditions and blend composition in the crystallization behaviour and lamellar structure of poly(butylene terephthalate) (PBT) in blends with acrylonitrile-butadiene-styrene copolymer (ABS) were studied. Differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS) and dynamic mechanical thermal analysis (DMTA) were used to observe those effects. Addition of reactive acrylic compatibilizer to the PBT/ABS blends has promoted an increase in the heat of crystallization of the related blends. The Long Period (L), obtained from the peak in the Lorentz-corrected SAXS pattern, was used to observe the effect in the lamellar structure of PBT phase in the blends. The results were in good agreement with the calculated values from de correlation function and the values of L do not show a significant dependence with the PBT mass fraction, either in the binary blends (PBT/ABS) or in the compatibilized blends. A slight but clear increase of the long period (from 3 to 5 angstrom) is noted for the systems injection molded at 240 deg C when compared to the ones molded at 260 deg C, although PBT crystallinity in the blends does not change significantly with blend composition or processing conditions. DMTA curves show a slight shift in the temperature of the tan {delta} main peaks for both PBT and ABS phases in the compatibilized blends, thereby indicating changes in the degree of miscibility or interaction between phases of those blends. Changes in the compatibilized blends miscibility may be responsible by the effects in the crystallization behaviour and lamellar structure of the PBT/ABS blends. (author)

Proton exchange membrane developed from novel blends of polybenzimidazole and poly(vinyl-1,2,4-triazole).

Science.gov (United States)

Hazarika, Mousumi; Jana, Tushar

2012-10-24

In continuation (J. Phys. Chem. B2008, 112, 5305; J. Colloid Interface Sci. 2010, 351, 374) of our quest for proton exchange membrane (PEM) developed from polybenzimidazole (PBI) blends, novel polymer blend membranes of PBI and poly(1-vinyl-1,2,4-triazole) (PVT) were prepared using a solution blending method. The aim of the work was to investigate the effect of the blend composition on the properties, e.g., thermo-mechanical stability, swelling, and proton conductivity of the blend membranes. The presence of specific interactions between the two polymers in the blends were observed by studying the samples using varieties of spectroscopic techniques. Blends prepared in all possible compositions were studied using a differential scanning calorimetry (DSC) and exhibited a single T(g) value, which lies between the T(g) value of the neat polymers. The presence of a single composition-dependent T(g) value indicated that the blend is a miscible blend. The N-H···N interactions between the two polymers were found to be the driving force for the miscibility. Thermal stability up to 300 °C of the blend membranes, obtained from thermogravimetric analysis, ensured their suitability as PEMs for high-temperature fuel cells. The proton conductivity of the blend membranes have improved significantly, compared to neat PBI, because of the presence of triazole moiety, which acts as a proton facilitator in the conduction process. The blend membranes showed a considerably lower increase in thickness and swelling ratio than that of PBI after doping with phosphoric acid (PA). We found that the porous morphology of the blend membranes caused the loading of a larger amount of PA and, consequently, higher proton conduction with lower activation energy, compared to neat PBI.

Studies of PVC/ENR blends: blend compositions

International Nuclear Information System (INIS)

Chantara Thevy Ratnam; Khairul Zaman Mohd Dahlan; Nasir, M.; Baharin, A.

2002-01-01

Blends of poly(vinyl chloride/epoxidized natural rubber (PVC/ENR) were prepared by using Bra bender Plasticorder at compositions ranging from 0-100% PVC. They were blended at 150 degree C mixing temperature, 50 rpm rotor speed and 10 minutes mixing time. The blends were characterized for tensile strength , elongation at break, glass transition temperatures and Fourier transform infra red spectroscopy (FTIR). Results revealed that as the PVC content increases the blend behaviour changes from elastomeric to glassy. However the blends found to be compatible at all compositions. (Author)

Tuning the pore composition by two simultaneous interfacial self-assembly processes: breath figures and coffee stain.

Science.gov (United States)

de León, Alberto S; del Campo, Adolfo; Fernández-García, Marta; Rodríguez-Hernández, Juan; Muñoz-Bonilla, Alexandra

2014-06-03

In the current paper, we prepared microstructured porous films by the breath figures approach using polymer blends consisting of polystyrene as the major component and an amphiphilic additive, either a synthetic block copolymer {two different polystyrene-b-poly[poly(ethylene glycol) methyl ether methacrylate] copolymers} or a series of commercial surfactants. Tetrahydrofuran was employed as the solvent. Confocal micro-Raman spectroscopy demonstrated the preferential location of the amphiphilic additives in the cavities of the film as a consequence of the breath figures mechanism. However, the distribution of the copolymer within the cavities varies depending upon the structure and, more precisely, the surface properties of the additives, leading to three different situations. First of all, the copolymer with a larger polystyrene segment, insoluble in the condensed water droplets, is homogeneously distributed along the whole surface of the cavities. On the contrary, when the copolymer is soluble in water (shorter polystyrene segment), it migrates inside the droplet and a coffee-stain phenomenon takes place during the water droplet evaporation, conducting to a ring-like deposition on the top edge of the cavities. Finally, when a water-soluble surfactant with high surface activity is used, the surfactant is solubilized inside the water droplets, which provokes a decrease on the surface tension and the coffee-ring effect is modified. In this situation, the copolymer covers the bottom of the pore.

Facile Control of the Porous Structure of Larch-Derived Mesoporous Carbons via Self-Assembly for Supercapacitors

Directory of Open Access Journals (Sweden)

Xin Zhao

2017-11-01

Full Text Available Mesoporous carbons have been successfully synthesized via self-assembly using larch-based resins as precursors and triblock copolymers as soft templates. The porous structure of mesoporous carbons can be tailored by adjusting the ratio of hydrophilic/hydrophobic (EO/PO units owing to interfacial curvature. Interestingly, the porous structures show a distinct change from vortex-like to worm-like pores, to stripe-like pores, and to ordered two-dimensional hexagonal pores as the ratio of hydrophilic/hydrophobic units increases, indicating the significant effect of EO/PO ratio on the porous structure. The mesoporous carbons as supercapacitor electrodes exhibit superior electrochemical capacitive performance and a high degree of reversibility after 2000 cycles for supercapacitors due to the well-defined mesoporosity of the carbon materials. Meanwhile, the superior carbon has a high specific capacitance of 107 F·g−1 in 6 M KOH at a current density of 10 A·g−1.

Rapid self-assembly of block copolymers to photonic crystals

Science.gov (United States)

Xia, Yan; Sveinbjornsson, Benjamin R; Grubbs, Robert H; Weitekamp, Raymond; Miyake, Garret M; Atwater, Harry A; Piunova, Victoria; Daeffler, Christopher Scot; Hong, Sung Woo; Gu, Weiyin; Russell, Thomas P.

2016-07-05

The invention provides a class of copolymers having useful properties, including brush block copolymers, wedge-type block copolymers and hybrid wedge and polymer block copolymers. In an embodiment, for example, block copolymers of the invention incorporate chemically different blocks comprising polymer size chain groups and/or wedge groups that significantly inhibit chain entanglement, thereby enhancing molecular self-assembly processes for generating a range of supramolecular structures, such as periodic nanostructures and microstructures. The present invention also provides useful methods of making and using copolymers, including block copolymers.

Nanocomposites based on hierarchical porous carbon fiber@vanadium nitride nanoparticles as supercapacitor electrodes.

Science.gov (United States)

Ran, Fen; Wu, Yage; Jiang, Minghuan; Tan, Yongtao; Liu, Ying; Kong, Lingbin; Kang, Long; Chen, Shaowei

2018-03-28

In this study, a hybrid electrode material for supercapacitors based on hierarchical porous carbon fiber@vanadium nitride nanoparticles is fabricated using the method of phase-separation mediated by the PAA-b-PAN-b-PAA tri-block copolymer. In the phase-separation procedure, the ionic block copolymer self-assembled on the surface of carbon nanofibers, and is used to adsorb NH 4 VO 3 . Thermal treatment at controlled temperatures under an NH 3  : N 2 atmosphere led to the formation of vanadium nitride nanoparticles that are distributed uniformly on the nanofiber surface. By changing the PAN to PAA-b-PAN-b-PAA ratio in the casting solution, a maximum specific capacitance of 240.5 F g -1 is achieved at the current density of 0.5 A g -1 with good rate capability at a capacitance retention of 72.1% at 5.0 A g -1 in an aqueous electrolyte of 6 mol L -1 KOH within the potential range of -1.10 to 0 V (rN/A = 1.5/1.0). Moreover, an asymmetric supercapacitor is assembled by using the hierarchical porous carbon fiber@vanadium nitride as the negative electrode and Ni(OH) 2 as the positive electrode. Remarkably, at the power density of 400 W kg -1 , the supercapacitor device delivers a better energy density of 39.3 W h kg -1 . It also shows excellent electrochemical stability, and thus might be used as a promising energy-storage device.

Lignin poly(lactic acid) copolymers

Energy Technology Data Exchange (ETDEWEB)

Olsson, Johan Vilhelm; Chung, Yi-Lin; Li, Russell Jingxian; Waymouth, Robert; Sattely, Elizabeth; Billington, Sarah; Frank, Curtis W.

2017-02-14

Provided herein are graft co-polymers of lignin and poly(lactic acid) (lignin-g-PLA copolymer), thermoset and thermoplastic polymers including them, methods of preparing these polymers, and articles of manufacture including such polymers.

Polyether-polyester graft copolymer

Science.gov (United States)

Bell, Vernon L. (Inventor)

1987-01-01

Described is a polyether graft polymer having improved solvent resistance and crystalline thermally reversible crosslinks. The copolymer is prepared by a novel process of anionic copolymerization. These polymers exhibit good solvent resistance and are well suited for aircraft parts. Previous aromatic polyethers, also known as polyphenylene oxides, have certain deficiencies which detract from their usefulness. These commercial polymers are often soluble in common solvents including the halocarbon and aromatic hydrocarbon types of paint thinners and removers. This limitation prevents the use of these polyethers in structural articles requiring frequent painting. In addition, the most popular commercially available polyether is a very high melting plastic. This makes it considerably more difficult to fabricate finished parts from this material. These problems are solved by providing an aromatic polyether graft copolymer with improved solvent resistance and crystalline thermally reversible crosslinks. The graft copolymer is formed by converting the carboxyl groups of a carboxylated polyphenylene oxide polymer to ionic carbonyl groups in a suitable solvent, reacting pivalolactone with the dissolved polymer, and adding acid to the solution to produce the graft copolymer.

Polyether/Polyester Graft Copolymers

Science.gov (United States)

Bell, Vernon L., Jr.; Wakelyn, N.; Stoakley, D. M.; Proctor, K. M.

1986-01-01

Higher solvent resistance achieved along with lower melting temperature. New technique provides method of preparing copolymers with polypivalolactone segments grafted onto poly (2,6-dimethyl-phenylene oxide) backbone. Process makes strong materials with improved solvent resistance and crystalline, thermally-reversible crosslinks. Resulting graft copolymers easier to fabricate into useful articles, including thin films, sheets, fibers, foams, laminates, and moldings.

Biointerfacial impedance characterization of reduced graphene oxide supported carboxyl pendant conducting copolymer based electrode

International Nuclear Information System (INIS)

Puri, Nidhi; Niazi, Asad; Srivastava, Avanish Kumar; Rajesh

2014-01-01

We report, a comprehensive physical and biointerfacial electrochemical characteristics of electrodeposited poly(pyrrole-co-pyrrolepropylic acid) (PPy-PPa) copolymer film on the reduced graphene oxide (RGO) sheets attached over a silane modified indium-tin-oxide coated glass, for biosensing applications. The highly specific cardiac myoglobin protein antibody, Ab-cMb, has been covalently immobilized on the copolymer film through its pendent carboxyl group by carbodiimide coupling reaction. The factor ‘n’ describing divergence of the system from ideal capacitor characteristics exhibits a low value (n = 0.59) in a constant phase element of the impedance. This low value of ‘n’ showing a porous rough microstructure of PPy-PPa film on RGO exhibiting a diffusive characteristic that has been replaced by dominant charge transfer characteristic (R et ) with n = 0.78 on biomolecular immobilization and subsequent immunoreaction. The bioelectrode exhibits a linear impedance response to human cardiac cMb marker in the range of 10 ng mL −1 to 1 μg mL −1 in phosphate buffer solution (PBS; pH 7.4) at a low frequency region of et sensitivity of 70.30 Ω cm 2 per decade

Membranes with highly ordered straight nanopores by selective swelling of fast perpendicularly aligned block copolymers.

Science.gov (United States)

Yin, Jun; Yao, Xueping; Liou, Jiun-You; Sun, Wei; Sun, Ya-Sen; Wang, Yong

2013-11-26

Membranes with uniform, straight nanopores have important applications in diverse fields, but their application is limited by the lack of efficient producing methods with high controllability. In this work, we reported on an extremely simple and efficient strategy to produce such well-defined membranes. We demonstrated that neutral solvents were capable of annealing amphiphilic block copolymer (BCP) films of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) with thicknesses up to 600 nm to the perpendicular orientation within 1 min. Annealing in neutral solvents was also effective to the perpendicular alignment of block copolymers with very high molecular weights, e.g., 362 000 Da. Remarkably, simply by immersing the annealed BCP films in hot ethanol followed by drying in air, the originally dense BCP films were nondestructively converted into porous membranes containing highly ordered, straight nanopores traversing the entire thickness of the membrane (up to 1.1 μm). Grazing incident small-angle X-ray spectroscopy confirmed the hexagonal ordering of the nanopores over large areas. We found that the overflow of P2VP chains from their reservoir P2VP cylinders and the deformation of the PS matrix in the swelling process contributed to the transformation of the solid P2VP cylinders to empty straight pores. The pore diameters can be tuned by either changing the swelling temperatures or depositing thin layers of metal oxides on the preformed membranes via atomic layer deposition with a subnanometer accuracy. To demonstrate the application of the obtained porous membranes, we used them as templates and produced centimeter-scale arrays of aligned nanotubes of metal oxides with finely tunable wall thicknesses.

Multicomponent Solvated Triblock Copolymer Network Systems: Fundamental Insights and Emerging Applications

Science.gov (United States)

Krishnan, Arjun Sitaraman

Block copolymers have received significant research attention in recent times due to their ability to spontaneously self-assemble into a variety of nanostructures. Thermoplastic elastomers composed of styrenic triblock copolymers are of great importance in applications such as adhesives and vibration dampening due to their shape memory, resilience and facile processing. The swelling of these polymers by adding midblock selective solvents or oligomers provides an easy route by which to modify the morphology and mechanical behavior of these systems. We first consider a ternary blend of a poly[styrene- b-(ethylene-co-butylene)-b-styrene] triblock copolymer (SEBS) and mixtures of two midblock selective co-solvents, with significantly different physical states. We use dynamic rheology to study the viscoelastic response of a wide variety of systems under oscillatory shear. Frequency spectra acquired at ambient temperature display viscoelastic behavior that shifts in the frequency domain depending on the co-solvent composition. For each copolymer concentration, all the frequency data can be shifted by time-composition superpositioning (tCS) to yield a single master-curve. tCS fails at low frequencies due to presence of endblock pullout, which is a fundamentally different relaxation process from segmental relaxation of the midblock. As an emerging technology, we examine SEBS-oil gels as dielectric elastomers. Dielectric elastomers constitute one class of electroactive polymers (EAPs), polymeric materials that respond to an electric stimulus by changing their macroscopic dimensions, thereby converting electrical energy into mechanical work. We use standard configuration of EAP devices involving stretching, or "prestraining," the elastomer film biaxially. The effect of experimental parameters such as film thickness and amount of prestrain on the (electro)mechanical properties of the material become apparent by recasting as-obtained electroactuation data into compressive

PEO-related block copolymer surfactants

DEFF Research Database (Denmark)

Mortensen, K.

2001-01-01

Non-ionic block copolymer systems based on hydrophilic poly(ethylene oxide) and more hydrophobic co-polymer blocks are used intensively in a variety of industrial and personal applications. A brief description on the applications is presented. The physical properties of more simple model systems...... of such PEG-based block copolymers in aqueous suspensions are reviewed. Based on scattering experiments using either X-ray or neutrons, the phase behavior is characterized, showing that the thermo-reversible gelation is a result of micellar ordering into mesoscopic crystalline phases of cubic, hexagonal...

Design, preparation, and application of ordered porous polymer materials

International Nuclear Information System (INIS)

Liu, Qingquan; Tang, Zhe; Ou, Baoli; Liu, Lihua; Zhou, Zhihua; Shen, Shaohua; Duan, Yinxiang

2014-01-01

Ordered porous polymer (OPP) materials have extensively application prospects in the field of separation and purification, biomembrane, solid supports for sensors catalysts, scaffolds for tissue engineering, photonic band gap materials owing to ordered pore arrays, uniform and tunable pore size, high specific surface area, great adsorption capacity, and light weight. The present paper reviewed the preparation techniques of OPP materials like breath figures, hard template, and soft template. Finally, the applications of OPP materials in the field of separation, sensors, and biomedicine are introduced, respectively. - Highlights: • Breath figures involve polymer casting under moist ambience. • Hard template employs monodisperse colloidal spheres as a template. • Soft template utilizes the etched block in copolymers as template

Strong and biocompatible three-dimensional porous silk fibroin/graphene oxide scaffold prepared by phase separation.

Science.gov (United States)

Wang, Shu-Dong; Ma, Qian; Wang, Ke; Ma, Pi-Bo

2018-05-01

Silk fibroin (SF) is blended with graphene oxide (GO) to prepare the strong and biocompatible three dimensional porous SF/GO blended scaffold via phase separation. GO could be well dispersed in SF solution and GO could also be well distributed in the SF scaffold. Furthermore, the introduction of GO can lead to structural change in the bended scaffold. Higher concentration of GO resulted in more compact structure and smaller pore size of the composite scaffolds without decreasing their porosity. Scanning electron microscopy and energy dispersive spectrometry results also reveal that SF and GO are homogeneous blended together. Analysis of chemical structures of the scaffold shows that addition of GO do not affect the crystalline structure of SF and it is evenly blended with SF. The blended scaffold has significantly higher breaking strength than the pure SF scaffold. In vitro study indicates that both pure SF scaffold and SF/GO composite scaffold support growth and proliferation of MC3T3-E1 osteoprogenitor cells. However, the addition of GO contribute to the proliferation of MC3T3-E1 osteoprogenitor. The testing results show that the blended scaffold is an appropriate candidate for tissue engineering. Copyright © 2018 Elsevier B.V. All rights reserved.

Supramolecular structure, phase behavior and thermo-rheological properties of a poly (L-lactide-co-ε-caprolactone) statistical copolymer.

Science.gov (United States)

Ugartemendia, Jone M; Muñoz, M E; Santamaria, A; Sarasua, J R

2015-08-01

PLAcoCL samples, both unaged, termed PLAcoCLu, and aged over time, PLAcoCLa, were prepared and analyzed to study the phase structure, morphology, and their evolution under non-quiescent conditions. X- ray diffraction, Differential Scanning Calorimetry and Atomic Force Microscopy were complemented with thermo-rheological measurements to reveal that PLAcoCL evolves over time from a single amorphous metastable state to a 3 phase system, made up of two compositionally different amorphous phases and a crystalline phase. The supramolecular arrangements developed during aging lead to a rheological complex behavior in the PLAcoCLa copolymer: Around Tt=131 °C thermo-rheological complexity and a peculiar chain mobility reduction were observed, but at T>Tt the thermo-rheological response of a homogeneous system was recorded. In comparison with the latter, the PLLA/PCL 70:30 physical blend counterpart showed double amorphous phase behavior at all temperatures, supporting the hypothesis that phase separation in the PLAcoCLa copolymer is caused by the crystallization of polylactide segment blocks during aging. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of blending poly(D,L-lactide) with poly(ethylene glycol) on the higher-order crystalline structures of poly(ethylene glycol) as revealed by small-angle X-ray scattering

International Nuclear Information System (INIS)

Tien, N D; Kimura, G; Yamashiro, Y; Fujiwara, H; Sasaki, S; Sakurai, S; Hoa, T P; Mochizuki, M

2011-01-01

Effects of blending poly(lactic acid) (PLA) with poly(ethylene glycol) (PEG) on higher-order crystalline structures of PEG were examined using small-angle X-ray scattering (SAXS). For this purpose, the fact that two polymers are both crystalline makes situtation much complicated. To simplify, non-crystalline PLA is suitable. Thus, we used poly(D,L-lactic acid) (DLPLA), which is random copolymer comprising D- and L-lactic acid moieties. Multiple scattering peaks arising from the regular crystalline lamellar structure were observed for the PEG homopolymer and the blends. Surprisingly, the structure is much more regular for the blend DLPLA/PEG at composition of 20/80 wt.% than for the PEG homopolymer. Also for this blend sample as well as for a PEG homopolymer, very peculiar SAXS profiles were observed just 1 deg. C below T m of PEG. This is found to be a particle scattering of plate-like objects, which has never been reported for polymer blends or crystalline polymers. Futhermore, it was found that there was strong hysteresis of the higher-order structure formation.

White Polymer Light-Emitting Diodes Based on Exciplex Electroluminescence from Polymer Blends and a Single Polymer.

Science.gov (United States)

Liang, Junfei; Zhao, Sen; Jiang, Xiao-Fang; Guo, Ting; Yip, Hin-Lap; Ying, Lei; Huang, Fei; Yang, Wei; Cao, Yong

2016-03-09

In this Article, we designed and synthesized a series of polyfluorene derivatives, which consist of the electron-rich 4,4'-(9-alkyl-carbazole-3,6-diyl)bis(N,N-diphenylaniline) (TPA-Cz) in the side chain and the electron-deficient dibenzothiophene-5,5-dioxide (SO) unit in the main chain. The resulting copolymer PF-T25 that did not comprise the SO unit exhibited blue light-emission with the Commission Internationale de L'Eclairage coordinates of (0.16, 0.10). However, by physically blending PF-T25 with a blue light-emitting SO-based oligomer, a novel low-energy emission correlated to exciplex emerged due to the appropriate energy level alignment of TPA-Cz and the SO-based oligomers, which showed extended exciton lifetime as confirmed by time-resolved photoluminescent spectroscopy. The low-energy emission was also identified in copolymers consisting of SO unit in the main chain, which can effectively compensate for the high-energy emission to produce binary white light-emission. Polymer light-emitting diodes based on the exciplex-type single greenish-white polymer exhibit the peak luminous efficiency of 2.34 cd A(-1) and the maximum brightness of 12 410 cd m(-2), with Commission Internationale de L'Eclairage color coordinates (0.27, 0.39). The device based on such polymer showed much better electroluminescent stability than those based on blending films. These observations indicated that developing a single polymer with the generated exciplex emission can be a novel and effective molecular design strategy toward highly stable and efficient white polymer light-emitting diodes.

Blend or not to blend: a study investigating faculty members perceptions of blended teaching

Directory of Open Access Journals (Sweden)

Mehmet A Ocak

2010-12-01

Full Text Available This study examined faculty members’ perceptions of blended teaching from several perspectives. A total of 73 faculty members in Turkish Higher Education context participated in the study by completing an online survey that combined quantitative and qualitative approaches. Based on a data analysis, the faculty members’ perceptions were sorted into six categories: (a satisfaction with blended teaching, (b perceived impact on the role of the faculty, (c perceived impact on student learning, (d perceived impact on student motivation, (e advantages of blended teaching, and (f disadvantages of blended teaching. Findings indicated that faculty members were likely to agree that blended teaching provides a high degree of satisfaction and that it requires more time and commitment from the faculty. The faculty members perceived that blended teaching improves student learning and, to some extent, improves motivation. The faculty members also emphasized the importance of institutional support and the use of technology to mitigate student problems. This study presents these faculty members’ perceptions, which are helpful for those planning to implement a blended teaching approach, and makes suggestions for trouble-shooting and taking advantage of the opportunities in a blended environment successfully.

Self-assembly behavior of poly(fluorenyl styrene)-block-poly(2-vinyl pyridine) and their blends with single wall carbon nanotubes (SWCNT)

Science.gov (United States)

Mezzenga, Raffaele; Li, Chaoxu; Hsu, Jung-Ching; Chen, Wen-Chang; Sugiyama, Kenji; Hirao, Akira

2010-03-01

We describe a supramolecular strategy to disperse carbon nanotubes in block copolymer matrices. To achieve the desired functions and morphologies, comb-type architectures in which one and two fluorene units attached on the styrene ring of polystyrene-block-poly(2-vinyl pyridine) were studied. Depending on the pendant fluorene units, the block ratio, the casting solvent and thermal annealing history, multiple morphologies were found. The phase diagram, compared to PS-b-P2VP, was interpreted in terms of the conformational asymmetry arising from grafting of fluorene units of variable lengths. Hydrogen bonds between COOH-SWCNT and P2VP favor miscibility of SWCNT within P2VP domains and the blending of these two components is reflected both on the final morphologies and on the electron conductivity of the blends.

Modification of bone graft by blending with lecithin to improve hydrophilicity and biocompatibility

International Nuclear Information System (INIS)

Wang, Y; Cui, F Z; Jiao, Y P; Hu, K; Fan, D D

2008-01-01

Lecithin was blended to improve the hydrophilicity and biocompatibility of bone graft containing poly(l-lactic acid) (PLLA). Solution blending and freeze drying were used to fabricate symmetrical scaffolds containing different percentages of lecithin (lecithin: PLLA = 0, 5, 10 wt%). Scanning electron microscopy showed that the scaffolds maintained the three-dimensional porous structure. A water uptake experiment proved the significant improvement of hydrophilicity of the blend scaffold. With the addition of lecithin, the compressive strength and compressive modulus decreased. When the weight ratio of lecithin to PLLA was up to 10%, the compressive strength was still more than the lower limit of natural cancellous bone. To test the biocompatibility of the scaffolds, cell culture in vitro and subcutaneous implantation in vivo were performed. MC3T3-E1 preosteoblastic cells were cultured on the scaffolds for 7 days. Methylthiazol tetrazolium assay and laser scanning confocal microscopy were used to exhibit proliferation and morphology of the cells. The subcutaneous implantation in rats tested inflammatory response to the scaffolds. The results proved the better biocompatibility and milder inflammatory reactions of the blend scaffold (lecithin: PLLA = 5%) compared with the scaffold without lecithin. The modified scaffold containing lecithin is promising for bone tissue engineering

Synthesis of porous carbon/silica nanostructured microfiber with ultrahigh surface area

Energy Technology Data Exchange (ETDEWEB)

Zhou, Dan; Dong, Yan; Cui, Liru; Lin, Huiming, E-mail: hiuminglin@gmail.com; Qu, Fengyu, E-mail: qufengyu2012@yahoo.cn, E-mail: qufengyu@hrbnu.edu.cn [Harbin Normal University, College of Chemistry and Chemical Engineering (China)

2014-12-15

Carbon/silica-nanostructured microfibers were synthesized via electrospinning method using phenol-formaldehyde resin and tetraethyl orthosilicate as carbon and silica precursor with triblock copolymer Pluronic P123 as soft template. The prepared samples show uniform microfiber structure with ∼1 μm in diameter and dozens of microns in length. Additionally, the mesopores in the material is about 2–6 nm. When the silica component was removed by HF, the porous carbon microfibers (PCMFs) were obtained. In addition, after the carbon/silica composites were calcined in air, the porous silica microfibers (PSiMFs) were obtained, revealing the converse porous nanostructure as PCMFs. It is a simple way to prepare PCMFs and PSiMFs with silica and carbon as the template to each other. Additionally, PCMFs possess an ultrahigh specific surface area (2,092 m{sup 2} g{sup −1}) and large pore volume. The electrochemical performance of the prepared PCMF material was investigated in 6.0 M KOH electrolyte. The PCMF electrode exhibits a high specific capacitance (252 F g{sup −1} at 0.5 A g{sup −1}). Then, superior cycling stability (97 % retention after 4,000 cycles) mainly is due to its unique nanostructure.

Biodegradable copolymers carrying cell-adhesion peptide sequences.

Science.gov (United States)

Proks, Vladimír; Machová, Lud'ka; Popelka, Stepán; Rypácek, Frantisek

2003-01-01

Amphiphilic block copolymers are used to create bioactive surfaces on biodegradable polymer scaffolds for tissue engineering. Cell-selective biomaterials can be prepared using copolymers containing peptide sequences derived from extracellular-matrix proteins (ECM). Here we discuss alternative ways for preparation of amphiphilic block copolymers composed of hydrophobic polylactide (PLA) and hydrophilic poly(ethylene oxide) (PEO) blocks with cell-adhesion peptide sequences. Copolymers PLA-b-PEO were prepared by a living polymerisation of lactide in dioxane with tin(II)2-ethylhexanoate as a catalyst. The following approaches for incorporation of peptides into copolymers were elaborated. (a) First, a side-chain protected Gly-Arg-Gly-Asp-Ser-Gly (GRGDSG) peptide was prepared by solid-phase peptide synthesis (SPPS) and then coupled with delta-hydroxy-Z-amino-PEO in solution. In the second step, the PLA block was grafted to it via a controlled polymerisation of lactide initiated by the hydroxy end-groups of PEO in the side-chain-protected GRGDSG-PEO. Deprotection of the peptide yielded a GRGDSG-b-PEO-b-PLA copolymer, with the peptide attached through its C-end. (b) A protected GRGDSG peptide was built up on a polymer resin and coupled with Z-carboxy-PEO using a solid-phase approach. After cleavage of the delta-hydroxy-PEO-GRGDSG copolymer from the resin, polymerisation of lactide followed by deprotection of the peptide yielded a PLA-b-PEO-b-GRGDSG block copolymer, in which the peptide is linked through its N-terminus.

Activated Porous Carbon Spheres with Customized Mesopores through Assembly of Diblock Copolymers for Electrochemical Capacitor.

Science.gov (United States)

Tang, Jing; Wang, Jie; Shrestha, Lok Kumar; Hossain, Md Shahriar A; Alothman, Zeid Abdullah; Yamauchi, Yusuke; Ariga, Katsuhiko

2017-06-07

A series of porous carbon spheres with precisely adjustable mesopores (4-16 nm), high specific surface area (SSA, ∼2000 m 2 g -1 ), and submicrometer particle size (∼300 nm) was synthesized through a facile coassembly of diblock polymer micelles with a nontoxic dopamine source and a common postactivation process. The mesopore size can be controlled by the diblock polymer, polystyrene-block-poly(ethylene oxide) (PS-b-PEO) templates, and has an almost linear dependence on the square root of the degree of polymerization of the PS blocks. These advantageous structural properties make the product a promising electrode material for electrochemical capacitors. The electrochemical capacitive performance was studied carefully by using symmetrical cells in a typical organic electrolyte of 1 M tetraethylammonium tetrafluoroborate/acetonitrile (TEA BF 4 /AN) or in an ionic liquid electrolyte of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF 4 ), displaying a high specific capacitance of 111 and 170 F g -1 at 1 A g -1 , respectively. The impacts of pore size distribution on the capacitance performance were thoroughly investigated. It was revealed that large mesopores and a relatively low ratio of micropores are ideal for realizing high SSA-normalized capacitance. These results provide us with a simple and reliable way to screen future porous carbon materials for electrochemical capacitors and encourage researchers to design porous carbon with high specific surface area, large mesopores, and a moderate proportion of micropores.

Mechanical properties of weakly segregated block copolymers : 1. Synergism on tensile properties of poly(styrene-b-n-butylmethacrylate) diblock copolymers

NARCIS (Netherlands)

Weidisch, R.; Michler, G.H.; Fischer, H.; Arnold, M.; Hofmann, S.; Stamm, M.

1999-01-01

Mechanical properties of poly(styrene-b-n-butylmethacrylate) diblock copolymers, PS-b-PBMA, with different lengths of the polystyrene block were investigated. The copolymers display a composition range where the tensile strength of the block copolymers exceeds the values of the corresponding

Oil recovery with vinyl sulfonic acid-acrylamide copolymers

Energy Technology Data Exchange (ETDEWEB)

Norton, C.J.; Falk, D.O.

1973-12-18

An aqueous polymer flood containing sulfomethylated alkali metal vinyl sulfonate-acrylamide copolymers was proposed for use in secondary or tertiary enhanced oil recovery. The sulfonate groups on the copolymers sustain the viscosity of the flood in the presence of brine and lime. Injection of the copolymer solution into a waterflooded Berea core, produced 30.5 percent of the residual oil. It is preferred that the copolymers are partially hydrolyzed.

Combined effects of petrographic and technological parameters on strength of porous coke substance

Energy Technology Data Exchange (ETDEWEB)

Dinel' t, V.M.; Shkoller, M.B.; Stankevich, A.S.; Korchuganova, G.S.

1983-01-01

A laboratory study was undertaken to study the combined effects of the basic petrographic characteristics of Kuzbas coal blends and the technological carbonization parameters on the structural strength of the porous coke. Strength tests were carried out on the original coke and the products of partial gasification with carbon dioxide under conditions simulating those inside blast furnaces. Properties of the 14 samples of Kuzbas coals and composition of the four coal blends made from them are listed. It was concluded that the structural strength of coke was most strongly influenced by the average reflectance index and bulk density of the charge. Also, charge compaction can largely offset the adverse influence of petrographic heterogeneity on the strength of the coke. 10 references, 3 tables.

Method of preparing porous, rigid ceramic separators for an electrochemical cell. [Patent application

Science.gov (United States)

Bandyopadhyay, G.; Dusek, J.T.

Porous, rigid separators for electrochemical cells are prepared by first calcining particles of ceramic material at temperatures above about 1200/sup 0/C for a sufficient period of time to reduce the sinterability of the particles. A ceramic powder that has not been calcined is blended with the original powder to control the porosity of the completed separator. The ceramic blend is then pressed into a sheet of the desired shape and sintered at a temperature somewhat lower than the calcination temperature. Separator sheets of about 1 to 2.5 mm thickness and 30 to 70% porosity can be prepared by this technique. Ceramics such as yttria, magnesium oxide, and magnesium-aluminium oxide have advantageously been used to form separators by this method.

Using ion-selective electrodes to study the drug release from porous cellulose matrices

DEFF Research Database (Denmark)

Vakili, Hossein; Genina, Natalja; Ehlers, Henrik

2012-01-01

-polymer solutions were prepared with the model drugs, using different blend ratios of ethylcellulose (EC) and hydroxypropyl cellulose (HPC). Two different solid dosage forms were used. Polymer films were produced by solvent casting method and drug containing porous cellulose samples were prepared by depositing...... the drug-polymer solutions onto filter paper substrates. The quality of the electrodes and the release profile of Pr+ and Ld+ were investigated with \\r\

Enhanced Dissolution of a Porous Carrier-Containing Ternary Amorphous Solid Dispersion System Prepared by a Hot Melt Method.

Science.gov (United States)

Hanada, Masataka; Jermain, Scott V; Williams, Robert O

2018-01-01

The focus of our study was to employ a solvent-free, thermal process to evaluate the use of a porous carrier in a drug-polymer-porous carrier ternary formulation containing a high drug load (e.g., ≥50% w/w). The purpose of the study was to improve the dissolution properties of the biopharmaceutical classification system class II drug, indomethacin, in the ternary formulation. The effect that the selected polymer has on properties of the formulation was studied, and the formulation characteristics of hypromellose (AF15), copovidone (VA64), and polyvinyl alcohol-polyethylene glycol graft copolymer was evaluated to understand differences in dissolution rates and drug adsorption onto the porous carrier. The ternary formulations were manufactured using a thermal technique that relied on heating and mixing, without the necessity of mechanical shear. All thermally processed granules that employed the porous carrier exhibited immediate release compared with crystalline indomethacin and physical mixtures. In addition, the ternary formulations maintained supersaturation compared with the binary formulations without polymer. The results of this study indicated that the thermally processed ternary formulations containing a porous carrier demonstrated a much improved dissolution profile in nonsink conditions. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Stability of Collagen Scaffold Implants for Animals with Iatrogenic Articular Cartilage Defects

Directory of Open Access Journals (Sweden)

Josef Jančář

2009-01-01

Full Text Available Synthesis and characterization of biodegradable hydrogels based on collagen modified by addition of synthetic biodegradable copolymer intended for preparation of porous scaffolds for mesenchymal stem cells used for possible implantation to animals with articular surface defects was investigated. The synthetic biodegradable tri-block copolymer used was the block copolymer of polyethylene glycol (PEG, polylactic acid (PLA, polyglycolic acid (PGA (PEG-PLGA endcapped with itaconic acid (ITA. The water-soluble carbodiimide and N-hydroxysuccimide system (EDC-NHS was chosen as the cross-linking agent used to control the rate of hydrogel resorption. Dependence of the physical properties of the prepared hydrogels on the concentration of the EDC-NHS cross-linker, reaction time and concentration of PEG-PLGA-ITA copolymer was examined. Swelling behaviour, thermal stability, surface morphology and degradation rate were also characterized. Based on the obtained results, it can be concluded that increase in concentration of the cross-linking agent, as well as prolonged cross-linking time and increased amount of synthetic copolymer lead to enhanced thermal stability of the gels together with a reduced swelling ratio and degradation rate in saline. The resorption rate of these gels used in preparation of cartilage scaffolds can be controlled over a wide time interval by varying the collagen/(PEG-PLGA-ITA blend composition or the conditions of the cross-linking reaction.

Fabrication of Completely Polymer-Based Solar Cells with p- and n-Type Semiconducting Block Copolymers with Electrically Inert Polystyrene

Directory of Open Access Journals (Sweden)

Eri Tomita

2018-02-01

Full Text Available It is widely recognized that fullerene derivatives show several advantages as n-type materials in photovoltaic applications. However, conventional [6,6]-phenyl-C61-butyric acid methyl ester (PCBM exhibits weak absorption in the visible region, and poor morphological stability, due to the facile aggregation. For further improvement of the device performance and durability, utilization of n-type polymeric materials instead of PCBM is considered to be a good way to solve the problems. In this study, we fabricated completely polymer-based solar cells utilizing p- and n-type block copolymers consisting of poly(3-hexylthiophene (P3HT and poly{[N,N′-bis(2-octyldodecylnaphthalene-1,4,5,8-bis(dicarboximide-2,6-diyl]-alt-5,5′-(2,2′-bithiophene} [P(NDI2OD-T2], respectively, containing common polystyrene (PSt inert blocks, which decreased the size of phase separated structures. Electron mobility in synthesized P(NDI2OD-T2-b-PSt film enhanced by a factor of 8 compared with homopolymer. The root mean square roughness of the blend film of two block copolymers (12.2 nm was decreased, compared with that of the simple homopolymers blend (18.8 nm. From the current density-voltage characteristics, it was confirmed that the introduction of PSt into both P3HT and P(NDI2OD-T2 improves short-circuit current density (1.16 to 1.73 mA cm−2 and power-conversion efficiency (0.24% to 0.32%. Better performance is probably due to the uniformity of the phase separation, and the enhancement of charge mobility.

21 CFR 177.1320 - Ethylene-ethyl acrylate copolymers.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-ethyl acrylate copolymers. 177.1320... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1320 Ethylene-ethyl acrylate copolymers. Ethylene-ethyl acrylate copolymers may be safely used to produce packaging materials, containers...

Sulfomethylated graft copolymers of xanthan gum and polyacrylamide

Energy Technology Data Exchange (ETDEWEB)

Cottrell, I.W.; Empey, R.A.; Racciato, J.S.

1978-08-08

A water-soluble anionic graft copolymer of xanthan gum and polyacrylamide is described in which at least part of the amide function of the acrylamide portion of the copolymer is sulfomethylated and the xanthan gum portion of the copolymer is unreacted with formaldehyde. The copolymer is sulfomethylated by reaction with formaldehyde and sodium metabisulfite. The formaldehyde does not cause any appreciable cross-linking between hydroxyl groups of the xanthan moieties. The sulfomethylation of the acrylamido group takes place at temperatures from 35 to 70 C. The pH is 10 or higher, typically from 12 to 13. The degree of anionic character may be varied by adjusting the molar ratio of formaldehyde and sodium metabisulfite with respect to the copolymer. 10 claims.

Block Copolymers: Synthesis and Applications in Nanotechnology

Science.gov (United States)

Lou, Qin

This study is focused on the synthesis and study of (block) copolymers using reversible deactivation radical polymerizations (RDRPs), including atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization. In particular, two primary areas of study are undertaken: (1) a proof-of-concept application of lithographic block copolymers, and (2) the mechanistic study of the deposition of titania into block copolymer templates for the production of well-ordered titania nanostructures. Block copolymers have the ability to undergo microphase separation, with an average size of each microphase ranging from tens to hundreds of nanometers. As such, block copolymers have been widely considered for nanotechnological applications over the past two decades. The development of materials for various nanotechnologies has become an increasingly studied area as improvements in many applications, such as those found in the semiconductor and photovoltaic industries are constantly being sought. Significant growth in developments of new synthetic methods ( i.e. RDRPs) has allowed the production of block copolymers with molecular (and sometimes atomic) definition. In turn, this has greatly expanded the use of block copolymers in nanotechnology. Herein, we describe the synthesis of statistical and block copolymers of 193 nm photolithography methacrylate and acrylate resist monomers with norbornyl and adamantyl moieties using RAFT polymerization.. For these resist (block) copolymers, the phase separation behaviors were examined by atomic force microscopy (AFM). End groups were removed from the polymers to avoid complications during the photolithography since RAFT end groups absorb visible light. Poly(glycidyl methacrylate-block-polystyrene) (PGMA-b-PS) was synthesize by ATRP and demonstrated that this block copolymer acts as both a lithographic UV (365 nm) photoresist and a self-assembly material. The PGMA segments can undergo cationic

21 CFR 177.1310 - Ethylene-acrylic acid copolymers.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-acrylic acid copolymers. 177.1310 Section... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1310 Ethylene-acrylic acid copolymers. The ethylene-acrylic acid copolymers identified in paragraph (a) of this section may be safely...

21 CFR 177.1312 - Ethylene-carbon monoxide copolymers.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-carbon monoxide copolymers. 177.1312... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1312 Ethylene-carbon monoxide copolymers. The ethylene-carbon monoxide copolymers identified in paragraph (a) of this section may be safely...

21 CFR 177.1350 - Ethylene-vinyl acetate copolymers.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-vinyl acetate copolymers. 177.1350 Section... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1350 Ethylene-vinyl acetate copolymers. Ethylene-vinyl acetate copolymers may be safely used as articles or components of articles...

21 CFR 177.1950 - Vinyl chloride-ethylene copolymers.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Vinyl chloride-ethylene copolymers. 177.1950... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1950 Vinyl chloride-ethylene copolymers. The vinyl chloride-ethylene copolymers identified in paragraph (a) of this section may be safely...

Antimicrobial activity of poly(acrylic acid) block copolymers

Energy Technology Data Exchange (ETDEWEB)

Gratzl, Günther, E-mail: guenther.gratzl@jku.at [Johannes Kepler University Linz, Institute for Chemical Technology of Organic Materials, Altenberger Str. 69, 4040 Linz (Austria); Paulik, Christian [Johannes Kepler University Linz, Institute for Chemical Technology of Organic Materials, Altenberger Str. 69, 4040 Linz (Austria); Hild, Sabine [Johannes Kepler University Linz, Institute of Polymer Science, Altenberger Str. 69, 4040 Linz (Austria); Guggenbichler, Josef P.; Lackner, Maximilian [AMiSTec GmbH and Co. KG, Leitweg 13, 6345 Kössen, Tirol (Austria)

2014-05-01

The increasing number of antibiotic-resistant bacterial strains has developed into a major health problem. In particular, biofilms are the main reason for hospital-acquired infections and diseases. Once formed, biofilms are difficult to remove as they have specific defense mechanisms against antimicrobial agents. Antimicrobial surfaces must therefore kill or repel bacteria before they can settle to form a biofilm. In this study, we describe that poly(acrylic acid) (PAA) containing diblock copolymers can kill bacteria and prevent from biofilm formation. The PAA diblock copolymers with poly(styrene) and poly(methyl methacrylate) were synthesized via anionic polymerization of tert-butyl acrylate with styrene or methyl methacrylate and subsequent acid-catalyzed hydrolysis of the tert-butyl ester. The copolymers were characterized via nuclear magnetic resonance spectroscopy (NMR), size-exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), elemental analysis, and acid–base titrations. Copolymer films with a variety of acrylic acid contents were produced by solvent casting, characterized by atomic force microscopy (AFM) and tested for their antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The antimicrobial activity of the acidic diblock copolymers increased with increasing acrylic acid content, independent of the copolymer-partner, the chain length and the nanostructure. - Highlights: • Acrylic acid diblock copolymers are antimicrobially active. • The antimicrobial activity depends on the acrylic acid content in the copolymer. • No salts, metals or other antimicrobial agents are needed.

Antimicrobial activity of poly(acrylic acid) block copolymers

International Nuclear Information System (INIS)

Gratzl, Günther; Paulik, Christian; Hild, Sabine; Guggenbichler, Josef P.; Lackner, Maximilian

2014-01-01

The increasing number of antibiotic-resistant bacterial strains has developed into a major health problem. In particular, biofilms are the main reason for hospital-acquired infections and diseases. Once formed, biofilms are difficult to remove as they have specific defense mechanisms against antimicrobial agents. Antimicrobial surfaces must therefore kill or repel bacteria before they can settle to form a biofilm. In this study, we describe that poly(acrylic acid) (PAA) containing diblock copolymers can kill bacteria and prevent from biofilm formation. The PAA diblock copolymers with poly(styrene) and poly(methyl methacrylate) were synthesized via anionic polymerization of tert-butyl acrylate with styrene or methyl methacrylate and subsequent acid-catalyzed hydrolysis of the tert-butyl ester. The copolymers were characterized via nuclear magnetic resonance spectroscopy (NMR), size-exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), elemental analysis, and acid–base titrations. Copolymer films with a variety of acrylic acid contents were produced by solvent casting, characterized by atomic force microscopy (AFM) and tested for their antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The antimicrobial activity of the acidic diblock copolymers increased with increasing acrylic acid content, independent of the copolymer-partner, the chain length and the nanostructure. - Highlights: • Acrylic acid diblock copolymers are antimicrobially active. • The antimicrobial activity depends on the acrylic acid content in the copolymer. • No salts, metals or other antimicrobial agents are needed

Preparation of porous carbon nanofibers derived from PBI/PLLA for supercapacitor electrodes.

Science.gov (United States)

Jung, Kyung-Hye; Ferraris, John P

2016-10-21

Porous carbon nanofibers were prepared by electrospinning blend solutions of polybenzimidazole/poly-L-lactic acid (PBI/PLLA) and carbonization. During thermal treatment, PLLA was decomposed, resulting in the creation of pores in the carbon nanofibers. From SEM images, it is shown that carbon nanofibers had diameters in the range of 100-200 nm. The conversion of PBI to carbon was confirmed by Raman spectroscopy, and the surface area and pore volume of carbon nanofibers were determined using nitrogen adsorption/desorption analyses. To investigate electrochemical performances, coin-type cells were assembled using free-standing carbon nanofiber electrodes and ionic liquid electrolyte. cyclic voltammetry studies show that the PBI/PLLA-derived porous carbon nanofiber electrodes have higher capacitance due to lower electrochemical impedance compared to carbon nanofiber electrode from PBI only. These porous carbon nanofibers were activated using ammonia for further porosity improvement and annealed to remove the surface functional groups to better match the polarity of electrode and electrolyte. Ragone plots, correlating energy density with power density calculated from galvanostatic charge-discharge curves, reveal that activation/annealing further improves energy and power densities.

Copolymers at the solid - liquid interface

NARCIS (Netherlands)

Wijmans, C.M.

1994-01-01

Copolymers consisting of both adsorbing and nonadsorbing segments can show an adsorption behaviour which is very different from that of homopolymers. We have mainly investigated the adsorption of AB diblock copolymers, which have one adsorbing block (anchor) and one nonadsorbing block

Effects of Additives on the Morphology and Performance of PPTA/PVDF in Situ Blend UF Membrane

Directory of Open Access Journals (Sweden)

Hong-Bin Li

2014-06-01

Full Text Available Poly(p-phenylene terephtalamide (PPTA, a high-performance polymer with high modulus and good hydrophilicity, is often used as a reinforced material. However, due to its high crystallity, micro-phase separation often occurs in the blends. In this paper, PPTA/poly(vinylidene fluoride (PVDF compatible blend solution was synthesized by in situ polycondensation. Blend ultra-filtration membrane was prepared through the immersion phase inversion process. In order to obtain desired pore structure, the effects of different additives including hydrophilic polymer (polyethylene glycol (PEG, inorganic salt (lithium chloride (LiCl and the surfactant (Tween-80 on the morphology and performance of PPTA/PVDF blend membranes were studied. The membrane formation process was investigated through ternary phase diagram (thermodynamics and viscosities (kinetics analysis. It was found that, with the increasing of LiCl content, a porous membrane structure with long finger-like pores was formed due to the accelerated demixing process which resulted in the increase of porosity and pore diameter as well as the enhancement of water flux and the decline of PEG rejection. When Tween content increased to over 3 wt%, dynamic viscosity became the main factor resulting in a decreased phase separation rate. The transfer of PEG and LiCl molecules onto membrane surface increased the surface hydrophilicity. The effect of Tween content on membrane hydrophilicity was also correlated with the compatibility of blend components.

Synthesis and characterization of waterborne polyurethane acrylate copolymers

International Nuclear Information System (INIS)

Sultan, Misbah; Bhatti, Haq Nawaz; Zuber, Mohammad; Barikani, Mehdi

2013-01-01

Polyurethane acrylate copolymers were synthesized by emulsion polymerization process. To reduce the environmental hazards, organic solvents were replaced by eco-friendly aqueous system. Concentration of polyurethane and acrylate monomer was varied to investigate the effect of chemical composition on performance properties of copolymers. FTIR spectroscopy was used as a key tool to record the chemical synthesis route. The synthesized copolymer emulsions were characterized by evaluating their particle size, viscosity, dry weight content, chemical and water resistance. Thermal decomposition was studied by thermogravimetric analysis. Scanning electron microscope was used to visualize the morphological structure of copolymers. The experimental results indicate better polyurethane acrylate compatibility till the ratio of 30/70. However, these copolymers exhibited synergistic effects between the two polymers and revealed a remarkable improvement in numerous coating properties

Equilibrium and kinetics study on hexavalent chromium adsorption onto diethylene triamine grafted glycidyl methacrylate based copolymers

International Nuclear Information System (INIS)

Maksin, Danijela D.; Nastasović, Aleksandra B.; Milutinović-Nikolić, Aleksandra D.; Suručić, Ljiljana T.; Sandić, Zvjezdana P.; Hercigonja, Radmila V.; Onjia, Antonije E.

2012-01-01

Highlights: ► Methacrylate based copolymers grafted with diethylene triamine as Cr(VI) sorbents. ► Chemisorption and pore diffusion are characteristics of this sorption system. ► Langmuir isotherm provided best fit and maximum adsorption capacity was 143 mg g −1 . ► Cr(VI) sorption onto amino-functionalized copolymer was endothermic and spontaneous. ► A simple, efficient and cost-effective hexavalent chromium removal method. - Abstract: Two porous and one non-porous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [abbreviated PGME] were prepared by suspension copolymerization and functionalized with diethylene triamine [abbreviated PGME-deta]. Samples were characterized by elemental analysis, mercury porosimetry, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Kinetics of Cr(VI) sorption by PGME-deta were investigated in batch static experiments, in the temperature range 25–70 °C. Sorption was rapid, with the uptake capacity higher than 80% after 30 min. Sorption behavior and rate-controlling mechanisms were analyzed using five kinetic models (pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion and Bangham model). Kinetic studies showed that Cr(VI) adsorption adhered to the pseudo-second-order model, with definite influence of pore diffusion. Equilibrium data was tested with Langmuir, Freundlich and Tempkin adsorption isotherm models. Langmuir model was the most suitable indicating homogeneous distribution of active sites on PGME-deta and monolayer sorption. The maximum adsorption capacity from the Langmuir model, Q max , at pH 1.8 and 25 °C was 143 mg g −1 for PGME2-deta (sample with the highest amino group concentration) while at 70 °C Q max reached the high value of 198 mg g −1 . Thermodynamic parameters revealed spontaneous and endothermic nature of Cr(VI) adsorption onto PGME-deta.

Biomimetic porous high-density polyethylene/polyethylene- grafted-maleic anhydride scaffold with improved in vitro cytocompatibility.

Science.gov (United States)

Sharma, Swati; Bhaskar, Nitu; Bose, Surjasarathi; Basu, Bikaramjit

2018-05-01

A major challenge for tissue engineering is to design and to develop a porous biocompatible scaffold, which can mimic the properties of natural tissue. As a first step towards this endeavour, we here demonstrate a distinct methodology in biomimetically synthesized porous high-density polyethylene scaffolds. Co-extrusion approach was adopted, whereby high-density polyethylene was melt mixed with polyethylene oxide to form an immiscible binary blend. Selective dissolution of polyethylene oxide from the biphasic system revealed droplet-matrix-type morphology. An attempt to stabilize such morphology against thermal and shear effects was made by the addition of polyethylene- grafted-maleic anhydride as a compatibilizer. A maximum ultimate tensile strength of 7 MPa and elastic modulus of 370 MPa were displayed by the high-density polyethylene/polyethylene oxide binary blend with 5% maleated polyethylene during uniaxial tensile loading. The cell culture experiments with murine myoblast C2C12 cell line indicated that compared to neat high-density polyethylene and high-density polyethylene/polyethylene oxide, the high-density polyethylene/polyethylene oxide with 5% polyethylene- grafted-maleic anhydride scaffold significantly increased muscle cell attachment and proliferation with distinct elongated threadlike appearance and highly stained nuclei, in vitro. This has been partly attributed to the change in surface wettability property with a reduced contact angle (∼72°) for 5% PE- g-MA blends. These findings suggest that the high-density polyethylene/polyethylene oxide with 5% polyethylene- grafted-maleic anhydride can be treated as a cell growth substrate in bioengineering applications.

Blended learning

DEFF Research Database (Denmark)

Dau, Susanne

2016-01-01

Blended Learning has been implemented, evaluated and researched for the last decades within different educational areas and levels. Blended learning has been coupled with different epistemological understandings and learning theories, but the fundamental character and dimensions of learning...... in blended learning are still insufficient. Moreover, blended learning is a misleading concept described as learning, despite the fact that it fundamentally is an instructional and didactic approach (Oliver & Trigwell, 2005) addressing the learning environment (Inglis, Palipoana, Trenhom & Ward, 2011......) instead of the learning processes behind. Much of the existing research within the field seems to miss this perspective. The consequence is a lack of acknowledgement of the driven forces behind the context and the instructional design limiting the knowledge foundation of learning in blended learning. Thus...

The influence of chain stretching on the phase behavior of multiblock copolymer and comb copolymer melts

NARCIS (Netherlands)

Angerman, HJ; ten Brinke, G

The subject of this paper is inspired by microphase-separated copolymer melts in which a small-scale structure is present inside one of the phases of a large-scale structure. Such a situation can arise in a diblock copolymer melt, if one of the blocks of the diblock is in itself a multiblock

Nanoporous polymeric nanofibers based on selectively etched PS-b-PDMS block copolymers.

Science.gov (United States)

Demirel, Gokcen B; Buyukserin, Fatih; Morris, Michael A; Demirel, Gokhan

2012-01-01

One-dimensional nanoporous polymeric nanofibers have been fabricated within an anodic aluminum oxide (AAO) membrane by a facile approach based on selective etching of poly(dimethylsiloxane) (PDMS) domains in polystyrene-block-poly(dimethylsiloxane) (PS-b-PDMS) block copolymers that had been formed within the AAO template. It was observed that prior to etching, the well-ordered PS-b-PDMS nanofibers are solid and do not have any porosity. The postetched PS nanofibers, on the other hand, had a highly porous structure having about 20-50 nm pore size. The nanoporous polymeric fibers were also employed as a drug carrier for the native, continuous, and pulsatile drug release using Rhodamine B (RB) as a model drug. These studies showed that enhanced drug release and tunable drug dosage can be achieved by using ultrasound irradiation. © 2011 American Chemical Society

Polyketones as alternating copolymers of carbon monoxide

International Nuclear Information System (INIS)

Belov, Gennady P; Novikova, Elena V

2004-01-01

Characteristic features of the catalytic synthesis of alternating copolymers of carbon monoxide with various olefins, dienes, styrene and its derivatives are considered. The diversity of catalyst systems used for the copolymerisation of carbon monoxide is demonstrated and their influence on the structure and the molecular mass of the resulting copolymers is analysed. The data on the structure and physicochemical and mechanical properties of this new generation of functional copolymers are generalised and described systematically for the first time.

21 CFR 177.2470 - Polyoxymethylene copolymer.

Science.gov (United States)

2010-04-01

... Components of Articles Intended for Repeated Use § 177.2470 Polyoxymethylene copolymer. Polyoxymethylene copolymer identified in this section may be safely used as an article or component of articles intended for... are available from the Center for Food Safety and Applied Nutrition (HFS-200), Food and Drug...

Nanoparticles based on novel amphiphilic polyaspartamide copolymers

International Nuclear Information System (INIS)

Craparo, Emanuela Fabiola; Teresi, Girolamo; Ognibene, Maria Chiara; Casaletto, Maria Pia; Bondi, Maria Luisa; Cavallaro, Gennara

2010-01-01

In this article, the synthesis of two amphiphilic polyaspartamide copolymers, useful to obtain polymeric nanoparticles without using surfactants or stabilizing agents, is described. These copolymers were obtained starting from α,β-poly-(N-2-hydroxyethyl)-dl-aspartamide (PHEA) by following a novel synthetic strategy. In particular, PHEA and its pegylated derivative (PHEA-PEG 2000 ) were functionalized with poly(lactic acid) (PLA) through 1,1'-carbonyldiimidazole (CDI) activation to obtain PHEA-PLA and PHEA-PEG 2000 -PLA graft copolymers, respectively. These copolymers were properly purified and characterized by 1 H-NMR, FT-IR, and Size Exclusion Chromatography (SEC) analyses, which confirmed that derivatization reactions occurred. Nanoparticles were obtained from PHEA-PLA and PHEA-PEG 2000 -PLA graft copolymers by using the high pressure homogenization-solvent evaporation method, avoiding the use of surfactants or stabilizing agents. Polymeric nanoparticles were characterized by dimensional analysis, before and after freeze-drying process, and Scanning Electron Microscopy (SEM). Zeta potential measurements and X-ray Photoelectron Spectroscopy (XPS) analysis demonstrated the presence of PEG and/or PHEA onto the PHEA-PEG 2000 -PLA and PHEA-PLA nanoparticle surface, respectively.

Amphiphilic copolymers for fouling-release coatings

DEFF Research Database (Denmark)

Noguer, Albert Camós; Olsen, Stefan Møller; Hvilsted, Søren

of the coatings [9,10,11]. This work shows the effect of an amphiphilic copolymer that induces hydrophilicity on the surface of the silicone-based fouling release coatings. The behaviour of these copolymers within the coating upon immersion and the interaction of these surface-active additives with other...

Poly(ferrocenylsilane)-block-Polylactide Block Copolymers

NARCIS (Netherlands)

Roerdink, M.; van Zanten, Thomas S.; Hempenius, Mark A.; Zhong, Zhiyuan; Feijen, Jan; Vancso, Gyula J.

2007-01-01

A PFS/PLA block copolymer was studied to probe the effect of strong surface interactions on pattern formation in PFS block copolymer thin films. Successful synthesis of PFS-b-PLA was demonstrated. Thin films of these polymers show phase separation to form PFS microdomains in a PLA matrix, and

Thermal degradation of polymer systems having liquid crystalline oligoester segment

Directory of Open Access Journals (Sweden)

Renato Matroniani

Full Text Available Abstract Block copolymers and blends comprised by liquid crystalline oligoester and polystyrene were prepared and their thermal stability were characterized by thermogravimetric analysis (TGA. The samples have shown three main decomposition temperatures due to (1 lost of flexible chain and decomposition of mesogenic segment, (2 decomposition of polystyrene and (3 final decomposition of oligoester rigid segment. Both copolymers and polymer blends presented lower thermal stability compared to polystyrene and oligoester. The residual mass after heating at 600 °C in copolymers and polymer blends were lower than those found in the oligoesters. A degradative process of aromatic segments of oligoester induced by decomposition of polystyrene is suggested.

Amphiphilic block copolymers for biomedical applications

Science.gov (United States)

Zupancich, John Andrew

Amphiphilic block copolymer self-assembly provides a versatile means to prepare nanoscale objects in solution. Control over aggregate shape is granted through manipulation of amphiphile composition and the synthesis of well-defined polymers offers the potential to produce micelles with geometries optimized for specific applications. Currently, polymer micelles are being investigated as vehicles for the delivery of therapeutics and attempts to increase efficacy has motivated efforts to incorporate bioactive ligands and stimuli-responsive character into these structures. This thesis reports the synthesis and self-assembly of biocompatible, degradable polymeric amphiphiles. Spherical, cylindrical, and bilayered vesicle structures were generated spontaneously by the direct dispersion of poly(ethylene oxide)-b-poly(gamma-methyl-ε-caprolactone) block copolymers in water and solutions were characterized with cryogenic transmission electron microscopy (cryo-TEM). The dependence of micelle structure on diblock copolymer composition was examined through the systematic variation of the hydrophobic block molecular weight. A continuous evolution of morphology was observed with coexistence of aggregate structures occurring in windows of composition intermediate to that of pure spheres, cylinders and vesicles. A number of heterobifunctional poly(ethylene oxide) polymers were synthesized for the preparation of ligand-functionalized amphiphilic diblock copolymers. The effect of ligand conjugation on block copolymer self-assembly and micelle morphology was also examined. An RGD-containing peptide sequence was efficiently conjugated to a set of well characterized poly(ethylene oxide)-b-poly(butadiene) copolymers. The reported aggregate morphologies of peptide-functionalized polymeric amphiphiles deviated from canonical structures and the micelle clustering, cylinder fragmentation, network formation, and multilayer vesicle generation documented with cryo-TEM was attributed to

Research Update: Triblock copolymers as templates to synthesize inorganic nanoporous materials

OpenAIRE

Yunqi Li; Bishnu Prasad Bastakoti; Yusuke Yamauchi

2016-01-01

This review focuses on the application of triblock copolymers as designed templates to synthesize nanoporous materials with various compositions. Asymmetric triblock copolymers have several advantages compared with symmetric triblock copolymers and diblock copolymers, because the presence of three distinct domains can provide more functional features to direct the resultant nanoporous materials. Here we clearly describe significant contributions of asymmetric triblock copolymers, especially p...

Micellization and Dynamics of a Block Copolymer

DEFF Research Database (Denmark)

Hvidt, Søren

2006-01-01

and copolymer mixtures, and evidence in favor of a multi-equilibria unimer-micelle model will be presented. Results obtained by liquid chromatographic methods will be shown and it will be demonstrated that commercial EPE copolymers are inhomogeneous at several levels and many of their unusual properties reflect...... ratios and temperature. The micellization process with increasing temperature has been followed by a number of techniques including differential scanning calorimetry, liquid chromatography, and surface tension measurements. Different micellization models have been tested for purified copolymers...

Acrylonitrile-methyl Methacrylate Copolymer Films Containing Microencapsulated n-Octadecane

Institute of Scientific and Technical Information of China (English)

LI Jun; HAN Na; ZHANG Xing-xiang

2006-01-01

Acrylonitrile-methyl methacrylate copolymer was synthesized in aqueous solution by Redox. The copolymer was mixed with 10 - 40 wt% of microencapsulated n-octadecane (MicroPCMs) in water. Copolymer films containing MicroPCMs were cast at room temperature in N, N-Dimethylformamide solution. The copolymer of acrylonitrile-methyl methacrylate and the copolymer films containing MicroPCMs were characterized by using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analyzer (TG), X-ray Diffrac tion (XRD) and Scanning Electron Microscopy (SEM), etc.The microcapsules in the films are evenly distributed in the copolymer matrix. The heat-absorbing temperatures and heat-evolving temperatures of the films are almost the same as that of the MicroPCMs, respectively, and fluctuate in a slight range. In addition, the enthalpy efficiency of MicroPCMs rises with the contents of MicroPCMs increasing.The crystallinity of the film increases with the contents of MicroPCMs increasing.

Supporting School Leaders in Blended Learning with Blended Learning

Science.gov (United States)

Acree, Lauren; Gibson, Theresa; Mangum, Nancy; Wolf, Mary Ann; Kellogg, Shaun; Branon, Suzanne

2017-01-01

This study provides a mixed-methods case-study design evaluation of the Leadership in Blended Learning (LBL) program. The LBL program uses blended approaches, including face-to-face and online, to prepare school leaders to implement blended learning initiatives in their schools. This evaluation found that the program designers effectively…

Photo-Induced Micellization of Block Copolymers

Directory of Open Access Journals (Sweden)

Satoshi Kuwayama

2010-11-01

Full Text Available We found novel photo-induced micellizations through photolysis, photoelectron transfer, and photo-Claisen rearrangement. The photolysis-induced micellization was attained using poly(4-tert-butoxystyrene-block-polystyrene diblock copolymer (PBSt-b-PSt. BSt-b-PSt showed no self-assembly in dichloromethane and existed as isolated copolymers. Dynamic light scattering demonstrated that the copolymer produced spherical micelles in this solvent due to irradiation with a high-pressure mercury lamp in the presence of photo-acid generators, such as bis(alkylphenyliodonium hexafluorophosphate, diphenyliodonium hexafluorophosphate, and triphenylsulfonium triflate. The 1H NMR analysis confirmed that PBSt-b-PSt was converted into poly(4-vinylphenol-block-PSt by the irradiation, resulting in self-assembly into micelles. The irradiation in the presence of the photo-acid generator also induced the micellization of poly(4-pyridinemethoxymethylstyrene-block-polystyrene diblock copolymer (PPySt-b-PSt. Micellization occurred by electron transfer from the pyridine to the photo-acid generator in their excited states and provided monodispersed spherical micelles with cores of PPySt blocks. Further, the photo-Claisen rearrangement caused the micellization of poly(4-allyloxystyrene-block-polystyrene diblock copolymer (PASt-b-PSt. Micellization was promoted in cyclohexane at room temperature without a catalyst. During micellization, the elimination of the allyl groups competitively occurred along with the photorearrangement of the 4-allyloxystyrene units into the 3-allyl-4-hydroxystyrene units.

Blended Learning

OpenAIRE

Bauerová, Andrea

2013-01-01

This thesis is focused on a new approach of education called blended learning. The history and developement of Blended Learning is described in the first part. Then the methods and tools of Blended Learning are evaluated and compared to the traditional methods of education. At the final part an efficient developement of the educational programs is emphasized.

Fast & scalable pattern transfer via block copolymer nanolithography

DEFF Research Database (Denmark)

Li, Tao; Wang, Zhongli; Schulte, Lars

2015-01-01

A fully scalable and efficient pattern transfer process based on block copolymer (BCP) self-assembling directly on various substrates is demonstrated. PS-rich and PDMS-rich poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) copolymers are used to give monolayer sphere morphology after spin-casting of s......A fully scalable and efficient pattern transfer process based on block copolymer (BCP) self-assembling directly on various substrates is demonstrated. PS-rich and PDMS-rich poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) copolymers are used to give monolayer sphere morphology after spin...... on long range lateral order, including fabrication of substrates for catalysis, solar cells, sensors, ultrafiltration membranes and templating of semiconductors or metals....

Improved permeation performance and fouling-resistance of Poly(vinyl chloride/Polycarbonate blend membrane with added Pluronic F127

Directory of Open Access Journals (Sweden)

Supateekan Pacharasakoolchai

2014-04-01

Full Text Available The aim of this work was to prepare and characterize poly(vinyl chloride (PVC/polycarbonate (PC blend membranes for use in ultrafiltration. Pluronic F127 was used as an additive to modify the membrane surface of the PVC/PC blended membranes. The PVC/PC blend membrane was first prepared using the phase inversion method from a casting solution of PVC with small amount of PC in N-methylpyrrolidone (NMP and water as the non-solvent. The morphologies structure and properties, such as tensile strength, water flux, and bovine serum albumin (BSA rejection of the blend membrane were studied. Increased amounts of PC resulted in an increase in the water flux and ability to reject protein. A concentration of 0.75 wt% PC provided the best improvement in tensile strength of blend membrane. Addition of different amounts of pluronic F127 to the casting solution of PVC/PC with a PC concentration of 0.75 wt% resulted in a decrease in the water contact angle that demonstrated the improvement of hydrophilicity of blend membrane. Scanning electron microscopy photographs showed that the modified PVC/PC membranes had a bigger pore volume in the porous sub-layer compared to the PVC/PC control membrane. The PVC/PC membrane with added Pluronic F127 exhibited a much higher flux and rejection of BSA in a protein filtration experiment than the PVC/PC membrane. An increase in flux recovery ratio of PVC/PC/pluronic 127 blend membrane indicated that the modified membranes could reduce membrane fouling useful for ultrafiltration.

Functionalized isothianaphthene monomers that promote quinoidal character in donor-acceptor copolymers for organic photovoltaics

KAUST Repository

Douglas, Jessica D.

2012-05-22

A series of low band gap isothianaphthene-based (ITN) polymers with various electron-withdrawing substituents and intrinsic quinoidal character were synthesized, characterized, and tested in organic photovoltaic (OPV) devices. The three investigated ITN cores contained either ester, imide, or nitrile functionalities and were each synthesized in only four linear steps. The relative electron-withdrawing strength of the three substituents on the ITN moiety was evaluated and correlated to the optical and electronic properties of ITN-based copolymers. The ester- and imide-containing p-type polymers reached device efficiencies as high as 3% in bulk heterojunction blends with phenyl C 61-butyric acid methyl ester (PC 61BM), while the significantly electron-deficient nitrile-functionalized polymer behaved as an n-type material with an efficiency of 0.3% in bilayer devices with poly(3-(4-n-octyl)phenylthiophene) (POPT). © 2012 American Chemical Society.

Morphology and electrical properties of electrochemically synthesized pyrrole–formyl pyrrole copolymer

Energy Technology Data Exchange (ETDEWEB)

Gholami, Mehrdad, E-mail: mehrdad897@um.edu.my [Department of Chemistry, University of Malaya, Kuala Lumpur 50603 (Malaysia); Department of Chemistry, Marvdasht Branch, Islamic Azad University, P.O. Box 465, Marvdasht (Iran, Islamic Republic of); Nia, Pooria Moozarm, E-mail: pooriamn@yahoo.com [Department of Chemistry, University of Malaya, Kuala Lumpur 50603 (Malaysia); Alias, Yatimah, E-mail: yatimah70@um.edu.my [Department of Chemistry, University of Malaya, Kuala Lumpur 50603 (Malaysia)

2015-12-01

Graphical abstract: - Highlights: • The (Py–co-FPy) copolymer was synthesized electrochemically. • This copolymer has 1.6 times higher surface coverage compared to polypyrrole. • This copolymer showed 2.5 times lower resistance compared to polypyrrole. • The conjugated structure between Py and FPy causes enhancement of conductivity. • This conducting copolymer has a strong potential to be used in various applications. - Abstract: A direct electrochemical copolymerization of pyrrole–formyl pyrrole (Py–co-FPy) was carried out by oxidative copolymerization of formyl pyrrole and pyrrole in LiClO{sub 4} aqueous solution through galvanostatic method. The (Py–co-FPy) copolymer was characterized using Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (FESEM), energy-filtering transmission electron microscope (EFTEM), thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The FESEM images showed that the synthesized copolymer had a hollow whelk-like helixes structure, which justifies the enhancement of charge transportation through the copolymer film. Cyclic voltammetry studies revealed that the electrocatalytic activity of synthesized copolymer has improved and the surface coverage in copolymer enhanced 1.6 times compared to polypyrrole alone. Besides, (Py–co-FPy) copolymer showed 2.5 times lower electrochemical charge transfer resistance (R{sub ct}) value in impedance spectroscopy. Therefore, this copolymer has a strong potential to be used in several applications such as sensor applications.

Fabrication of hierarchical porous N-doping carbon membrane by using ;confined nanospace deposition; method for supercapacitor

Science.gov (United States)

Wang, Guoxu; Liu, Meng; Du, Juan; Liu, Lei; Yu, Yifeng; Sha, Jitong; Chen, Aibing

2018-03-01

The membrane carbon materials with hierarchical porous architecture are attractive because they can provide more channels for ion transport and shorten the ions transport path. Herein, we develop a facile way based on "confined nanospace deposition" to fabricate N-dopi-ng three dimensional hierarchical porous membrane carbon material (N-THPMC) via coating the nickel nitrate, silicate oligomers and triblock copolymer P123 on the branches of commercial polyamide membrane (PAM). During high temperature treatment, the mesoporous silica layer and Ni species serve as a "confined nanospace" and catalyst respectively, which are indispensable elements for formation of carbon framework, and the gas-phase carbon precursors which derive from the decomposition of PAM are deposited into the "confined nanospace" forming carbon framework. The N-THPMC with hierarchical macro/meso/microporous structure, N-doping (2.9%) and large specific surface area (994m2 g-1) well inherits the membrane morphology and hierarchical porous structure of PAM. The N-THPMC as electrode without binder exhibits a specific capacitance of 252 F g-1 at the current density of 1 A g-1 in 6 M KOH electrolyte and excellent cycling stability of 92.7% even after 5000 cycles.

Effect of chain extension on rheology and tensile properties of PHB and PHB-PLA blends

Science.gov (United States)

Bousfield, Glenn

Poly(3-hydroxybutyrate), referred to as PHB, is a bacterially-synthesized and biodegradable polymer which is being considered as a substitute for non-biodegradable bulk polymers like polypropylene. PHB is naturally extremely isotactic and naturally has a very high degree of crystallinity, resulting in a stiff but brittle material. The stability of PHB crystals also means that the melting point of the polymer is approximately 170°C, high with respect to similar polymers. For instance, the melting point of poly(4-hydroxybutyrate) is only 53°C (Saito, Nakamura, Hiramitsu, & Doi, 1996). Above 170°C, PHB is subject to a thermomechanical degradation mechanism, meaning that the polymer cannot be melted without degrading. One possible solution to the problem of degradation is to add a chain extender to the molten polymer to increase average molecular weight to counteract the molecular weight lost to degradation. In this work, a variety of chain extenders (JoncrylRTM ADR 4368-C, pyromellitic dianhydride, hexamethylene diisocyanate, polycarbodiimide) were compounded with a random copolymer of 98 mol% 3-hydroxybutyrate and 2 mol% 3-hydroxyvalerate (referred to as PHB) in concentrations ranging from 0.25% to 4%, to determine which chain extender functionality worked best with PHB. Molecular weight change was inferred from torque monitored during compounding, and from complex viscosity determined from parallel-plate rheology. None of the chain extenders changed the rate of degradation of PHB, although Joncryl increased the complex viscosity of the polymer. PHB was also blended with Poly(L-lactic acid), referred to as PLLA in PHB/PLLA ratios of 100/0, 75/25, 50/50, 25/75 and 0/100, to determine the effect of blending on the thermal stability of PHB. Again, thermal stability was determined by monitoring torque during compounding and by measuring complex viscosity through parallel-plate rheology. Blends in which PHB was the more abundant phase, as well as the 50% PHB/50% PLA

Production of polymer composites by radiation and chemical treatments from recycled plastic wastes and their applications

International Nuclear Information System (INIS)

Khaffaga, M.R.A.

2009-01-01

Different applied methods have been proposed for the recycling of poly (ethylene terephthalate)(PET) and its blends with other polymers to obtain useful products. These methods are based on blending with different polymers or compounding with radiation synthesized copolymers based on maleic anhydride with methyl methacrylate, styrene and vinyl acetate. On the other hand, the methods proposed to improve the miscibility of mixed polymers are based on different methods of gamma and electron beam irradiation at various doses (30-50 kGy). Also , the addition of compatibilizers based on LDPE graft copolymer with comonomer composed of ethylene glycol (EG) and acrylic acid (AAc) as well as radiation synthesized copolymer based on acrylic acid and styrene (Sty) monomers during mixing. The modified properties were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), mechanical testing and studying the affinity for acid, based and disperse dyes. Based on the results obtained throughout this work, few conclusions may made:(1) The composites of PET with copolymers is effective than the blending with other polymers. (2) The pre method of gamma or electron beam irradiation is effectively improved the miscibility of PET/LDPE or PET/PS blends than the direct method of irradiation.(3) The addition of EG/AAc or AAc/Sty copolymers during mixing improved the miscibility than the use of graft copolymer.

Block copolymer directed synthesis of mesoporous TiO 2 for dye-sensitized solar cells

KAUST Repository

Nedelcu, Mihaela

2009-01-01

The morphology of TiO2 plays an important role in the operation of solid-state dye-sensitized solar cells. By using polyisoprene-block- ethyleneoxide (PI-b-PEO) copolymers as structure directing agents for a sol-gel based synthesis of mesoporous TiO2, we demonstrate a strategy for the detailed control of the semiconductor morphology on the 10 nm length scale. The careful adjustment of polymer molecular weight and titania precursor content is used to systematically vary the material structure and its influence upon solar cell performance is investigated. Furthermore, the use of a partially sp 2 hybridized structure directing polymer enables the crystallization of porous TiO2 networks at high temperatures without pore collapse, improving its performance in solid-state dye-sensitized solar cells. © 2009 The Royal Society of Chemistry.

21 CFR 177.1340 - Ethylene-methyl acrylate copolymer resins.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-methyl acrylate copolymer resins. 177.1340... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1340 Ethylene-methyl acrylate copolymer resins. Ethylene-methyl acrylate copolymer resins may be safely used as articles or components of...

POLYCAPROLACTONE-POLY (ETHYLENE GLYCOL) BLOCK COPOLYMER Ⅲ DRUG RELEASE BEHAVIOR

Institute of Scientific and Technical Information of China (English)

BEI Jianzhong; WANG Zhifeng; WANG Shenguo

1995-01-01

The drug release behavior of degradable polymer - polycaprolactone-poly (ethylene glycol)block copolymer(PCE) in vitro was investigated by using 5-Fluoro-uracil (5-Fu) as a model drug under a condition of pH 7.4 at 37℃. It is found that the release rate of 5-Fu from PCE increased with increasing polyether content of the copolymer. The results show that the increasing polyether content of the copolymer caused increasing hydrophilicity and decreasing crystallinity of the PCE copolymer. Thus, the drug release behavior and the degradable property of the PCE can be controlled by adjusting the composition of the copolymer.

[Phase transition in polymer blends and structure of ionomers and copolymers]. [Annual report, April 1, 1989--June 30, 1993

Energy Technology Data Exchange (ETDEWEB)

1993-07-01

The main thrust of the program in the past 3 years are summarized: SAXS instrumentation development; structure and dynamics of macro- and supra-molecules, phase transitions in polymer blends and solutions, structure of ionomers, and fractals and anisotropic systems.

Versatile antifouling polyethersulfone filtration membranes modified via surface grafting of zwitterionic polymers from a reactive amphiphilic copolymer additive.

Science.gov (United States)

Zhao, Yi-Fan; Zhang, Pei-Bin; Sun, Jian; Liu, Cui-Jing; Yi, Zhuan; Zhu, Li-Ping; Xu, You-Yi

2015-06-15

Here we describe the development of versatile antifouling polyethersulfone (PES) filtration membranes modified via surface grafting of zwitterionic polymers from a reactive amphiphilic copolymer additive. Amphiphilic polyethersulfone-block-poly(2-hydroxyethyl methacrylate) (PES-b-PHEMA) was beforehand designed and used as the blending additive of PES membranes prepared by phase inversion technique. The surface enriched PHEMA blocks on membrane surface acted as an anchor to immobilize the initiating site. Poly(sulfobetaine methacrylate) (PSBMA) were subsequently grafted onto the PES blend membranes by surface-initiated atom transfer radical polymerization (SI-ATRP). The analysis of surface chemistry confirmed the successful grafting of zwitterionic PSBMA brushes on PES membrane surface. The resulted PES-g-PSBMA membranes were capable of separating proteins from protein solution and oil from oil/water emulsion efficiently. Furthermore, the modified membranes showed high hydrophilicity and strongly antifouling properties due to the incorporation of well-defined PSBMA layer. In addition, the PES-g-PSBMA membranes exhibited excellent blood compatibility and durability during the washing process. The developed antifouling PES membranes are versatile and can find their applications in protein filtration, blood purification and oil/water separation, etc. Copyright © 2015 Elsevier Inc. All rights reserved.

Biologically Safe Poly(l-lactic acid) Blends with Tunable Degradation Rate: Microstructure, Degradation Mechanism, and Mechanical Properties.

Science.gov (United States)

Oyama, Hideko T; Tanishima, Daisuke; Ogawa, Ryohei

2017-04-10

Although poly(l-lactic acid) (PLLA) is reputed to be biodegradable in the human body, its hydrophobic nature lets it persist for ca. 5.5 years. This study demonstrates that biologically safe lactide copolymers, poly(aspartic acid-co-l-lactide) (PAL) and poly(malic acid-co-l-lactide) (PML), dispersed in the PLLA function as detonators (triggers) for its hydrolytic degradation under physiological conditions. The copolymers significantly enhance hydrolysis, and consequently, the degradation rate of PLLA becomes easily tunable by controlling the amounts of PAL and PML. The present study elucidates the effects of uniaxial drawing on the structural development, mechanical properties, and hydrolytic degradation under physiological conditions of PLLA blend films. At initial degradation stages, the mass loss was not affected by uniaxial drawing; however, at late degradation stages, less developed crystals as well as amorphous chains were degradable at low draw ratio (DR), whereas not only highly developed crystals but also the oriented amorphous chains became insensitive to hydrolysis at high DR. Our work provides important molecular level results that demonstrate that biodegradable materials can have superb mechanical properties and also disappear in a required time under physiological conditions.

Enhanced Transdermal Permeability via Constructing the Porous Structure of Poloxamer-Based Hydrogel

Directory of Open Access Journals (Sweden)

Wen-Yi Wang

2016-11-01

Full Text Available A major concern for transdermal drug delivery systems is the low bioavailability of targeted drugs primarily caused by the skin’s barrier function. The resistance to the carrier matrix for the diffusion and transport of drugs, however, is routinely ignored. This study reports a promising and attractive approach to reducing the resistance to drug transport in the carrier matrix, to enhance drug permeability and bioavailability via enhanced concentration-gradient of the driving force for transdermal purposes. This approach simply optimizes and reconstructs the porous channel structure of the carrier matrix, namely, poloxamer 407 (P407-based hydrogel matrix blended with carboxymethyl cellulose sodium (CMCs. Addition of CMCs was found to distinctly improve the porous structure of the P407 matrix. The pore size approximated to normal distribution as CMCs were added and the fraction of pore number was increased by over tenfold. Transdermal studies showed that P407/CMCs saw a significant increase in drug permeability across the skin. This suggests that P407/CMC with improved porous structure exhibits a feasible and promising way for the development of transdermal therapy with high permeability and bioavailability, thereby avoiding or reducing use of any chemical enhancers.

Relations between blended learning possibilities and teachers' approaches to blended learning

DEFF Research Database (Denmark)

Stenalt, Maria Hvid; Nielsen, Tobias Alsted; Bager-Elsborg, Anna

Higher Education has embraced blended learning as a way of enhancing quality in teaching and helping students to learn. This presentation addresses relations between blended learning possiblities presented to teachers in a teacher training project and teachers’ approaches to blended learning. We...... suggest that in order to identify the level of impact of integrating technologies in teaching and learning, we need to understand the factors influencing approaches to design of courses for blended contexts. Participants in the teacher training project come from the Department of Law at Aarhus University......: • Optain locally-embedded knowledge about blended learning • Develop opportunities for law students to receive (more) feedback • Comply with strategic aims The results so far suggest that teachers provide a disciplinary perspective on the key dimensions of blended learning, which influences...

Research Update: Triblock copolymers as templates to synthesize inorganic nanoporous materials

Directory of Open Access Journals (Sweden)

Yunqi Li

2016-04-01

Full Text Available This review focuses on the application of triblock copolymers as designed templates to synthesize nanoporous materials with various compositions. Asymmetric triblock copolymers have several advantages compared with symmetric triblock copolymers and diblock copolymers, because the presence of three distinct domains can provide more functional features to direct the resultant nanoporous materials. Here we clearly describe significant contributions of asymmetric triblock copolymers, especially polystyrene-block-poly(2-vinylpyridine-block-poly(ethylene oxide (abbreviated as PS-b-P2VP-b-PEO.

Amphiphilic brushes from metallo-supramolecular block copolymers

NARCIS (Netherlands)

Guillet, P.; Fustin, C.A.; Wouters, D.; Höppener, S.; Schubert, U.S.; Gohy, J.M.W.

2009-01-01

A novel strategy to control the formation of amphiphilic brushes from metallo-supramol. block copolymers is described. The investigated copolymer consists of a polystyrene block linked to a poly(ethylene oxide) one via a charged bis-terpyridine ruthenium(ii) complex (PS-[Ru]-PEO). The initial

Iodinated glycidyl methacrylate copolymer as a radiopaque material for biomedical applications.

Science.gov (United States)

Dawlee, S; Jayabalan, M

2013-07-01

Polymeric biomaterial was synthesized by copolymerizing 50:50 mol% of monomers, glycidyl methacrylate and methyl methacrylate. Iodine atoms were then grafted to the epoxide groups of glycidyl methacrylate units, rendering the copolymer radiopaque. The percentage weight of iodine in the present copolymer was found to be as high as 23%. The iodinated copolymer showed higher glass transition temperature and thermal stability in comparison with unmodified polymer. Radiographic analysis showed that the copolymer possessed excellent radiopacity. The iodinated copolymer was cytocompatible to L929 mouse fibroblast cells. The in vivo toxicological evaluation by intracutaneous reactivity test of the copolymer extracts has revealed that the material was nontoxic. Subcutaneous implantation of iodinated copolymer in rats has shown that the material was well tolerated. Upon explantation and histological examination, no hemorrhage, infection or necrosis was observed. The samples were found to be surrounded by a vascularized capsule consisting of connective tissue cells. The results indicate that the iodinated copolymer is biocompatible and may have suitable applications as implantable materials.

Controlling block copolymer phase behavior using ionic surfactant

Energy Technology Data Exchange (ETDEWEB)

Ray, D.; Aswal, V. K. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India E-mail: debes.phys@gmail.com (India)

2016-05-23

The phase behavior of poly(ethylene oxide)-poly(propylene oxide-poly(ethylene oxide) PEO-PPO-PEO triblock copolymer [P85 (EO{sub 26}PO{sub 39}EO{sub 26})] in presence of anionic surfactant sodium dodecyl sulfate (SDS) in aqueous solution as a function of temperature has been studied using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The measurements have been carried out for fixed concentrations (1 wt%) of block copolymer and surfactants. Each of the individual components (block copolymer and surfactant) and the nanoparticle–surfactant mixed system have been examined at varying temperature. The block copolymer P85 forms spherical micelles at room temperature whereas shows sphere-to-rod like micelle transition at higher temperatures. On the other hand, SDS surfactant forms ellipsoidal micelles over a wide temperature range. Interestingly, it is found that phase behavior of mixed micellar system (P85 + SDS) as a function of temperature is drastically different from that of P85, giving the control over the temperature-dependent phase behavior of block copolymers.

Supramolecular Cross-Links in Poly(alkyl methacrylate) Copolymers and Their Impact on the Mechanical and Reversible Adhesive Properties.

Science.gov (United States)

Heinzmann, Christian; Salz, Ulrich; Moszner, Norbert; Fiore, Gina L; Weder, Christoph

2015-06-24

Hydrogen-bonded, side-chain-functionalized supramolecular poly(alkyl methacrylate)s were investigated as light- and temperature-responsive reversible adhesives that are useful for bonding and debonding on demand applications. Here, 2-hydroxyethyl methacrylate (HEMA) was functionalized with 2-ureido-4[1H]pyrimidinone (UPy) via a hexamethylenediisocyanate (HMDI) linker, to create a monomer (UPy-HMDI-HEMA) that serves to form supramolecular cross-links by way of forming quadruple hydrogen bonded dimers. UPy-HMDI-HEMA was copolymerized with either hexyl methacrylate or butyl methacrylate to create copolymers comprising 2.5, 5, or 10 mol % of the cross-linker. The mechanical properties of all (co)polymers were investigated with stress-strain experiments and dynamic mechanical analysis. Furthermore, the adhesive properties were studied at temperatures between 20 and 60 °C by testing single lap joints formed with stainless steel substrates. It was found that increasing the concentration of the UPy-HMDI-HEMA cross-linker leads to improved mechanical and adhesive properties at elevated temperatures. Concurrently, the reversibility of the bond formation remained unaffected, where rebonded samples displayed the same adhesive strength as regularly bonded samples. Debonding on demand abilities were also tested exemplarily for one copolymer, which for light-induced debonding experiments was blended with a UV-absorber that served as light-heat converter. Single lap joints were subjected to a constant force and heated or irradiated with UV light until debonding occurred. The necessary debonding temperature was comparable for direct heating and UV irradiation and varied between 28 and 82 °C, depending on the applied force. The latter also influenced the debonding time, which under the chosen conditions ranged from 30 s to 12 min.

Blended Learning

NARCIS (Netherlands)

Van der Baaren, John

2009-01-01

Van der Baaren, J. (2009). Blended Learning. Presentation given at the Mini symposium 'Blended Learning the way to go?'. November, 5, 2009, The Hague, The Netherlands: Netherlands Defence Academy (NDLA).

78 FR 20032 - Styrene-Ethylene-Propylene Block Copolymer; Tolerance Exemption

Science.gov (United States)

2013-04-03

...-Ethylene-Propylene Block Copolymer; Tolerance Exemption AGENCY: Environmental Protection Agency (EPA... for residues of styrene-ethylene-propylene block copolymer (CAS Reg. No. 108388-87-0) when used as an...-ethylene-propylene block copolymer on food or feed commodities. DATES: This regulation is effective April 3...

Polyethylene-Based Tadpole Copolymers

KAUST Repository

Alkayal, Nazeeha

2017-02-15

Novel well-defined polyethylene-based tadpole copolymers ((c-PE)-b-PS, PE: polyethylene, PS: polystyrene) with ring PE head and linear PS tail are synthesized by combining polyhomologation, atom transfer radical polymerization (ATRP), and Glaser coupling reaction. The -OH groups of the 3-miktoarm star copolymers (PE-OH)-b-PS, synthesized by polyhomologation and ATRP, are transformed to alkyne groups by esterification with propiolic acid, followed by Glaser cyclization and removal of the unreacted linear with Merrifield\\'s resin-azide. The characterization results of intermediates and final products by high-temperature size exclusion chromatography, H NMR spectroscopy, and differential scanning calorimetry confirm the tadpole topology.

Polyamide copolymers having 2,5-furan dicarboxamide units

Science.gov (United States)

Chisholm, Bret Ja; Samanta, Satyabrata

2017-09-19

Polyamide copolymers, and methods of making and using polyamide copolymers, having 2,5-furan dicarboxamide units are disclosed herein. Such polymers can be useful for engineering thermoplastics having advantageous physical and/or chemical properties.

Dynamic photoinduced realignment processes in photoresponsive block copolymer films: effects of the chain length and block copolymer architecture.

Science.gov (United States)

Sano, Masami; Shan, Feng; Hara, Mitsuo; Nagano, Shusaku; Shinohara, Yuya; Amemiya, Yoshiyuki; Seki, Takahiro

2015-08-07

A series of block copolymers composed of an amorphous poly(butyl methacrylate) (PBMA) block connected with an azobenzene (Az)-containing liquid crystalline (PAz) block were synthesized by changing the chain length and polymer architecture. With these block copolymer films, the dynamic realignment process of microphase separated (MPS) cylinder arrays of PBMA in the PAz matrix induced by irradiation with linearly polarized light was studied by UV-visible absorption spectroscopy, and time-resolved grazing incidence small angle X-ray scattering (GI-SAXS) measurements using a synchrotron beam. Unexpectedly, the change in the chain length hardly affected the realignment rate. In contrast, the architecture of the AB-type diblock or the ABA-type triblock essentially altered the realignment feature. The strongly cooperative motion with an induction period before realignment was characteristic only for the diblock copolymer series, and the LPL-induced alignment change immediately started for triblock copolymers and the PAz homopolymer. Additionally, a marked acceleration in the photoinduced dynamic motions was unveiled in comparison with a thermal randomization process.

21 CFR 177.1020 - Acrylonitrile/butadiene/sty-rene co-polymer.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Acrylonitrile/butadiene/sty-rene co-polymer. 177... SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances.../butadiene/sty-rene co-polymer. Acrylonitrile/butadiene/styrene copolymer identified in this section may be...

Renewable Pentablock Copolymers Containing Bulky Natural Rosin for Tough Bioplastics

Science.gov (United States)

Rahman, Md Anisur; Ganewatta, Mitra S.; Lokupitiya, Hasala N.; Liang, Yuan; Stefik, Morgan; Tang, Chuanbing

Renewable polymers have received significant attention due to environmental concerns on petrochemical counterparts. One of the most abundant natural biomass is resin acids. However, most polymers derived from resin acids are low molecular weight and brittle because of the high chain entanglement molecular weight resulted from the bulky hydrophenanthrene pendant group. It is well established that the brittleness can be overcome by synthesizing multi-block copolymers with low entanglement molecular weight components. We investigated the effects of chain architecture and microdomain orientation on mechanical properties of both tri and pentablock copolymers. We synthesized rosin-containing A-B-A-B-A type pentablock and A-B-A type triblock copolymers to improve their mechanical properties. Pentablock copolymers showed higher strength and better toughness as compared to triblock copolymers, both superior to homopolymers. The greater toughness of pentablock copolymers is due to the presence of the rosin based midblock chains that act as bridging chains between two polynorbornene blocks.

Ion Transport in Nanostructured Block Copolymer/Ionic Liquid Membranes

OpenAIRE

Hoarfrost, Megan Lane

2012-01-01

Incorporating an ionic liquid into one block copolymer microphase provides a platform for combining the outstanding electrochemical properties of ionic liquids with a number of favorable attributes provided by block copolymers. In particular, block copolymers thermodynamically self-assemble into well-ordered nanostructures, which can be engineered to provide a durable mechanical scaffold and template the ionic liquid into continuous ion-conducting nanochannels. Understanding how the additio...

Green-Yellow Electroluminescence from a host-dopant blended system as the active layer in a bilayer polymer light emitting diode: Poly(n-vinyl carbazole) as the host and a new soluble thiophene based copolymer [poly(2,2‧-BT)-co-(3-DDT)] as the dopant

Science.gov (United States)

Shahalizad, Afshin; Ahmadi-Kandjani, Sohrab; Movla, Hossein; Omidi, Hafez; Massoumi, Bakhshali; Zakerhamidi, Mohammad Sadegh; Entezami, Ali Akbar

2014-11-01

A new type of bilayer Polymer Light Emitting Diode (PLED) which emits green-yellow light is reported. In this PLED, a novel thiophene-based copolymer [poly(2,2‧-BT)-co-(3-DDT)] with an excellent electron transporting property has been doped in hole transporting and electron blocking poly(n-vinylcarbazole) (PVK). Formation of type-II heterojunctions among nm-size features in PVK:poly(2,2‧-BT)-co-(3-DDT) blended system makes exciplex and electroplex emissions would be dominant in the Electroluminescence (EL) spectrum of the device. These cross recombinations between electrons in the LUMO of poly(2,2‧-BT)-co-(3-DDT) and holes in the HOMO of PVK is a reason for the low driving voltage of the PLED because there is no need for the charge carriers to hop or tunnel to the adjacent polymer. Morphological investigations demonstrate that the mixing degree between the components is high, favoring formation of exciplexes and electroplexes at the interface of the components.

Investigation of ionic conduction in PEO-PVDF based blend polymer electrolytes

Science.gov (United States)

Patla, Subir Kumar; Ray, Ruma; Asokan, K.; Karmakar, Sanat

2018-03-01

We investigate the effect of blend host polymer on solid polymer electrolyte (SPE) films doped with ammonium iodide (NH4I) salt using a variety of experimental techniques. Structural studies on the composite SPEs show that the blending of Poly(ethylene oxide) (PEO)-Poly(vinylidene fluoride) (PVDF) polymers in a suitable ratio enhances the amorphous fraction of the polymer matrix and facilitates fast ion conduction through it. We observe that the addition of a small amount of PVDF in the PEO host polymer enhances the ion - polymer interaction leading to more ion dissociation. As a result, the effective number of mobile charge carriers within the polymer matrix increases. Systematic investigation in these blend SPEs shows that the maximum conductivity (1.01 × 10-3 S/cm) is obtained for PEO - rich (80 wt. % PEO, 20 wt. % PVDF) composites at 35 wt. % NH4I concentration at room temperature. Interestingly, at higher salt concentrations (above 35 wt. %), the conductivity is found to decrease in this system. The reduction of conductivity at higher salt concentrations is the consequence of decrease in the carrier concentration due to the formation of an ion pair and ion aggregates. PVDF-rich compositions (20 wt. % PEO and 80 wt. % PVDF), on the other hand, show a very complex porous microstructure. We also observe a much lower ionic conductivity (maximum ˜ 10-6 S/cm at 15 wt. % salt) in these composite systems relative to PEO-rich composites.

Polymer blends

Energy Technology Data Exchange (ETDEWEB)

Allen, Scott D.; Naik, Sanjeev

2017-08-22

The present invention provides, among other things, extruded blends of aliphatic polycarbonates and polyolefins. In one aspect, provided blends comprise aliphatic polycarbonates such as poly(propylene carbonate) and a lesser amount of a crystalline or semicrystalline polymer. In certain embodiments, provided blends are characterized in that they exhibit unexpected improvements in their elongation properties. In another aspect, the invention provides methods of making such materials and applications of the materials in applications such as the manufacture of consumer packaging materials.

Poly(ortho-phenylenediamine-co-aniline) based copolymer with improved capacitance

Science.gov (United States)

Olmedo-Martínez, Jorge L.; Farías-Mancilla, Bárbara I.; Vega-Rios, Alejandro; Zaragoza-Contreras, E. Armando

2017-10-01

A poly(ortho-phenylenediamine-co-aniline) copolymer is synthesized via the oxidative route, using a 1:1 M ratio of aniline to ortho-phenylenediamine (oPDA) and ammonium persulfate as the oxidizing agent. Infrared spectroscopy indicates that the copolymer contains the functional groups typically present in polyaniline and poly(ortho-phenylenediamine); whereas UV-vis-NIR spectroscopy shows that the copolymer adopts a phenazine-type structure. Cyclic voltammetry evidences the copolymer synthesis, as a redox peak at -65 mV, different from those exhibited by polyaniline (160 mV and 600 mV) or poly(o-phenylenediamine) (-240 mV) is observed. Finally, electrochemical impedance spectroscopy and the charge/discharge test provide support to propose the copolymer application in electrodes for supercapacitors.

Bactericidal and Hemocompatible Coating via the Mixed-Charged Copolymer.

Science.gov (United States)

Fan, Xiao-Li; Hu, Mi; Qin, Zhi-Hui; Wang, Jing; Chen, Xia-Chao; Lei, Wen-Xi; Ye, Wan-Ying; Jin, Qiao; Ren, Ke-Feng; Ji, Jian

2018-03-28

Cationic antibacterial coating based on quaternary ammonium compounds, with an efficient and broad spectrum bactericidal property, has been widely used in various fields. However, the high density of positive charges tends to induce weak hemocompatibility, which hinders the application of the cationic antibacterial coating in blood-contacting devices and implants. It has been reported that a negatively charged surface can reduce blood coagulation, showing improved hemocompatibility. Here, we describe a strategy to combine the cationic and anionic groups by using mixed-charged copolymers. The copolymers of poly (quaternized vinyl pyridine- co- n-butyl methacrylate- co-methacrylate acid) [P(QVP- co- nBMA- co-MAA)] were synthesized through free radical copolymerization. The cationic group of QVP, the anionic group of MAA, and the hydrophobic group of nBMA were designed to provide bactericidal capability, hemocompatibility, and coating stability, respectively. Our findings show that the hydrophilicity of the copolymer coating increased, and its zeta potential decreased from positive charge to negative charge with the increase of the anionic/cationic ratio. Meanwhile, the bactericidal property of the copolymer coating was kept around a similar level compared with the pure quaternary ammonium copolymer coating. Furthermore, the coagulation time, platelet adhesion, and hemolysis tests revealed that the hemocompatibility of the copolymer coating improved with the addition of the anionic group. The mixed-charged copolymer combined both bactericidal property and hemocompatibility and has a promising potential in blood-contacting antibacterial devices and implants.

SYNTHESIS OF STYRENE-METHYL METHACRYLATE BLOCK COPOLYMER BY POLYAZOAMIDE AS INITIATOR

Institute of Scientific and Technical Information of China (English)

WANG Zhongyi; WEI Jeqing

1996-01-01

Polyazoamide(PAA) was used as initiator to prepare block copolymer P(MMA-b-St) by free radical polymerization. The fraction of block copolymer was about 50%. The structure of the block-copolymer was characterized by IR and the results of 1H-NMR and GPC showed that the content of the block and the molecular weight (-Mw) of the prepolymer and block copolymer could be controlled by varying the mol ratio of styrene/PAA and MMA/prepolymer. DSC and TEM results revealed that the block copolymer has two separated glass transition temperatures and phase separation within the domain structure.

Microtome Sliced Block Copolymers and Nanoporous Polymers as Masks for Nanolithography

DEFF Research Database (Denmark)

Shvets, Violetta; Schulte, Lars; Ndoni, Sokol

2014-01-01

Introduction. Block copolymers self-assembling properties are commonly used for creation of very fine nanostructures [1]. Goal of our project is to test new methods of the block-copolymer lithography mask preparation: macroscopic pieces of block-copolymers or nanoporous polymers with cross...... PDMS can be chemically etched from the PB matrix by tetrabutylammonium fluoride in tetrahydrofuran and macroscopic nanoporous PB piece is obtained. Both block-copolymer piece and nanoporous polymer piece were sliced with cryomicrotome perpendicular to the axis of cylinder alignment and flakes...... of etching patterns appear only under the certain parts of thick flakes and are not continuous. Although flakes from block copolymer are thinner and more uniform in thickness than flakes from nanoporous polymer, quality of patterns under nanoporous flakes appeared to be better than under block copolymer...

21 CFR 177.1570 - Poly-1-butene resins and butene/ethylene copolymers.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Poly-1-butene resins and butene/ethylene copolymers... resins and butene/ethylene copolymers. The poly-1-butene resins and butene/ethylene copolymers identified... the catalytic polymerization of 1-butene liquid monomer. Butene/ethylene copolymers are produced by...

Hydrogen bonding strength of diblock copolymers affects the self-assembled structures with octa-functionalized phenol POSS nanoparticles.

Science.gov (United States)

Lu, Yi-Syuan; Yu, Chia-Yu; Lin, Yung-Chih; Kuo, Shiao-Wei

2016-02-28

In this study, the influence of the functional groups by the diblock copolymers of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP), poly(styrene-b-2-vinylpyridine) (PS-b-P2VP), and poly(styrene-b-methyl methacrylate) (PS-b-PMMA) on their blends with octa-functionalized phenol polyhedral oligomeric silsesquioxane (OP-POSS) nanoparticles (NPs) was investigated. The relative hydrogen bonding strengths in these blends follow the order PS-b-P4VP/OP-POSS > PS-b-P2VP/OP-POSS > PS-b-PMMA/OP-POSS based on the Kwei equation from differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopic analyses. Small-angle X-ray scattering and transmission electron microscopic analyses show that the morphologies of the self-assembly structures are strongly dependent on the hydrogen bonding strength at relatively higher OP-POSS content. The PS-b-P4VP/OP-POSS hybrid complex system with the strongest hydrogen bonds shows the order-order transition from lamellae to cylinders and finally to body-centered cubic spheres upon increasing OP-POSS content. However, PS-b-P2VP/OP-POSS and PS-b-PMMA/OP-POSS hybrid complex systems, having relatively weaker hydrogen bonds, transformed from lamellae to cylinder structures at lower OP-POSS content (50 wt%).

Co-polymer Films for Sensors

Science.gov (United States)

Ryan, Margaret A. (Inventor); Jewell, April D. (Inventor); Taylor, Charles (Inventor); Yen, Shiao-Pin S. (Inventor); Kisor, Adam (Inventor); Manatt, Kenneth S. (Inventor); Blanco, Mario (Inventor); Goddard, William A. (Inventor); Homer, Margie L. (Inventor); Shevade, Abhijit V. (Inventor)

2012-01-01

Embodiments include a sensor comprising a co-polymer, the co-polymer comprising a first monomer and a second monomer. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is polystyrene and the second monomer is poly-2-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium benzylamine chloride. Other embodiments are described and claimed.

Blended learning

DEFF Research Database (Denmark)

Staugaard, Hans Jørgen

2012-01-01

Forsøg på at indkredse begrebet blended learning i forbindelse med forberedelsen af projekt FlexVid.......Forsøg på at indkredse begrebet blended learning i forbindelse med forberedelsen af projekt FlexVid....

Biomimetic block copolymer particles with gated nanopores and ultrahigh protein sorption capacity

KAUST Repository

Yu, Haizhou

2014-06-17

The design of micro-or nanoparticles that can encapsulate sensitive molecules such as drugs, hormones, proteins or peptides is of increasing importance for applications in biotechnology and medicine. Examples are micelles, liposomes and vesicles. The tiny and, in most cases, hollow spheres are used as vehicles for transport and controlled administration of pharmaceutical drugs or nutrients. Here we report a simple strategy to fabricate microspheres by block copolymer self-assembly. The microsphere particles have monodispersed nanopores that can act as pH-responsive gates. They contain a highly porous internal structure, which is analogous to the Schwarz P structure. The internal porosity of the particles contributes to their high sorption capacity and sustained release behaviour. We successfully separated similarly sized proteins using these particles. The ease of particle fabrication by macrophase separation and self-assembly, and the robustness of the particles makes them ideal for sorption, separation, transport and sustained delivery of pharmaceutical substances. © 2014 Macmillan Publishers Limited.

Biomimetic block copolymer particles with gated nanopores and ultrahigh protein sorption capacity

Science.gov (United States)

Yu, Haizhou; Qiu, Xiaoyan; Nunes, Suzana P.; Peinemann, Klaus-Viktor

2014-06-01

The design of micro- or nanoparticles that can encapsulate sensitive molecules such as drugs, hormones, proteins or peptides is of increasing importance for applications in biotechnology and medicine. Examples are micelles, liposomes and vesicles. The tiny and, in most cases, hollow spheres are used as vehicles for transport and controlled administration of pharmaceutical drugs or nutrients. Here we report a simple strategy to fabricate microspheres by block copolymer self-assembly. The microsphere particles have monodispersed nanopores that can act as pH-responsive gates. They contain a highly porous internal structure, which is analogous to the Schwarz P structure. The internal porosity of the particles contributes to their high sorption capacity and sustained release behaviour. We successfully separated similarly sized proteins using these particles. The ease of particle fabrication by macrophase separation and self-assembly, and the robustness of the particles makes them ideal for sorption, separation, transport and sustained delivery of pharmaceutical substances.

21 CFR 177.1360 - Ethylene-vinyl acetate-vinyl alcohol copolymers.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Ethylene-vinyl acetate-vinyl alcohol copolymers... for Use as Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1360 Ethylene-vinyl acetate-vinyl alcohol copolymers. Ethylene-vinyl acetate-vinyl alcohol copolymers (CAS Reg. No. 26221-27-2...

HPMA and HEMA copolymer bead interactions with eukaryotic cells

Directory of Open Access Journals (Sweden)

Cristina D. Vianna-Soares

2004-09-01

Full Text Available Two different hydrophilic acrylate beads were prepared via aqueous suspension polymerization. Beads produced of a hydroxypropyl methacrylate (HPMA and ethyleneglycol methacrylate (EDMA copolymer were obtained using a polyvinyl alcohol suspending medium. Copolymers of 2hydroxyethyl methacrylate (HEMA, methyl methacrylate (MMA and ethyleneglycol methacrylate (EDMA beads were obtained using magnesium hydroxide as the suspending agent. Following characterization by scanning electron microscopy (SEM, nitrogen sorption analysis (NSA and mercury intrusion porosimetry (MIP, the beads were cultured with monkey fibroblasts (COS7 to evaluate their ability to support cell growth, attachment and adhesion. Cell growth behavior onto small HPMA/EDMA copolymer beads and large HEMA/MMA/EDMA copolymer beads is evaluated regarding their hidrophilicity/hidrophobicity and surface roughness.

Functionalization of Block Copolymer Vesicle Surfaces

Directory of Open Access Journals (Sweden)

Wolfgang Meier

2011-01-01

Full Text Available In dilute aqueous solutions certain amphiphilic block copolymers self-assemble into vesicles that enclose a small pool of water with a membrane. Such polymersomes have promising applications ranging from targeted drug-delivery devices, to biosensors, and nanoreactors. Interactions between block copolymer membranes and their surroundings are important factors that determine their potential biomedical applications. Such interactions are influenced predominantly by the membrane surface. We review methods to functionalize block copolymer vesicle surfaces by chemical means with ligands such as antibodies, adhesion moieties, enzymes, carbohydrates and fluorophores. Furthermore, surface-functionalization can be achieved by self-assembly of polymers that carry ligands at their chain ends or in their hydrophilic blocks. While this review focuses on the strategies to functionalize vesicle surfaces, the applications realized by, and envisioned for, such functional polymersomes are also highlighted.

Sorption of Aromatic Compounds with Copolymer Sorbent Materials Containing β-Cyclodextrin

Directory of Open Access Journals (Sweden)

Lee D. Wilson

2011-08-01

Full Text Available Urethane copolymer sorbent materials that incorporate β-cyclodextrin (CD have been prepared and their sorption properties with chlorinated aromatic compounds (i.e., pentachlorophenol, 2,4-dichlorophenol and 2,4-dichlorophenoxy acetic acid have been evaluated. The sorption properties of granular activated carbon (GAC were similarly compared in aqueous solution at variable pH conditions. The sorbents displayed variable BET surface areas as follows: MDI-X copolymers (< 101 m2/g, CDI-X copolymers (< 101 m2/g, and granular activated carbon (GAC ~103 m2/g. The sorption capacities for the copolymers sorbents are listed in descending order, as follows: GAC > CDI-3 copolymer ≈ MDI-3 copolymer. The sorption capacity for the aromatic adsorbates with each sorbent are listed in descending order, as follows: 2,4-dichlorophenol > 2,4-dichlorophenoxy acetic acid > pentachlorophenol. In general, the differences in the sorption properties of the copolymer sorbents with the chlorinated organics were related to the following factors: (i surface area of the sorbent; (ii CD content and accessibility; and (iii and the chemical nature of the sorbent material.

Morphology and parameters of crystallization the blend PE/Epoxy/PE-co-PEG

International Nuclear Information System (INIS)

Becker, Daniela; Coelho, Luiz Antonio Ferreira; Nack, Fernanda; Silva, Bruna Louise

2014-01-01

This study aims to evaluate the morphology and crystallization parameters of high density polyethylene (HDPE) with different concentrations of epoxy (DGEBA / OTBG), and the compatibility of this system was used and the copolymer polyethylene-block-poly (ethylene glycol) (PEG-co-PE). The blends were obtained by mechanical mixing on a torque rheometer (Haake). Determined the crystallization parameters of the test matrix differential scanning calorimetry (DSC) and by X-ray diffraction (XRD). The morphology of the system was analyzed by transmission electron microscopy (TEM). It was observed by XRD analysis that the addition of compatibilizer and epoxy resins do not interfere with the crystal structure of HDPE, indicating that the increase in crystallinity associated with the crystallization kinetics. It was observed that the compatibilizing helped the adhesion, reducing the size of the dispersed phase becomes a more stable morphology and obtaining a distribution of the dispersed epoxy phase. (author)

Self-assembled Block Copolymer Membranes with Bioinspired Artificial Channels

KAUST Repository

Sutisna, Burhannudin

2018-04-01

Nature is an excellent design that inspires scientists to develop smart systems. In the realm of separation technology, biological membranes have been an ideal model for synthetic membranes due to their ultrahigh permeability, sharp selectivity, and stimuliresponse. In this research, fabrications of bioinspired membranes from block copolymers were studied. Membranes with isoporous morphology were mainly prepared using selfassembly and non-solvent induced phase separation (SNIPS). An effective method that can dramatically shorten the path for designing new isoporous membranes from block copolymers via SNIPS was first proposed by predetermining a trend line computed from the solvent properties, interactions and copolymer block sizes of previously-obtained successful systems. Application of the method to new copolymer systems and fundamental studies on the block copolymer self-assembly were performed. Furthermore, the manufacture of bioinspired membranes was explored using (1) poly(styrene-b-4-hydroxystyrene-b-styrene) (PS-b-PHS-b-PS), (2) poly(styrene-bbutadiene- b-styrene) (PS-b-PB-b-PS) and (3) poly(styrene-b-γ-benzyl-L-glutamate) (PSb- PBLG) copolymers via SNIPS. The structure formation was investigated using smallangle X-ray scattering (SAXS) and time-resolved grazing-Incidence SAXS. The PS-b- PHS-b-PS membranes showed preferential transport for proteins, presumably due to the hydrogen bond interactions within the channels, electrostatic attraction, and suitable pore dimension. Well-defined nanochannels with pore sizes of around 4 nm based on PS-b- PB-b-PS copolymers could serve as an excellent platform to fabricate bioinspired channels due to the modifiable butadiene blocks. Photolytic addition of thioglycolic acid was demonstrated without sacrificing the self-assembled morphology, which led to a five-fold increase in water permeance compared to that of the unmodified. Membranes with a unique feather-like structure and a lamellar morphology for dialysis and

Selective porous gates made from colloidal silica nanoparticles

Directory of Open Access Journals (Sweden)

Roberto Nisticò

2015-11-01

Full Text Available Highly selective porous films were prepared by spin-coating deposition of colloidal silica nanoparticles on an appropriate macroporous substrate. Silica nanoparticles very homogenous in size were obtained by sol–gel reaction of a metal oxide silica precursor, tetraethyl orthosilicate (TEOS, and using polystyrene-block-poly(ethylene oxide (PS-b-PEO copolymers as soft-templating agents. Nanoparticles synthesis was carried out in a mixed solvent system. After spin-coating onto a macroporous silicon nitride support, silica nanoparticles were calcined under controlled conditions. An organized nanoporous layer was obtained characterized by a depth filter-like structure with internal porosity due to interparticle voids. Permeability and size-selectivity were studied by monitoring the diffusion of probe molecules under standard conditions and under the application of an external stimulus (i.e., electric field. Promising results were obtained, suggesting possible applications of these nanoporous films as selective gates for controlled transport of chemical species in solution.

Efeito da compatibilização da mistura NBR/EVA sobre sua morfologia de fase co-contínua Effect of the compatibilization of NBR/EVA blends on co-continuous morphology

Directory of Open Access Journals (Sweden)

Bluma G. Soares

2003-01-01

Full Text Available O objetivo deste trabalho foi investigar a influência do poli (etileno-co-acetato de vinila funcionalizado com grupos mercaptana (EVALSH nas propriedades reológicas, morfológicas e dinamico-mecânicas de misturas envolvendo borracha nitrílica (NBR e copolímero de etileno - acetato de vinila (EVA. Experiências envolvendo extração seletiva da fase NBR associadas à análise de microscopia eletrônica de varredura indicaram que estruturas do tipo co-contínuas são formadas em uma faixa de composição de 30 a 60 % em massa de EVA. A adição de EVALSH não afetou esta faixa de co-continuidade, porém deslocou o limiar de percolação para menores teores de EVA. Este comportamento foi mais pronunciado em misturas ricas em NBR. A faixa de co-continuidade também foi evidenciada a partir de análise dinamico-mecânica. Dados reológicos revelaram também que a adição de EVALSH aumentou a viscosidade do sistema para misturas ricas em NBR.The influence of ethylene-vinyl acetate copolymer functionalized with mercapto groups (EVALSH on rheological, morphological and dynamic mechanical properties of nitrilic rubber (NBR/ ethylene - vinyl acetate copolymer (EVA blends has been investigated. Selective extraction experiments of NBR phase and scanning electron micrography suggest that co-continuous morphologies were formed in a range of blend compositions from 30 to 60 wt% of EVA. The addition of EVALSH did not affect the co-continuous range but shifted the percolation threshold of NBR-richer blends towards lower amount of EVA. The co-continuous range was also evidenced by dynamic mechanical analysis. Rheological data also revealed that the presence of EVALSH increased the viscosity of the blends containing higher amounts of NBR.

Polyether based segmented copolymers with uniform aramid units

NARCIS (Netherlands)

Niesten, M.C.E.J.

2000-01-01

Segmented copolymers with short, glassy or crystalline hard segments and long, amorphous soft segments (multi-block copolymers) are thermoplastic elastomers (TPE’s). The hard segments form physical crosslinks for the amorphous (rubbery) soft segments. As a result, this type of materials combines

Polystyrene/Hyperbranched Polyester Blends and Reactive Polystyrene/Hyperbranched Polyester Blends

National Research Council Canada - National Science Library

Mulkern, Thomas

1999-01-01

.... In this work, the incorporation of HBPs in thermoplastic blends was investigated. Several volume fractions of hydroxyl functionalized hyperbranched polyesters were melt blended with nonreactive polystyrene (PS...

Synthesis and Characterization of Stimuli Responsive Block Copolymers, Self-Assembly Behavior and Applications

Energy Technology Data Exchange (ETDEWEB)

Determan, Michael Duane [Iowa State Univ., Ames, IA (United States)

2005-12-17

The central theme of this thesis work is to develop new block copolymer materials for biomedical applications. While there are many reports of stimuli-responsive amphiphilic [19-21] and crosslinked hydrogel materials [22], the development of an in situ gel forming, pH responsive pentablock copolymer is a novel contribution to the field, Figure 1.1 is a sketch of an ABCBA pentablock copolymer. The A blocks are cationic tertiary amine methacrylates blocked to a central Pluronic F127 triblock copolymer. In addition to the prerequisite synthetic and macromolecular characterization of these new materials, the self-assembled supramolecular structures formed by the pentablock were experimentally evaluated. This synthesis and characterization process serves to elucidate the important structure property relationships of these novel materials, The pH and temperature responsive behavior of the pentablock copolymer were explored especially with consideration towards injectable drug delivery applications. Future synthesis work will focus on enhancing and tuning the cell specific targeting of DNA/pentablock copolymer polyplexes. The specific goals of this research are: (1) Develop a synthetic route for gel forming pentablock block copolymers with pH and temperature sensitive properties. Synthesis of these novel copolymers is accomplished with ATRP, yielding low polydispersity and control of the block copolymer architecture. Well defined macromolecular characteristics are required to tailor the phase behavior of these materials. (2) Characterize relationship between the size and shape of pentablock copolymer micelles and gel structure and the pH and temperature of the copolymer solutions with SAXS, SANS and CryoTEM. (3) Evaluate the temperature and pH induced phase separation and macroscopic self-assembly phenomenon of the pentablock copolymer. (4) Utilize the knowledge gained from first three goals to design and formulate drug delivery formulations based on the multi

Anhydric maleic functionalization and polyethylene glycol grafting of lactide-co-trimethylene carbonate copolymers

Energy Technology Data Exchange (ETDEWEB)

Díaz, A.; Valle, L.; Franco, L. del [Departament d' Enginyeria Química, Universitat Politècnica de Catalunya, Av. Diagonal 647, Barcelona E-08028 (Spain); Sarasua, J.R. [Department of Mining-Metallurgy Engineering and Materials Science, University of the Basque Country (UPV/EHU), Bilbao (Spain); Estrany, F. [Departament d' Enginyeria Química, Universitat Politècnica de Catalunya, Av. Diagonal 647, Barcelona E-08028 (Spain); Puiggalí, J., E-mail: Jordi.Puiggali@upc.es [Department of Mining-Metallurgy Engineering and Materials Science, University of the Basque Country (UPV/EHU), Bilbao (Spain)

2014-09-01

Lactide and trimethylene carbonate copolymers were successfully grafted with polyethylene glycol via previous functionalization with maleic anhydride and using N,N′-diisopropylcarbodiimide as condensing agent. Maleinization led to moderate polymer degradation. Specifically, the weight average molecular weight decreased from 36,200 to 30,200 g/mol for the copolymer having 20 mol% of trimethylene carbonate units. Copolymers were characterized by differential scanning calorimetry, thermogravimetry and X-ray diffraction. Morphology of spherulites and lamellar crystals was evaluated with optical and atomic force microscopies, respectively. The studied copolymers were able to crystallize despite the randomness caused by the trimethylene carbonate units and the lateral groups. Contact angle measurements indicated that PEG grafted copolymers were more hydrophilic than parent copolymers. This feature justified that enzymatic degradation in lipase medium and proliferation of both epithelial-like and fibroblast-like cells were enhanced. Grafted copolymers were appropriate to prepare regular drug loaded microspheres by the oil-in-water emulsion method. Triclosan release from loaded microspheres was evaluated in two media. - Highlights: • Pegylated copolymers of lactide and trimethylene carbonate have been synthesized. • Grafting with polyethylene glycol was able via maleic anhydride functionalization. • Drug-loaded microspheres could be prepared from new pegylated copolymers. • Hydrophilicity of lactide/trimethylene carbonate copolymers increased by pegylation. • New pegylated copolymers supported cell adhesion and proliferation.

Surface morphology of PS-PDMS diblock copolymer films

DEFF Research Database (Denmark)

Andersen, T.H.; Tougaard, S.; Larsen, N.B.

2001-01-01

Spin coated thin films (∼400 Å) of poly(styrene)–poly(dimethylsiloxane) (PS–PDMS) diblock copolymers have been investigated using X-ray Photoelectron Spectroscopy and Atomic Force Microscopy. Surface segregation of the poly(dimethylsiloxane) blocks was studied for five diblock copolymers which ra...

Reactivity Ratios for Organotin Copolymer Systems

Directory of Open Access Journals (Sweden)

Mohamed H. El-Newehy

2010-04-01

Full Text Available Di(tri-n-butyltin itaconate (DTBTI and monoethyl tributyltin fumarate (METBTF were synthesized as organotin monomers. The organotin monomers were copolymerized with styrene (ST and methyl methacrylate (MMA via a free radical polymerization technique. The overall conversion was kept low (£15% wt/wt for all studied samples and the copolymer composition was determined from tin analysis. The synthesized monomers and copolymers were characterized by elemental analysis, 1H- and 13C-NMR, and FTIR spectroscopy.

Thermo-stabilized, porous polyimide microspheres prepared from nanosized SiO2 templating via in situ polymerization

Directory of Open Access Journals (Sweden)

M. Q. Liu

2015-01-01

Full Text Available In this article, we addressed a feasible and versatile method of the fabrication of porous polyimide microspheres presenting excellent heat resistance. The preparation process consisted of two steps. Firstly, a novel polyimide/nano-silica composite microsphere was prepared via the self-assembly structures of poly(amic acid (PAA, precursor of PI/nanosized SiO2 blends after in situ polymerization, following the two-steps imidization. Subsequently, the encapsulated nanoparticles were etched away by hydrofluoric acid treatment, giving rise to the pores. It is found the composite structure of PI/SiO2 is a precondition of the formation of nanoporous structures, furthermore, the morphology of the resultant pore could be relatively tuned by changing the content and initial morphology of silica nano-particles trapped into PI matrix. The thermal properties of the synthesized PI porous spheres were studied, indicating that the introduction of nanopores could not effectively influence the thermal stabilities of PI microspheres. Moreover, the fabrication technique described here may be extended to other porous polymer systems.

SANS and SAXS study of block copolymer/homopolymer mixtures

International Nuclear Information System (INIS)

Hasegawa, Hirokazu; Tanaka, Hideaki; Hashimoto, Takeji; Han, C.C.

1991-01-01

The lateral and vertical components of the radius of gyration for a single block copolymer chain and those of a single homopolymer chain in the lamellar microdomain space formed by a mixture of diblock copolymers and homopolymers were investigated by means of small-angle neutron scattering (SANS) and the microdomain structures by small-angle X-ray scattering (SAXS). The homopolymers whose molecular weights are much smaller than that of the corresponding chains of the block copolymers were used so that the homopolymers were uniformly solubilized in the corresponding microdomains. The SANS result suggests that the homopolymer chains in the microdomain space as well as the block copolymer chains are more compressed in the direction parallel to the interface and more stretched in the direction perpendicular to the interface than the corresponding unperturbed polymer chains with the same molecular weight. On increasing the volume fraction of the homopolymers the thickness of the lamellar microdomains increases. The block copolymer chains were found to undergo an isochoric affine deformation on addition of the homopolymers or with the change of the thickness of the lamellar microdomains. (orig.)

Slip-spring model of entangled rod-coil block copolymers

Science.gov (United States)

Wang, Muzhou; Likhtman, Alexei E.; Olsen, Bradley D.

2015-03-01

Understanding the dynamics of rod-coil block copolymers is important for optimal design of functional nanostructured materials for organic electronics and biomaterials. Recently, we proposed a reptation theory of entangled rod-coil block copolymers, predicting the relaxation mechanisms of activated reptation and arm retraction that slow rod-coil dynamics relative to coil and rod homopolymers, respectively. In this work, we introduce a coarse-grained slip-spring model of rod-coil block copolymers to further explore these mechanisms. First, parameters of the coarse-grained model are tuned to match previous molecular dynamics simulation results for coils, rods, and block copolymers. For activated reptation, rod-coil copolymers are shown to disfavor configurations where the rod occupies curved portions of the entanglement tube of randomly varying curvature created by the coil ends. The effect of these barriers on diffusion is quantitatively captured by considering one-dimensional motion along an entanglement tube with a rough free energy potential. Finally, we analyze the crossover between the two mechanisms. The resulting dynamics from both mechanisms acting in combination is faster than from each one individually.

Palm oil biodiesel synthesized with potassium loaded calcined hydrotalcite and effect of biodiesel blend on elastomer properties

Energy Technology Data Exchange (ETDEWEB)

Trakarnpruk, Wimonrat; Porntangjitlikit, Suriya [Petrochemistry and Polymer Science, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand)

2008-07-15

Biodiesel was prepared from palm oil by transesterification with methanol in the presence of 1.5%K loaded-calcined Mg-Al hydrotalcite. Fatty acid methyl esters content of 96.9% and methyl ester yield of 86.6% were achieved using a 30:1 methanol to oil molar ratio at 100{sup o}C for 6 h and 7 wt% catalyst. The biodiesel was characterized and its impact on elastomer properties was evaluated. The compatibility of B10 diesel blend (10% biodiesel) with six types of elastomers commonly found in fuel systems (NBR, HNBR, NBR/PVC, acrylic rubber, co-polymer FKM, and terpolymer FKM) were investigated. The physical properties of elastomers after immersion in tested fuels (for 22, 670, and 1008 h at 100{sup o}C) were measured according to American Society of Testing and Materials (ASTM). These include swelling (mass change and volume change), hardness, tensile and elongation, as well as the dynamic mechanical property. The results showed that properties of NBR, NBR/PVC and acrylic rubber were affected more than other elastomers. This is due to the absorption and dissolving of biodiesel by rubber in these samples. Co-polymer FKM and terpolymer FKM which are fluoroelastomers show little property change. (author)

Sorption of Aromatic Compounds with Copolymer Sorbent Materials Containing β-Cyclodextrin.

Science.gov (United States)

Wilson, Lee D; Mohamed, Mohamed H; Berhaut, Christopher L

2011-08-29

Urethane copolymer sorbent materials that incorporate β-cyclodextrin (CD) have been prepared and their sorption properties with chlorinated aromatic compounds (i.e., pentachlorophenol, 2,4-dichlorophenol and 2,4-dichlorophenoxy acetic acid) have been evaluated. The sorption properties of granular activated carbon (GAC) were similarly compared in aqueous solution at variable pH conditions. The sorbents displayed variable BET surface areas as follows: MDI-X copolymers (granular activated carbon (GAC ~10³ m²/g). The sorption capacities for the copolymers sorbents are listed in descending order, as follows: GAC > CDI-3 copolymer ≈ MDI-3 copolymer. The sorption capacity for the aromatic adsorbates with each sorbent are listed in descending order, as follows: 2,4-dichlorophenol > 2,4-dichlorophenoxy acetic acid > pentachlorophenol. In general, the differences in the sorption properties of the copolymer sorbents with the chlorinated organics were related to the following factors: (i) surface area of the sorbent; (ii) CD content and accessibility; and (iii) and the chemical nature of the sorbent material.

Influence of Chirality in Ordered Block Copolymer Phases

Science.gov (United States)

Prasad, Ishan; Grason, Gregory

2015-03-01

Block copolymers are known to assemble into rich spectrum of ordered phases, with many complex phases driven by asymmetry in copolymer architecture. Despite decades of study, the influence of intrinsic chirality on equilibrium mesophase assembly of block copolymers is not well understood and largely unexplored. Self-consistent field theory has played a major role in prediction of physical properties of polymeric systems. Only recently, a polar orientational self-consistent field (oSCF) approach was adopted to model chiral BCP having a thermodynamic preference for cholesteric ordering in chiral segments. We implement oSCF theory for chiral nematic copolymers, where segment orientations are characterized by quadrupolar chiral interactions, and focus our study on the thermodynamic stability of bi-continuous network morphologies, and the transfer of molecular chirality to mesoscale chirality of networks. Unique photonic properties observed in butterfly wings have been attributed to presence of chiral single-gyroid networks, this has made it an attractive target for chiral metamaterial design.

Block copolymer-nanoparticle hybrid self-assembly

KAUST Repository

Hoheisel, Tobias N.; Hur, Kahyun; Wiesner, Ulrich B.

2015-01-01

© 2014 Published by Elsevier Ltd. Polymer-inorganic hybrid materials provide exciting opportunities as they may display favorable properties from both constituents that are desired in applications including catalysis and energy conversion and storage. For the preparation of hybrid materials with well-defined morphologies, block copolymer-directed nanoparticle hybrids present a particularly promising approach. As will be described in this review, once the fundamental characteristics for successful nanostructure formation at or close to the thermodynamic equilibrium of these nanocomposites are identified, the approach can be generalized to various materials classes. In addition to the discussion of recent materials developments based on the use of AB diblock copolymers as well as ABC triblock terpolymers, this review will therefore emphasize progress in the fundamental understanding of the underlying formation mechanisms of such hybrid materials. To this end, critical experiments for, as well as theoretical progress in the description of these nanostructured block copolymer-based hybrid materials will be discussed. Rather than providing a comprehensive overview, the review will emphasize work by the Wiesner group at Cornell University, US, on block copolymer-directed nanoparticle assemblies as well as their use in first potential application areas. The results provide powerful design criteria for wet-chemical synthesis methodologies for the generation of functional nanomaterials for applications ranging from microelectronics to catalysis to energy conversion and storage.

Melt-processable, radiation cross-linkable E--CTFE copolymer compositions

International Nuclear Information System (INIS)

Robertson, A.B.; Schaffhauser, R.J.

1976-01-01

Melt-processable, radiation cross-linkable ethylene/chlorotrifluoroethylene copolymer compositions are provided which contain about 0.1 to 5 percent by weight of the copolymer of a radiation cross-linking promoter, about 0.01 to 5 percent by weight of an anti-oxidant and about 0.1 to 30 precent by weight of an acid scavenger. Such compositions do not give off odors when irradiated to cross-link the copolymer and do not develop bubbles after irradiation. 15 claims, no drawings

Micro pore arrays in free standing cyclic olefin copolymer membranes: fabrication and surface functionalization strategies for in-vitro barrier tissue models

Science.gov (United States)

Gel, M.; Kandasamy, S.; Cartledge, K.; Be, C. L.; Haylock, D.

2013-12-01

In recent years there has been growing interest in micro engineered in-vitro models of tissues and organs. These models are designed to mimic the in-vivo like physiological conditions with a goal to study human physiology in an organ-specific context or to develop in-vitro disease models. One of the challenges in the development of these models is the formation of barrier tissues in which the permeability is controlled locally by the tissues cultured at the interface. In-vitro models of barrier tissues are typically created by generating a monolayer of cells grown on thin porous membranes. This paper reports a robust preparation method for free standing porous cyclic olefin copolymer (COC) membranes. We also demonstrate that gelatin coated membranes facilitate formation of highly confluent monolayer of HUVECs. Membranes with thickness in the range of 2-3 um incorporating micro pores with diameter approximately 20 um were fabricated and integrated with microfluidic channels. The performance of the device was demonstrated with a model system mimicking the endothelial barrier in bone marrow sinusoids.

Patchy micelles based on coassembly of block copolymer chains and block copolymer brushes on silica particles.

Science.gov (United States)

Zhu, Shuzhe; Li, Zhan-Wei; Zhao, Hanying

2015-04-14

Patchy particles are a type of colloidal particles with one or more well-defined patches on the surfaces. The patchy particles with multiple compositions and functionalities have found wide applications from the fundamental studies to practical uses. In this research patchy micelles with thiol groups in the patches were prepared based on coassembly of free block copolymer chains and block copolymer brushes on silica particles. Thiol-terminated and cyanoisopropyl-capped polystyrene-block-poly(N-isopropylacrylamide) block copolymers (PS-b-PNIPAM-SH and PS-b-PNIPAM-CIP) were synthesized by reversible addition-fragmentation chain transfer polymerization and chemical modifications. Pyridyl disulfide-functionalized silica particles (SiO2-SS-Py) were prepared by four-step surface chemical reactions. PS-b-PNIPAM brushes on silica particles were prepared by thiol-disulfide exchange reaction between PS-b-PNIPAM-SH and SiO2-SS-Py. Surface micelles on silica particles were prepared by coassembly of PS-b-PNIPAM-CIP and block copolymer brushes. Upon cleavage of the surface micelles from silica particles, patchy micelles with thiol groups in the patches were obtained. Dynamic light scattering, transmission electron microscopy, and zeta-potential measurements demonstrate the preparation of patchy micelles. Gold nanoparticles can be anchored onto the patchy micelles through S-Au bonds, and asymmetric hybrid structures are formed. The thiol groups can be oxidized to disulfides, which results in directional assembly of the patchy micelles. The self-assembly behavior of the patchy micelles was studied experimentally and by computer simulation.

Responsive Copolymers for Enhanced Petroleum Recovery

Energy Technology Data Exchange (ETDEWEB)

McCormick, C.; Hester, R.

2001-02-27

The objectives of this work was to: synthesize responsive copolymer systems; characterize molecular structure and solution behavior; measure rheological properties of aqueous fluids in fixed geometry flow profiles; and to tailor final polymer compositions for in situ rheology control under simulated conditions. This report focuses on the synthesis and characterization of novel stimuli responsive copolymers, the investigation of dilute polymer solutions in extensional flow and the design of a rheometer capable of measuring very dilute aqueous polymer solutions at low torque.

Nanoparticle-enabled delivery of surfactants in porous media.

Science.gov (United States)

Nourafkan, Ehsan; Hu, Zhongliang; Wen, Dongsheng

2018-06-01

The adsorption of surfactants on the reservoir rocks surface is a serious issue in many energy and environment related areas. Learning from the concept of drug delivery in the nano-medicine field, this work proposes and validates the concept of using nanoparticles to deliver a mixture of surfactants into a porous medium. TiO 2 nanoparticles (NPs) are used as carriers for a blend of surfactants mixtures including anionic alkyl aryl sulfonic acid (AAS) and nonionic alcohol ethoxylated (EA) at the optimum salinity and composition conditions. The transport of NPs through a core sample of crushed sandstone grains and the adsorption of surfactants are evaluated. By using TiO 2 NPs, the adsorption of surfactant molecules can be significantly reduced, i.e. half of the initial adsorption value. The level of surfactant adsorption reduction is related to the NPs transport capability through the porous medium. An application study shows that comparing to surfactant flooding alone, the total oil recovery can be increased by 7.81% of original oil in place (OOIP) by using nanoparticle bonded surfactants. Such work shows the promise of NP as an effective surfactant carrier for sandstone reservoirs, which could have many potential applications in enhanced oil recovery (EOR) and environmental remediation. Copyright © 2018 Elsevier Inc. All rights reserved.

Profiling Student Behaviour in a Blended Course: Closing the Gap Between Blended Teaching and Blended Learning

NARCIS (Netherlands)

Bos, Nynke; Brand-Gruwel, Saskia

2018-01-01

Blended learning is often associated with student-oriented learning in which students have varying degrees of control over their learning process. However, the current notion of blended learning is often a teacher- oriented approach in which the teacher identifies the used learning technologies and

Effect of blending temperature on the mechanical properties of PVC/ENR blend upon irradiation

International Nuclear Information System (INIS)