Poly(n-isopropylacrylamide)-based hydrogel coatings on magnetite nanoparticles via atom transfer radical polymerization

Energy Technology Data Exchange (ETDEWEB)

Frimpong, Reynolds A; Hilt, J Zach [Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506 (United States)], E-mail: hilt@engr.uky.edu

2008-04-30

Core magnetite (Fe{sub 3}O{sub 4}) nanoparticles have been functionalized with a model intelligent hydrogel system based on the temperature responsive polymer poly(n-isopropyl acrylamide) (PNIPAAm) to obtain magnetically responsive core-shell nanocomposites. Fe{sub 3}O{sub 4} nanoparticles were obtained from a one-pot co-precipitation method which provided either oleic acid (hydrophobic) or citric acid (hydrophilic) coated nanoparticles. Subsequent ligand exchange of these coatings with various bromine alkyl halides and a bromo silane provided initiating sites for functionalization with NIPAAm using atom transfer radical polymerization (ATRP). The bromine alkyl halides that were used were 2-bromo-2-methyl propionic acid (BMPA) and 2-bromopropionyl bromide (BPB). The bromo silane that was used was 3-bromopropyl trimethoxysilane (BPTS). The intelligent polymeric shell consists of NIPAAm crosslinked with poly(ethylene glycol) 400 dimethacrylate (PEG400DMA). Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) were used to confirm the presence of the polymeric shell. Dynamic light scattering (DLS) was used to characterize the nanocomposites for particle size changes with temperature. Their magnetic and temperature responsiveness show great promise for further biomedical applications. This platform for functionalizing magnetic nanoparticles with intelligent hydrogels promises to impact a wide range of medical and biological applications of magnetic nanoparticles.

Poly(n-isopropylacrylamide)-based hydrogel coatings on magnetite nanoparticles via atom transfer radical polymerization

International Nuclear Information System (INIS)

Frimpong, Reynolds A; Hilt, J Zach

2008-01-01

Core magnetite (Fe 3 O 4 ) nanoparticles have been functionalized with a model intelligent hydrogel system based on the temperature responsive polymer poly(n-isopropyl acrylamide) (PNIPAAm) to obtain magnetically responsive core-shell nanocomposites. Fe 3 O 4 nanoparticles were obtained from a one-pot co-precipitation method which provided either oleic acid (hydrophobic) or citric acid (hydrophilic) coated nanoparticles. Subsequent ligand exchange of these coatings with various bromine alkyl halides and a bromo silane provided initiating sites for functionalization with NIPAAm using atom transfer radical polymerization (ATRP). The bromine alkyl halides that were used were 2-bromo-2-methyl propionic acid (BMPA) and 2-bromopropionyl bromide (BPB). The bromo silane that was used was 3-bromopropyl trimethoxysilane (BPTS). The intelligent polymeric shell consists of NIPAAm crosslinked with poly(ethylene glycol) 400 dimethacrylate (PEG400DMA). Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) were used to confirm the presence of the polymeric shell. Dynamic light scattering (DLS) was used to characterize the nanocomposites for particle size changes with temperature. Their magnetic and temperature responsiveness show great promise for further biomedical applications. This platform for functionalizing magnetic nanoparticles with intelligent hydrogels promises to impact a wide range of medical and biological applications of magnetic nanoparticles

Synthesis of thermoresponsive poly(N-isopropylacrylamide) brush on silicon wafer surface via atom transfer radical polymerization

Energy Technology Data Exchange (ETDEWEB)

Turan, Eylem; Demirci, Serkan [Department of Chemistry, Faculty of Art and Science, Gazi University, 06500 Besevler, Ankara (Turkey); Caykara, Tuncer, E-mail: caykara@gazi.edu.t [Department of Chemistry, Faculty of Art and Science, Gazi University, 06500 Besevler, Ankara (Turkey)

2010-08-31

Thermoresponsive poly(N-isopropylacrylamide) [poly(NIPAM)] brush on silicon wafer surface was prepared by combining the self-assembled monolayer of initiator and atom transfer radical polymerization (ATRP). The resulting polymer brush was characterized by in situ reflectance Fourier transform infrared spectroscopy, atomic force microscopy and ellipsometry techniques. Gel permeation chromatography determination of the number-average molecular weight and polydispersity index of the brush detached from the silicon wafer surface suggested that the surface-initiated ATRP method can provide relatively homogeneous polymer brush. Contact angle measurements exhibited a two-stage increase upon heating over the board temperature range 25-45 {sup o}C, which is in contrast to the fact that free poly(NIPAM) homopolymer in aqueous solution exhibits a phase transition at ca. 34 {sup o}C within a narrow temperature range. The first de-wetting transition takes place at 27 {sup o}C, which can be tentatively attributed to the n-cluster induced collapse of the inner region of poly(NIPAM) brush close to the silicon surface; the second de-wetting transition occurs at 38 {sup o}C, which can be attributed to the outer region of poly(NIPAM) brush, possessing much lower chain density compared to that of the inner part.

'Smart' Diblock Copolymers as Templates for Magnetic-Core Gold-Shell Nanoparticle Synthesis

International Nuclear Information System (INIS)

Nash, Michael A.; Lai, James J.; Hoffman, Allan S.; Yager, Paul; Stayton, Partick S.

2010-01-01

We report a new strategy for synthesizing temperature-responsive γ-Fe 2 O 3 -core/Au-shell nanoparticles (Au-mNPs) from diblock copolymer micelles. The amphiphilic diblock copolymer chains were synthesized using reversible addition-fragmentation chain-transfer (RAFT) with a thermally responsive 'smart' poly(N-isopropylacrylamide) (pNIPAAm) block and an amine-containing poly(N,N-dimethylaminoethylacrylamide) (DMAEAm) block that acted as a reducing agent during gold shell formation. The Au-mNPs reversibly aggregated upon heating the solution above the transition temperature of pNIPAAm, resulting in a red-shifted localized surface plasmon resonance.

Depletion of abundant plasma proteins by poly(N-isopropylacrylamide-acrylic acid) hydrogel particles

DEFF Research Database (Denmark)

Such-Sanmartín, Gerard; Ventura-Espejo, Estela; Jensen, Ole N

2014-01-01

the application of pH-sensitive poly(N-isopropylacrylamide-acrylic acid) hydrogel particles for removal of abundant plasma proteins, prior to proteome analysis by MS. Protein depletion occurs by two separate mechanisms: (1) hydrogel particles incubated with low concentrations of plasma capture abundant proteins...... proteins are released and recovered in the eluate. We developed a series of distinct depletion protocols that proved useful for sample depletion and fractionation and facilitated targeted analysis of putative biomarkers such as IGF1-2, IBP2-7, ALS, KLK6-7, ISK5, and PLF4 by selected reaction monitoring...

Magnetic hollow poly(N-isopropylacrylamide-co-N,N'-methylenebisacrylamide-co-glycidyl acrylate) particles prepared by inverse emulsion polymerization

Czech Academy of Sciences Publication Activity Database

Macková, Hana; Horák, Daniel; Petrovský, Eduard; Kovářová, Jana

2013-01-01

Roč. 291, č. 1 (2013), s. 205-213 ISSN 0303-402X R&D Projects: GA ČR GAP503/10/0664; GA AV ČR(CZ) KAN401220801 EU Projects: European Commission(XE) 259796 - DIATOOLS Institutional research plan: CEZ:AV0Z40500505; CEZ:AV0Z30120515 Keywords : magnetic * poly(N-isopropylacrylamide) * particles Subject RIV: EE - Microbiology, Virology Impact factor: 2.410, year: 2013

Temperature- and pH-sensitive nanohydrogels of poly(N-Isopropylacrylamide for food packaging applications: modelling the swelling-collapse behaviour.

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Clara Fuciños

Full Text Available Temperature-sensitive poly(N-isopropylacrylamide (PNIPA nanohydrogels were synthesized by nanoemulsion polymerization in water-in-oil systems. Several cross-linking degrees and the incorporation of acrylic acid as comonomer at different concentrations were tested to produce nanohydrogels with a wide range of properties. The physicochemical properties of PNIPA nanohydrogels, and their relationship with the swelling-collapse behaviour, were studied to evaluate the suitability of PNIPA nanoparticles as smart delivery systems (for active packaging. The swelling-collapse transition was analyzed by the change in the optical properties of PNIPA nanohydrogels using ultraviolet-visible spectroscopy. The thermodynamic parameters associated with the nanohydrogels collapse were calculated using a mathematical approach based on the van't Hoff analysis, assuming a two-state equilibrium (swollen to collapsed. A mathematical model is proposed to predict both the thermally induced collapse, and the collapse induced by the simultaneous action of two factors (temperature and pH, or temperature and organic solvent concentration. Finally, van't Hoff analysis was compared with differential scanning calorimetry. The results obtained allow us to solve the problem of determining the molecular weight of the structural repeating unit in cross-linked NIPA polymers, which, as we show, can be estimated from the ratio of the molar heat capacity (obtained from the van't Hoff analysis to the specific heat capacity (obtained from calorimetric measurements.

Protein valves prepared by click reaction grafting of poly(N-isopropylacrylamide) to electrospun poly(vinyl chloride) fibrous membranes

Science.gov (United States)

Guo, Jian-Wei; Lin, Zhen-Yu; Chang, Chi-Jung; Lu, Chien-Hsing; Chen, Jem-Kun

2018-05-01

In this study, poly(vinyl chloride) (PVC) was electrospun into fibrous membranes and then reacted with NaN3 to generate azido-terminated PVC fibrous membranes. A propargyl-terminated poly(N-isopropylacrylamide) (PNIPAAm) was also synthesized and then grafted, through click reactions, onto the azido-terminated PVC fiber surface. Protrusion-, scale-, and joint-like structures of the PNIPAAm grafts on the PVC fibers were formed upon increasing the molecular weight of the PNIPAAm grafts. The PNIPAAm-grafted PVC fibrous mats exhibited completely wetted surfaces at 25 °C because of their high roughness. The static water contact angle of the PNIPAAm-grafted PVC fibrous mats reached 140° when the temperature was increased to 45 °C. This thermoresponsive behavior was significantly greater than that of the PNIPAAm grafted on a flat surface. Temperature-responsive membranes were constructed having a pore size of 1.38 μm and applied as protein valves to block and release an antibody (fluorescein-conjugated AffiniPure goat anti-rabbit IgG). At 25 °C, the collection efficiency remained at 94% for antibody concentrations up to 60 ng/L. As the temperature increased to 45 °C, the collection efficiency decreased abruptly, to 4%, when the antibody concentration was greater than 20 ng/L. Accordingly, this system of PNIPAAm-grafted PVC fibers functioned as a protein valve allowing the capture and concentration of proteins.

Synthesis of block copolymers derived from N-trityl-(S)-serine and pyrene end-labeled poly(methyl methacrylate) or poly(N-isopropylacrylamide) via ATRP

International Nuclear Information System (INIS)

Buruiana, Emil C.; Podasca, Viorica; Buruiana, Tinca

2012-01-01

A new monomer bearing N-trityl-L-serine methyl ester in structure, methacryloyloxyethyl carbamoyloxy–N-trityl methyl serine (MTS), was prepared to be further polymerized by atom transfer radical polymerization (ATRP) with pyrene-endcapped poly(methyl methacrylate) (Py–PMMA–Br) or poly(N-isopropylacrylamide) (Py–PNIPA–Br). The resulting block copolymers, poly(methyl methacrylate–block–methacryloyloxyethyl carbamoyloxy–N-trityl methyl serine) (Py–PMMA–b–PMTS) and poly(N-isopropylacrylamide–block–methacryloyloxyethyl carbamoyloxy–N-trityl methyl serine (Py–PNIPA–b–PMTS) were characterized by 1 H ( 13 C) NMR, ultraviolet, FTIR and fluorescence spectroscopy, thermal analysis, differential scanning calorimetry (DSC), atomic force microscopy (AFM), scanning electron microscopy (SEM), and gel permeation chromatography (GPC) measurements. The chemical composition in Py–PMMA–b–PMTS was estimated from the 1 H NMR analysis that indicated a ratio of the repeating units of 46:19 (MMA:MTS). For the Py–PNIPA–b–PMTS the composition rate in the copolymer was 61:25 (NIPA:MTS). Quenching of the pyrene species with N,N-diethylaniline, nitrobenzene, nitrophenol, potassium iodide, p-nitrotoluene and tetracyanoquinodimethane (TCNQ) in DMF solution excited at 348 nm was evidenced, more efficiently being nitrophenol and TCNQ. In this case, the monomer emission at 388–409 nm underwent a significant decrease caused of an electron transfer from the electron-reach photoexcited pyrene molecule to the electron-deficient quenchers. - Highlights: ► Diblock copolymers combine the fluorescence of pyrene–PMMA (PNIPA) with the characteristics of PMTS. ► Such copolymers could be used for nitroderivatives detecting. ► UV/vis and fluorescence measurements give a good correlation for LCST of Py–PNIPA–Br.

Poly(N-isopropylacrylamide and Copolymers: A Review on Recent Progresses in Biomedical Applications

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Sonia Lanzalaco

2017-10-01

Full Text Available The innate ability of poly(N-isopropylacrylamide (PNIPAAm thermo-responsive hydrogel to copolymerize and to graft synthetic polymers and biomolecules, in conjunction with the highly controlled methods of radical polymerization which are now available, have expedited the widespread number of papers published in the last decade—especially in the biomedical field. Therefore, PNIPAAm-based hydrogels are extensively investigated for applications on the controlled delivery of active molecules, in self-healing materials, tissue engineering, regenerative medicine, or in the smart encapsulation of cells. The most promising polymers for biodegradability enhancement of PNIPAAm hydrogels are probably poly(ethylene glycol (PEG and/or poly(ε-caprolactone (PCL, whereas the biocompatibility is mostly achieved with biopolymers. Ultimately, advances in three-dimensional bioprinting technology would contribute to the design of new devices and medical tools with thermal stimuli response needs, fabricated with PNIPAAm hydrogels.

Cloud point enhancement profile of libraries of modified Poly(N-isopropylmethacrylamide)

International Nuclear Information System (INIS)

Tavares, Alexandre Guilherme Silva; Silveira, Kelly Cristine da; Lucas, Elizabete Fernandes

2016-01-01

Full text: Poly(N-isopropyl methacrylamide) (PNIPMAM) based polymers are commercially available. These polymers present low cloud point, which may result in precipitation problems when applying for petroleum exploration [1]. Production of oil and gas has high temperature points, which can induce loss of activity for kinetic hydrate inhibitors (KHI), causing blockages by hydrates in pipes, fittings or valves. Hydrophobic groups can be added to modify PNIPMAM based polymers for hydrate inhibition during petroleum production. The cloud point enhancement profile of series of modified polymers was studied in this work. We synthesized poly(N-isopropyl methacrylamide-co-acrylic acid), P(NIPMAM-co-AA), by standard polymerization using AIBN as initiator. Series of modified polymers using two different groups (terc-butil and cyclopentyl) were studied. The characterization was made by nuclear magnetic resonance (NMR) to confirm the chemical structure; titration was used to determine the acrylic acid content for all synthesized polymers; Gel Permeation Chromatography (GPC) was applied to determine molar mass and polydispersity. A carbodiimide mediated coupling reaction (CMC) [2] was used to post synthetically modify the base polymer P(NIPMAM-co-AA) with N-(3-dimethylaminopropyl)-N’- ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) as activation agents. The cloud point experiment was carried out with deionized water and brine water where small vials with polymer solution were heated at 12 deg C/min rate. The temperature when the solution became turbid was monitored. The modified PNIPMAM based polymers presented a significant enhancement on cloud point temperature, up to 80 deg C, in comparison to unmodified polymer, P(NIPMAM-co- AA). References: [1] Mady, M. F.; Kelland, M.A. Energy and Fuels,28, 5714 (2014) [2] Silveira, K.C.; Sheng, Q.; Tian, W.; Lucas, E.F.; Wood, C.D. J. Appl. Poly. Sci.,132, 42797 (2015). (author)

Semi-interpenetrating networks based on POLY(N-isopropyl acrilamide and POLY(N-vinylpyrrolidone

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Žugić Dragana

2007-01-01

Full Text Available Three series of semi-interpenetrating polymer networks based on cross-linked poly(N-isopropylacrylamide, PNIPA, and 1, 2 and 3 wt% of linear poly(N-vinylpyrrolidone, PVP, were synthesized in order to improve the mechanical properties of PNIPA gels. The effect of the incorporation of the linear PVP polymer into the temperature responsive networks on the phase transition temperature, swelling behavior and mechanical properties was studied. Polymer networks with four different crosslinking densities were prepared with various molar ratios (25/1 to 100/1 of the monomer (N-isopropylacrylamide to the cross linker (N,N'-methylene-bisacrylamide. The hydrogels were characterized by determination of the equilibrium degree of swelling at 25 °C, the dynamic shear modulus and the effective crosslinking density, as well as the ultimate hydrogel properties, such as the tensile strength and elongation at break. Furthermore, the deswelling kinetics of the hydrogels was also studied by measuring their water retention capacity. The inclusion of the linear hydrophilic PVP in the PNIPA networks increased the equilibrium degree of swelling, the highest values of which were obtained for samples with 2 and 3 wt% of PVP and the NIPA/MBA molar ratio of 75/1 and 100/1. The highest reinforcement effect, evaluated from the ratio of G'red(semi-IPN to G'red(PNIPA, was obtained by incorporation of 2 wt% PVP. The tensile strength of the semi-IPNs reinforced with linear PVP was higher than that of the PNIPA networks. The elongation at break of these semi-IPNs varied between 22 and 55%, which are 22^11% larger than those for single PNIPA networks. The tensile measurements confirmed that the presence of 2 wt% of the linear polymer significantly reinforced the PNIPA network.

Hydration of poly( N-isopropylacrylamide) brushes on micro-silica beads measured by a fluorescent probe

Science.gov (United States)

Hattori, Yusuke; Nagase, Kenichi; Kobayashi, Jun; Kikuchi, Akihiko; Akiyama, Yoshikatsu; Kanazawa, Hideko; Okano, Teruo

2010-05-01

Hydration of poly( N-isopropylacrylamide) brushes on silica micro-beads was investigated using a fluorescent probe method. The free ends, the bottom, and the random of brushes were labeled with dansyl group. The emission spectra at the thin brushes were reduced with increasing temperature regardless of their labeling locations. At the free ends of thick brushes, the emission intensity was enhanced at 500 nm and reduced at 455 nm by heating, which was corresponding to the local micro-environmental change around the free ends. The spectral shift was speculated to be due to the enhancement of the flexibility and the hydration of thick brushes.

Segment-segment interactions of poly(N-isopropylacrylamide) in aqueous methanol solutions by using small-angle scattering

International Nuclear Information System (INIS)

Shimizu, S.; Kurita, K.; Furusaka, M.

2002-01-01

Small-angle neutron and X-ray scattering from semidilute solutions of poly(N-isopropylacrylamide) in D 2 O, methanol and methanol-water mixtures has been measured in the poor solvent regime. The binary and the ternary cluster integrals of polymer segments were determined from the concentration dependence of the correlation length at several temperatures just below the lower critical solution temperature. Then, contributions of segment-segment interactions to the entropy and the enthalpy have been calculated from the temperature dependence of interaction parameters and it has been found that both values are positive in the D 2 O and the methanol-water systems at a small content of methanol, while both values are negative in the other system. (orig.)

Effect of the shell on the transport properties of poly(glycerol) and Poly(ethylene imine) nanoparticles

International Nuclear Information System (INIS)

Adeli, M.; Haag, R.; Zarnegar, Z.

2007-01-01

Dendritic core-shell architectures containing poly (glycerol) and poly (ethylene imine) cores and poly(lactide) shell (PG-PLA and PEI-PLA respectively) were synthesized. Analogous of these core-shell architectures containing the same cores but poly (L-lactide) shell (PG-PLLA and PEI-PLLA, respectively) were also synthesized. In this work PG and PEI were used as macroinitiator for ring opening polymerization of the lactid and L-lactide monomers. Different molar ratios of monomer to end functional groups of PG ([LA]/[OH]) and PEI ([LA]/[NHn] (n = 1 or 2)) were used to prepare the core-shell architectures with different shell thickness. These core-shell architectures were able to encapsulate and transport the small guest molecules. Their transport capacity (TC) depended on the type and thickness of the shells. TC of core-shell architectures containing PLLA shell was higher than that for their analogs containing PLA shell. The diameter of core-shell architectures was between 20-80 nm. The rate of release of guest molecules from chloroform solution of nanocarriers to water phase was investigated and it depended on the type of the core, shell and solvent

Controlled Synthesis and Fluorescence Tracking of Highly Uniform Poly(N-isopropylacrylamide) Microgels.

Science.gov (United States)

Virtanen, Otto L J; Purohit, Ashvini; Brugnoni, Monia; Wöll, Dominik; Richtering, Walter

2016-09-08

Stimuli-sensitive poly(N-isopropylacrylamide) (PNIPAM) microgels have various prospective practical applications and uses in fundamental research. In this work, we use single particle tracking of fluorescently labeled PNIPAM microgels as a showcase for tuning microgel size by a rapid non-stirred precipitation polymerization procedure. This approach is well suited for prototyping new reaction compositions and conditions or for applications that do not require large amounts of product. Microgel synthesis, particle size and structure determination by dynamic and static light scattering are detailed in the protocol. It is shown that the addition of functional comonomers can have a large influence on the particle nucleation and structure. Single particle tracking by wide-field fluorescence microscopy allows for an investigation of the diffusion of labeled tracer microgels in a concentrated matrix of non-labeled microgels, a system not easily investigated by other methods such as dynamic light scattering.

Study of structural morphologies of thermoresponsive diblock AB and triblock BAB copolymers (A = poly(N-isopropylacrylamide), B = polystyrene)

Science.gov (United States)

Rodríguez-Hidalgo, María del Rosario; Soto-Figueroa, César; Vicente, Luis

2018-03-01

Structural morphologies of diblock AB and triblock BAB copolymers (A = poly(N-isopropylacrylamide), B = polystyrene) in aqueous environment have been investigated by dissipative particle dynamics (DPD). In triblock copolymers insoluble PS blocks contract while soluble pNIPAM blocks stay at the periphery forming looped chains as corona. As the temperature is increased there is a continuous morphological transition and micelles form ellipsoidal structures with segregated polymer zones. The phase transition of looped pNIPAM chains occurs at lower temperature than for linear chains and within broader temperature range. It is discussed how the chain topology of pNIPAM affects the phase transition.

Optical and rheological studies on weak gel-sol transition in aqueous solutions of poly(N-isopropylacrylamide-block-polystyrene

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S. Sanjeevi Prasath

2017-07-01

Full Text Available The optical and rheological properties of aqueous solutions of block copolymer composed of low molecular weight poly(N-isopropylacrylamide-b-polystyrene are studied as a function of temperature. From light scattering measurements the block copolymer solution is found to form micelles at very low concentrations and the critical micellar concentration is identified as 0.005 wt%. Apart from the concentration dependence, a unique temperature dependent micelle formation is noted at 34 °C. Further, temperature dependent refractive index measurements shows that the refractive index increases with temperature (beyond the lower critical solution temperature, 31.6 °C of the polymer, and is attributed to the stable rearrangement of the proximal hydrophobic isopropyl-polystyrene chains in the collapsed polymer so as to overcome the steric hindrance effects offered by the hydrophobic chains. In the polymer concentrations investigated for rheological studies, the solution flows, yet manifested solid like behavior with G' > G" with the modulus being frequency dependent and the magnitude of G' two-fold higher than G" implying a weak gel state. Weak gel states are in general noted at high temperatures in most of the polymer systems, contrary to this, in our studies weak gel state is observed at lower temperature. Further, a transition from weak gel to sol state is observed at slightly elevated temperatures. The reason for the existence of weak gel state below the lower critical solution temperature is due to the micellar entanglements of poly(N-isopropylacrylamide-b-polystyrene with one another and whereas above the lower critical solution temperature disentanglement of the micelles makes the system behave like a viscoelastic liquid.

The use of magnetic poly(N-isopropylacrylamide) microspheres for separation of DNA from probiotic dairy products

Czech Academy of Sciences Publication Activity Database

Macková, Hana; Horák, Daniel; Trachtová, Š.; Rittich, B.; Španová, A.

2012-01-01

Roč. 1, č. 2 (2012), s. 235-240 ISSN 2164-9634 R&D Projects: GA AV ČR(CZ) KAN401220801; GA MŠk 2B06053; GA MŠk 7E12054 EU Projects: European Commission(XE) 259796 - DIATOOLS Institutional research plan: CEZ:AV0Z40500505 Institutional support: RVO:61389013 Keywords : magnetic particles * thermosensitive * poly(N-isopropylacrylamide) Subject RIV: EE - Microbiology, Virology

Preparation and Investigation of Poly (N-isopropylacrylamide-acrylamide Membranes in Temperature Responsive Drug Delivery

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Elham Khodaverdi

2010-06-01

Full Text Available Objective(sPhysiological changes in the body may be utilized as potential triggers for controlled drug delivery. Based on these mechanisms, stimulus–responsive drug delivery has been developed.Materials and MethodsIn this study, a kind of poly (N-isopropylacrylamide-acrylamide membrane was prepared by radical copolymerization. Changes in swelling ratios and diameters of the membrane were investigated in terms of temperature. On-off regulation of drug permeation through the membrane was then studied at temperatures below and above the phase transition temperature of the membrane. Two drugs, vitamin B12 and acetaminophen were chosen as models of high and low molecular weights here, respectively. ResultsIt was indicated that at temperatures below the phase transition temperature of the membrane, copolymer was in a swollen state. Above the phase transition temperature, water was partially expelled from the functional groups of the copolymer. Permeation of high molecular weight drug models such as vitamin B12 was shown to be much more distinct at temperatures below the phase transition temperature when the copolymer was in a swollen state. At higher temperatures when the copolymer was shrunken, drug permeation through the membrane was substantially decreased. However for acetaminophen, such a big change in drug permeation around the phase transition temperature of the membrane was not observed. ConclusionAccording to the pore mechanism of drug transport through hydrogels, permeability of solutes decreased with increasing molecular size. As a result, the relative permeability, around the phase transition temperature of the copolymer, was higher for solutes of high molecular weight.

Segment-segment interactions of poly(N-isopropylacrylamide) in aqueous methanol solutions by using small-angle scattering

CERN Document Server

Shimizu, S; Furusaka, M

2002-01-01

Small-angle neutron and X-ray scattering from semidilute solutions of poly(N-isopropylacrylamide) in D sub 2 O, methanol and methanol-water mixtures has been measured in the poor solvent regime. The binary and the ternary cluster integrals of polymer segments were determined from the concentration dependence of the correlation length at several temperatures just below the lower critical solution temperature. Then, contributions of segment-segment interactions to the entropy and the enthalpy have been calculated from the temperature dependence of interaction parameters and it has been found that both values are positive in the D sub 2 O and the methanol-water systems at a small content of methanol, while both values are negative in the other system. (orig.)

Poly(N-isopropylacrylamide-co-methacrylic acid microgel stabilized copper nanoparticles for catalytic reduction of nitrobenzene

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Farooqi Zahoor H.

2015-09-01

Full Text Available Poly(N-isopropylacrylamide-co-methacrylic acid microgels [p(NIPAM-co-MAAc] were synthesized by precipitation polymerization of N-isopropylacrylamide and methacrylic acid in aqueous medium. These microgels were characterized by dynamic light scattering and Fourier transform infrared spectroscopy. These microgels were used as micro-reactors for in situ synthesis of copper nanoparticles using sodium borohydride (NaBH4 as reducing agent. The hybrid microgels were used as catalysts for the reduction of nitrobenzene in aqueous media. The reaction was performed with different concentrations of cat­alyst and reducing agent. A linear relationship was found between apparent rate constant (kapp and amount of catalyst. When the amount of catalyst was increased from 0.13 to 0.76 mg/mL then kapp was increased from 0.03 to 0.14 min-1. Activation parameters were also determined by performing reaction at two different temperatures. The catalytic process has been discussed in terms of energy of activation, enthalpy of activation and entropy of activation. The synthesized particles were found to be stable even after 14 weeks and showed catalytic activity for the reduction of nitrobenzene.

Development of thermosensitive poly(n-isopropylacrylamide-co-((2-dimethylamino) ethyl methacrylate))-based nanoparticles for controlled drug release

Energy Technology Data Exchange (ETDEWEB)

Peng, Cheng-Liang; Luo, Tsai-Yueh; Lin, Wuu-Jyh [Isotope Application Division, Institute of Nuclear Energy Research, PO Box 3-27, Longtan Taoyuan 325, Taiwan (China); Tsai, Han-Min; Yang, Shu-Jyuan; Lin, Chia-Fu; Shieh, Ming-Jium, E-mail: soloman@ntu.edu.tw [Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, No 1, Section 1, Jen-Ai Road, Taipei 10051, Taiwan (China)

2011-07-01

Thermosensitive nanoparticles based on poly(N-isopropylacrylamide-co-((2-dimethylamino)ethylmethacrylate)) (poly(NIPA-co-DMAEMA)) copolymers were successfully fabricated by free radical polymerization. The lower critical solution temperature (LCST) of the synthesized nanoparticles was 41 deg. C and a temperature above which would cause the nanoparticles to undergo a volume phase transition from 140 to 100 nm, which could result in the expulsion of encapsulated drugs. Therefore, we used the poly(NIPA-co-DMAEMA) nanoparticles as a carrier for the controlled release of a hydrophobic anticancer agent, 7-ethyl-10-hydroxy-camptothecin (SN-38). The encapsulation efficiency and loading content of SN-38-loaded nanoparticles at an SN-38/poly(NIPA-co-DMAEMA) ratio of 1/10 (D/P = 1/10) were about 80% and 6.293%, respectively. Moreover, the release profile of SN-38-loaded nanoparticles revealed that the release rate at 42 deg. C (above LCST) was higher than that at 37 deg. C (below LCST), which demonstrated that the release of SN-38 could be controlled by increasing the temperature. The cytotoxicity of the SN-38-loaded poly(NIPA-co-DMAEMA) nanoparticles was investigated in human colon cancer cells (HT-29) to compare with the treatment of an anticancer drug, Irinotecan (CPT-11). The antitumor efficacy evaluated in a C26 murine colon tumor model showed that the SN-38-loaded nanoparticles in combination with hyperthermia therapy efficiently suppressed tumor growth. The results indicate that these thermo-responsive nanoparticles are potential carriers for controlled drug delivery.

Designing a Poly (N-isopropylacrylamide) Nanocapsule for Magnetic Field-assisted Drug Delivery

Science.gov (United States)

Denmark, Daniel; Mukherjee, Pritish; Witanachchi, Sarath

2014-03-01

The method of synthesis and the characteristics of polymer based nanocapsules as biomedical drug delivery systems are presented. Magnetic iron oxide nanoparticles have been incorporated into these capsules for effective guidance with external magnetic fields to transport therapeutic compounds to various parts of the human body. Once they have reached their destination they can be stimulated to release the drug to the target tissue through externally applied fields. The polymeric material that constitutes the capsules is specifically designed to melt away with the external stimuli to deliver the therapeutic bio agents near the target tissue. In this work we use nebulization to create aqueous poly (N-isopropylacrylamide) nanoparticles that decompose after being heated beyond their transition temperature. Transmission Electron Microscopic imaging (TEM) and dynamic light scattering (DLS) experiments have been conducted to study the decomposition of the capsules under external stimuli. Distribution of the magnetic nanoparticles within the capsules and their role in delivering the bio agents have been investigated by the Magnetic Force Microscopy (MFM).

Thermodynamics of aqueous solutions containing poly (N-isopropylacrylamide)

Energy Technology Data Exchange (ETDEWEB)

Poschlad, K. [Technical University of Berlin, Chair of Thermodynamics TK 7, Strasse des 17, Juni 135, 10623 Berlin (Germany); Enders, S., E-mail: sabine.enders@tu-berlin.d [Technical University of Berlin, Chair of Thermodynamics TK 7, Strasse des 17, Juni 135, 10623 Berlin (Germany)

2011-03-15

Hydrogels undergo reversible and discontinuous volume changes in response to variation of solution conditions such as solvent composition, temperature, salt concentration, and pH. In this contribution we focus our attention on the experimental and theoretical investigation of these swelling equilibria of aqueous cross-linked poly (N-isopropylacrylamide) solutions as well as on the connected demixing behavior of the linear polymer dissolved in water. For the experimental study of the (liquid + liquid) equilibrium an alternative method based on refractive index measurements is suggested. In order to calculate the swelling behavior a model combining an expression for the Gibbs free energy of mixing with an expression for the elastic network is applied. As a model for the Gibbs free energy of mixing the UNIQUAC-approach and the Koningsveld-Kleintjens model are used. For the elastic network contribution again two different theories, namely the phantom network theory and the affine network theory, were applied. Whereas the type of network theory has only a small influence on the calculation results, the Gibbs free energy of mixing has a large impact. Using the UNIQUAC-approach the swelling equilibria can be correlated close to the experimental data, however, this model predicts a homogeneous mixture for linear polymer chains in water. In contrast to this situation the Koningsveld-Kleintjens model does a good job in calculating the swelling equilibria as well as the demixing curve, however, the adjustable parameter must be changed slightly.

Ocular Biocompatibility of Poly-N-Isopropylacrylamide (pNIPAM

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Luiz H. Lima

2016-01-01

Full Text Available Purpose. To study the safety of intravitreal injections of poly-N-isopropylacrylamide (pNIPAM tissue adhesive in rabbit eyes. Methods. Twelve study rabbits received an intravitreal injection of 0.1 mL 50% pNIPAM in the right eye. Follow-up examinations included color fundus photography, fundus fluorescein angiography (FA, optical coherence tomography (OCT, and electroretinography (ERG. Subsequent to the last follow-up assessment, the rabbits were sacrificed and histopathological study on the scleral incision sites was performed. Results. All study animals developed mild to moderate levels of inflammatory reaction in the conjunctiva, anterior chamber, and the anterior vitreous during the first month of follow-up. After this period, the level of the inflammatory reaction progressively decreased and completely disappeared after the third month of follow-up. The lens and cornea remained clear during the entire follow-up period. OCT and FA did not show areas of retinal damage or neovascularization. Histological and ERG studies of eyes injected with pNIPAM demonstrated absence of retinal toxicity. Conclusion. Intravitreal injections of pNIPAM were nontoxic in this animal study, and pNIPAM may be safe to be used as a bioadhesive in certain retinal diseases.

Synthesis of thermoresponsive poly(N-isopropylacrylamide)/clay nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Kim, J.P.; Lyu, S.G. [Yeungnam Univeristy, Kyongsan (Korea); Bae, K.S. [Andong Institute of Information and Technology, Andong (Korea); Sur, G.S. [Yeungnam Univeristy, Kyungsan (Korea)

2001-03-01

MAPTAC-MMT was prepared by exchanging the mineral cation (sodium montmorillonite) with 3-(methacryloyl amino) propyltrimethyl ammonium chloride, thus rendering the mineral organophilic and forming polymerizable moieties directly bonded to the surface of montmorillonite (MMT). Thermoresponsive nanocomposites (PNIPAM-MMT) were synthesized by polymerization of N-isopropyl acrylamide in an aqueous suspension of MAPTAC-MMT at room temperature. Thermoresponsive nanocomposites exhibited a low critical solution temperature (LCST) similar to unmodified poly(N-isopropyl acrylamide) (PNIPAM). The LCST of thermoresponsive nanocomposites decreased in proportion to the amount of MAPTAC-MMT. TGA results showed that the thermal stability of thermoresponsieve nanocomposites was improved compared to PNIPAM itself the thermoresponsive polymer. (author). 25 refs., 9 figs.

Design and synthesis study of the thermo-sensitive poly (N-vinylpyrrolidone-b- N, N-diethylacrylamide).

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Zhang, Xiayun; Yang, Zhongduo; Xie, Dengmin; Liu, Donglei; Chen, Zhenbin; Li, Ke; Li, Zhizhong; Tichnell, Brandon; Liu, Zhen

2018-01-01

The reversible addition fragmentation chain transfer (RAFT) polymerization method was adopted here to prepare a series of thermo-sensitive copolymers, poly (N,N-diethyl- acrylamide-b-N-vinylpyrrolidone). Their structures, molecular weight distribution and temperature sensitivity performances were characterized by the nuclear magnetic resonance ( 1 HNMR), the gel permeation chromatography (GPC) and the fluorescence spectrophotometer, respectively. It has been identified that the synthesis reaction of the block copolymer was living polymerization. The thermo-sensitivity study suggested that N-vinylpyrrolidone (NVP), played a key role on the lower critical solution temperature (LCST) performance.

The evaluation of temperature and pH influences on equilibrium swelling of poly(n-isopropylacrylamide-co-acrylic acid hydrogels

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Zdravković Aleksandar S.

2017-01-01

Full Text Available Hydrogels are synthesized by the method of radical polymerization of monomers: N-isopropylacrylamide (NIPAM and acrylic acid (AA. Characterization of poly(N-isopropylacrylamide- co-acrylic acid hydrogels, p(NIPAM/AA, has been performed by Fourier transform infrared spectroscopy (FTIR, X-ray diffraction (XRD and by determination of the swelling behaviour in aqueous solutions at different temperatures (25, 31 and 37°C and pH values (2.2, 4.5, 6 and 6.8. After lyophilisation in the solution at pH 6 and temperature of 25°C, p(NIPAM/AA hydrogels have rapidly reached equilibrium degree of swelling, αe, in comparison to non-lyophilized samples. The mechanism of solvent transport within matrix in lyophilized samples corresponds to less Fickian diffusion, whereas Super case II diffusion is characteristic for non-lyophilized samples. p(NIPAM/AA hydrogel with 1.5 mol% of ethylene glycol dimethacrylate (EGDM at the temperature of 25°C and pH 6.8, has reached the highest swelling equilibrium degree, αe = 259.8. The results of swelling studies have shown that p(NIPAM/AA hydrogels can be classified as superabsorbent polymers (SAPs. For the evaluation of pH and temperature influences on synthesized hydrogels swelling, a full three-level experimental design has been used. Two-factor interaction model (2FI is the most optimal model of a full three-level experimental design for representing the swelling equilibrium degree of p(NIPAM/AA hydrogels as a function of investigated parameters, i.e., temperature and pH. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR-34012

Waterborne Electrospinning of Poly(N-isopropylacrylamide) by Control of Environmental Parameters.

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Schoolaert, Ella; Ryckx, Paulien; Geltmeyer, Jozefien; Maji, Samarendra; Van Steenberge, Paul H M; D'hooge, Dagmar R; Hoogenboom, Richard; De Clerck, Karen

2017-07-19

With increasing toxicity and environmental concerns, electrospinning from water, i.e., waterborne electrospinning, is crucial to further exploit the resulting nanofiber potential. Most water-soluble polymers have the inherent limitation of resulting in water-soluble nanofibers, and a tedious chemical cross-linking step is required to reach stable nanofibers. An interesting alternative route is the use of thermoresponsive polymers, such as poly(N-isopropylacrylamide) (PNIPAM), as they are water-soluble beneath their lower critical solution temperature (LCST) allowing low-temperature electrospinning while the obtained nanofibers are water-stable above the LCST. Moreover, PNIPAM nanofibers show major potential to many application fields, including biomedicine, as they combine the well-known on-off switching behavior of PNIPAM, thanks to its LCST, with the unique properties of nanofibers. In the present work, based on dedicated turbidity and rheological measurements, optimal combinations of polymer concentration, environmental temperature, and relative humidity are identified allowing, for the first time, the production of continuous, bead-free PNIPAM nanofibers electrospun from water. More specifically, PNIPAM gelation was found to occur well below its LCST at higher polymer concentrations leading to a temperature regime where the viscosity significantly increases without compromising the polymer solubility. This opens up the ecological, water-based production of uniform PNIPAM nanofibers that are stable in water at temperatures above PNIPAM's LCST, making them suitable for various applications, including drug delivery and switchable cell culture substrates.

Stability of poly(N-isopropylacrylamide-co-acrylic acid polymer microgels under various conditions of temperature, pH and salt concentration

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Zahoor H. Farooqi

2017-03-01

Full Text Available This research article describes the colloidal stability of poly(N-isopropylacrylamide-co-acrylic acid [P(NIPAM-co-AAc] polymer microgels with different acrylic acid contents in aqueous medium under various conditions of temperature, pH and sodium chloride concentrations. Three samples of multi-responsive P(NIPAM-co-AAc polymer microgels were synthesized using different amounts of acrylic acid by free radical emulsion polymerization. Dynamic laser light scattering was used to investigate the responsive behavior and stability of the prepared microgels under various conditions of pH, temperature and ionic strength. The microgels were found to be stable at all pH values above the pKa value of acrylic acid moiety in the temperature range from 15 to 60 °C in the presence and absence of sodium chloride. Increase in temperature, salt concentration and decrease in pH causes aggregation and decreases the stability of microgels due to the decrease in hydrophilicity.

Modifying the Aggregation Behavior of Poly (N-Isopropylacrylamide) Thermoreversible Gel by a Bile Salt

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Kumar, Anitha C [Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036 (India); Boral, Shilpi [Polymer and Biophysics Laboratory, School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110 067 (India); Bohidar, H B [Polymer and Biophysics Laboratory, School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110 067 (India); Mishra, Ashok K [Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036 (India)

2007-09-15

One possible method of altering the critical solution temperature (CST) of poly (N-isopropylacrylamide) (PNIPAM) gel is the addition of surfactants. Because of the biological origin of bile salts, their inclusion in PNIPAM could lead to better biocompatibility when the materials are used for biomedical applications. The gelling behaviour of PNIPAM was studied at various concentrations: PNIPAM concentrations in the range of 1% to 12% (w/v) and sodium cholate (NaC) concentrations varied from 0 to 20 mM. From fluorescence, DLS, rheology and turbidity studies it was found that in the presence of NaC, the CST shifts to lower temperature. This effect of the bile salt is in contrast to the effect of conventional surfactants which are known to shift the CST to higher values, due to mutual solubilization. A study of fluorescence spectroscopic parameters like fluorescence anisotropy, spectral shift, intensity and DLS measurements suggest that a NaC-induced aggregation could be responsible for this unusual observation.

Tough Al-alginate/poly(N-isopropylacrylamide) hydrogel with tunable LCST for soft robotics.

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Zheng, Wen Jiang; An, Ning; Yang, Jian Hai; Zhou, Jinxiong; Chen, Yong Mei

2015-01-28

Tough Al-alginate/poly(N-isopropylacrylamide) (PNIPAM) hydrogel has been synthesized by introducing an interpenetrating network with hybrid physically cross-linked alginate and chemically cross-linked PNIPAM. Varying the concentration of AlCl3 regulates the mechanical properties of the tough hydrogel and tunes its lower critical solution temperature (LCST) as well. The tough Al-alginate/PNIPAM exhibits 6.3 ± 0.3 MPa of compressive stress and 9.95 of uniaxial stretch. Tunability of LCST is also achieved in a wide range within 22.5-32 °C. A bending beam actuator and a four-arm gripper made of bilayer (Na-alginate/PNIPAM)/(Al-alginate/PNIPAM) hydrogel as prototype of all-hydrogel soft robotics are demonstrated. A finite element (FE) simulation model is developed to simulate the deformation of the soft robotics. The FE simulation not only reproduces the deformation process of performed experiments but also predicts more complicated devices that can be explored in the future. This work broadens the application of temperature-responsive PNIPAM-based hydrogels.

IPN's of N-isopropylacrylamide and N-acryloxysuccinimide, Synthesis and Characterization

International Nuclear Information System (INIS)

Ortega, A.

2006-01-01

Hydrogels based on N-isopropylacrylamide (NIPAAm) and one activated monomer are of interest as vesicle immobilizing devices. In this paper we chose NIPAAm because its thermal sensitivity and its lower critical solution temperature (LCST) around 33degree used in immunoassays, bioseparations, controlled release systems and enzyme reactor. The NIPAAm hydrogels retain the thermosensitivity and this property is useful to control the release from vesicles immobilized on the gel. We chose N-acryloxysuccinimide (NAS) to provide a functional group which is readily displaced by the amino groups of lysine, and polylysine as the anchoring element of vesicles, and also as a crosslinking agent of NAS. Sequential interpenetrating networks IPN's made of poly(N-isopropylacrylamide) (PNIPAAm) and NAS were synthesized by gamma irradiation NIPAAm solutions, with and without the crosslinking agent N,N'-methylenebisacrylamide (BIS), at a dose rate of 3.05 kGy/h and then DMF solution of NAS polymers were crosslinked inside of the PNIPAAm hydrogels with polylysine. Poly (NAS) were obtained by irradiation of the monomer NAS (synthesized by Pollak method), and their molecular weight determined by GPC. IPN's were characterized in their thermosensitivity properties (limited swelling time, LCST and water retention), chemical composition (FTIR and elemental analysis), thermal properties (DSC and TGA) and morphology (SEM). LCST of NIPAAm hydrogel was found at 31degree and 29degree on interpenetrating networks of PNIPAm and PNAS crosslinked by polylysine. SEM of NIPAAm hydrogels irradiated at 60 kGy, present homogeneous structure and well defined pores; IPN's presents small cells within large, more or less well defined homogeneous cells

Thermo-and pH-sensitive hydrogel membranes composed of poly(N-isopropylacrylamide)-hyaluronan for biomedical applications: Influence of hyaluronan incorporation on the membrane properties.

Science.gov (United States)

Kamoun, Elbadawy A; Fahmy, Alaa; Taha, Tarek H; El-Fakharany, Esmail M; Makram, Mohamed; Soliman, Hesham M A; Shehata, Hassan

2018-01-01

Interpenetrating hydrogel membranes consisting of pH-sensitive hyaluronan (HA) and thermo-sensitive poly(N-isopropylacrylamide) (PNIPAAM) were synthesized using redox polymerization, followed by N,N-methylenebisacrylamide (BIS) and epichlorohydrin (EPI) were added as chemical crosslinkers. The interaction between membrane compositions has been characterized by FTIR spectroscopy and discussed intensively. The result indicates that HA incorporation in membranes increase the gel fraction, swelling uptake, and the flexibility/elasticity of crosslinked membranes, however it reduced oppositely the mechanical elongation of membranes. PNIPAAm-HA hydrogels responded to both temperature and pH changes and the stimuli-responsiveness was reversible. However, in vitro bioevaluation results revealed that the released ampicillin during the burst release time was sharply influenced and increased with increasing HA contents in membranes; afterwards it became sustainable. Whereas, high HA contents in hydrogels unexpectedly impacted negatively on the cells viability, owing to the viscosity of cell culture media changed. A big resistance was observed against microbial growth of Staphylococcus aureus, Salmonella typhi, and Candida albicans in case of pure PNIPAAm hydrogel membranes without HA or ampicillin. However, HA incorporation or the loaded ampicillin in membranes showed unexpected easily microbial growth. The fast release performance with dual pH-thermo-sensitive hydrogels were suggested as promising materials for quick drug carrier in the biomedical field. Copyright © 2017 Elsevier B.V. All rights reserved.

Surface plasmon resonance methodology for monitoring polymerization kinetics and morphology changes of brushes—evaluated with poly(N-isopropylacrylamide)

Energy Technology Data Exchange (ETDEWEB)

Emilsson, Gustav [Dept. of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg (Sweden); Schoch, Rafael L.; Oertle, Philipp [Biozentrum and the Swiss Nanoscience Institute, University of Basel, 4056 Basel (Switzerland); Xiong, Kunli [Dept. of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg (Sweden); Lim, Roderick Y.H. [Biozentrum and the Swiss Nanoscience Institute, University of Basel, 4056 Basel (Switzerland); Dahlin, Andreas B., E-mail: adahlin@chalmers.se [Dept. of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg (Sweden)

2017-02-28

Highlights: • Real-time monitoring of thickness and the kinetics of polymerization. • Probing brush height both above and below the lower critical solution temperature. • Quantitative analysis of thermal actuation of poly(N-isopropylacrylamide) brushes. - Abstract: Polymerization from surfaces and the resulting “brushes” have many uses in the development of novel materials and functional interfaces. However, it is difficult to accurately monitor the polymerization rate, which limits the use of polymer brushes in applications where control of thickness is desirable. We present a new methodology based on angular surface plasmon resonance (SPR) which provides real-time measurements of the thickness evolution during atom transfer radical polymerization, using poly(N-isopropylacrylamide) as an example. Our data analysis shows that the growth is linear with a rate of ∼20 nm/min in a water/methanol mixture up to ∼100 nm after which chain termination gradually reduces the growth rate. Further, we introduce an improved method in SPR which makes it possible to determine changes in brush height and refractive index during switching of responsive polymers. The ratio between heights in the coil to globule transition at 32 °C in water was found to be almost 5, independent of the initial absolute height up to ∼200 nm, in agreement with theory. Complementary quartz crystal microbalance and atomic force microscopy data confirm the accuracy of our results. With the methodology presented here the established SPR technique can be used for quantitative characterization of surface-initiated polymerization and responsive polymer brushes.

Thermally switchable adhesions of polystyrene-block-poly(n-isopropylacrylamide) copolymer pillar array mimicking climb attitude of geckos

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Chen, Jem-Kun; Wang, Jing-Hong; Chang, Jia-Yaw; Fan, Shih-Kang

2012-09-01

Inspired by the gecko foot pad, we fabricated polystyrene-block-poly(N-isopropylacrylamide) (PS-b-PNIPAAm) copolymer pillar array to mimic climbing attitude of a gecko, alternately attach to and detach from a surface. The pillar array structure of the PS segment significantly enhances both of the hydrophilic and hydrophobic property of PNIPAAm segment tips at 25 and 50 °C, respectively, which could generate alternating adhesive forces of approximately 120 and 11 nN. The dramatic change in adhesive and friction force difference at 25 and 50 °C may guide the design of bio-inspired artificial analogues, which could approach gecko's climbing behavior.

Radiation preparation of drug carriers based on poly(N-isopropylacrylamide) hydrogels, their loading capacities and controlled release rates for dexamethasone and tegafur

International Nuclear Information System (INIS)

Hoang Dang Sang; Nguyen Van Binh; Tran Bang Diep; Nguyen Thi Thom; Hoang Phuong Thao; Pham Duy Duong; Tran Minh Quynh

2015-01-01

Thermo-sensitive hydrogels have great potential in some applications. In order to use as the drug delivery systems, the hydrogels should be biocompatibility. New polymers with more biocompatibility and better biodegradability, and environmental friendly crosslinking agents would be necessary for the successful drug carriers. Poly (N-isopropylacrylamide-co-dimethylacrylamide) based hydrogels have been prepared from the admixture solutions of N-isopropylacrylamide (NIPA) and N,N’-dimethyl acrylamide (DMA) by radiation copolymerization and crosslinking at radiation dose of 20 kGy as reported in our previous study. Water swelling behaviour of the resulting hydrogels were much depended on their nature such as initial ratio of NIPA and DMA. The drug-loaded hydrogels were prepared by merging hydrogel in the solutions containing corresponding drugs. Loading capacity of the hydrogels were about 48.6 and 95.7 mg per g dried hydrogel for dexamethasone and tegafur. The release studies showed that the presence of ions in simulated body fluid and temperature of the solution much affecting to in vitro release behaviors of hydrogels for dexamethasone and tegafur. The release rates were fast for both drug models. The result also revealed that these drug carriers were biocompatibility without skin irritation, suggested the drug-loaded hydrogels may be used as controlled release drug delivery systems. (author)

Antimicrobial activity of silver nanoparticles encapsulated in poly-N-isopropylacrylamide-based polymeric nanoparticles.

Science.gov (United States)

Qasim, Muhammad; Udomluck, Nopphadol; Chang, Jihyun; Park, Hansoo; Kim, Kyobum

2018-01-01

In this study, we analyzed the antimicrobial activities of poly- N -isopropylacrylamide (pNIPAM)-based polymeric nanoparticles encapsulating silver nanoparticles (AgNPs). Three sizes of AgNP-encapsulating pNIPAM- and pNIPAM-NH 2 -based polymeric nanoparticles were fabricated. Highly stable and uniformly distributed AgNPs were encapsulated within polymeric nanoparticles via in situ reduction of AgNO 3 using NaBH 4 as the reducing agent. The formation and distribution of AgNPs was confirmed by UV-visible spectroscopy, transmission electron microscopy, and inductively coupled plasma optical emission spectrometry, respectively. Both polymeric nanoparticles showed significant bacteriostatic activities against Gram-negative ( Escherichia coli ) and Gram-positive ( Staphylococcus aureus ) bacteria depending on the nanoparticle size and amount of AgNO 3 used during fabrication.

Stimuli-responsive poly(N-vinylcaprolactam-co-2-methoxyethyl acrylate) core–shell microgels: facile synthesis, modulation of surface properties and controlled internalisation into cells†

NARCIS (Netherlands)

Melle, A.; Balaceanu, A.; Kather, M.; Wu, Yaodong; Gau, E.; Sun, W.; Huang, Xiaobin; Shi, X; Karperien, Hermanus Bernardus Johannes; Pich, A.

2016-01-01

Herein we report the synthesis of biocompatible stimuli-responsive core–shell microgels consisting of a poly(N-vinylcaprolactam) (PVCL) core and a poly(2-methoxyethyl acrylate) (PMEA) corona via one-step surfactant-free precipitation copolymerization. The copolymerization process was investigated by

Single-Chain Conformation for Interacting Poly(N-isopropylacrylamide in Aqueous Solution

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Boualem Hammouda

2015-04-01

Full Text Available The demixing phase behavior of Poly(N-isopropylacrylamide (PNIPAM aqueous solution is investigated using small-angle neutron scattering. This polymer phase separates upon heating and demixes around 32 °C. The pre-transition temperature range is characterized by two scattering modes; a low-Q (large-scale signal and a high-Q dissolved chains signal. In order to get insight into this pre-transition region, especially the origin of the low-Q (large-scale structure, the zero average contrast method is used in order to isolate single-chain conformations even in the demixing polymers transition region. This method consists of measuring deuterated and non-deuterated polymers dissolved in mixtures of deuterated and non-deuterated water for which the polymer scattering length density matches the solvent scattering length density. A fixed 4% polymer mass fraction is used in a contrast variation series where the d-water/h-water fraction is varied in order to determine the match point. The zero average contrast (match point sample displays pure single-chain scattering with no interchain contributions. Our measurements prove that the large scale structure in this polymer solution is due to a transient polymer network formed through hydrophobic segment-segment interactions. Scattering intensity increases when the temperature gets close to the phase boundary. While the apparent radius of gyration increases substantially at the Lower Critical Solution Temperature (LCST transition due to strong interchain correlation, the single-chain true radius of gyration has been found to decrease slightly with temperature when approaching the transition.

Temperature-responsive nanogel multilayers of poly(N-vinylcaprolactam) for topical drug delivery.

Science.gov (United States)

Zavgorodnya, Oleksandra; Carmona-Moran, Carlos A; Kozlovskaya, Veronika; Liu, Fei; Wick, Timothy M; Kharlampieva, Eugenia

2017-11-15

We report nanothin temperature-responsive hydrogel films of poly(N-vinylcaprolactam) nanoparticles (νPVCL) with remarkably high loading capacity for topical drug delivery. Highly swollen (νPVCL) n multilayer hydrogels, where n denotes the number of nanoparticle layers, are produced by layer-by-layer hydrogen-bonded assembly of core-shell PVCL-co-acrylic acid nanoparticles with linear PVPON followed by cross-linking of the acrylic acid shell with either ethylene diamine (EDA) or adipic acid dihydrazide (AAD). We demonstrate that a (νPVCL) 5 film undergoes dramatic and reversible swelling up to 9 times its dry thickness at pH = 7.5, indicating 89v/v % of water inside the network. These hydrogels exhibit highly reversible ∼3-fold thickness changes with temperature variations from 25 to 50°C at pH = 5, the average pH of human skin. We also show that a (νPVCL) 30 hydrogel loaded with ∼120µgcm -2 sodium diclofenac, a non-steroidal anti-inflammatory drug used for osteoarthritis pain management, provides sustained permeation of this drug through an artificial skin membrane for up to 24h at 32°C (the average human skin surface temperature). The cumulative amount of diclofenac transported at 32°C from the (νPVCL) 30 hydrogel after 24h is 12 times higher than that from the (νPVCL) 30 hydrogel at 22°C. Finally, we demonstrate that the (νPVCL) hydrogels can be used for multiple drug delivery by inclusion of Nile red, fluorescein and DAPI dyes within the νPVCL nanoparticles prior to hydrogel assembly. Using confocal microscopy we observed the presence of separate dye-loaded νPVCL compartments within the hydrogel matrix with all three dyes confined to the nanogel particles without intermixing between the dyes. Our study provides opportunity for development of temperature-responsive multilayer hydrogel coatings made via the assembly of core-shell nanogel particles which can be used for skin-sensitive materials for topical drug delivery. Copyright © 2017

A versatile characterization of poly(N-isopropylacrylamide-co-N,N'-methylene-bis-acrylamide hydrogels for composition, mechanical strength, and rheology

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J. Kovacs

2013-01-01

Full Text Available Poly(N-isopropylacrylamide-co-N,N'-methylene-bisacrylamide (P(NIPAAm-co-MBA hydrogels were prepared in water using redox initiator. The copolymer composition at high conversion (> 95% was determined indirectly by HPLC (high performance liquid chromatography analysis of the leaching water and directly by solid state 13C CP MAS NMR (cross polarization magic angle spinning nuclear magnetic resonance spectroscopy of the dried gels, and was found to be close to that of the feed. The effect of cross-linker (MBA content in the copolymer was investigated in the concentration range of 1.1–9.1 mol% (R:90–10; R = mol NIPAAm/mol MBA on the rheological behaviour and mechanical strength of the hydrogels. Both storage and loss modulus decreased with decreasing cross-linker content as revealed by dynamic rheometry. Gels R70 and R90 with very low cross-linker content (1.2–1.5 mol% MBA have a very loose network structure, which is significantly different from those with higher cross-linker content manifesting in higher difference in storage modulus. The temperature dependence of the damping factor served the most accurate determination of the volume phase transition temperature, which was not affected by the cross-link density in the investigated range of MBA concentration. Gel R10 with highest cross-linker content (9.1 mol% MBA behaves anomalously due to heterogeneity and the hindered conformation of the side chains of PNIPAAm.

A novel injectable thermoresponsive and cytocompatible gel of poly(N-isopropylacrylamide) with layered double hydroxides facilitates siRNA delivery into chondrocytes in 3D culture

NARCIS (Netherlands)

Yang, H.Y.; Ee, R.J. van; Timmer, K.; Craenmehr, E.G.M.; Huang, J.H.; Öner, C.; Dhert, W.J.A.; Kragten, A.H.M.; Willems, N.; Grinwis, G.C.M.; Tryfonidou, M.A.; Papen-Botterhuis, N.E.; Creemers, L.B.

2015-01-01

Hybrid hydrogels composed of poly(N-isopropylacrylamide) (pNIPAAM) and layered double hydroxides (LDHs) are presented in this study as novel injectable and thermoresponsive materials for siRNA delivery, which could specifically target several negative regulators of tissue homeostasis in

A novel injectable thermoresponsive and cytocompatible gel of poly(N-isopropylacrylamide) with layered double hydroxides facilitates siRNA delivery into chondrocytes in 3D culture

NARCIS (Netherlands)

Yang, Hsiao-yin; van Ee, Renz J; Timmer, Klaas; Craenmehr, Eric G M; Huang, Julie H; Oner, F. Cumhur; Dhert, Wouter J A; Kragten, Angela H M; Willems, Nicole; Grinwis, Guy C M; Tryfonidou, Marianna A; Papen-Botterhuis, Nicole E; Creemers, Laura B

Hybrid hydrogels composed of poly(N-isopropylacrylamide) (pNIPAAM) and layered double hydroxides (LDHs) are presented in this study as novel injectable and thermoresponsive materials for siRNA delivery, which could specifically target several negative regulators of tissue homeostasis in

Preparation and Characterization of a Novel Hybrid Hydrogel Composed of Bombyx mori Fibroin and Poly(N-isopropylacrylamide

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Ting Wang

2013-01-01

Full Text Available A novel hybrid hydrogel was prepared and investigated based on silkworm silk fibroin and poly(N-isopropylacrylamide (PNIPAAm. PNIPAAm was introduced to silk fibroin, the resultant composite hydrogel was examined, and freeze-dried SF/PNIPAAm scaffold was analyzed using LB-550 dynamic light scattering particle-size analyzer, circular dichroism (CD, and scanning electron microscopy (SEM. Our results suggested that the hybrid hydrogels owned the porous sponge-like structures, and the gelation time of SF/PNIPAAm hybrids decreased with an increase in temperature and concentration of each polymer. Results of rheological analysis suggested that the rheological property of resultant SF/PNIPAAm gel depended on the concentration combinations as well as the aging time, which elapsed after mixing the two polymers. Results of CD spectra demonstrated that pH showed little influence on the secondary structure of silk fibroin, and significant changes of , , and G* as surrounding increase temperature above the lower critical solution temperature (LCST.

Thermo-responsive wound dressings by grafting chitosan and poly(N-isopropylacrylamide) to plasma-induced graft polymerization modified non-woven fabrics

International Nuclear Information System (INIS)

Chen, Jyh-Ping; Kuo, Chang-Yi; Lee, Wen-Li

2012-01-01

Highlights: ► Poly(N-isopropylacrylamide) and chitosan were grafted to polypropylene non-wovens. ► An easily stripped off thermo-responsive wound dressing was developed. ► The wound dressing is biocompatible, has antibacterial and wound healing abilities. ► The bigraft non-woven will be a potential wound dressing for biomedical use. - Abstract: To obtain a chitosan wound dressings with temperature-responsive characteristics, polypropylene (PP) non-woven fabric (NWF) was modified by direct current pulsed oxygen plasma-induced grafting polymerization of acrylic acid (AAc) to improve hydrophilicity and to introduce carboxylic acid groups. Conjugation of chitosan and poly(N-isopropylacrylamide) (PNIPAAm) followed by using water-soluble carbodiimide as a coupling agent to form a novel bigraft PP-g-chitosan-g-PNIPAAm wound dressing. The amount of chitosan and PNIPAAm grafted to PP-g-chitosan-g-PNIPAAm were 83.0 ± 4.6 μg/cm 2 and 189.5 ± 8.2 μg/cm 2 , respectively. The surface chemical composition and microstructure of the NWF were studied by electron spectroscopy for chemical analysis (ESCA) and scanning electron microscopy (SEM). The linkages between AAc, chitosan, and PNIPAAm were confirmed with the formation of amide bonds. Physical properties of the NWF were characterized and potentials of these NWFs as wound dressings were evaluated using SD rat as the animal model. NWFs contained PNIPAAm were better than those contained only chitosan in wound healing rates and the wound areas covered by PP-g-chitosan-g-PNIPAAm wound dressings healed completely in 17 days.

Dissolution and Solubility Enhancement of the Highly Lipophilic Drug Phenytoin via Interaction with Poly(N-isopropylacrylamide-co-vinylpyrrolidone) Excipients.

Science.gov (United States)

Widanapathirana, Lakmini; Tale, Swapnil; Reineke, Theresa M

2015-07-06

Excipients of natural or synthetic origin play an important role in pharmaceutical performance to enhance the solubility, bioavailability, release, and stability of insoluble drugs. Herein, a series of seven excipient models was prepared by both homopolymerization and copolymerization of 1-vinyl-2-pyrrolidone (VP) and N-isopropylacrylamide (NIPAAm) by free radical polymerization yielding two homopolymers poly(VP) and poly(NIPAAm) and five copolymers of poly(NIPAAm-co-VP) at difference compositions. While the VP monomer provided aqueous solubility at a variety of conditions to the excipient, the incorporation of NIPAAm into the copolymer offered additional hydrogen bond donating sites to optimize the drug-polymer interactions in the system. Due to the presence of NIPAAm, the copolymers were sensitive to temperature as well. It was found that as the proportion of VP was increased (from 0 to 100%), the lower critical solution temperature (LCST) and the water solubility of the polymer models increased. To examine the role of specific drug-polymer interactions during dissolution on drug solubility and bioavailability, the polymers were formulated with the anticonvulsant drug phenytoin, which is a poorly water-soluble BCS class II drug where oral absorption is limited by the drug solubility. Amorphous solid dispersions (ASD) were prepared via spray drying of phenytoin with the polymer excipient models to contain 10% and 25% by weight drug loading. Physical characterization of the ASDs by powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) revealed that the polymers held the drug in a high-energy amorphous phase in all the formulations prepared. All ASDs exhibited improved in vitro dissolution rates compared to drug only and physical mixtures of the polymers and the drug. Drug solubility was the highest with the ASDs containing poly(NIPAAm-co-VP) 60:40 and 50:50, which showed a solubility enhancement of near 14-fold increase compared to pure drug

Fluorescence ON–OFF switching using micelle of stimuli-responsive double hydrophilic block copolymers: Nile Red fluorescence in micelles of poly(acrylic acid-b-N-isopropylacrylamide)

Energy Technology Data Exchange (ETDEWEB)

Yee, Min Min; Tsubone, Miyabi; Morita, Takuya [Department of Chemistry, Graduate School of Science & Engineering, Saga University, 1 Honjo, Saga 840-8502 (Japan); Yusa, Shin-ichi [Department of Materials Science and Chemistry, University of Hyogo, 2167 Shosha, Himeji 671-2280 (Japan); Nakashima, Kenichi, E-mail: nakashik@cc.saga-u.ac.jp [Department of Chemistry, Graduate School of Science & Engineering, Saga University, 1 Honjo, Saga 840-8502 (Japan)

2016-08-15

The dual-mode fluorescence ON–OFF switching of Nile Red (NR) by using stimuli-responsive polymeric micelle of poly(acrylic acid-b-N-isopropylacrylamide) (PAA-b-PNIPAM) has been studied. PAA-b-PNIPAM, one of double hydrophilic block copolymers, is known to form PNIPAM-core/PAA-corona micelles in aqueous solutions when the temperature of the solution is elevated up to the lower critical solution temperature (LCST) of PNIPAM block. It also forms PAA-core/PNIPAM-corona micelles when the anionic PAA block is charge-neutralized with cationic cetyltrimethylammonium ion. Fluorescence properties of NR in the micelles are elucidated by observing various fluorescence parameters such as intensity, polarization, and quantum yield. It is found that the fluorescence intensity is negligibly low (OFF-state) when PAA-b-PNIPAM exists as a form of unimer, whereas it is remarkably enhanced (ON-state) when the PNIPAM-core or PAA-core micelles are formed. These results demonstrate that a novel fluorescence ON–OFF switching system can be constructed by using PAA-b-PNIPAM micelles and NR.

Fabrication, thermal properties and thermal stabilities of microencapsulated n-alkane with poly(lauryl methacrylate) as shell

International Nuclear Information System (INIS)

Qiu, Xiaolin; Lu, Lixin; Wang, Ju; Tang, Guoyi; Song, Guolin

2015-01-01

Highlights: • Microencapsulation of octadecane and paraffin by crosslinked poly(lauryl methacrylate). • Octadecane microcapsules have a melting enthalpy of about 118 J g −1 . • Weight loss temperatures of the microcapsules were increased by 67 °C and 28 °C. • Phase change enthalpies decreased by around 10 wt% after 500 thermal cycles. • Foams with microcapsules can be applied for passive temperature control. - Abstract: Microencapsulation of n-octadecane or paraffin with poly(lauryl methacrylate) (PLMA) shell was performed by a suspension-like polymerization. The polymer shell was crosslinked by pentaerythritol tetraacrylate (PETRA). The surface morphologies of microcapsules were investigated by scanning electron microscopy (SEM). Phase change properties, thermal reliabilities and thermal stabilities of microcapsules were determined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The n-octadecane microcapsule exhibits higher melting enthalpy (118.0 J g −1 ) and crystallization enthalpy (108.3 J g −1 ) compared with the paraffin microcapsule. The thermal resistant temperatures were enhanced by more than 25 °C when n-alkanes were microencapsulated by PLMA. The PCM contents of microcapsules decreased by less than 4 wt% and 6 wt% after 500 and 1000 thermal cycles, respectively. Heat-up experiments indicated that microcapsule-treated foams exhibited upgraded thermal regulation capacities. Consequently, microencapsulated n-octadecane or paraffin with PLMA as shell possesses good potentials for heat storage and thermal regulation.

Investigation on the structure of temperature-responsive N-isopropylacrylamide microgels containing a new hydrophobic crosslinker

Directory of Open Access Journals (Sweden)

G. Roshan Deen

2015-12-01

Full Text Available Temperature-responsive poly(N-isopropylacrylamide microgels crosslinked with a new hydrophobic chemical crosslinker was prepared by surfactant-mediated precipitation emulsion polymerization. The temperature-responsive property of the microgel and the influence of the crosslinker on the swelling behaviour was studied systematically by light scattering and small-angle X-ray scattering (SAXS. The radius of gyration (Rg and the hydrodynamic radius (Rh of the microgels decreased with increase in temperature due to the volume-phase transition from a swollen to a collapsed state. The ratio of Rg/Rh below the transition temperature was lower than that of hard-spheres due to the lower crosslinking density of the microgels. The SAXS data were analysed by a model in which the microgels were modelled as core-shell particles with a graded interface. The model at intermediate temperatures included a central core and a more diffuse outer layer describing pending polymer chains with a low crosslinking density. In the fully swollen state, the microgels were modelled with a single component with a broad graded surface. In the collapsed state, they were modelled as homogeneous and relatively compact particles. The polymer volume fraction inside the microgel was also derived based on the model and was found to increase with increase in the temperature as a result of collapse of the microgel to compact particles. The polymer volume fraction in the core of the microgel in the collapsed state was about 60% which is higher than that of similar microgels crosslinked with hydrophilic and flexible crosslinkers.

Design of poly(vinylidene fluoride)-g-p(hydroxyethyl methacrylate-co-N-isopropylacrylamide) membrane via surface modification for enhanced fouling resistance and release property

International Nuclear Information System (INIS)

Zhao, Guili; Chen, Wei Ning

2017-01-01

Highlights: • PVDF modified membranes were designed by grafting PNIPAAm, PHEMA and their copolymer. • Fouling resistance and release property of membrane were both improved after modification. • Bacterial attachment and detachment were investigated to evaluate fouling release property. • Improvement of the antifouling property was justified by surface property analysis. • The copolymer modified membrane exhibited higher performance to release foulant. - Abstract: Thermo-sensitive polymer poly(N-isopropylacrylamide) (PNIPAAm), hydrophilic polymer poly(hydroxyethyl methacrylate) (PHEMA) and copolymer p(hydroxyethyl methacrylate-co-N-isopropylacrylamide) [P(HEMA-co-NIPAAm)] were synthesized onto poly(vinylidene fluoride) (PVDF) membrane via atom transfer radical polymerization (ATRP) in order to improve not only fouling resistance but also fouling release property. The physicochemical properties of membranes including hydrophilicity, morphology and roughness were examined by contact angle analyzer, scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. The antifouling property of membranes was improved remarkably after surface modification according to protein and bacterial adhesion testing, and filtration experiment. Minimum protein adsorption and bacterial adhesion were both obtained on PVDF-g-P(HEMA-co-NIPAAm) membrane, with reduction by 44% and 71% respectively compared to the pristine membrane. The minimum bacterial cells after detachment at 25 °C were observed on the PVDF-g-P(HEMA-co-NIPAAm) membrane with the detachment rate of 77%, indicating high fouling release property. The filtration testing indicated that the copolymer modified membrane exhibited high resistance to protein fouling and the foulant on the surface was released and removed easily by washing, suggesting high fouling release and easy-cleaning capacity. This study provides useful insight in the combined “fouling resistance” and “fouling release�

Design of poly(vinylidene fluoride)-g-p(hydroxyethyl methacrylate-co-N-isopropylacrylamide) membrane via surface modification for enhanced fouling resistance and release property

Energy Technology Data Exchange (ETDEWEB)

Zhao, Guili [Nanyang Environment and Water Research Institute, Interdisciplinary Graduate School, Nanyang Technological University, 1 Cleantech Loop, Singapore 637141 (Singapore); Advanced Environmental Biotechnology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, Singapore 637141 (Singapore); School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459 (Singapore); Chen, Wei Ning, E-mail: WNChen@ntu.edu.sg [School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459 (Singapore)

2017-03-15

Highlights: • PVDF modified membranes were designed by grafting PNIPAAm, PHEMA and their copolymer. • Fouling resistance and release property of membrane were both improved after modification. • Bacterial attachment and detachment were investigated to evaluate fouling release property. • Improvement of the antifouling property was justified by surface property analysis. • The copolymer modified membrane exhibited higher performance to release foulant. - Abstract: Thermo-sensitive polymer poly(N-isopropylacrylamide) (PNIPAAm), hydrophilic polymer poly(hydroxyethyl methacrylate) (PHEMA) and copolymer p(hydroxyethyl methacrylate-co-N-isopropylacrylamide) [P(HEMA-co-NIPAAm)] were synthesized onto poly(vinylidene fluoride) (PVDF) membrane via atom transfer radical polymerization (ATRP) in order to improve not only fouling resistance but also fouling release property. The physicochemical properties of membranes including hydrophilicity, morphology and roughness were examined by contact angle analyzer, scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. The antifouling property of membranes was improved remarkably after surface modification according to protein and bacterial adhesion testing, and filtration experiment. Minimum protein adsorption and bacterial adhesion were both obtained on PVDF-g-P(HEMA-co-NIPAAm) membrane, with reduction by 44% and 71% respectively compared to the pristine membrane. The minimum bacterial cells after detachment at 25 °C were observed on the PVDF-g-P(HEMA-co-NIPAAm) membrane with the detachment rate of 77%, indicating high fouling release property. The filtration testing indicated that the copolymer modified membrane exhibited high resistance to protein fouling and the foulant on the surface was released and removed easily by washing, suggesting high fouling release and easy-cleaning capacity. This study provides useful insight in the combined “fouling resistance” and “fouling release�

Fabrication, thermal properties and thermal stabilities of microencapsulated n-alkane with poly(lauryl methacrylate) as shell

Energy Technology Data Exchange (ETDEWEB)

Qiu, Xiaolin, E-mail: shirleyqiu2009@gmail.com [Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology, School of Mechanical Engineering, Jiangnan University, Wuxi 214122 (China); Lu, Lixin; Wang, Ju [Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology, School of Mechanical Engineering, Jiangnan University, Wuxi 214122 (China); Tang, Guoyi [Advanced Materials Institute and Clearer Production Key Laboratory, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Key Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Haidian District, Beijing 100084 (China); Song, Guolin [Advanced Materials Institute and Clearer Production Key Laboratory, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China)

2015-11-20

Highlights: • Microencapsulation of octadecane and paraffin by crosslinked poly(lauryl methacrylate). • Octadecane microcapsules have a melting enthalpy of about 118 J g{sup −1}. • Weight loss temperatures of the microcapsules were increased by 67 °C and 28 °C. • Phase change enthalpies decreased by around 10 wt% after 500 thermal cycles. • Foams with microcapsules can be applied for passive temperature control. - Abstract: Microencapsulation of n-octadecane or paraffin with poly(lauryl methacrylate) (PLMA) shell was performed by a suspension-like polymerization. The polymer shell was crosslinked by pentaerythritol tetraacrylate (PETRA). The surface morphologies of microcapsules were investigated by scanning electron microscopy (SEM). Phase change properties, thermal reliabilities and thermal stabilities of microcapsules were determined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The n-octadecane microcapsule exhibits higher melting enthalpy (118.0 J g{sup −1}) and crystallization enthalpy (108.3 J g{sup −1}) compared with the paraffin microcapsule. The thermal resistant temperatures were enhanced by more than 25 °C when n-alkanes were microencapsulated by PLMA. The PCM contents of microcapsules decreased by less than 4 wt% and 6 wt% after 500 and 1000 thermal cycles, respectively. Heat-up experiments indicated that microcapsule-treated foams exhibited upgraded thermal regulation capacities. Consequently, microencapsulated n-octadecane or paraffin with PLMA as shell possesses good potentials for heat storage and thermal regulation.

Starch and chitosan oligosaccharides as interpenetrating phases in poly(N-isopropylacrylamide) injectable gels

Energy Technology Data Exchange (ETDEWEB)

Vieira, Jacquelin N.; Posada, James J. [Chemistry Department, B" 5IDA Research Group, Universidad Simón Bolívar, Caracas (Venezuela, Bolivarian Republic of); Rezende, Rodrigo A. [Divisão de Tecnologias Tridimensionais–Centro de Tecnologia da Informação Renato Archer, Campinas, SP (Brazil); Sabino, Marcos A., E-mail: msabino@usb.ve [Chemistry Department, B" 5IDA Research Group, Universidad Simón Bolívar, Caracas (Venezuela, Bolivarian Republic of); Divisão de Tecnologias Tridimensionais–Centro de Tecnologia da Informação Renato Archer, Campinas, SP (Brazil)

2014-04-01

Thermosensitive interpenetrating gels were prepared by physically blending poly(N-isopropylacrylamide) (PNIPA) as the matrix and the following polysaccharides as interpenetrating phases: chitosan oligosaccharides (identified as QNAD and QNED) and soluble starch (STARCH). The molecular weight of the dispersed phase, the free water/bound water ratio and the thermosensitivity (transition temperature: LCST) of the gels were determined. It was found that these gels are pseudoplastic and that their viscosity depends on the molecular weight of the dispersed phase. LCST transition occurred around 35–37 °C. The morphology of the porosity of the freeze-dried samples was studied by Scanning Electron Microscopy (SEM). An in vitro test of cell hemolysis on blood agar showed that these gels are noncytotoxic. According to the results obtained, these interpenetrating gels show characteristics of an injectable material, and have a transition LCST at body temperature, which reinforces their potential to be used in the surgical field and as scaffolds for tissue engineering. - Highlights: • Physical blends were prepared to obtain thermosensitive gels PNIPA/polysaccharides. • Rheological test allowed verifying the injectability of the gels. • Gels showed a LCST ∼ 37 °C, which makes them interesting for biomedical applications. • Porosity is a function of hydrophobicity/hydrophilicity/molecular weight of phases. • The PNIPA/starch gel showed better morphology as scaffold for tissue engineering.

Novel thermo-sensitive core-shell nanoparticles for targeted paclitaxel delivery

International Nuclear Information System (INIS)

Li Yuanpei; Pan Shirong; Zhang Wei; Du Zhuo

2009-01-01

Novel thermo-sensitive nanoparticles self-assembled from poly(N,N-diethylacrylamide- co-acrylamide)-block-poly(γ-benzyl L-glutamate) were designed for targeted drug delivery in localized hyperthermia. The lower critical solution temperature (LCST) of nanoparticles was adjusted to a level between physiological body temperature (37 deg. C) and that used in local hyperthermia (about 43 deg. C). The temperature-dependent performances of the core-shell nanoparticles were systemically studied by nuclear magnetic resonance (NMR), circular dichroism (CD), fluorescence spectroscopy, dynamic light scattering (DLS), and atom force microscopy (AFM). The mean diameter of the nanoparticles increased slightly from 110 to 129 nm when paclitaxel (PTX), a poorly water-soluble anti-tumor drug, was encapsulated. A stability study in bovine serum albumin (BSA) solution indicated that the PTX loaded nanoparticles may have a long circulation time under physiological environments as the LCST was above physiological body temperature and the shell remained hydrophilic at 37 deg.C. The PTX release profiles showed thermo-sensitive controlled behavior. The proliferation inhibiting activity of PTX loaded nanoparticles was evaluated against Hela cells in vitro, compared with Taxol (a formulation of paclitaxel dissolved in Cremophor EL and ethanol). The cytotoxicity of PTX loaded nanoparticles increased obviously when hyperthermia was performed. The nanoparticles synthesized here could be an ideal candidate for thermal triggered anti-tumor PTX delivery system.

Gelation mechanism of poly(N-isopropylacrylamide)-clay nanocomposite hydrogels synthesized by photopolymerization.

Science.gov (United States)

Ferse, Bernhard; Richter, Sven; Eckert, Franziska; Kulkarni, Amit; Papadakis, Christine M; Arndt, Karl-Friedrich

2008-11-04

The gelation process of poly-(N-isopropylacrylamide)-clay nanocomposite hydrogels (PNIPAAm-clay NC gels) was investigated by dynamic and static light scattering (DLS and SLS), as well as by fluorescence correlation spectroscopy (FCS). The photopolymerization method chosen for the radical polymerizing system ensured that, when the irradiation is removed, the reaction stopped immediately. Experiments showed that shortly before the gelation threshold is reached, no changes in the DLS autocorrelation functions appear, while the monomer conversion can be observed by 1H NMR spectroscopy. These results correspond to the formation of microparticles, in which the PNIPAAm chains are closely attached to the clay platelets. During the further polymerization process, clay clusters are developed before the sol-gel threshold is reached. FCS measurements were performed to obtain information on the motion of the clay platelets inside the NC gel. The DLS method gives only an average of the motions in the gel. In a time window between 10 micros and 1 s, the clay sheets labeled with Rhodamine B show no characteristic motions.

Characterization of temperature and pH-responsive poly-N-isopropylacrylamide-co-polymer nanoparticles for the release of antimicrobials

International Nuclear Information System (INIS)

Hill, Laura E; Gomes, Carmen L

2014-01-01

Chitosan and alginate are both pH-responsive biopolymers extracted from crustacean exoskeletons and brown algae, respectively. Poly-N-isopropylacrylamide (PNIPAAM) is a hydrogel that becomes hydrophobic at a lower-critical solution temperature. This study sought to combine pH- and temperature-responsive polymers via crosslinking, in order to create a dual-stimuli responsive polymer for hydrophobic antimicrobial compounds delivery, improving their antimicrobial effects. Cinnamon bark extract (CBE) was used as a model for hydrophobic antimicrobial. Two co-polymers were synthesized to create two nanoparticles types: chitosan-co-PNIPAAM and alginate-co-PNIPAAM. Nanoparticles were formed from the resulting co-polymers using a self-assembly top-down process followed by glutaraldehyde or calcium chloride crosslinking. These nanoparticles were then used as controlled delivery vehicles for CBE, whose rapid release could be triggered by specific external stimuli. For the same pH and temperature conditions, the chitosan-co-PNIPAAM nanoparticles were significantly more potent bacterial inhibitors against both pathogens and also exhibited a faster CBE release over time as well as slightly higher entrapment efficiency. The alginate-co-PNIPAAM nanoparticles were significantly smaller and exhibited a slow, gradual release over a long time period. Although both nanoparticles were able to effectively inhibit pathogen growth at lower (P < 0.05) concentration than free CBE, the chitosan-co-PNIPAAM nanoparticles were more effective in delivering a natural antimicrobial with controlled release against foodborne pathogens. (paper)

Systematic investigation of the synthesis of core-shell poly(styrene-co-acrylic acid) colloids with varying shell thickness and core diameter

DEFF Research Database (Denmark)

Hinge, Mogens; Keiding, Kristian

2006-01-01

the morphology of the material for an specific application is going on. It is known from SFEP of styrene that the final colloidal size can be controlled by adjusting the ionic strength of the synthesis feed [1] and it is suggested that adding acrylic acid to the synthesis will result in a change...... in polymerization locus from the core to the surface [2]. There is at present not performed a systematically investigation in controlling the core size and shell thickness of poly(styrene-co-acrylic acid) core-shell colloids  (poly(ST-co-AA)).   Poly(ST-co-AA) colloids were synthesized by free-radical surfactant......-free emulsion co-polymerization (SFECP) at 70°C, using styrene as monomer and acrylic acid as co-monomer. Different batches of poly(ST-co-AA) colloids were synthesized with varying ionic strength and acrylic acid concentrations in the synthesis feed. The produced poly(ST-co-AA) colloids were analysed...

Influence of Temperature on the Colloidal Stability of Polymer-Coated Gold Nanoparticles in Cell Culture Media.

Science.gov (United States)

Zyuzin, Mikhail V; Honold, Tobias; Carregal-Romero, Susana; Kantner, Karsten; Karg, Matthias; Parak, Wolfgang J

2016-04-06

The temperature-dependence of the hydrodynamic diameter and colloidal stability of gold-polymer core-shell particles with temperature-sensitive (poly(N-isopropylacrylamide)) and temperature-insensitive shells (polyallylaminine hydrochloride/polystyrensulfonate, poly(isobutylene-alt-maleic anhydride)-graft-dodecyl) are investigated in various aqueous media. The data demonstrate that for all nanoparticle agglomeration, i.e., increase in effective nanoparticle size, the presence of salts or proteins in the dispersion media has to be taken into account. Poly(N-isopropylacrylamide) coated nanoparticles show a reversible temperature-dependent increase in size above the volume phase transition of the polymer shell when they are dispersed in phosphate buffered saline or in media containing protein. In contrast, the nanoparticles coated with temperature-insensitive polymers show a time-dependent increase in size in phosphate buffered saline or in medium containing protein. This is due to time-dependent agglomeration, which is particularly strong in phosphate buffered saline, and induces a time-dependent, irreversible increase in the hydrodynamic diameter of the nanoparticles. This demonstrates that one has to distinguish between temperature- and time-induced agglomerations. Since the size of nanoparticles regulates their uptake by cells, temperature-dependent uptake of thermosensitive and non-thermosensitive nanoparticles by cells lines is compared. No temperature-specific difference between both types of nanoparticles could be observed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Intelligent anticancer drug delivery performances of two poly(N-isopropylacrylamide)-based magnetite nanohydrogels.

Science.gov (United States)

Poorgholy, Nahid; Massoumi, Bakhshali; Ghorbani, Marjan; Jaymand, Mehdi; Hamishehkar, Hamed

2018-08-01

This article evaluates the anticancer drug delivery performances of two nanohydrogels composed of poly(N-isopropylacrylamide-co-itaconic anhydride) [P(NIPAAm-co-IA)], poly(ethylene glycol) (PEG), and Fe 3 O 4 nanoparticles. For this purpose, the magnetite nanohydrogels (MNHGs) were loaded with doxorubicin hydrochloride (DOX) as a universal anticancer drug. The morphologies and magnetic properties of the DOX-loaded MNHGs were investigated using transmission electron microscopy (TEM) and vibrating-sample magnetometer (VSM), respectively. The sizes and zeta potentials (ξ) of the MNHGs and their corresponding DOX-loaded nanosystems were also investigated. The DOX-loaded MNHGs showed the highest drug release values at condition of 41 °C and pH 5.3. The drug-loaded MNHGs at physiological condition (pH 7.4 and 37 °C) exhibited negligible drug release values. In vitro cytotoxic effects of the DOX-loaded MNHGs were extensively evaluated through the assessing survival rate of HeLa cells using the MTT assay, and there in vitro cellular uptake into the mentioned cell line were examined using fluorescent microscopy and fluorescence-activated cell sorting (FACS) flow cytometry analyses. As the results, the DOX-loaded MNHG1 exhibited higher anticancer drug delivery performance in the terms of cytotoxic effect and in vitro cellular uptake. Thus, the developed MNHG1 can be considered as a promising de novo drug delivery system, in part due to its pH and thermal responsive drug release behavior as well as proper magnetite character toward targeted drug delivery.

Propiedades mecánicas de hidrogeles de poli(N-sopropilacrilamida-Co-ácido itacónico

Directory of Open Access Journals (Sweden)

Valdeturren, N. E.

2001-04-01

Full Text Available It is well known that polymers of N-isopropylacrylamide (NIPA show lower critical solution temperature (LCST behavior in water and its gels have a volume phase transition at about 34 °C in water. In this study, we reported the polimerization of NIPA in the presence of N,N'-methylenebisacrylamide (BIS. Poly(N-isopropylacrylamide and poly(N-isopropylacrylamide-co-itaconic acid hydrogels were obtained by swelling the resultant solid xerogels to equilibrium in water. The effects of monomer composition and concentration of added cross-linking agent on the swelling behavior and mechanical properties of these hydrogels at 22 and 37 °C were investigated, the latter involving measurements of shear in a DMTA system. The storage moduli at 22 °C lay within the range 9.08-5.08 KPa. At a fixed BIS concentration, an increase from 22 to 37 °C resulted in an increase in the shear moduli and the effective crosslinking density (ν_e and a decrease in the interaction parameter hydrogel/water, χ.

Los hidrogeles de N-isopropilacrilamida (NIPA son matrices orgánicas termosensibles que sufren una transición de fase en volumen en agua a su temperatura crítica consoluta inferior (LCST, que está alrededor de 34 °C. En este trabajo presentamos la polimerización de NIPA utilizando como entrecruzante N,N'-metilenbisacrilamida (BIS . Los hidrogeles de poli(N-isopropilacrilamida y poli(N-isopropilacrilamida-co-ácido itacónico se obtuvieron hinchando hasta el equilibrio los xerogeles resultantes. Se evaluaron los efectos de la composición de comonómeros y la concentración de agente entrecruzante sobre el comportamiento de hinchamiento y las propiedades mecánicas de estos hidrogeles a 22 y 37 °C. Las medidas mecánicas se hicieron en un DMTA. El módulo de almacenamiento a 22 °C presentó valores comprendidos entre 9,08 y 5,08 KPa. A una concentración constante de BIS, un incremento en la temperatura de 22 a 37 °C ocasionó un aumento del m

Comparison of mesenchymal stem cells released from poly(N-isopropylacrylamide) copolymer film and by trypsinization

International Nuclear Information System (INIS)

Yang Lei; Liu Tianqing; Song Kedong; Jiang Lili; Wu Shuang; Guo Wenhua; Cheng Fang; Lu, Jian R

2012-01-01

Temperature-responsive platforms containing poly(N-isopropylacrylamide) (PNIPAAm) have been developed as an effective substitute for enzymatic treatment to recover adherent cells, but it remains unclear whether this alternative harvesting method tends to support stem cells preserving them being primitive. This study mainly investigated the biological properties of mesenchymal stem cells derived from rat bone marrow and human adipose tissue (BM-MSCs and AT-MSCs) after being cultured on PNIPAAm copolymer films and recovered by temperature drop, and compared the cells harvested from glass coverslips with trypsinization as controls. The experimental results demonstrated that after three serial passages, the released MSCs from thermal liftoff showed no significant differences in cell morphology, immunophenotype and osteogenesis for BM-MSCs or adipogenesis for AT-MSCs, but had higher viability, stronger proliferation and higher adipogenic differentiation for BM-MSCs or higher osteogenic differentiation for AT-MSCs compared with the trypsinization group. Besides, more proteins remained around or within the cell membranes upon temperature drop. It is concluded that cell detachment with more extracellular matrix proteins facilitates the maintenance of membrane proteins, and accordingly preserves MSC properties related to viability, proliferation and differentiation to some extent. This indicates that the PNIPAAm copolymer films and their matching cooling treatment can be used as effective alternatives to the existing culture substrates and traditional enzymatic digestion for MSCs. (paper)

A facile method for preparing porous, optically active, magnetic Fe3 O4 @poly(N-acryloyl-leucine) inverse core/shell composite microspheres.

Science.gov (United States)

Liu, Dong; Deng, Jianping; Yang, Wantai

2014-01-01

The first synthesis of porous, optically active, magnetic Fe3 O4 @poly(N-acryloyl-leucine) inverse core/shell composite microspheres is reported, in which the core is constructed of chiral polymer and the shell is constructed of Fe3 O4 NPs. The microspheres integrate three significant concepts, "porosity", "chirality", and "magneticity", in one single microspheric entity. The microspheres consist of Fe3 O4 nanoparticles and porous optically active microspheres, and thus combine the advantages of both magnetic nanoparticles and porous optically active microspheres. The pore size and specific surface area of the microspheres are characterized by N2 adsorption, from which it is found that the composite microspheres possess a desirable porous structure. Circular dichroism and UV-vis absorption spectroscopy measurements demonstrate that the microspheres exhibit the expected optical activity. The microspheres also have high saturation magnetization of 14.7 emu g(-1) and rapid magnetic responsivity. After further optimization, these novel microspheres may potentially find applications in areas such as asymmetric catalysis, chiral adsorption, etc. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Morphology and film formation of poly(butyl methacrylate)-polypyrrole core-shell latex particles

NARCIS (Netherlands)

Huijs, F; Lang, J

Core-shell latex particles made of a poly(butyl methacrylate) (PBMA) core and a thin polypyrrole (PPy) shell were synthesized by two-stage polymerization. In the first stage, PBMA latex particles were synthesized in a semicontinuous process by free-radical polymerization. PBMA latex particles were

Electrostatic Self-Assembly of Au Nanoparticles onto Thermosensitive Magnetic Core-Shell Microgels for Thermally Tunable and Magnetically Recyclable Catalysis.

Science.gov (United States)

Liu, Guoqiang; Wang, Daoai; Zhou, Feng; Liu, Weimin

2015-06-01

A facile route to fabricate a nanocomposite of Fe3O4@poly[N-isopropylacrylamide (NIPAM)-co-2-(dimethylamino)ethyl methacrylate (DMAEMA)]@Au (Fe3O4@PND@Au) is developed for magnetically recyclable and thermally tunable catalysis. The negatively charged Au nanoparticles with an average diameter of 10 nm are homogeneously loaded onto positively charged thermoresponsive magnetic core-shell microgels of Fe3O4@poly(NIPAM-co-DMAEMA) (Fe3O4@PND) through electrostatic self-assembly. This type of attachment offers perspectives for using charged polymeric shell on a broad variety of nanoparticles to immobilize the opposite-charged nanoparticles. The thermosensitive PND shell with swollen or collapsed properties can be as a retractable Au carrier, thereby tuning the aggregation or dispersion of Au nanoparticles, which leads to an increase or decrease of catalytic activity. Therefore, the catalytic activity of Fe3O4@PND@Au can be modulated by the volume transition of thermosensitive microgel shells. Importantly, the mode of tuning the aggregation or dispersion of Au nanoparticles using a thermosensitive carrier offers a novel strategy to adjust and control the catalytic activity, which is completely different with the traditional regulation mode of controlling the diffusion of reactants toward the catalytic Au core using the thermosensitive poly(N-isopropylacrylamide) network as a nanogate. Concurrent with the thermally tunable catalysis, the magnetic susceptibility of magnetic cores enables the Fe3O4@PND@Au nanocomposites to be capable of serving as smart nanoreactors for thermally tunable and magnetically recyclable catalysis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon Nanotubes Reinforced Maleic Anhydride-Modified Xylan-g-Poly(N-isopropylacrylamide) Hydrogel with Multifunctional Properties

Science.gov (United States)

Liu, Xinxin; Song, Tao; Chang, Minmin; Meng, Ling; Wang, Xiaohui; Sun, Runcang; Ren, Junli

2018-01-01

Introducing multifunctional groups and inorganic material imparts xylan-based hydrogels with excellent properties, such as responsiveness to pH, temperature, light, and external magnetic field. In this work, a composite hydrogel was synthesized by introducing acid treated carbon nanotubes (AT-CNTs) into the maleic anhydride modified xylan grafted with poly(N-isopropylacrylamide) (MAX-g-PNIPAM) hydrogels network. It was found that the addition of AT-CNTs affected the MAX-g-PNIPAM hydrogel structure, the swelling ratio and mechanical properties, and imparted the hydrogel with new properties of electrical conductivity and near infrared region (NIR) photothermal conversion. AT-CNTs could reinforce the mechanical properties of MAX-g-PNIPAM hydrogels, being up to 83 kPa for the compressive strength when the amount was 11 wt %, which was eight times than that of PNIPAM hydrogel and four times than that of MAX-g-PNIPAM hydrogel. The electroconductibility was enhanced by the increase of AT-CNTs amounts. Meanwhile, the composite hydrogel also exhibited multiple shape memory and NIR photothermal conversion properties, and water temperature was increased from 26 °C to 56 °C within 8 min under the NIR irradiation. Thus, the AT-CNTs reinforced MAX-g-PNIPAM hydrogel possessed promising multifunctional properties, which offered many potential applications in the fields of biosensors, thermal-arrest technology, and drug-controlled release. PMID:29495611

Isothermal titration calorimetric studies of the acid-base properties of poly(N-isopropylacrylamide-co-4-vinylpyridine) cationic polyelectrolyte colloidal microgels

International Nuclear Information System (INIS)

Seidel, J.; Pinkrah, V.T.; Mitchell, J.C.; Chowdhry, B.Z.; Snowden, M.J.

2004-01-01

Isothermal titration calorimetry (ITC) and potentiometric titration were used to study the protonation properties of the 4-vinylpyridine (4-VP) moiety in cationic poly(N-isopropylacrylamide-co-4-vinylpyridine) colloidal microgels [poly(NIPAM-co-4-VP)]. Calorimetric pH titrations were performed using microgels of different 4-VP content and the influence of ionic strength and counter ions have been examined. The calorimetric titration output consists of several thermal contributions reflecting the complex nature of the interactions in the aqueous microgel dispersions. In contrast to the potentiometric results, the calorimetric titration data could not be completely described by a theoretical model solely taking into account protonation equilibria. Deviations from the proposed model correlate with swelling or shrinking of the gel particles. The calorimetric results also reveal a pronounced counter-ion effect of perchlorate compared to chloride ions. In the presence of perchlorate ions, small secondary thermal effects accompany protonation of the 4-VP moiety due, in part, to kinetically limited conformational changes in the co-polymer microgel

Effects of hydrophobic drug-polyesteric core interactions on drug loading and release properties of poly(ethylene glycol)-polyester-poly(ethylene glycol) triblock core-shell nanoparticles

International Nuclear Information System (INIS)

Khoee, Sepideh; Hassanzadeh, Salman; Goliaie, Bahram

2007-01-01

BAB amphiphilic triblock copolymers consisting of poly(ethylene glycol) (B) (PEG) as the hydrophilic segment and different polyesters (A) as the hydrophobic block were prepared by a polycondensation reaction as efficient model core-shell nanoparticles to assay the effect of interactions between the hydrophobic drug and the polyesteric core in terms of drug loading content and release profile. PEG-poly(hexylene adipate)-PEG (PEG-PHA-PEG) and PEG-poly(butylene adipate)-PEG (PEG-PBA-PEG) to PEG-poly(ethylene adipate)-PEG (PEG-PEA-PEG) core-shell type nanoparticles entrapping quercetin (an anticarcinogenic, allergy inhibitor and antibacterial agent), were prepared by a nanoprecipitation method and characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and x-ray diffraction (XRD) techniques. It was found that the obtained nanoparticles showed a smooth surface and spherical shape with controllable sizes in the range of 64-74 nm, while drug loading varied from 7.24% to 19% depending on the copolymer composition and the preparation conditions. The in vitro release behaviour exhibited a sustained release and was affected by the polymer-drug interactions. UV studies revealed the presence of hydrogen bonding as the main existing interaction between quercetin and polyesters in the nanosphere cores

Measurement of the dynamic behavior of thin poly(N-isopropylacrylamide) hydrogels and their phase transition temperatures measured using reflectometric interference spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Okada, Fuminori [Konica Minolta, INC. (Japan); Akiyama, Yoshikatsu, E-mail: akiyama.yoshikatsu@twmu.ac.jp, E-mail: akiyama.yoshikatsu@abmes.twmu.ac.jp; Kobayashi, Jun [Tokyo Women’s Medical University (TWIns), Institute of Advanced Biomedical Engineering and Science (Japan); Ninomiya, Hidetaka [Konica Minolta, INC. (Japan); Kanazawa, Hideko [Keio University, Faculty of Pharmacy (Japan); Yamato, Masayuki; Okano, Teruo [Tokyo Women’s Medical University (TWIns), Institute of Advanced Biomedical Engineering and Science (Japan)

2015-03-15

Temperature-responsive cell culture surfaces prepared by modifying tissue-culture polystyrene with nanoscale poly(N-isopropylacrylamide) (PIPAAm) hydrogels are widely used as intelligent surfaces for the fabrication of various cell sheets that change with temperature. In this work, the characteristics of nanoscale PIPAAm hydrogels were phenomenologically elucidated on the basis of time-dependent surface evaluations under conditions of changing temperature. Because the dynamic characteristics of the nanoscale hydrogel did not exhibit good performance, the nanoscale PIPAAm hydrogel was analyzed by monitoring its temperature-dependent dynamic swelling/deswelling changes using reflectometric interference spectroscopy (RIfS) on an instrument equipped with a microfluidic system. RIfS measurements under ambient atmosphere provided the precise physical thickness of the dry PIPAAm hydrogel (6.7 nm), which agreed with the atomic force microscopy results (6.6 nm). Simulations of the reflectance spectra revealed that changes in the wavelength of the minimum reflectance (Δλ) were attributable to the changes in the refractive index of the thin PIPAAm hydrogel induced by a temperature-dependent volume phase transition. The temperature-dependent Δλ change was used to monitor the swelling/deswelling behavior of the nanoscale PIPAAm hydrogel. In addition, the phase transition temperature of the thin PIPAAm hydrogel under aqueous conditions was also determined to be the inflection point of the plot of the change in Δλ as a function of temperature. The dynamic behavior of a thin PIPAAm hydrogel chemically deposited on a surface was readily analyzed using a new analytical system with RIfS and microfluidic devices.

Multiple-stimuli responsive bioelectrocatalysis based on reduced graphene oxide/poly(N-isopropylacrylamide) composite films and its application in the fabrication of logic gates.

Science.gov (United States)

Wang, Lei; Lian, Wenjing; Yao, Huiqin; Liu, Hongyun

2015-03-11

In the present work, reduced graphene oxide (rGO)/poly(N-isopropylacrylamide) (PNIPAA) composite films were electrodeposited onto the surface of Au electrodes in a fast and one-step manner from an aqueous mixture of a graphene oxide (GO) dispersion and N-isopropylacrylamide (NIPAA) monomer solutions. Reflection-absorption infrared (IR) and Raman spectroscopies were employed to characterize the successful construction of the rGO/PNIPAA composite films. The rGO/PNIPAA composite films exhibited reversible potential-, pH-, temperature-, and sulfate-sensitive cyclic voltammetric (CV) on-off behavior to the electroactive probe ferrocenedicarboxylic acid (Fc(COOH)2). For instance, after the composite films were treated at -0.7 V for 7 min, the CV responses of Fc(COOH)2 at the rGO/PNIPAA electrodes were quite large at pH 8.0, exhibiting the on state. However, after the films were treated at 0 V for 30 min, the CV peak currents became much smaller, demonstrating the off state. The mechanism of the multiple-stimuli switchable behaviors for the system was investigated not only by electrochemical methods but also by scanning electron microscopy and X-ray photoelectron spectroscopy. The potential-responsive behavior for this system was mainly attributed to the transformation between rGO and GO in the films at different potentials. The film system was further used to realize multiple-stimuli responsive bioelectrocatalysis of glucose catalyzed by the enzyme of glucose oxidase and mediated by the electroactive probe of Fc(COOH)2 in solution. On the basis of this, a four-input enabled OR (EnOR) logic gate network was established.

IPN's of Acrylic Acid and N-Isopropylacrylamide by Gamma and Electron Beam Irradiation

International Nuclear Information System (INIS)

Burillo, G.

2006-01-01

In recent years, temperature and pH sensitive hydrogels have been investigated widely because of their unique properties and versatile applications in medicine and biotechnology, as well as drug delivery. However a serious limitation of hydrogels in many applications is the low mechanical strength of such gels when highly swollen. To overcome this problem, sensitive hydrogels were prepared with satisfactory mechanical properties as a semi-interpenetranting network, where one of them is a mechanically stable polymer. In this work temperature sensitive monomer N-isopropylacrylamide (NIPAAm) and a pH sensitive monomer, acrylic acid (AAc) were prepared as an interpenetranting network by a sequential method. Poly (AAc) hydrogels were prepared in glass tubes 3 mm inner diameter, at room temperature from an aqueous solutions 50%vol under argon atmosphere, and irradiated with a Co 6 0 gamma source, at doses from 5 to 30 kGy and dose rate of 3 kGy/h. Poly (AAc) hydrogels were also prepared by electron beam irradiation with a Van de Graaff at a dose rate of 19.4 kGy/min, and radiation doses from 10 to 30 kGy. After polymerization and crosslinking, the gels were washed in water during 48 h, and dried in vacuo to constant weight. Poly (NIPAAm) as secondary gel was synthetized directly within the primary gels in aqueous solution with the croslinker N, N' methylenebisacrylamide (BIS), the accelerator N,N,N , N tetramethyl ethylenediamidne TMEDA, and potasium persulfate as initiator. Equilibrium swelling properties of hydrogels were studied in pH 2.2-8 range and temperature 10-45degree; LCST and pH critic point of the IPN's were determined; the composition of the interpenetrating network was measured by elemental analysis, and the morphological structure characterized by SEM. The volume of the cells of PAAC hydrogels decreased with increase in radiation dose, their mechanic hardness increased and they lost elasticity. The interpenetrating networks of samples with PAAc irradiated

New Linear and Star-Shaped Thermogelling Poly([R]-3-hydroxybutyrate) Copolymers.

Science.gov (United States)

Barouti, Ghislaine; Liow, Sing Shy; Dou, Qingqing; Ye, Hongye; Orione, Clément; Guillaume, Sophie M; Loh, Xian Jun

2016-07-18

The synthesis of multi-arm poly([R]-3-hydroxybutyrate) (PHB)-based triblock copolymers (poly([R]-3-hydroxybutyrate)-b-poly(N-isopropylacrylamide)-b-[[poly(methyl ether methacrylate)-g-poly(ethylene glycol)]-co-[poly(methacrylate)-g-poly(propylene glycol)

The One-Step Pickering Emulsion Polymerization Route for Synthesizing Organic-Inorganic Nanocomposite Particles

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Kaushal Rege

2010-02-01

Full Text Available Polystyrene-silica core-shell nanocomposite particles are successfully prepared via one-step Pickering emulsion polymerization. Possible mechanisms of Pickering emulsion polymerization are addressed in the synthesis of polystyrene-silica nanocomposite particles using 2,2-azobis(2-methyl-N-(2-hydroxyethylpropionamide (VA-086 and potassium persulfate (KPS as the initiator. Motivated by potential applications of “smart” composite particles in controlled drug delivery, the one-step Pickering emulsion polymerization route is further applied to synthesize polystyrene/poly(N-isopropylacrylamide (PNIPAAm-silica core-shell nanoparticles with N-isopropylacrylamide incorporated into the core as a co-monomer. The polystyrene/PNIPAAm-silica composite nanoparticles are temperature sensitive and can be taken up by human prostate cancer (PC3-PSMA cells.

Surface sulfonamide modification of poly(N-isopropylacrylamide)-based block copolymer micelles to alter pH and temperature responsive properties for controlled intracellular uptake.

Science.gov (United States)

Cyphert, Erika L; von Recum, Horst A; Yamato, Masayuki; Nakayama, Masamichi

2018-06-01

Two different surface sulfonamide-functionalized poly(N-isopropylacrylamide)-based polymeric micelles were designed as pH-/temperature-responsive vehicles. Both sulfadimethoxine- and sulfamethazine-surface functionalized micelles were characterized to determine physicochemical properties, hydrodynamic diameters, zeta potentials, temperature-dependent size changes, and lower critical solution temperatures (LCST) in both pH 7.4 and 6.8 solutions (simulating both physiological and mild low pH conditions), and tested in the incorporation of a proof-of-concept hydrophobic antiproliferative drug, paclitaxel. Cellular uptake studies were conducted using bovine carotid endothelial cells and fluorescently labeled micelles to evaluate if there was enhanced cellular uptake of the micelles in a low pH environment. Both variations of micelles showed enhanced intracellular uptake under mildly acidic (pH 6.8) conditions at temperatures slightly above their LCST and minimal uptake at physiological (pH 7.4) conditions. Due to the less negative zeta potential of the sulfamethazine-surface micelles compared to sulfadimethoxine-surface micelles, and the proximity of their LCST to physiological temperature (37°C), the sulfamethazine variation was deemed more amenable for clinically relevant temperature and pH-stimulated applications. Nevertheless, we believe both polymeric micelle variations have the capacity to be implemented as an intracellular drug or gene delivery system in response to mildly acidic conditions. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1552-1560, 2018. © 2018 Wiley Periodicals, Inc.

Radiation polymerization and crosslinking of N-isopropylacrylamide in aqueous solution and in solid state

International Nuclear Information System (INIS)

Safranj, A.; Yoshida, Masaru; Omichi, Hideki; Nagaoka, Noriyasu; Kubota, Hitoshi; Katakai, Ryoichi.

1995-01-01

Poly(N-isopropylacrylamide) hydrogels were synthesized by radiation induced simultaneous polymerization and cross-linking. Aqueous monomer solutions and pure monomer, without crosslinker, were irradiated in nitrogen atmosphere at a 60 Co gamma source. The conversion from monomer to polymer and cross-linked gel was investigated as a function of temperature and monomer concentration. The swelling behavior of the gels showed clear dependence on the synthesis conditions. (author)

Thermosensitive Behavior and Antibacterial Activity of Cotton Fabric Modified with a Chitosan-poly(N-isopropylacrylamide Interpenetrating Polymer Network Hydrogel

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Boxiang Wang

2016-03-01

Full Text Available To increase the themosensitive behavior and antibacterial activity of cotton fabric, a series of poly (N-isopropylacrylamide/chitosan (PNIPAAm/Cs hydrogels was synthesized by interpenetrating polymer network (IPN technology using a redox initiator. The IPN PNIPAAm/Cs hydrogel was characterized by Fourier transform infrared spectroscopy (FT-IR, differential scanning calorimetry (DSC, and thermogravimetric analysis (TGA. The results indicated that the IPN PNIPAAm/Cs hydrogel has a lower critical solution temperature (LCST at 33 °C. The IPN hydrogel was then used to modify cotton fabric using glutaric dialdehyde (GA as a crosslinking agent following a double-dip-double-nip process. The results demonstrated that the modified cotton fabric showed obvious thermosensitive behavior and antibacterial activity. The contact angle of the modified cotton fabric has a sharp rise around 33 °C, and the modified cotton fabric showed an obvious thermosensitive behavior. The bacterial reduction of modified cotton fabric against Staphylococcus aureus (S. aureus and Escherichia coli (E. coli were more than 99%. This study presents a valuable route towards smart textiles and their applications in functional clothing.

Ternary polyplex micelles with PEG shells and intermediate barrier to complexed DNA cores for efficient systemic gene delivery.

Science.gov (United States)

Li, Junjie; Chen, Qixian; Zha, Zengshi; Li, Hui; Toh, Kazuko; Dirisala, Anjaneyulu; Matsumoto, Yu; Osada, Kensuke; Kataoka, Kazunori; Ge, Zhishen

2015-07-10

Simultaneous achievement of prolonged retention in blood circulation and efficient gene transfection activity in target tissues has always been a major challenge hindering in vivo applications of nonviral gene vectors via systemic administration. Herein, we constructed novel rod-shaped ternary polyplex micelles (TPMs) via complexation between the mixed block copolymers of poly(ethylene glycol)-b-poly{N'-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} (PEG-b-PAsp(DET)) and poly(N-isopropylacrylamide)-b-PAsp(DET) (PNIPAM-b-PAsp(DET)) and plasmid DNA (pDNA) at room temperature, exhibiting distinct temperature-responsive formation of a hydrophobic intermediate layer between PEG shells and pDNA cores through facile temperature increase from room temperature to body temperature (~37 °C). As compared with binary polyplex micelles of PEG-b-PAsp(DET) (BPMs), TPMs were confirmed to condense pDNA into a more compact structure, which achieved enhanced tolerability to nuclease digestion and strong counter polyanion exchange. In vitro gene transfection results demonstrated TPMs exhibiting enhanced gene transfection efficiency due to efficient cellular uptake and endosomal escape. Moreover, in vivo performance evaluation after intravenous injection confirmed that TPMs achieved significantly prolonged blood circulation, high tumor accumulation, and promoted gene expression in tumor tissue. Moreover, TPMs loading therapeutic pDNA encoding an anti-angiogenic protein remarkably suppressed tumor growth following intravenous injection into H22 tumor-bearing mice. These results suggest TPMs with PEG shells and facilely engineered intermediate barrier to inner complexed pDNA have great potentials as systemic nonviral gene vectors for cancer gene therapy. Copyright © 2015 Elsevier B.V. All rights reserved.

Temperature sensitive surfaces and methods of making same

Science.gov (United States)

Liang, Liang [Richland, WA; Rieke, Peter C [Pasco, WA; Alford, Kentin L [Pasco, WA

2002-09-10

Poly-n-isopropylacrylamide surface coatings demonstrate the useful property of being able to switch charateristics depending upon temperature. More specifically, these coatings switch from being hydrophilic at low temperature to hydrophobic at high temperature. Research has been conducted for many years to better characterize and control the properties of temperature sensitive coatings. The present invention provides novel temperature sensitive coatings on articles and novel methods of making temperature sensitive coatings that are disposed on the surfaces of various articles. These novel coatings contain the reaction products of n-isopropylacrylamide and are characterized by their properties such as advancing contact angles. Numerous other characteristics such as coating thickness, surface roughness, and hydrophilic-to-hydrophobic transition temperatures are also described. The present invention includes articles having temperature-sensitve coatings with improved properties as well as improved methods for forming temperature sensitive coatings.

UV-assisted room temperature gas sensing of GaN-core/ZnO-shell nanowires

International Nuclear Information System (INIS)

Park, Sunghoon; Ko, Hyunsung; Kim, Soohyun; Lee, Chongmu

2014-01-01

GaN is highly sensitive to low concentrations of H 2 in ambient air and is almost insensitive to most other common gases. However, enhancing the sensing performance and the detection limit of GaN is a challenge. This study examined the H 2 -gas-sensing properties of GaN nanowires encapsulated with ZnO. GaN-core/ZnO-shell nanowires were fabricated by using a two-step process comprising the thermal evaporation of GaN powders and the atomic layer deposition of ZnO. The core-shell nanowires ranged from 80 to 120 nm in diameter and from a few tens to a few hundreds of micrometers in length, with a mean shell layer thickness of ∼8 nm. Multiple-networked pristine GaN nanowire and ZnO-encapsulated GaN (or GaN-core/ZnO-shell) nanowire sensors showed responses of 120 - 147% and 179 - 389%, respectively, to 500 - 2,500 ppm of H 2 at room temperature under UV (254 nm) illumination. The underlying mechanism of the enhanced response of the GaN nanowire to H 2 gas when using ZnO encapsulation and UV irradiation is discussed.

Fabrication of a temperature-responsive and recyclable MoS2 nanocatalyst through composting with poly (N-isopropylacrylamide)

Science.gov (United States)

Liu, Yan; Chen, Pengpeng; Nie, Wangyan; Zhou, Yifeng

2018-04-01

A temperature-responsive, recyclable nanocatalyst was fabricated by composting the exfoliated molybdenum disulfide (MoS2) nanosheets with poly (N-isopropylacry lamide) (PNIPAM). The structure and morphology of MoS2/PNIPAM nanocatalyst was fully characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Thermogravimetry analysis (TGA), Scanning electron microscope (SEM) and Transmission electron microscopy (TEM). The temperature-responsive properties of the MoS2/PNIPAM nanocatalyst were confirmed by Dynamic Light Scattering (DLS) and Ultraviolet-visible ((UV-vis)) absorption spectroscopy. The catalytic activities of the MoS2/PNIPAM nanocatalyst were studied using the reduction reaction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as the model reaction. Results showed that the catalytic activity of the MoS2/PNIPAM nanocatalyst could be regulated by temperature. Furthermore, when the temperature went higher than the low critical solution temperature (LCST) of PNIPAM, the MoS2/PNIPAM nanocatalyst tended to aggregated to form bulk materials from homogeneous suspension.

Small-Angle Neutron Scattering Study of Structural Changes in Temperature-Sensitive Microgel Colloids

NARCIS (Netherlands)

Stieger, M.A.; Richtering, W.; Pedersen, J.S.; Lindner, P.

2004-01-01

The structure of temperature-sensitive poly(N-isopropylacrylamide) microgels in dilute suspension was investigated by means of small-angle neutron scattering. A direct modeling expression for the scattering intensity distribution was derived which describes very well the experimental data at all

Synthesis of attapulgite/N-isopropylacrylamide and its use in drug release

Energy Technology Data Exchange (ETDEWEB)

Li, Xiaomo [Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huaian 223300 (China); Faculty of Chemistry, Northeast Normal University, Changchun 130024, Jilin (China); Zhong, Hui, E-mail: huizhong@hytc.edu.cn [Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huaian 223300 (China); Faculty of Chemistry, Northeast Normal University, Changchun 130024, Jilin (China); Li, Xiaorong, E-mail: lxr206206@163.com [Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huaian 223300 (China); Jia, Feifei [Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huaian 223300 (China); Faculty of Chemistry, Northeast Normal University, Changchun 130024, Jilin (China); Cheng, Zhipeng; Zhang, Lili; Yin, Jingzhou; An, Litao [Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huaian 223300 (China); Guo, Liping, E-mail: guolp078@nenu.edu.cn [Faculty of Chemistry, Northeast Normal University, Changchun 130024, Jilin (China)

2014-12-01

Environmentally sensitive hydrogels as one of the most potential drug delivery systems have gained considerable interest in recent years. In the present study, we synthesized a newly temperature-responsive composite hydrogel based on attapulgite (ATP) and poly (N-isopropylacrylamide) (PNIPAM) as the localized drug carriers for drug delivery. The as-prepared ATP/PNIPAM hydrogel has large aperture which significantly improved the quantity of adsorption of drugs, exhibiting the excellent properties of drug release. The scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) were used to characterize the ATP/PNIPAM. The swelling/deswelling behaviors and the release of ciprofloxacin lactate were studied. When the temperature was below the low critical solution temperature (LCST), the swelling property of hydrogels was excellent and the swelling rate was large. And, the drug release rate increased with the increase of the content of attapulgite in the composite hydrogel when it was put in the buffer solution (pH 7.38) at 37.0 °C. Therefore, the composite hydrogels might be very useful for its application in biomedical fields. - Highlights: • Attapulgite/N-isopropylacrylamide hydrogels were synthesized and characterized. • The swelling property of hydrogels was excellent when temperature was below 34.0 °C. • The composite hydrogels were used for the release of ciprofloxacin lactate. • The drug release rate increased with the increase of the content of attapulgite.

Radiation synthesis of a water-soluble temperature sensitive polymer, activated copolymer and applications in immobilization of proteins

International Nuclear Information System (INIS)

Zhai Maolin; Ha Hongfei; Wu Jilan

1993-01-01

In this work the radiation polymerization of N-isopropylacrylamide (NIPAAM) in aqueous solutions has been carried out and a water-soluble, temperature sensitive polymer and copolymer were obtained by using γ-rays from Co-60 source at room temperature. We have gained the optimum dose and dose-rate of radiation synthesis of linear polyNIPAAM through determining conversion yield and viscosity. In order to immobilize protein (BSA) and enzyme (HRP) into this water-soluble polymer, we prepared an activated copolymer, poly(N-isopropylacrylamide-co-N-acryloxysuccinimide). The BSA and HRP has been immobilized onto the activated copolymer. The BSA (HRP)/copolymer conjugates still kept the original thermally sensitive properties of the linear polyNIPAAM. The conjugation yield of BSA to the activated copolymer decreased with increasing dose. Immobilized HRP was stable at 0 o C for a long time and has, at least, 4 days stability at room temperature. Immobilized HRP activity was lowered when the temperature was raised. This phenomenon was reversible and the immobilized HRP regained activity. The optimum pH of the immobilized HRP shifted from ca.5 upward to ca. 7. (author)

Effects of Culture Substrate Made of Poly(N-isopropylacrylamide-co-acrylic acid Microgels on Osteogenic Differentiation of Mesenchymal Stem Cells

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Zhuojun Dai

2016-09-01

Full Text Available Poly(N-isopropylacrylamide (PNIPAM-based polymers and gels are widely known and studied for their thermoresponsive property. In the biomaterials category, they are regarded as a potential cell culture substrate, not only because of their biocompatibility, but also their special character of allowing controlled detachment of cells via temperature stimulus. Previous research about PNIPAM-based substrates mostly concentrated on their effects in cell adhesion and proliferation. In this study, however, we investigate the influence of the PNIPAM-based substrate on the differentiation capacity of stem cells. Especially, we choose P(NIPAM-AA microgels as a culture dish coating and mesenchymal stem cells (MSCs are cultured on top of the microgels. Interestingly, we find that the morphology of MSCs changes remarkably on a microgel-coated surface, from the original spindle form to a more stretched and elongated cell shape. Accompanied by the alternation in morphology, the expression of several osteogenesis-related genes is elevated even without inducing factors. In the presence of full osteogenic medium, MSCs on a microgel substrate show an enhancement in the expression level of osteopontin and alizarin red staining signals, indicating the physical property of substrate has a direct effect on MSCs differentiation.

Tacticity-Dependent Interchain Interactions of Poly(N-Isopropylacrylamide in Water: Toward the Molecular Dynamics Simulation of a Thermoresponsive Microgel

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Gaio Paradossi

2017-04-01

Full Text Available The discovery that the lower critical solution temperature (LCST of poly(N-Isopropylacrylamide (PNIPAM in water is affected by the tacticity opens the perspective to tune the volume phase transition temperature of PNIPAM microgels by changing the content of meso dyads in the polymer network. The increased hydrophobicity of isotactic-rich PNIPAM originates from self-assembly processes in aqueous solutions also below the LCST. The present work aims to detect the characteristics of the pair interaction between polymer chains, occurring in a concentration regime close to the chain overlap concentration, by comparing atactic and isotactic-rich PNIPAM solutions. Using atomistic molecular dynamics simulations, we successfully modelled the increased association ability of the meso-dyad-rich polymer in water below the LCST, and gain information on the features of the interchain junctions as a function of tacticity. Simulations carried out above the LCST display the PNIPAM transition to the insoluble state and do not detect a relevant influence of stereochemistry on the structure of the polymer ensemble. The results obtained at 323 K provide an estimate of the swelling ratio of non-stereocontrolled PNIPAM microgels which is in agreement with experimental findings for microgels prepared with low cross-linker/monomer feed ratios. This study represents the first step toward the atomistic modelling of PNIPAM microgels with a controlled tacticity.

Core-Shell-Corona Micelles with a Responsive Shell.

Science.gov (United States)

Gohy, Jean-François; Willet, Nicolas; Varshney, Sunil; Zhang, Jian-Xin; Jérôme, Robert

2001-09-03

A reactor for the synthesis of gold nanoparticles is one of the uses of a poly(styrene)-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) triblock copolymer (PS-b-P2VP-b-PEO) which forms core-shell-corona micelles in water. Very low polydispersity spherical micelles are observed that consist of a PS core surrounded by a pH-sensitive P2VP shell and a corona of PEO chains end-capped by a hydroxyl group. The corona can act as a site for attaching responsive or sensing molecules. © 2001 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.

Ferromagnetism in poly(N-perfluorophenylpyrrole)

Energy Technology Data Exchange (ETDEWEB)

Čík, G., E-mail: gabriel.cik@stuba.sk [Department of Environmental Engineering, Faculty of Chemical and Food Technology, Slovak University of Technology, 812 37 Bratislava (Slovakia); Šeršeň, F. [Institute of Chemistry, Faculty of Natural Sciences, Comenius University, 842 15 Bratislava (Slovakia); Dlháň, L. [Department of Inorganic Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology, 812 37 Bratislava (Slovakia); Zálupský, P. [Department of Organic Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology, 812 37 Bratislava (Slovakia); Rapta, P. [Department of Physical Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology, 812 37 Bratislava (Slovakia); Hrnčariková, K. [Department of Organic Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology, 812 37 Bratislava (Slovakia); Plecenik, T. [Department of Experimental Physics, Faculty of Mathematics, Physics and Informatics, Comenius University, 842 48 Bratislava (Slovakia)

2015-10-01

Magnetic properties of the synthesized poly(N-perfluorophenylpyrrole) were studied. The synthesized polymer dissolves in common organic solvents. By the zero-field cooling-field cooling method (ZFC–FC) we found that at low temperatures (T{sub b}<50 K) the synthetic polymer reaches a state with prevailing ferromagnetism. The synthesized polymer retained ferromagnetism even at 300 K. The anomalous magnetic behavior was explained in terms of spin–spin interaction of triplet polarons. As can be seen from the calculated spin density of SOMO and SOMO 1 such a state arise as a consequence of 1-D spin interactions of polarons. Based on the calculated and visualized spin density (SOMO) on the polymer chain such interactions can be explained by the theory of flat-band-ferromagnetism. - Highlights: • We synthesized a new conducting polymer poly(N-perfluorophenylpyrrole). • By the ZFC–FC and EPR methods we measured magnetic properties of the prepared polymer. • We discussed stability and interactions of the polarons in triplet states. • At low temperatures the synthesized polymer reached ferromagnetism.

Application of Polymerization Activator in the Course of Synthesis of N-Isopropylacrylamide Derivatives for Thermally Triggered Release of Naproxen Sodium

Directory of Open Access Journals (Sweden)

Monika Gasztych

2018-02-01

Full Text Available Poly-N-isopropylacrylamide (polyNIPA is an extensively studied polymer in the field of controlled drug delivery. PolyNIPA contains carbonyl and amide groups along a hydrophobic chain. In an aqueous environment, crosslinked polyNIPA forms a gel characterized by a reversible volume phase transition temperature (VPTT, in response to changes in the external environment excited by the temperature factor. NIPA-based polymers were synthesized by a surfactant-free precipitation polymerization (SFPP method at a temperature of 70 °C using the free radical initiator potassium persulfate (KPS and at 35 °C using redox initiator system KPS with N,N,N’,N’-tetramethylethylenediamine (TEMED. The synthesized products were evaluated via dynamic light scattering (DLS, nuclear magnetic resonance (NMR and Fourier-transform infrared spectroscopy (FTIR. The chemical structure, molecular mass, and hydrodynamic diameter of obtained particles, as well as the effects of synthesized polymers on the release of the active substance, naproxen sodium (NS, from hydroxypropyl methyl cellulose (HPMC-based hydrogels were assessed. The use of the TEMED activator affected the particle size, as well as the release kinetics of NS. The insertion of TEMED into reactant mixtures may be applied to modify the release kinetics of NS from hydrogel preparations.

Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires.

Science.gov (United States)

Song, Erdong; Li, Qiming; Swartzentruber, Brian; Pan, Wei; Wang, George T; Martinez, Julio A

2016-01-08

The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN core of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. Selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power.

Facile Synthesis of Magnetic Copolymer Microspheres Based on Poly(glycidyl methacrylate-co-N-isopropylacrylamide/Fe3O4 by Suspension Photopolymerization

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Siti Zulaikha Mazlan

2014-01-01

Full Text Available Magnetic copolymer based on poly(glycidyl methacrylate-co-N-isopropylacrylamide microspheres was prepared by 2,2-dimethoxy-2-phenylacetophenone- (DMPP- photo initiated and poly(vinyl alcohol- (PVA- stabilized single step suspension photopolymerization. The effect of chemical interaction, morphology, and thermal properties by adding 0.1% w/v Fe3O4 in the copolymer was investigated. Infrared analysis (FTIR showed that (C=C band disappeared after copolymerization, indicating that the magnetic copolymer microspheres were successfully synthesized and two important bands at 908 cm−1 and 1550 cm−1 appear. These are associated with the epoxy group stretching of GMA and secondary amide (N–H/C–H deformation vibration of NIPAAm in magnetic microspheres. The X-ray diffraction (XRD result proved the incorporation of Fe3O4 nanoparticles with copolymer microspheres as peak of Fe3O4 was observed. Morphology study revealed that magnetic copolymer exhibited uniform spheres and smoother appearance when entrapped with Fe3O4 nanoparticles. The lowest percentage of Fe3O4 nanoparticles leached from the copolymer microspheres was obtained at pH 7. Finally, thermal property of the copolymer microspheres was improved by adding a small amount of Fe3O4 nanoparticles that has been shown from the thermogram.

Effect of N-isopropylacrylamide on the preparation and properties of microencapsulated phase change materials

International Nuclear Information System (INIS)

Li, Dan; Wang, Jianping; Wang, Yanan; Li, Wei; Wang, Xuechen; Shi, Haifeng; Zhang, Xingxiang

2016-01-01

NIPAm (N-isopropylacrylamide), a thermosensitive monomer, was introduced into a system for synthesis of MicroPCMs (microencapsulated phase change materials) through free radical emulsion polymerization with n-oct (n-octadecane) as the core and cross-linked PMMA (poly (methyl methacrylate)) as the shell. The effect of NIPAm on the formation mechanism, surface morphologies, crystallization properties, and thermal stabilities of the MicroPCMs were studied using FTIR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy), DSC (differential scanning calorimetry), and TGA (thermogravimetric analysis), respectively. The results indicate that addition of NIPAm causes a significant increase in the enthalpy of the heterogeneous nucleation (approximately 2–4 times more than without NIPAm). The diameter distribution of microcapsules becomes narrower (the PDI (polydispersity index) has a minimum of 0.073) and the encapsulation ratio and encapsulation efficiency increase. On the contrary, the microcapsules that have some irregular holes were obtained by adding NIPAm prepolymer. - Highlights: • We designed and synthesized a lower supercooling microPCMs with the PNIPAm as nucleating agent. • Optimum dosage of monomer PNIPAm is 1.8 g. • The mass loss of microcapsules is less than 0.6% after repeated thermal cycling. • The formation mechanism of the microcapsules is discussed.

Facile fabrication of siloxane @ poly (methylacrylic acid) core-shell microparticles with different functional groups

Energy Technology Data Exchange (ETDEWEB)

Zhao, Zheng-Bai; Tai, Li; Zhang, Da-Ming; Jiang, Yong, E-mail: yj@seu.edu.cn [Southeast University, School of Chemistry and Chemical Engineering (China)

2017-02-15

Siloxane @ poly (methylacrylic acid) core-shell microparticles with functional groups were prepared by a facile hydrolysis-condensation method in this work. Three different silane coupling agents 3-methacryloxypropyltrimethoxysilane (MPS), 3-triethoxysilylpropylamine (APTES), and 3-glycidoxypropyltrimethoxysilane (GPTMS) were added along with tetraethoxysilane (TEOS) into the polymethylacrylic acid (PMAA) microparticle ethanol dispersion to form the Si@PMAA core-shell microparticles with different functional groups. The core-shell structure and the surface special functional groups of the resulting microparticles were measured by transmission electron microscopy and FTIR. The sizes of these core-shell microparticles were about 350–400 nm. The corresponding preparation conditions and mechanism were discussed in detail. This hydrolysis-condensation method also could be used to functionalize other microparticles which contain active groups on the surface. Meanwhile, the Si@PMAA core-shell microparticles with carbon-carbon double bonds and amino groups have further been applied to prepare hydrophobic coatings.

Facile fabrication of siloxane @ poly (methylacrylic acid) core-shell microparticles with different functional groups

International Nuclear Information System (INIS)

Zhao, Zheng-Bai; Tai, Li; Zhang, Da-Ming; Jiang, Yong

2017-01-01

Siloxane @ poly (methylacrylic acid) core-shell microparticles with functional groups were prepared by a facile hydrolysis-condensation method in this work. Three different silane coupling agents 3-methacryloxypropyltrimethoxysilane (MPS), 3-triethoxysilylpropylamine (APTES), and 3-glycidoxypropyltrimethoxysilane (GPTMS) were added along with tetraethoxysilane (TEOS) into the polymethylacrylic acid (PMAA) microparticle ethanol dispersion to form the Si@PMAA core-shell microparticles with different functional groups. The core-shell structure and the surface special functional groups of the resulting microparticles were measured by transmission electron microscopy and FTIR. The sizes of these core-shell microparticles were about 350–400 nm. The corresponding preparation conditions and mechanism were discussed in detail. This hydrolysis-condensation method also could be used to functionalize other microparticles which contain active groups on the surface. Meanwhile, the Si@PMAA core-shell microparticles with carbon-carbon double bonds and amino groups have further been applied to prepare hydrophobic coatings.

Core Cross-linked Star Polymers for Temperature/pH Controlled Delivery of 5-Fluorouracil

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Elizabeth Sánchez-Bustos

2016-01-01

Full Text Available RAFT polymerization with cross-linking was used to prepare core cross-linked star polymers bearing temperature sensitive arms. The arms consisted of a diblock copolymer containing N-isopropylacrylamide (NIPAAm and 4-methacryloyloxy benzoic acid (4MBA in the temperature sensitive block and poly(hexyl acrylate forming the second hydrophobic block, while ethyleneglycol dimethacrylate was used to form the core. The acid comonomer provides pH sensitivity to the arms and also increases the transition temperature of polyNIPAAm to values in the range of 40 to 46°C. Light scattering and atomic force microscopy studies suggest that loose core star polymers were obtained. The star polymers were loaded with 5-fluorouracil (5-FU, an anticancer agent, in values of up to 30 w/w%. In vitro release experiments were performed at different temperatures and pH values, as well as with heating and cooling temperature cycles. Faster drug release was obtained at 42°C or pH 6, compared to normal physiological conditions (37°C, pH 7.4. The drug carriers prepared acted as nanopumps changing the release kinetics of 5-FU when temperatures cycles were applied, in contrast with release rates at a constant temperature. The prepared core cross-linked star polymers represent advanced drug delivery vehicles optimized for 5-FU with potential application in cancer treatment.

Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires

International Nuclear Information System (INIS)

Song, Erdong; Martinez, Julio A; Li, Qiming; Pan, Wei; Wang, George T; Swartzentruber, Brian

2016-01-01

The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN core of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. Selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power. (paper)

Thermo-responsive poly(N-isopropylacrylamide)-grafted hollow fiber membranes for osteoblasts culture and non-invasive harvest

Energy Technology Data Exchange (ETDEWEB)

Zhuang, Meiling, E-mail: zhuangmeiling2006@126.com; Liu, Tianqing, E-mail: liutq@dlut.edu.cn; Song, Kedong, E-mail: kedongsong@dlut.edu.cn; Ge, Dan, E-mail: gedan@dlut.edu.cn; Li, Xiangqin, E-mail: xiangqinli@163.com

2015-10-01

Hollow fiber membrane (HFM) culture system is one of the most important bioreactors for the large-scale culture and expansion of therapeutic cells. However, enzymatic and mechanical treatments are traditionally applied to harvest the expanded cells from HFMs, which inevitably causes harm to the cells. In this study, thermo-responsive cellulose acetate HFMs for cell culture and non-invasive harvest were prepared for the first time via free radical polymerization in the presence of cerium (IV). ATR-FTIR and elemental analysis results indicated that the poly(N-isopropylacrylamide) (PNIPAAm) was covalently grafted on HFMs successfully. Dynamic contact angle measurements at different temperatures revealed that the magnitude of volume phase transition was decreased with increasing grafted amount of PNIPAAm. And the amount of serum protein adsorbed on HFMs surface also displayed the same pattern. Meanwhile osteoblasts adhered and spread well on the surface of PNIPAAm-grafted HFMs at 37 °C. And Calcein-AM/PI staining, AB assay, ALP activity and OCN protein expression level all showed that PNIPAAm-grafted HFMs had good cell compatibility. After incubation at 20 °C for 120 min, the adhering cells on PNIPAAm-grafted HFMs turned to be round and detached after being gently pipetted. These results suggest that thermo-responsive HFMs are attractive cell culture substrates which enable cell culture, expansion and the recovery without proteolytic enzyme treatment for the application in tissue engineering and regenerative medicine. - Highlights: • PNIPAAm-grafted HFMs exhibited thermoresponsive characteristic. • The OB cells could adhere and spread well on the surface of PNIPAAm-grafted HFMs. • PNIPAAm-grafted HFMs do not significantly impact ALP activity and OCN protein expression level of OB cells. • Cell could be detached from PNIPAAm-grafted HFMs when temperature decreased from 37 °C to 20 °C.

Surface zwitterionicalization of poly(vinylidene fluoride) membranes from the entrapped reactive core-shell silica nanoparticles.

Science.gov (United States)

Zhu, Li-Jing; Zhu, Li-Ping; Zhang, Pei-Bin; Zhu, Bao-Ku; Xu, You-Yi

2016-04-15

We demonstrate the preparation and properties of poly(vinylidene fluoride) (PVDF) filtration membranes modified via surface zwitterionicalization mediated by reactive core-shell silica nanoparticles (SiO2 NPs). The organic/inorganic hybrid SiO2 NPs grafted with poly(methyl meth acrylate)-block-poly(2-dimethylaminoethyl methacrylate) copolymer (PMMA-b-PDMAEMA) shell were prepared by surface-initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization and then used as a membrane-making additive of PVDF membranes. The PDMAEMA exposed on membrane surface and pore walls were quaternized into zwitterionic poly(sulfobetaine methacrylate) (PSBMA) using 1,3-propane sultone (1,3-PS) as the quaternization agent. The membrane surface chemistry and morphology were analyzed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The hydrophilicity, permeability and antifouling ability of the investigated membranes were evaluated in detail. It was found that the PSBMA chains brought highly-hydrophilic and strong fouling resistant characteristics to PVDF membranes due to the powerful hydration of zwitterionic surface. The SiO2 cores and PMMA chains in the hybrid NPs play a role of anchors for the linking of PSBMA chains to membrane surface. Compared to the traditional strategies for membrane hydrophilic modification, the developed method in this work combined the advantages of both blending and surface reaction. Copyright © 2016 Elsevier Inc. All rights reserved.

Cytotoxicity of Paclitaxel in biodegradable self-assembled core-shell poly(lactide-co-glycolide ethylene oxide fumarate) nanoparticles.

Science.gov (United States)

He, Xuezhong; Ma, Junyu; Mercado, Angel E; Xu, Weijie; Jabbari, Esmaiel

2008-07-01

Biodegradable core-shell polymeric nanoparticles (NPs), with a hydrophobic core and hydrophilic shell, are developed for surfactant-free encapsulation and delivery of Paclitaxel to tumor cells. Poly (lactide-co-glycolide fumarate) (PLGF) and Poly (lactide-fumarate) (PLAF) were synthesized by condensation polymerization of ultra-low molecular weight poly(L: -lactide-co-glycolide) (ULMW PLGA) with fumaryl chloride (FuCl). Similarly, poly(lactide-co-ethylene oxide fumarate) (PLEOF) macromer was synthesized by reacting ultra-low molecular weight poly(L: -lactide) (ULMW PLA) and PEG with FuCl. The blend PLGF/PLEOF and PLAF/PLEOF macromers were self-assembled into NPs by dialysis. The NPs were characterized with respect to particle size distribution, morphology, and loading efficiency. The physical state and miscibility of Paclitaxel in NPs were characterized by differential scanning calorimetry. Tumor cell uptake and cytotoxicity of Paclitaxel loaded NPs were measured by incubation with HCT116 human colon carcinoma cells. The distribution of NPs in vivo was assessed with Apc(Min/+)mouse using infrared imaging. PLEOF macromer, due to its amphiphilic nature, acted as a surface active agent in the process of self-assembly which produced core-shell NPs with PLGF/PLAF and PLEOF macromers as the core and shell, respectively. The encapsulation efficiency ranged from 70 to 56% and it was independent of the macromer but decreased with increasing concentration of Paclitaxel. Most of the PLGF and PLAF NPs degraded in 15 and 28 days, respectively, which demonstrated that the release was dominated by hydrolytic degradation and erosion of the matrix. As the concentration of Paclitaxel was increased from 0 to 10, and 40 mug/ml, the viability of HCT116 cells incubated with free Paclitaxel decreased from 100 to 65 and 40%, respectively, while those encapsulated in PLGF/PLEOF NPs decreased from 93 to 54 and 28%. Groups with Paclitaxel loaded NPs had higher cytotoxicity compared to

On the molecular origin of the cooperative coil-to-globule transition of poly(N-isopropylacrylamide) in water.

Science.gov (United States)

Tavagnacco, L; Zaccarelli, E; Chiessi, E

2018-04-18

By means of atomistic molecular dynamics simulations we investigate the behaviour of poly(N-isopropylacrylamide), PNIPAM, in water at temperatures below and above the lower critical solution temperature (LCST), including the undercooled regime. The transition between water soluble and insoluble states at the LCST is described as a cooperative process involving an intramolecular coil-to-globule transition preceding the aggregation of chains and the polymer precipitation. In this work we investigate the molecular origin of such cooperativity and the evolution of the hydration pattern in the undercooled polymer solution. The solution behaviour of an atactic 30-mer at high dilution is studied in the temperature interval from 243 to 323 K with a favourable comparison to available experimental data. In the water soluble states of PNIPAM we detect a correlation between polymer segmental dynamics and diffusion motion of bound water, occurring with the same activation energy. Simulation results show that below the coil-to-globule transition temperature PNIPAM is surrounded by a network of hydrogen bonded water molecules and that the cooperativity arises from the structuring of water clusters in proximity to hydrophobic groups. Differently, the perturbation of the hydrogen bond pattern involving water and amide groups occurs above the transition temperature. Altogether these findings reveal that even above the LCST PNIPAM remains largely hydrated and that the coil-to-globule transition is related with a significant rearrangement of the solvent in the proximity of the surface of the polymer. The comparison between the hydrogen bonding of water in the surrounding of PNIPAM isopropyl groups and in the bulk displays a decreased structuring of solvent at the hydrophobic polymer-water interface across the transition temperature, as expected because of the topological extension along the chain of such interface. No evidence of an upper critical solution temperature behaviour

Study of the Molecular Dynamics of Multiarm Star Polymers with a Poly(ethyleneimine) Core and Poly(lactide) Multiarms.

Science.gov (United States)

Román, Frida; Colomer, Pere; Calventus, Yolanda; Hutchinson, John M

2017-02-04

Multiarm star polymers, denoted PEI x -PLA y and containing a hyperbranched poly(ethyleneimine) (PEI) core of different molecular weights x and poly(lactide) (PLA) arms with y ratio of lactide repeat units to N links were used in this work. Samples were preconditioned to remove the moisture content and then characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS). The glass transition temperature, T g , is between 48 and 50 °C for all the PEI x -PLA y samples. The dielectric curves show four dipolar relaxations: γ, β, α, and α' in order of increasing temperature. The temperatures at which these relaxations appear, together with their dependence on the frequency, allows relaxation maps to be drawn, from which the activation energies of the sub- T g γ- and β-relaxations and the Vogel-Fulcher-Tammann parameters of the α-relaxation glass transition are obtained. The dependence of the characteristic features of these relaxations on the molecular weight of the PEI core and on the ratio of lactide repeat units to N links permits the assignation of molecular motions to each relaxation. The γ-relaxation is associated with local motions of the -OH groups of the poly(lactide) chains, the β-relaxation with motions of the main chain of poly(lactide), the α-relaxation with global motions of the complete assembly of PEI core and PLA arms, and the α'-relaxation is related to the normal mode relaxation due to fluctuations of the end-to-end vector in the PLA arms, without excluding the possibility that it could be a Maxwell-Wagner-Sillars type ionic peak because the material may have nano-regions of different conductivity.

Study of the Molecular Dynamics of Multiarm Star Polymers with a Poly(ethyleneimine Core and Poly(lactide Multiarms

Directory of Open Access Journals (Sweden)

Frida Román

2017-02-01

Full Text Available Multiarm star polymers, denoted PEIx-PLAy and containing a hyperbranched poly(ethyleneimine (PEI core of different molecular weights x and poly(lactide (PLA arms with y ratio of lactide repeat units to N links were used in this work. Samples were preconditioned to remove the moisture content and then characterized by thermogravimetric analysis (TGA, differential scanning calorimetry (DSC and dielectric relaxation spectroscopy (DRS. The glass transition temperature, Tg, is between 48 and 50 °C for all the PEIx-PLAy samples. The dielectric curves show four dipolar relaxations: γ, β, α, and α′ in order of increasing temperature. The temperatures at which these relaxations appear, together with their dependence on the frequency, allows relaxation maps to be drawn, from which the activation energies of the sub-Tg γ- and β-relaxations and the Vogel–Fulcher–Tammann parameters of the α-relaxation glass transition are obtained. The dependence of the characteristic features of these relaxations on the molecular weight of the PEI core and on the ratio of lactide repeat units to N links permits the assignation of molecular motions to each relaxation. The γ-relaxation is associated with local motions of the –OH groups of the poly(lactide chains, the β-relaxation with motions of the main chain of poly(lactide, the α-relaxation with global motions of the complete assembly of PEI core and PLA arms, and the α′-relaxation is related to the normal mode relaxation due to fluctuations of the end-to-end vector in the PLA arms, without excluding the possibility that it could be a Maxwell–Wagner–Sillars type ionic peak because the material may have nano-regions of different conductivity.

Thermosensitive microgels of poly-n-isopropylacrylamide for drug carriers - practical approach to synthesis

Czech Academy of Sciences Publication Activity Database

Musial, W.; Pluta, J.; Michálek, Jiří

2015-01-01

Roč. 72, č. 3 (2015), s. 409-422 ISSN 0001-6837 Institutional support: RVO:61389013 Keywords : microgel * N-isopropylacrylamide * emulsion polymerization Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.877, year: 2015 http://www.ptfarm.pl/pub/File/Acta_Poloniae/2015/3/409.pdf

Small-angle neutron scattering from poly(NIPA-co-AMPS) gels

DEFF Research Database (Denmark)

Travas-Sejdic, J.; Easteal, A.; Knott, R.

2000-01-01

was reversed; that is the lower cross-link density, the higher the scattered intensity. Therefore, the role of cross-links at high temperature was to suppress microphase separation. The fitting of the experimental data with the Rabin and Panyukov theory indicated qualitative agreement.......The microstructure of the poly( N-isopropylacrylamide-co-acrylamido- 2-methyl-1-propane sulphonic acid) gel, poly( NIPA-co-AMPS), was investigated as a function of temperature and cross-link density using the small angle neutron scattering technique. The sample temperature was varied in the range...... 30 to 55C. Two different behaviours of poly( NIPA-co-AMPS) gels were observed. At low temperature (30C), the magnitude of the scattered intensity increased with cross-link density suggesting that additional cross-links introduced more inhomogeneities in the gel network. At high temperatures the trend...

Fabrication of poly(o-anisidine) coated silica core-shell microspheres and their electrorheological response

Science.gov (United States)

Lee, Chul Joo; Choi, Hyoung Jin

2017-11-01

In this work, silica/poly(o-anisidine) (POA) core-shell structured microspheres were synthesized by coating the silica core surface with POA with a help of a chemical grafting agent, N-[(3-trimethoxylsilyl)-propyl] aniline. The synthesized silica microspheres were then applied as a polymer/inorganic composite particle-based electrorheological (ER) fluid. The morphology of the silica/POA microspheres was examined by using both transmission electron microscopy and scanning electron microscopy, while their thermal properties and chemical structure were checked by thermogravimetric analysis and Fourier-transform infrared spectroscopy, respectively. The ER properties of the silica/POA particle-based ER fluid were examined by using a Couette-type rotational rheometer equipped with a high-voltage power supplier and analyzed by the Bingham model and modified Mason number. In order to obtain additional information about the electrical polarization properties, the dielectric spectra were measured by an LCR meter and fitted by using the Cole-Cole equation. Furthermore, suspension stability of the ER fluid was tested using Turbiscan.

Synthesis, characterization and fabrication of copper nanoparticles in N-isopropylacrylamide based co-polymer microgels for degradation of p-nitrophenol

Directory of Open Access Journals (Sweden)

Farooqi Zahoor H.

2015-03-01

Full Text Available Poly(N-isopropylacrylamide-co-acrylic acid [P(NIPAM-co-AAc] microgels were synthesized by precipitation polymerization. Copper nanoparticles were successfully fabricated inside the microgels by in-situ reduction of copper ions in an aqueous medium. The microgels were characterized by Fourier Transform Infrared Spectroscopy (FT-IR and Dynamic Light Scattering (DLS. Hydrodynamic radius of P(NIPAM-co-AAc microgel particles increased with an increase in pH in aqueous medium at 25 °C. Copper-poly(N-isopropylacrylamide-co-acrylic acid [Cu-P(NIPAM-co-AAc] hybrid microgels were used as a catalyst for the reduction of 4-nitrophenol (4-NP. Effect of temperature, concentration of sodium borohydride (NaBH4 and catalyst dosage on the value of apparent rate constant (kapp for catalytic reduction of 4-NP in the presence of Cu-P(NIPAM-co-AAc hybrid microgels were investigated by UV-Vis spectrophotometry. It was found that the value of kapp for catalytic reduction of 4-NP in the presence of Cu-P(NIPAM-co-AAc hybrid microgel catalyst increased with an increase in catalyst dosage, temperature and concentration of NaBH4 in aqueous medium. The results were discussed in terms of diffusion of reactants towards catalyst surface and swelling-deswelling of hybrid microgels.

Partially Hydrolyzed Poly(n-propyl-2-oxazoline): Synthesis, Aqueous Solution Properties, and Preparation of Gene Delivery Systems.

Science.gov (United States)

Mees, Maarten; Haladjova, Emi; Momekova, Denitsa; Momekov, Georgi; Shestakova, Pavletta S; Tsvetanov, Christo B; Hoogenboom, Richard; Rangelov, Stanislav

2016-11-14

Random copolymers of n-propyl-2-oxazoline and ethylenimine (PPrOx-PEI) were prepared by partial acidic hydrolysis of poly(n-propyl-2-oxazoline) (PPrOx). Dynamic and electrophoretic light scattering and diffusion-ordered NMR spectroscopy were utilized to investigate aqueous solution properties of the copolymers. Above a specific cloud point temperature, well-defined nanoparticles were formed. The latter consisted of a core composed predominantly of PPrOx and a thin positively charged shell from PEI moieties that mediated formation of polyplexes with DNA. The polyplexes were prepared at 65 °C at varying N/P (amine-to-phosphate groups) ratios. They underwent structural changes upon temperature variations 65-25-37 °C depending on N/P. At N/P < 2, the polyplex particles underwent minor changes because of formation of a surface layer of DNA that acted as a barrier and prevented swelling and disintegration of the initial particles. Dramatic rearrangements at N/P ≥ 2 resulting in large swollen microgel particles were overcome by coating of the polyplex particles with a cross-linked polymeric shell. The shell retained the colloidal stability and preserved the physicochemical parameters of the initial polyplex particles while it reduced the high surface potential values. Progressive loss of cytotoxicity upon complexation with DNA and coating of polyplex particles was displayed.

Poly[n]catenanes: Synthesis of molecular interlocked chains

Science.gov (United States)

Wu, Qiong; Rauscher, Phillip M.; Lang, Xiaolong; Wojtecki, Rudy J.; de Pablo, Juan J.; Hore, Michael J. A.; Rowan, Stuart J.

2017-12-01

As the macromolecular version of mechanically interlocked molecules, mechanically interlocked polymers are promising candidates for the creation of sophisticated molecular machines and smart soft materials. Poly[n]catenanes, where the molecular chains consist solely of interlocked macrocycles, contain one of the highest concentrations of topological bonds. We report, herein, a synthetic approach toward this distinctive polymer architecture in high yield (~75%) via efficient ring closing of rationally designed metallosupramolecular polymers. Light-scattering, mass spectrometric, and nuclear magnetic resonance characterization of fractionated samples support assignment of the high-molar mass product (number-average molar mass ~21.4 kilograms per mole) to a mixture of linear poly[7-26]catenanes, branched poly[13-130]catenanes, and cyclic poly[4-7]catenanes. Increased hydrodynamic radius (in solution) and glass transition temperature (in bulk materials) were observed upon metallation with Zn2+.

Injectable Thermoresponsive Hydrogel Formed by Alginate-g-Poly(N-isopropylacrylamide) That Releases Doxorubicin-Encapsulated Micelles as a Smart Drug Delivery System.

Science.gov (United States)

Liu, Min; Song, Xia; Wen, Yuting; Zhu, Jing-Ling; Li, Jun

2017-10-18

In this work, we have synthesized a thermoresponsive copolymer, alginate-g-poly(N-isopropylacrylamide) (alginate-g-PNIPAAm) by conjugating PNIPAAm to alginate, where PNIPAAm with different molecular weights and narrow molecular weight distribution was synthesized by atomic transfer radical polymerization. The copolymer dissolved in water or phosphate-buffered saline buffer solution at room temperature and formed self-assembled micelles with low critical micellization concentrations when the temperature increased to above their critical micellization temperatures. At higher concentration, that is, 7.4 wt % in water, the copolymer formed solutions at 25 °C and turned into thermosensitive hydrogels when temperature increased to the body temperature (37 °C). Herein, we hypothesized that the thermoresponsive hydrogels could produce self-assembled micelles with the dissolution of the alginate-g-PNIPAAm hydrogels in a biological fluid or drug release medium. If the drug was hydrophobic, the hydrogel eventually could release and produce drug-encapsulated micelles. In our experiments, we loaded the anticancer drug doxorubicin (DOX) into the alginate-g-PNIPAAm hydrogels and demonstrated that the hydrogels released DOX-encapsulated micelles in a sustained manner. The slowly released DOX-loaded micelles enhanced the cellular uptake of DOX in multidrug resistant AT3B-1 cells, showing the effect of overcoming the drug resistance and achieving better efficiency for killing the cancer cells. Therefore, the injectable thermoresponsive hydrogels formed by alginate-g-PNIPAAm and loaded with DOX turned into a smart drug delivery system, releasing DOX-encapsulated micelles in a sustained manner, showing great potential for overcoming the drug resistance in cancer therapy.

Poly(N-isopropylacrylamide) hydrogel/chitosan scaffold hybrid for three-dimensional stem cell culture and cartilage tissue engineering.

Science.gov (United States)

Mellati, Amir; Kiamahalleh, Meisam Valizadeh; Madani, S Hadi; Dai, Sheng; Bi, Jingxiu; Jin, Bo; Zhang, Hu

2016-11-01

Providing a controllable and definable three-dimensional (3D) microenvironment for chondrogenic differentiation of mesenchymal stem cells (MSCs) remains a great challenge for cartilage tissue engineering. In this work, poly(N-isopropylacrylamide) (PNIPAAm) polymers with the degrees of polymerization of 100 and 400 (NI100 and NI400) were prepared and the polymer solutions were introduced into the preprepared chitosan porous scaffolds (CS) to form hybrids (CSNI100 and CSNI400, respectively). SEM images indicated that the PNIPAAm gel partially occupied chitosan pores while the interconnected porous structure of chitosan was preserved. MSCs were incorporated within the hybrid and cell proliferation and chondrogenic differentiation were monitored. After 7-day incubation of the cell-laden constructs in a growth medium, the cell viability in CSNI100 and CSNI400 were 54 and 108% higher than that in CS alone, respectively. Glycosaminoglycan and total collagen contents increased 2.6- and 2.5-fold after 28-day culture of cell-laden CSNI400 in the chondrogenic medium. These results suggest that the hybrid structure composed of the chitosan porous scaffold and the well-defined PNIPAAm hydrogel, in particular CSNI400, is suitable for 3D stem cell culture and cartilage tissue engineering. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2764-2774, 2016. © 2016 Wiley Periodicals, Inc.

Microstructures of poly(N-methylpyrrole) and their interaction with morphine

Energy Technology Data Exchange (ETDEWEB)

Teixeira-Dias, Bruno [Departament d' Enginyeria Quimica, ETSEIB, Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028, Barcelona (Spain); Center for Research in Nanoengineering, Universitat Politecnica de Catalunya, Campus Sud, Edifici C' , C/Pasqual i Vila s/n, 08028, Barcelona (Spain); Aleman, Carlos, E-mail: carlos.aleman@upc.edu [Departament d' Enginyeria Quimica, ETSEIB, Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028, Barcelona (Spain); Center for Research in Nanoengineering, Universitat Politecnica de Catalunya, Campus Sud, Edifici C' , C/Pasqual i Vila s/n, 08028, Barcelona (Spain); Estrany, Francesc [Center for Research in Nanoengineering, Universitat Politecnica de Catalunya, Campus Sud, Edifici C' , C/Pasqual i Vila s/n, 08028, Barcelona (Spain); Unitat de Quimica Industrial, EUETIB, Universitat Politecnica de Catalunya, Comte d' Urgell 187, 08036, Barcelona (Spain); Azambuja, Denise S. [Institute of Chemistry, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500 - CEP 91501-970, Porto Alegre, RS (Brazil); Armelin, Elaine, E-mail: elaine.armelin@upc.edu [Departament d' Enginyeria Quimica, ETSEIB, Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028, Barcelona (Spain); Center for Research in Nanoengineering, Universitat Politecnica de Catalunya, Campus Sud, Edifici C' , C/Pasqual i Vila s/n, 08028, Barcelona (Spain)

2011-06-30

Graphical abstract: . Display Omitted Highlights: > Poly(N-methylpyrrole)/poly(styrenesulfonic acid) hollow microstructures has been prepared using gas templates. > The dimensions, abundance and texture of the microstructures have been electrochemically controlled. > Poly(N-methylpyrrole)/poly(styrenesulfonic acid) microstructures act as efficient morphine sensors. - Abstract: Microstructures of poly(N-methylpyrrole) have been generated by direct electrochemical oxidation of N-methylpyrrole with poly(styrenesulfonic acid) in aqueous solution, using a micelle formation mechanism with gas bubble templates. These microstructures present a 'doughnut'-like morphology with diameters ranging from 20 to 100 {mu}m. Other anionic surfactants, such as camphorsulfonic acid and {beta}-naphthalenesulfonic acid, have been also employed, results evidencing that the morphology of the microstructures depends on the nature of the surfactant electrolytes. The dimensions, abundance and texture of the microstructures have been modulated by varying the surfactant molecules, the electrochemical technique, and the distance between the working and counter-electrode. The generated microstructures have been characterized using electrochemical techniques, Raman and infrared spectroscopies, scanning electron microscopy and atomic force microscopy. Hollow microstructures-containing films made of poly(N-methylpyrrole)/poly(styrenesulfonic acid), which present remarkable electroactivity and electrostability, has been proved to interact with morphine molecules. Thus, systems based on this prominent material show a high ability to capture the drug molecules and to retain them for a long period of time.

Glass transition of poly (methyl methacrylate) filled with nanosilica and core-shell structured silica

DEFF Research Database (Denmark)

Song, Yihu; Bu, Jing; Zuo, Min

2017-01-01

transition and segmental dynamics of PMMA in the nanocomposites prepared via solution casting was compared. The remarkable depression (≥10 °C) of glass transition temperature (Tg) induced by the incorporation of SiO2 and CS was both observed at low loadings. Here, different mechanisms were responsible...... for the effect of SiO2 and CS on the segmental acceleration of PMMA matrix. The formation of rigid amorphous fraction (RAF) layer around SiO2 with the thickness of 16.4 nm led to the adjacent molecular packing frustration, while the “lubrication” effect of nonwetting interface between the grafted crosslinked......Core-shell (CS) nanocomposite particles with 53.4 wt% cross-linked poly (methyl methacrylate) (PMMA) shell of 11.6 nm in thickness were fabricated via miniemulsion polymerization of methyl methacrylate in the presence of modified nanosilica. The influence of nanosilica and CS nanoparticles on glass...

Separación, purificación y caracterización de poli-hidroxibutirato

OpenAIRE

Grisel María Ortega-Arias-Carbajal; Antonio Bell-García

2014-01-01

La problemática generada por el uso indiscriminado de plásticos sintéticos y su persistencia en el ambiente ha estimulado la investigación para el desarrollo de nuevos materiales y procesos de produc- ción que permitan generar plásticos que presenten propiedades similares pero que tengan un período de degradación más corto. Entre estos materiales se encuentran los poli-hidroxialcanoatos, que constituyen polímeros biodegradables, siendo el poli- ß -hidroxibutirato, su forma más simple. El pres...

Highly temperature responsive core-shell magnetic particles: synthesis, characterization and colloidal properties.

Science.gov (United States)

Rahman, Md Mahbubor; Chehimi, Mohamed M; Fessi, Hatem; Elaissari, Abdelhamid

2011-08-15

Temperature responsive magnetic polymer submicron particles were prepared by two step seed emulsion polymerization process. First, magnetic seed polymer particles were obtained by emulsion polymerization of styrene using potassium persulfate (KPS) as an initiator and divinylbenzne (DVB) as a cross-linker in the presence of oil-in-water magnetic emulsion (organic ferrofluid droplets). Thereafter, DVB cross-linked magnetic polymer particles were used as seed in the precipitation polymerization of N-isopropylacrylamide (NIPAM) to induce thermosensitive PNIPAM shell onto the hydrophobic polymer surface of the cross-linked magnetic polymer particles. To impart cationic functional groups in the thermosensitive PNIPAM backbone, the functional monomer aminoethylmethacrylate hydrochloride (AEMH) was used to polymerize with NIPAM while N,N'-methylenebisacrylamide (MBA) and 2, 2'-azobis (2-methylpropionamidine) dihydrochloride (V-50) were used as a cross-linker and as an initiator respectively. The effect of seed to monomer (w/w) ratio along with seed nature on the final particle morphology was investigated. Dynamic light scattering (DLS) results demonstrated particles swelling at below volume phase transition temperature (VPTT) and deswelling above the VPTT. The perfect core (magnetic) shell (polymer) structure of the particles prepared was confirmed by Transmission Electron Microscopy (TEM). The chemical composition of the particles were determined by thermogravimetric analysis (TGA). The effect of temperature, pH, ionic strength on the colloidal properties such as size and zeta potential of the micron sized thermo-sensitive magnetic particles were also studied. In addition, a short mechanistic discussion on the formation of core-shell morphology of magnetic polymer particles has also been discussed. Copyright © 2011 Elsevier Inc. All rights reserved.

Novel chiral core-shell silica microspheres with trans-(1R,2R)-diaminocyclohexane bridged in the mesoporous shell: synthesis, characterization and application in high performance liquid chromatography.

Science.gov (United States)

Wu, Xiabing; You, Linjun; Di, Bin; Hao, Weiqiang; Su, Mengxiang; Gu, Yu; Shen, Lingling

2013-07-19

Novel chiral core-shell silica microspheres with trans-(1R,2R)-diaminocyclohexane (DACH) moiety bridged in the mesoporous shell were synthesized using layer-by-layer method. The chiral mesoporous shell around the nonporous silica core was formed by the co-condensation of N,N'-bis-[(triethoxysilyl)propyl]-trans-(1R,2R)-bis-(ureido)-cyclohexane (DACH-BS) and tetraethoxysilane (TEOS) using octadecyltrimethylammonium chloride (C18TMACl) and triblock poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) copolymer (P123) as the templates. The functionalized core-shell silica microspheres were characterized and tested as chiral stationary phases for high performance liquid chromatography (HPLC). R/S-1,1'-bi-2,2'-naphthol, R/S-6,6'-dibromo-1,1'-bi-2-naphthol and R/S-1,1'-bi-2,2'-phenanthrol were enantioseparated rapidly on the column packed with the DACH core-shell silica particles. Moreover, the column packed with core-shell particles exhibited better performance than the column packed with the DACH functionalized periodic mesoporous organosilicas. Copyright © 2013 Elsevier B.V. All rights reserved.

Globalización de la política pública: mediación neoliberal en Colombia, política económica, 1990-2006

Directory of Open Access Journals (Sweden)

Adolfo Rodríguez Bernal

2007-01-01

Full Text Available La transnacionalización de la política pública en la década de los 80, es resultado de tres cambios notables operados en el orden mundial: reconfiguración del escenario global, en lo conflictual geográfico y económico, reordenamiento en el modelo de mercado y transformación en el ciclo de política pública. Estos cambios están asociados a la caracterización del espacio geográfico económico, desigual y desequilibrado; a la construcción del nuevo referencial del mercado en la reorientación de la acción pública y al cambio en la expansión del ciclo de política pública en el escenario mundial. El modelo global de mercado, en su proyección transnacional, ha servido de directriz a la mediación de la política económica de los gobiernos neoliberales en Colombia, 1990-2006, en el proceso de su adopción, adaptación y ajuste con el fin de garantizar su ejecución e implementación. La aceptación obligada o la imposición “negociada” de la política económica nacional pasa por la adopción de política financiera, condicionada por el endeudamiento externo; la adaptación de la transferencia de tecnología como política productiva; y, la cesión del mercado interior a las ETN. Las tendencias observadas, fundamentan la nueva estructura de mercado con capacidad explicativa de sus resultados, en escenarios financieros, productivos y comerciales. Las consecuencias para Colombia se traducen en crecimiento del endeudamiento financiero, acelerada desindustrialización del país y reducción del mercado ante las transnacionales. En esta situación, todo proyecto nacional resulta utópico por la pérdida de soberanía económica para la industrialización, para el manejo y control de los recursos naturales y para garantizar la seguridad alimentaria y espacios del mercado necesarios a su avance.

Temperature and anion responsive self-assembly of ionic liquid block copolymers coating gold nanoparticles

Science.gov (United States)

Li, Junbo; Zhao, Jianlong; Wu, Wenlan; Liang, Ju; Guo, Jinwu; Zhou, Huiyun; Liang, Lijuan

2016-06-01

In this paper, double hydrophilic ionic liquid block copolymers (ILBCs), poly poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine)]- block-(N-isopropylacrylamide) (PMMPImB- b-PNIPAAm) was first synthesized by reversible additionfragmentation chain transfer (RAFT) and then attached on the surface of gold nanoparticles (Au NPs) via a strong gold-sulfur bonding for preparing hybrid nanoparticles (PMMPImB- b-PNIPAAm-@-Au NPs). The hybrid NPs had a three layers micelle-like structure, including a gold core, thermo-responsive inner shell and anion responsive outer corona. The self-assembling behavior of thermal- and anion-response from shell and corona were respectively investigated by change of temperature and addition of (CF3SO2)2N-. The results showed the hybrid NPs retained a stable dispersion beyond the lower critical solution temperature (LCST) because of the space or electrostatic protecting by outer PMMPImB. However, with increasing concentration of (CF3SO2)2N-, the micellization of self-assembling PMMPImB- b-PNIPAAm-@-Au NPs was induced to form micellar structure containing the core with hydrophobic PMMPImB-(CF3SO2)2N- surrounded by composite shell of Au NPs-PNIPAAm via the anionresponsive properties of ILBCs. These results indicated that the block copolymers protected plasmonic nanoparticles remain self-assembling properties of block copolymers when phase transition from outer corona polymer.

Strippable core-shell polymer emulsion for decontamination of radioactive surface contamination

International Nuclear Information System (INIS)

Hwang, Ho-Sang; Seo, Bum-Kyoung; Lee, Kune-Woo

2011-01-01

In this study, the core-shell composite polymer for decontamination from the surface contamination was synthesized by the method of emulsion polymerization and blends of polymers. The strippable polymer emulsion is composed of the poly(styrene-ethyl acrylate) [poly(St-EA)] composite polymer, poly(vinyl alcohol) (PVA) and polyvinylpyrrolidone (PVP). The morphology of the poly(St-EA) composite emulsion particle was core-shell structure, with polystyrene (PS) as the core and poly(ethyl acrylate) (PEA) as the shell. Core-shell polymers of styrene (St)/ethyl acrylate (EA) pair were prepared by sequential emulsion polymerization in the presence of sodium dodecyl sulfate (SDS) as an emulsifier using ammonium persulfate (APS) as an initiator. Related tests and analysis confirmed the success in synthesis of composite polymer. The products are characterized by FT-IR spectroscopy, TGA that were used, respectively, to show the structure, the thermal stability of the prepared polymer. Two-phase particles with a core-shell structure were obtained in experiments where the estimated glass transition temperature and the morphologies of emulsion particles. Decontamination factors of the strippable polymeric emulsion were evaluated with the polymer blend contents. (author)

Facile synthesis of silver immobilized-poly(methyl methacrylate)/polyethyleneimine core-shell particle composites

Energy Technology Data Exchange (ETDEWEB)

Jenjob, Somkieath [Department of Chemistry, Faculty of Science, Mahidol University, 999 Phuttamonthon 4 Road, Salaya, Nakhon Pathom 73170 (Thailand); Center of Excellence for Innovation in Chemistry (PERCH-CIC), Department of Chemistry, Faculty of Science, Mahidol University, Rama 6 Road, Ratchathewi, Bangkok 10400 (Thailand); Tharawut, Teeralak [Department of Chemistry, Faculty of Science, Mahidol University, 999 Phuttamonthon 4 Road, Salaya, Nakhon Pathom 73170 (Thailand); Sunintaboon, Panya, E-mail: panya.sun@mahidol.ac.th [Department of Chemistry, Faculty of Science, Mahidol University, 999 Phuttamonthon 4 Road, Salaya, Nakhon Pathom 73170 (Thailand); Center of Excellence for Innovation in Chemistry (PERCH-CIC), Department of Chemistry, Faculty of Science, Mahidol University, Rama 6 Road, Ratchathewi, Bangkok 10400 (Thailand); Center for Alternative Energy, Faculty of Science, Mahidol University, 999 Phuttamonthon 4 Road, Salaya, Nakhon Pathom 73170 (Thailand)

2012-10-01

A facile route to synthesize silver-embedded-poly(methyl methacrylate)/polyethyleneimine (PMMA/PEI-Ag) core-shell particle composites was illustrated in this present work. PMMA/PEI core-shell particle templates were first prepared by a surfactant-free emulsion polymerization. PEI on the templates' surface was further used to complex and reduce Ag{sup +} ions (from silver nitrate solution) to silver nanoparticles (AgNPs) at ambient temperature, resulting in the PMMA/PEI-Ag particle composites. The formation of AgNPs was affected by the pHs of the reaction medium. The pH of reaction medium at 6.5 was optimal for the formation of PMMA/PEI-Ag with good colloidal stability, which was confirmed by size and size distribution, FTIR spectroscopy, UV-vis spectroscopy and X-ray diffraction. Moreover, the amount of AgNO{sub 3} solution (4.17-12.50 g) was found to affect the formation of AgNPs. Transmission electron microscopy (TEM) indicated that the AgNPs were incorporated in the PMMA/PEI core-shell matrix, and had 6-10 nm in diameter. AgNPs immobilized on PMMA/PEI core-shell particles were also investigated by energy dispersive X-ray spectroscopy analysis mode extended from scanning electron microscopy (SEM/EDS). Furthermore, the presence of AgNPs was found to influence the thermal degradation behavior of PMMA/PEI particle composites as observed through thermogravimetric analysis (TGA). Highlights: Black-Right-Pointing-Pointer A 2-step synthesis of Ag immobilized-PMMA/PEI particle composites was shown. Black-Right-Pointing-Pointer PMMA/PEI core-shell templates were first formed and PEI assisted AgNP formation. Black-Right-Pointing-Pointer Formation of PMMA/PEI-Ag was affected by pH of medium and amount of AgNO{sub 3}. Black-Right-Pointing-Pointer PMMA/PEI-Ag can be confirmed by color change, UV-vis, TEM, SEM with EDS, and X-ray. Black-Right-Pointing-Pointer Effect of AgNPs on thermal degradation of PMMA/PEI-Ag can be observed through TGA.

Synthesis and characterization of poly (n-butyl acrylate)-poly (methyl methacrylate) latex interpenetrating polymer networks by radiation-induced seeded emulsion polymerization

Energy Technology Data Exchange (ETDEWEB)

Yu Haibo [Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Peng Jing [Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China)], E-mail: jpeng@pku.edu.cn; Zhai Maolin; Li Jiuqiang; Wei Genshuan [Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Qiao Jinliang [Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); SINOPEC Beijing Research Institute of Chemical Industry, Beijing 100013 (China)

2007-11-15

A series of latex interpenetrating polymer networks (LIPNs) were prepared via a two-stage emulsion polymerization of methyl methacrylate (MMA) or mixture of MMA and n-butyl acrylate (n-BA) on crosslinked poly(n-butyl acrylate)(PBA) seed latex using {sup 60}Co {gamma}-ray radiation. The particles of resultant latex were produced with diameters between 150 and 250 nm. FTIR spectra identified the formation of crosslinked copolymers of PMMA or P(MMA-co-BA). Dynamic light scattering (DLS) showed that with increasing n-BA concentration in second-stage monomers, the particle size of LIPN increased. Transmission electron microscope(TEM) photographs showed that the morphology of resultant acrylate interpenetrating polymer network (IPN) latex varied from the distinct core-shell structure to homogenous particle structure with the increase of n-BA concentration, and the morphology was mainly controlled by the miscibility between crosslinked PBA seed and second-stage copolymers and polarity of P(MMA-co-BA)copolymers. In addition, differential scanning calorimeter (DSC) measurements indicated the existence of reinforced miscibility between PBA seed and P(MMA-co-BA)copolymer in prepared LIPNs.

Poly[ n ]catenanes: Synthesis of molecular interlocked chains

Energy Technology Data Exchange (ETDEWEB)

Wu, Qiong; Rauscher, Phillip M.; Lang, Xiaolong; Wojtecki, Rudy J.; de Pablo, Juan J.; Hore, Michael J. A.; Rowan, Stuart J.

2017-11-30

As the macromolecular version of mechanically interlocked molecules, mechanically interlocked polymers are promising candidates for the creation of sophisticated molecular machines and smart soft materials. Poly[n]catenanes, where the molecular chains consist solely of interlocked macrocycles, contain one of the highest concentrations of topological bonds. We report, herein, a synthetic approach toward this distinctive polymer architecture in high yield (similar to 75%) via efficient ring closing of rationally designed metallosupramolecular polymers. Light-scattering, mass spectrometric, and nuclear magnetic resonance characterization of fractionated samples support assignment of the high-molar mass product (number-average molar mass similar to 21.4 kilograms per mole) to a mixture of linear poly[7-26]catenanes, branched poly[13-130]catenanes, and cyclic poly[4-7]catenanes. Increased hydrodynamic radius (in solution) and glass transition temperature (in bulk materials) were observed upon metallation with Zn2+.

Interpolymer complexes based on the core/shell micelles. Interaction of polystyrene-block-poly(methacrylic acid) micelles with linear poly(2-vinylpyridine) in 1,4-dioxane water mixtures and in aqueous media

Czech Academy of Sciences Publication Activity Database

Matějíček, P.; Uchman, M.; Lokajová, J.; Štěpánek, M.; Procházka, K.; Špírková, Milena

2007-01-01

Roč. 111, č. 29 (2007), s. 8394-8401 ISSN 1520-6106. [International Symposium on Polyelectrolytes /6./. Dresden, 04.09.2006-08.09.2006] R&D Projects: GA ČR GA203/04/0490; GA AV ČR IAA400500505 Institutional research plan: CEZ:AV0Z40500505 Keywords : polystyrene-block-poly(methacrylic acid) * poly(2-vinylpyridine) * core/shell micelles * light scattering * atomic force microscopy Subject RIV: CD - Macromolecular Chemistry Impact factor: 4.086, year: 2007

Entrappment of alkaline protease and {beta}-galactosidase in radiation stitched together poly-N-vinylcaprolactam.; Vklyuchenie shchelochnoj proteazy i {beta}-galaktozidazy v radiatsionno sshityj poli-N-vinilkaprolaktam.

Energy Technology Data Exchange (ETDEWEB)

Davidenko, T I; Kravchenko, I A [AN Ukrainskoj SSR, Odessa (Ukraine). Fiziko-Khimicheskij Inst.

1996-03-01

The gel formations by poly-N-vinylcaprolactam upon its {gamma}-irradiation by the 20-25 kGy dose as a results of partial polymer stitching together is shown, which is confirmed by the CD-and thermogravimetric data. By the alkaline protease and {beta}-galactosidase entrapment in poly-N- vinylcaprolactam stitched together by {gamma}-irradiation, the active preparations are obtained with 90-98 % and 30-35 % activity retained for alkaline protease and {beta}-galactosidase, respectively. The increased stability of alkaline protease at acidic pH values and higher temperature was noted, and for {beta}-galactosidase - the possibility of repeated use of the obtained preparation for lactose hydrolysis.

Microwave-assisted synthesis and characterization of poly(acrylic)/SiO2-TiO2 core-shell nanoparticle hybrid thin films

International Nuclear Information System (INIS)

Chien, Wen-Chen; Yu, Yang-Yen; Chen, Po-Kan; Yu, Hui-Huan

2011-01-01

In this study, poly(acrylic)/SiO 2 -TiO 2 core-shell nanoparticle hybrid thin films were successfully synthesized by microwave-assisted polymerization. The coupling agent 3-(trimethoxysilyl) propyl methacrylate (MSMA) was hydrolyzed with colloidal SiO 2 -TiO 2 core-shell nanoparticles, and then polymerized with two acrylic monomers and initiator to form a precursor solution. The results of this study showed that the spin-coated hybrid films had relatively good surface planarity, high thermal stability, a tunable refractive index (1.525 2 -TiO 2 core-shell nanoparticle hybrid thin films, for potential use in optical applications.

Numancia: relación necrópolis-poblado

Directory of Open Access Journals (Sweden)

Jimeno Martínez, Alfredo

1996-12-01

Full Text Available This paper studies the relationship between the Celtiberian cemetery and the Numancia city sieged by Scipio (133 b.c.. A first part is dedicated to present the location problems of the Celtiberian cemetery during the present century, and the archaeological data of the cemetery are also analyzed. In the second part the stratigraphie questions and the problems to differentiate the city of the II century b.C. are explained. Finally the basis is established for the relationship between the city and the cemetery.Este trabajo estudia la relación entre la necrópolis celtibérica y la Numancia del cerco de Escipión (133 a. C.. En la primera parte se exponen las dificultades para la localización de la necrópolis a lo largo de este siglo y los datos arqueológicos que está aportando su excavación. En la segunda se abordan los problemas estratigráficos y la dificultad de diferenciar la ciudad del 133 a.C. Finalmente se establecen las bases de relación entre necrópolis y poblado.

The Synthesis of Backbone Thermo and pH Responsive Hyperbranched Poly(Bis(N,N-Propyl Acryl Amides by RAFT

Directory of Open Access Journals (Sweden)

Shijiao Zhou

2016-04-01

Full Text Available Hyperbranched poly(methylene-bis-acrylamide, poly(bis(N,N-propyl acryl amide (HPNPAM and poly(bis(N,N-butyl acryl amide were synthesized by reversible addition-fragmentation chain transfer polymerization. HPNPAMs showed lower critical solution temperature (LCST due to an appropriate ratio between hydrophilic and hydrophobic groups. The effects of reaction conditions on polymerization were investigated in detail. The structure of HPNPAM was characterized by 1H NMR, FT-IR, Muti detector-size exclusion chromatography (MDSEC and Ultravioletvisble (UV-Vis. The α value reached 0.20 and DB was 90%, indicating HPNPAMs with compact topology structure were successfully prepared. LCSTs were tuned by Mw and the pH value of the solution. The change of molecular size was assayed by dynamic light scattering and scanning electron microscope. These results indicated that the stable uniform nanomicelles were destroyed and macromolecules aggregated together, forming large particles as temperature exceeded LCST. In addition, after the cells were incubated for 24 h, the cell viability reached 80%, which confirmed this new dual responsive HPNPAM had low cytotoxicity.

Low frequency ac conduction and dielectric relaxation in poly(N ...

Indian Academy of Sciences (India)

The ac conductivity and dielectric constant of poly(N-methyl pyrrole) thin films have been investigated in the temperature range 77–350 K and in the frequency range 102–106 Hz. The well defined loss peaks have been observed in the temperature region where measured ac conductivity approaches dc conductivity.

Regulating drug release from pH- and temperature-responsive electrospun CTS-g-PNIPAAm/poly(ethylene oxide) hydrogel nanofibers

International Nuclear Information System (INIS)

Yuan, Huihua; Li, Biyun; Liang, Kai; Lou, Xiangxin; Zhang, Yanzhong

2014-01-01

Temperature- and pH-responsive polymers have been widely investigated as smart drug release systems. However, dual-sensitive polymers in the form of nanofibers, which is advantageous in achieving rapid transfer of stimulus to the smart polymeric structures for regulating drug release behavior, have rarely been explored. In this study, chitosan-graft-poly(N-isopropylacrylamide) (CTS-g-PNIPAAm) copolymer was synthesized by using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxy succinimide (NHS) as grafting agents to graft carboxyl-terminated PNIPAAm (PNIPAAm-COOH) chains onto the CTS biomacromolecules, and then CTS-g-PNIPAAm with or without bovine serum albumin (BSA) was fabricated into nanofibers through electrospinning using poly(ethylene oxide) (PEO, 10 wt%) as a fiber-forming facilitating additive. The BSA laden CTS-g-PNIPAAm/PEO hydrogel nanofibers were tested to determine their drug release profiles by varying pH and temperature. Finally, cytotoxicity of the CTS-g-PNIPAAm/PEO hydrogel nanofibers was evaluated by assaying the L929 cell proliferation using the MTT method. It was found that the synthesized CTS-g-PNIPAAm possessed a temperature-induced phase transition and lower critical solution temperature (LCST) at 32° C in aqueous solutions. The rate of BSA release could be well modulated by altering the environmental pH and temperature of the hydrogel nanofibers. The CTS-g-PNIPAAm/PEO hydrogel nanofibers supported L929 cell growth, indicative of appropriate cytocompatibility. Our current work could pave the way towards developing multi-stimuli responsive nanofibrous smart materials for potential applications in the fields of drug delivery and tissue engineering. (paper)

pH- and temperature-sensitive polymeric microspheres for drug delivery: the dissolution of copolymers modulates drug release.

Science.gov (United States)

Fundueanu, Gheorghe; Constantin, Marieta; Stanciu, Cristina; Theodoridis, Georgios; Ascenzi, Paolo

2009-12-01

Most pH-/temperature-responsive polymers for controlled release of drugs are used as cross-linked hydrogels. However, the solubility properties of the linear polymers below and above the lower critical solution temperature (LCST) are not exploited. Here, the preparation and characterization of poly (N-isopropylacrylamide-co-methacrylic acid-co-methyl methacrylate) (poly (NIPAAm-co-MA-co-MM)) and poly (N-isopropylacrylamide-co-acrylamide) (poly (NIPAAm-co-AAm)), known as "smart" polymers (SP), is reported. Both poly (NIPAAm-co-MA-co-MM) and poly (NIPAAm-co-AAm) display pH- and temperature-responsive properties. Poly (NIPAAm-co-MA-co-MM) was designed to be insoluble in the gastric fluid (pH = 1.2), but soluble in the intestinal fluid (pH = 6.8 and 7.4), at the body temperature (37 degrees C). Poly (NIPAAm-co-AAm) was designed to have a lower critical solution temperature (LCST) corresponding to 37 degrees C at pH = 7.4, therefore it is not soluble above the LCST. The solubility characteristics of these copolymers were exploited to modulate the rate of release of drugs by changing pH and/or temperature. These copolymers were solubilized with hydrophobic cellulose acetate butyrate (CAB) and vitamin B(12) (taken as a water soluble drug model system) in an acetone/methanol mixture and dispersed in mineral oil. By a progressive evaporation of the solvent, the liquid droplets were transformed into loaded CAB/SP microspheres. Differential scanning calorimetric studies and scanning electron microscopy analysis demonstrated that the polymeric components of the microspheres precipitated separately during solvent evaporation forming small microdomains. Moreover, vitamin B(12) was found to be molecularly dispersed in both microdomains with no specific affinity for any polymeric component of microspheres. The release of vitamin B(12) was investigated as a function of temperature, pH, and the CAB/SP ratio.

Synthesis and characterization of novel N-substituted poly aniline by Triton X-100

International Nuclear Information System (INIS)

Arsalani, N.; Khavei, M.; Entezami, A. A.

2003-01-01

A new N-substituted poly aniline is synthesized by insertion of polyether chain in the form of Triton X-100 onto the poly aniline backbone. In the preparation method, firstly the emeraldine base poly aniline was reacted with Na H to produce the N-anionic doped poly aniline and then contacted with chlorinated Triton X-100. The prepared N-substituted poly aniline was characterized by UV-vis, FTIR, 1 H NMR spectroscopy techniques and elemental analysis. The physical properties of synthesized polymer such as electrical conductivity, thermal and electro activity properties were also studied. The prepared polymer has good solubility in common organic solvents such as T HF and chloroform

Poly(glycidyl methacrylate)-A soft template for the facile preparation of poly(glycidyl methacrylate) core-copper nanoparticle shell nanocomposite

Science.gov (United States)

Mohammed Safiullah, S.; Abdul Wasi, K.; Anver Basha, K.

2015-12-01

Poly(glycidyl methacrylate) core/copper nanoparticle shell nanocomposite (PGMA/Cu nanohybrid) was prepared by simple two step method (i) The synthesis of poly(glycidyl methacrylate) (PGMA) beads by free radical suspension polymerization followed by (ii) direct deposition of copper nanoparticles (CuNPs) on activated PGMA beads. The PGMA beads were used as a soft template to host the CuNPs without surface modification of it. In this method the CuNPs were formed by chemical reduction of copper salts using sodium borohydride in water medium and deposited directly on the activated PGMA. Two different concentrations of copper salts were employed to know the effect of concentration on the shape and size of nanoparticles. The results showed that, the different sizes and shapes of CuNPs were deposited on the PGMA matrix. The X-ray Diffraction study results showed that the CuNPs were embedded on the surface of the PGMA matrix. The scanning electron microscopic images revealed that the fabrication of CuNPs on the PGMA matrix possess different shapes and changes the morphology and nature of PGMA beads significantly. The fluorescent micrograph also confirmed that the CuNPs were doped on the PGMA surface. The thermal studies have demonstrated that the CuNPs deposition on the surface of PGMA beads had a significant effect.

Core-shell structure of Miglyol/poly(D,L-lactide)/Poloxamer nanocapsules studied by small-angle neutron scattering.

Science.gov (United States)

Rübe, Andrea; Hause, Gerd; Mäder, Karsten; Kohlbrecher, Joachim

2005-10-03

The contrast variation technique in small angle neutron scattering (SANS) was used to investigate the inner structure of nanocapsules on the example of poly(D,L-lactide) (PLA) nanocapsules. The determination of the PLA and Poloxamer shell thickness was the focus of this study. Highest sensitivity on the inner structure of the nanocapsules was obtained when the scattering length density of the solvent was varied between the one of the Miglyol core and the PLA shell. According to the fit data the PLA shell thickness was 9.8 nm. The z-averaged radius determined by SANS experiments correlated well with dynamic light scattering (DLS) results, although DLS values were systematically slightly higher than the ones measured by SANS. This could be explained by taking into account the influence of Poloxamer attached to the nanocapsules surface. For a refined fit model with a second shell consisting of Poloxamer, SANS values and DLS values fitted well with each other. The characterization method presented here is significant because detailed insights into the nanocapsule and the Poloxamer shell were gained for the first time. This method could be used to develop strategies for the optimization of the shell properties concerning controlled release and to study changes in the shell structure during degradation processes.

Boronic Acid functionalized core-shell polymer nanoparticles prepared by distillation precipitation polymerization for glycopeptide enrichment.

Science.gov (United States)

Qu, Yanyan; Liu, Jianxi; Yang, Kaiguang; Liang, Zhen; Zhang, Lihua; Zhang, Yukui

2012-07-16

The boronic acid-functionalized core-shell polymer nanoparticles, poly(N,N-methylenebisacrylamide-co-methacrylic acid)@4-vinylphenylboronic acid (poly(MBA-co-MAA)@VPBA), were successfully synthesized for enriching glycosylated peptides. Such nanoparticles were composed of a hydrophilic polymer core prepared by distillation precipitation polymerization (DPP) and a boronic acid-functionalized shell designed for capturing glycopeptides. Owing to the relatively large amount of residual vinyl groups introduced by DPP on the core surface, the VPBA monomer was coated with high efficiency, working as the shell. Moreover, the overall polymerization route, especially the use of DPP, made the synthesis of nanoparticles facile and time-saving. With the poly(MBA-co-MAA)@VPBA nanoparticles, 18 glycopeptides from horseradish peroxidase (HRP) digest were captured and identified by MALDI-TOF mass spectrometric analysis, relative to eight glycopeptides enriched by using commercially available meta-aminophenylboronic acid agarose under the same conditions. When the concentration of the HRP digest was decreased to as low as 5 nmol, glycopeptides could still be selectively isolated by the prepared nanoparticles. Our results demonstrated that the synthetic poly(MBA-co-MAA)@VPBA nanoparticles might be a promising selective enrichment material for glycoproteome analysis. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of thermal-responsive chitosan-graft-N-isopropylacrylamide membranes via γ-ray irradiation

International Nuclear Information System (INIS)

Mu Qing; Fang Yue'e

2006-01-01

Poly(N-isopropylacrylamide) (PNIPAAm) has been attracting increasing attention because of its thermosensitivity. Many authors have studied the reaction of chitosan with NIPAAm, with most of the interest being focused on hydrogels. Few research programs, however, were about chitosan membranes grafted with NIPAAm monomer. In this study, a novel thermo-sensitive switching membrane was prepared by radiation-induced simultaneous grafting of NIPAAm onto chitosan membrane. Fourier transform infrared spectroscopy (FT-IR) was used to identify structure of the grafted membranes. Compared to FT-IR spectra of pristine chitosan, the new band at 1535 cm-1 in the grafted membrane was attributed to amide II of PNIPAAm. This indicated that NIPAAm was introduced onto the chitosan membrane. Surface morphology of the grafted membrane was different from the pristine chitosan membrane. The SEM images revealed cypress leaf-like structures adhered tightly to the grafted membrane surface, in comparison to smooth surface of the pristine chitosan membrane. Pure water flux measurements showed that the grafted membrane decreased with the increasing temperature, while water flux of pristine chitosan membrane was constant. It was found that the grafted membrane was sensitive to temperature. The effects of dose, dose rate and the concentration of NIPAAm on the grafting percentage were discussed. The graft yield increased with the monomer concentration and the absorbed dose. (authors)

Chemo-enzymatic modification of poly-N-acetyllactosamine (LacNAc oligomers and N,N-diacetyllactosamine (LacDiNAc based on galactose oxidase treatment

Directory of Open Access Journals (Sweden)

Christiane E. Kupper

2012-05-01

Full Text Available The importance of glycans in biological systems is highlighted by their various functions in physiological and pathological processes. Many glycan epitopes on glycoproteins and glycolipids are based on N-acetyllactosamine units (LacNAc; Galβ1,4GlcNAc and often present on extended poly-LacNAc glycans ([Galβ1,4GlcNAc]n. Poly-LacNAc itself has been identified as a binding motif of galectins, an important class of lectins with functions in immune response and tumorigenesis. Therefore, the synthesis of natural and modified poly-LacNAc glycans is of specific interest for binding studies with galectins as well as for studies of their possible therapeutic applications. We present the oxidation by galactose oxidase and subsequent chemical or enzymatic modification of terminal galactose and N-acetylgalactosamine residues of poly-N-acetyllactosamine (poly-LacNAc oligomers and N,N-diacetyllactosamine (LacDiNAc by galactose oxidase. Product formation starting from different poly-LacNAc oligomers was characterised and optimised regarding formation of the C6-aldo product. Further modification of the aldehyde containing glycans, either by chemical conversion or enzymatic elongation, was established. Base-catalysed β-elimination, coupling of biotin–hydrazide with subsequent reduction to the corresponding hydrazine linkage, and coupling by reductive amination to an amino-functionalised poly-LacNAc oligomer were performed and the products characterised by LC–MS and NMR analysis. Remarkably, elongation of terminally oxidised poly-LacNAc glycans by β3GlcNAc- and β4Gal-transferase was also successful. In this way, a set of novel, modified poly-LacNAc oligomers containing terminally and/or internally modified galactose residues were obtained, which can be used for binding studies and various other applications.

Investigation of Complexation of Linear Poly(N-vinyl-2-pyrrolidone) with Poly(methacrylic acid-co-methyl methacrylate) Gel

OpenAIRE

Liu, Guoqin; Yan, Guojin; Zou, Wenjun; Li, Zhengxin

2011-01-01

The contraction of poly(methacrylic acid-co-methyl methacrylate) (P(MAA-co-MMA)) gel induced by complexation with linear poly(N-vinyl-2-pyrrolidone) (PVP) is quite different from that of poly(acrylic acid) (PAA) or poly(methacrylic acid) (PMAA) gel. It was found that the concentration of PVP has a strong effect on the complexation with P(MAA-co-MMA) gel. When PVP was introduced into the P(MAA-co-MMA) network, its dynamic mechanic properties vary greatly between complexed and uncomplexed netwo...

Emission Characteristics of InGaN/GaN Core-Shell Nanorods Embedded in a 3D Light-Emitting Diode.

Science.gov (United States)

Jung, Byung Oh; Bae, Si-Young; Lee, Seunga; Kim, Sang Yun; Lee, Jeong Yong; Honda, Yoshio; Amano, Hiroshi

2016-12-01

We report the selective-area growth of a gallium nitride (GaN)-nanorod-based InGaN/GaN multiple-quantum-well (MQW) core-shell structure embedded in a three-dimensional (3D) light-emitting diode (LED) grown by metalorganic chemical vapor deposition (MOCVD) and its optical analysis. High-resolution transmission electron microscopy (HR-TEM) observation revealed the high quality of the GaN nanorods and the position dependence of the structural properties of the InGaN/GaN MQWs on multiple facets. The excitation and temperature dependences of photoluminescence (PL) revealed the m-plane emission behaviors of the InGaN/GaN core-shell nanorods. The electroluminescence (EL) of the InGaN/GaN core-shell-nanorod-embedded 3D LED changed color from green to blue with increasing injection current. This phenomenon was mainly due to the energy gradient and deep localization of the indium in the selectively grown InGaN/GaN core-shell MQWs on the 3D architecture.

The study of poly-Si n+pp+ solar cells

International Nuclear Information System (INIS)

Aboud, S.R.

1990-01-01

The electrical and optical properties such as (activation energy, optical energy gap, and gap state density) of the polycrystalline silicon (poly-Si) have been studied. A comparative study between the chemical and mechanical polishing to clean and polish the poly-Si surface were done through the measurement of the reflectivity of these surfaces. A group of solar cells of type n + pp + were prepared, using p-type poly-Si wafers (SISLO). Solar cells were also prepared using single silicon (Sing-Si) with and, without (BSF) to study the effect of (BSF) on Sing-Si cell and a comparative study between poly-Si cell and Sing-Si cell under the same conditions. 2 tabs.; 45 figs.; 49 refs

Synthesis and characterization of a thermo-sensitive poly( N-methyl acryloylglycine methyl ester) used as a drug release carrier

Science.gov (United States)

Deng, Kui-Lin; Zhong, Hai-Bin; Jiao, Yi-Suo; Fan, Ting; Qiao, Xiao; Zhang, Peng-Fei; Ren, Xiao-Bo

2010-06-01

In this article, poly( N-methyl acryloylglycine methyl ester) (PNMAME) was prepared as a novel thermosensitive material with a lower critical solution temperature (LCST) at around 49.5°C. The chemical structures of the monomer NMAME and PNMAME were characterized by 1H NMR and IR measurements. The LCST was investigated systematically as a function of PNMAME concentration, inorganic salt solution and pH value. The results indicated that LCST of PNMAME was obviously dependent on PNMAME concentration and pH. The LCST was increased with a decrease in pH value and PNMAME concentration. To obtain a thermo-sensitive hydrogel with the phase transition temperature close to human body temperature, the copolymerization was conducted between NMAME and N-acryloylglycine ethyl ester (NAGEE). The release behavior of caffeine was evaluated at different temperatures and contents of cross-linkers ( N, N-methylenebis(acrylamide) (NMBA)). The increase of cross-linker content led to a decrease in the release rate of caffeine due to higher crossing density in the hydrogel network. In addition, a faster release of caffeine from the hydrogel with 3% NMBA at 37°C was found in contrast to that at 18°C.

In vitro behavior of human mesenchymal stem cells on poly(N-isopropylacrylamide) based biointerfaces obtained by matrix assisted pulsed laser evaporation

Science.gov (United States)

Icriverzi, Madalina; Rusen, Laurentiu; Sima, Livia Elena; Moldovan, Antoniu; Brajnicov, Simona; Bonciu, Anca; Mihailescu, Natalia; Dinescu, Maria; Cimpean, Anisoara; Roseanu, Anca; Dinca, Valentina

2018-05-01

The use of smart coatings with tunable characteristics in bioengineering fields is directly correlated with the surface chemical and topographical properties, the method of preparation, and also with the type of cells implied for the specific application. In this work, a versatile surface modification technique based on the use of lasers (Matrix-Assisted Pulsed Laser Evaporation (MAPLE)) was used to yield poly(N-isopropylacrylamide) (pNIPAM) and its derivatives (amine, azide and amide terminated pNIPAM) functional and termoresponsive thin films. Surface properties of pNIPAM and its derivative films such as morphology, roughness and hydrophobic/hydrophilic character, as well as the thermoresponsive capacity were investigated by atomic force microscopy and contact angle measurements. The chemical characteristics of the pNIPAM based thin films were analysed by Fourier Transform Infrared Spectroscopy (FTIR). The chemical functionality was kept for all the samples obtained by MAPLE and the thermoresponse was demonstrated by the change in the contact angle and thickness values when the temperature was shifted from 37 °C to 24 °C for all the materials tested, with a smaller change for maleimide terminated pNIPAM. Biological assays performed in vitro (fluorescence microscopy and Scanning Electron Microscopy (SEM)) confirmed the conditioning of the early mesenchymal stem cell (MSC) growth by specific chemistry of the coatings. The cell imaging analysis revealed no cytotoxic effect of pNIPAM surfaces irrespective of type of functionalization. An increased proliferation rate of the cells grown on pNIPAM-azide surfaces and a lower cell density on pNIPAM-maleimide surfaces compared to the pNIPAM surfaces was observed, which can direct their use to potential surfaces in regenerative medicine approaches.

Dynamic studies of poly(di-n-alkyl itaconate)s

CERN Document Server

Arrighi, V; Gagliardi, S; McEwen, I J; Telling, M T F

2002-01-01

We report a preliminary dynamic study of poly(di-n-alkyl itaconate)s with varying side chain length n. QENS measurements were carried out on two backscattering spectrometers, IRIS at ISIS and IN10 at the ILL in the temperature range of 4 to 350 K. We show that molecular motion can be detected well below the polymer glass transition for all samples. It is possible to distinguish different dynamic processes. The temperature range over which these are observed is dependent on the length of the side chain, n. The intermediate scattering function, I(Q,t), was determined from the IRIS and found to obey time-temperature superposition. We show that the I(Q,t) data at different temperatures can be overlapped using the same time-scale shift factors, indicating that the relaxation process is common to all the polymers investigated. (orig.)

Solid polymer/salt electrolytes based on linear poly((N-2-cyanoethyl)ethylenimine)

International Nuclear Information System (INIS)

Erickson, M.; Frech, R.; Glatzhofer, D.T.

2003-01-01

There has been growing interest in the structure, properties, ionic association, and conductivity in poly(acrylonitrile) (PAN)/salt systems and its structural analogues. We have developed a simple procedure to cyanoethylate the nitrogen atoms (>95% by 1 H-NMR) of linear poly(ethylenimine) (PEI) to form poly((N-2-cyanoethyl)ethylenimine) (PCEEI). IR studies indicate that, like PAN, a second nitrile stretching band develops for PCEEI on addition of LiTf, indicating coordination of nitrile groups to Li cations. However, spectroscopic data on the triflate ions indirectly suggest that, unlike PAN/LiTf systems, PCEEI systems contain significant proportions of 'free' Li cations at high LiTf concentrations. Initial results indicate the RT ionic conductivity in the PCEEI systems is on the order of 10 -8 S cm -1 at a composition of N:Li=6:1 and was found to be largely independent of LiTf concentration over a range of sample concentrations. The nature of the relative concentrations of ionic species of LiTf in PCEEI was determined with infrared spectroscopy. Results of room temperature and variable temperature complex impedance measurements are presented

Investigation of Complexation of Linear Poly(N-vinyl-2-pyrrolidone with Poly(methacrylic acid-co-methyl methacrylate Gel

Directory of Open Access Journals (Sweden)

Guoqin Liu

2011-01-01

Full Text Available The contraction of poly(methacrylic acid-co-methyl methacrylate (P(MAA-co-MMA gel induced by complexation with linear poly(N-vinyl-2-pyrrolidone (PVP is quite different from that of poly(acrylic acid (PAA or poly(methacrylic acid (PMAA gel. It was found that the concentration of PVP has a strong effect on the complexation with P(MAA-co-MMA gel. When PVP was introduced into the P(MAA-co-MMA network, its dynamic mechanic properties vary greatly between complexed and uncomplexed networks. It had the following results: (1 the higher modulus ratio; (2 a slight contraction of gel.

Investigation of nanocomposites made with poly(methacrylic acid-co-methyl methacrylate/poly(N-vinyl-2-pyrrolidone/multi-walled carbon nanotubes

Directory of Open Access Journals (Sweden)

Liu Guoqin

2014-01-01

Full Text Available Poly(methacrylic acid-co-methyl methacrylate (P(MAA-co-MMA was prepared in the presence of poly(N-vinyl-2-pyrrolidone (PVP and multiwalled carbon nanotubes (MWNTs via ultrasonic assisted solution free radical polymerization, i.e., P(MAA-co-MMA/PVP/MWNTs nanocomposites. The morphology, glassy-state storage modulus, thermal behavior and swelling characteristics of P(MAA-co-MMA/PVP/MWNTs nanocomposites were investigated. Scanning electron micrographs (SEM revealed that MWNTs at low concentration could be uniformly dispersed into P(MAA-co-MMA/PVP blends. With increasing MWNTs weight fraction, the average glassy-state modulus, glass transition temperatures and decomposition temperature of the nanocomposites increased, but their swelling characteristics decreased.

Investigation of nanocomposites made with poly(methacrylic acid-co-methyl methacrylate)/poly(N-vinyl-2-pyrrolidone)/multi-walled carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Guoqin, Liu; Wei, Miao [College of Material Science and Engineering, Henan University of Technology (China); Lin-Jian, Shangguan, E-mail: mikepolymer@126.com [School of Mechanical Engineering, North China University of Water Conservancy and Electric Power (China)

2014-06-01

Poly(methacrylic acid-co-methyl methacrylate) (P(MAA-co-MMA)) was prepared in the presence of poly(N-vinyl-2-pyrrolidone) (PVP) and multi-walled carbon nanotubes (MWNTs) via ultrasonic assisted solution free radical polymerization, i.e., P(MAA-co-MMA)/PVP/MWNTs nanocomposites. The morphology, glassy-state storage modulus, thermal behavior and swelling characteristics of P(MAA-co-MMA)/PVP/MWNTs nanocomposites were investigated. Scanning electron micrographs (SEM) revealed that MWNTs at low concentration could be uniformly dispersed into P(MAA-co-MMA)/PVP blends. With increasing MWNTs weight fraction, the average glassy-state modulus, glass transition temperatures and decomposition temperature of the nanocomposites increased, but their swelling characteristics decreased. (author)

Synthesis and characterization of water-dispersed CdSe/CdS core-shell quantum dots prepared via Layer-by-layer Method capped with carboxylic-functionalized poly(vinyl alcohol)

Energy Technology Data Exchange (ETDEWEB)

Ramanery, Fabio Pereira; Mansur, Alexandra Ancelmo Piscitelli; Mansur, Herman Sander, E-mail: hmansur@demet.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Metalurgia e Engenharia dos Materiais. Centro de Nanociencia, Nanotecnologia e Inovacao

2014-08-15

The main goal of this work was to synthesize CdSe/CdS (core-shell) nanoparticles stabilized by polymer ligand using entirely aqueous colloidal chemistry at room temperature. First, the CdSe core was prepared using precursors and acid-functionalized poly(vinyl alcohol) as the capping ligand. Next, a CdS shell was grown onto the CdSe core via the layer-by-layer technique. The CdS shell was formed by two consecutive monolayers, as estimated by empirical mathematical functions. The nucleation and growth of CdSe quantum dots followed by CdS shell deposition were characterized by UV-vis spectroscopy, photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM). The results indicated a systematic red-shift of the absorption and emission spectra after the deposition of CdS, indicating the shell growth onto the CdSe core. TEM coupled with electron diffraction analysis revealed the presence of CdSe/CdS with an epitaxial shell growth. Therefore, it may be concluded that CdSe/CdS quantum dots with core-shell nanostructure were effectively synthesized.(author)

Fabrication and characterization of novel multilayered structures by stereocomplexion of poly(D-lactic acid)/poly(L-lactic acid) and self-assembly of polyelectrolytes

OpenAIRE

Elena Dellacasa; Li Zhao; Gesheng Yang; Laura Pastorino; Gleb B. Sukhorukov

2016-01-01

The enantiomers poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA) were alternately adsorbed directly on calcium carbonate (CaCO3) templates and on poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) multilayer precursors in order to fabricate a novel layer-by-layer (LBL) assembly. A single layer of poly(L-lysine) (PLL) was used as a linker between the (PDLA/PLLA)n stereocomplex and the cores with and without the polymeric (PSS/PAH)n/PLL multilayer precursor (PEM). N...

Micro/nanoencapsulated n-nonadecane with poly(methyl methacrylate) shell for thermal energy storage

International Nuclear Information System (INIS)

Sarı, Ahmet; Alkan, Cemil; Biçer, Alper; Altuntaş, Ayşe; Bilgin, Cahit

2014-01-01

Graphical abstract: This paper was aimed to prepare, characterize and determinate of thermal energy storage properties of PMMA/C19 micro/nanocapsules as a novel encapsulated phase change material (M/N-EPCM). The chemical structure of the prepared M/N-EPCM was verified using FTIR spectroscopy method. The analysis results obtained from POM and SEM indicated that the synthesized capsules had virtually spherical-shape. The PSD analysis indicated that the M/N-EPCM capsules had mean diameter of 8.18 μm and the percentage of the capsules with nanosize was 4.90 (v/v). The DSC results showed that the synthesized M/N-PCM had a melting temperature and total latent heat value as 31.23 °C and 139.20 J/g, respectively. It can be also deduced from all results that the synthesized M/N-EPCM had promising thermal energy storage potential due to its good latent heat thermal energy storage properties, thermal durability, thermal reliability, chemical stability, thermal conductivity and phase change reversibility properties. - Highlights: • The chemical structure of the prepared M/N-EPCM was verified using FTIR spectroscopy method. • POM and SEM results indicated that the M/N-EPCM had virtually spherical shape-appearance. • The M/N-EPCM had mean diameter of 8.18 μm and the percentage of the capsules with nanosize was 4.90 (v/v). • The M/N-PCM had a melting temperature and total latent heat value as 31.23 °C and 139.20 J/g, respectively. • The M/N-EPCM had promising thermal energy storage potential. - Abstract: This paper was aimed to prepare, characterize and determine the thermal energy storage properties of poly(methyl methacrylate) (PMMA)/n-nonadecane (C19) capsules as a novel micro/nanoencapsulated phase change material (M/N-EPCM). The M/N-EPCM was fabricated via emulsion polymerization reaction of methylmethacrylate (MMA) monomer occurred around C19 used as core material. The chemical structure of the prepared M/N-EPCM was verified using Fourier transform infrared

Thermodynamic Interactions between Polystyrene and Long-Chain Poly(n-Alkyl Acrylates) Derived from Plant Oils.

Science.gov (United States)

Wang, Shu; Robertson, Megan L

2015-06-10

Vegetable oils and their fatty acids are promising sources for the derivation of polymers. Long-chain poly(n-alkyl acrylates) and poly(n-alkyl methacrylates) are readily derived from fatty acids through conversion of the carboxylic acid end-group to an acrylate or methacrylate group. The resulting polymers contain long alkyl side-chains with around 10-22 carbon atoms. Regardless of the monomer source, the presence of alkyl side-chains in poly(n-alkyl acrylates) and poly(n-alkyl methacrylates) provides a convenient mechanism for tuning their physical properties. The development of structured multicomponent materials, including block copolymers and blends, containing poly(n-alkyl acrylates) and poly(n-alkyl methacrylates) requires knowledge of the thermodynamic interactions governing their self-assembly, typically described by the Flory-Huggins interaction parameter χ. We have investigated the χ parameter between polystyrene and long-chain poly(n-alkyl acrylate) homopolymers and copolymers: specifically we have included poly(stearyl acrylate), poly(lauryl acrylate), and their random copolymers. Lauryl and stearyl acrylate were chosen as model alkyl acrylates derived from vegetable oils and have alkyl side-chain lengths of 12 and 18 carbon atoms, respectively. Polystyrene is included in this study as a model petroleum-sourced polymer, which has wide applicability in commercially relevant multicomponent polymeric materials. Two independent methods were employed to measure the χ parameter: cloud point measurements on binary blends and characterization of the order-disorder transition of triblock copolymers, which were in relatively good agreement with one another. The χ parameter was found to be independent of the alkyl side-chain length (n) for large values of n (i.e., n > 10). This behavior is in stark contrast to the n-dependence of the χ parameter predicted from solubility parameter theory. Our study complements prior work investigating the interactions between

The micellization and dissociation transitions of thermo-, pH- and sugar-sensitive block copolymer investigated by laser light scattering

Directory of Open Access Journals (Sweden)

Y. C. Tang

2012-08-01

Full Text Available A triple-stimuli responsive polymer, poly(3-acrylamidophenylboronic acid-b-poly(N-isopropylacrylamide (PAAPBA-b-PNIPAM, has been synthesized by reversible addition-fragmentation chain transfer polymerization. Temperature, pH, and fructose induced micellization and dissociation transition of block copolymer was investigated by a combination of static and dynamic laser light scattering. PAAPBA-b-PNIPAM copolymer self-assembles into micelles with PAAPBA block as core and PNIPAM as shell in lower pH aqueous solution at room temperature. Increasing the temperature causes the micelle to shrink due to the dehydration of PNIPAM segments at pH 6.2. After the elevation of solution pH from 6.2 to 10.0, the increase in the hydrophilicity of PAAPBA block leads to an expulsion of unimers from micelles. In addition, the fructose addition further enhances the dissociation of micelles. Our experiments demonstrate that the micelle to unimer transition process proceeds via the step-by-step sequential expulsion of individual chains.

Thermodynamic characterization of poly(4-hydroxystyrene)-g-[poly(propyleneoxide-b-ethylene oxide)] thermoresponsive brush copolymers

Energy Technology Data Exchange (ETDEWEB)

Thanassoulas, Angelos, E-mail: athanas@rrp.demokritos.gr [Biomolecuar Physics Laboratory, National Centre for Scientific Research “Demokritos”, 153 10 Aghia Paraskevi (Greece); Papadopoulos, Athanasios [Biomolecuar Physics Laboratory, National Centre for Scientific Research “Demokritos”, 153 10 Aghia Paraskevi (Greece); Pispas, Stergios [Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 11635 Athens (Greece); Zhao, Junpeng; Zhang, Guangzhao [Faculty of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Nounesis, George [Biomolecuar Physics Laboratory, National Centre for Scientific Research “Demokritos”, 153 10 Aghia Paraskevi (Greece)

2016-08-20

Highlights: • PPO-b-PEO core-shell brush copolymers exhibit thermoresponsive behavior in aqueous solutions. • Their thermal transitions strongly depend on their architecture and chemical composition. • These copolymer transitions follow a coil-to-globule mechanism. • It is possible to fine-tune their thermoresponsiveness to a wide range of temperatures. - Abstract: Thermoresponsive brush copolymers with poly(4-hydroxystyrene) backbones and poly(propyleneoxide-b-ethylene oxide) side chains were synthesized via a “grafting from” technique. The thermoresponsive behavior of four samples with different compositions has been investigated in dilute aqueous solutions by high-accuracy differential scanning calorimetry measurements. Thermal transitions involving both core contraction and intermolecular aggregation have been observed for all the copolymers in this study. The temperature where these thermal transitions occur is strongly associated to the architecture and chemical composition of the copolymers, allowing for fine-tuning of their thermoresponsiveness in a wide range of temperatures.

Synthesis of biodegradable plastic from tapioca with N-Isopropylacrylamid and chitosan using glycerol as plasticizer

Science.gov (United States)

Syaubari; Safwani, S.; Riza, M.

2018-04-01

One of natural polymers that can be used as raw material in the manufacture of biodegradable plastic is tapioca and chitosan. The addition of other compounds such as glycerol as plasticizer is to improve the characteristics of the plastic that already produced. N- Isopropylacrylamid (NIPAm) is an organic compound that can be synthesized into a polymer or polymer grafting which also biodegradable too. This research aims tostudy the synthesis of biodegradable plastics from tapioca with the addition of chitosan, NIPAm, poly(NIPAm) and analyze the characteristics of biodegradable plastics that already produced. This research was done in three stages, there are (1) polymerization NIPAm, (2) the grafting of chitosan-poly NIPAm and (3) the synthesis of biodegradable plastics from starch mixture with variation of addition chitosan, NIPAm, poly(NIPAm), chitosan-graft-poly(NIPAm) and also variations of glycerol as plasticizer. The results of this research is a thin sheet of plastic which is will get analyzed for the characteristics of functional groups, mechanical, morphological and its biodegradability. FTIR spectra showed the grafting process with the new group formation of CO single-bond at 850 cm-1. Plastic with the addition of NIPAm and 1 ml glycerol has the highest tensile strength value about 31.1 MPa. Plastic with poly(NIPAm) and 4 ml glycerol produces the highest elongation value about 153.72%. Plastic with Chitosan-graft-poly(NIPAm) with 1 ml glycerol has the longest biodegradation because of the small mass-loss for six weeks which is about 6.6%.

Effect of pH and temperature upon self-assembling process between poly(aspartic acid) and Pluronic F127.

Science.gov (United States)

Nita, Loredana E; Chiriac, Aurica P; Bercea, Maria

2014-07-01

The present investigation was made in order to evaluate the capability of self-assembling of the two water soluble polymers, respectively, poly(aspartic acid) and Pluronic F127 into well interpenetrated mixture, and to evidence the connection effects intervened during polymer complex formation to exhibit good stability once formed, as well to understand and correlate the binding strength and the interval between better association domains. The effect of pH and temperature on the interpolymeric complex formation between poly(aspartic acid) and Pluronic F127 was studied by combining rheology with light scattering technique. The solution mixtures between poly(aspartic acid) and Pluronic F127 are Newtonian fluids for all ratios among them. Depending on the polymeric mixture composition and experimental temperature, positive or negative deviations of the experimental values from the additive dependence appear. An interesting behavior was registered around 1/1 wt. ratio between the two polymers, when the hydrodynamic diameter of the interpenetrated polymeric particles decreased suddenly. This allows us to conclude the formation of core-shell micelle structure with poly(aspartic acid) core and Pluronic F127 as shell, performed through strong interactions between polymers. This behavior was sustained by the increase of absolute value of zeta potential owing to the decrease of functional groups number at the surface of micelles. Copyright © 2014 Elsevier B.V. All rights reserved.

Structure of poly(di-n-hexylsilane) in nanoporous materials

International Nuclear Information System (INIS)

Korotkova, I.; Sakhno, T.; Drobit'ko, I.; Sakhno, Yu.; Ostapenko, N.

2010-01-01

Graphical abstract: On the basis of theoretical calculations using TD/CEP-31G method we found and interpreted the complexation mechanism of poly(di-n-hexylsilane) incorporated in nanoporous materials. - Abstract: In this work the effects of solvent polarity and conformation changing on the electronic characteristics of poly(di-n-hexylsilane) incorporated in the nanoporous materials are calculated. The dependence of energy levels of electronic-excited states of investigated compounds is analyzed as a function of the Si-Si-Si-Si twist angle and length of Si-Si and Si-C bonds. The possibility of complex formation between silicon atom of polymer and oxygen ions of nanoporous materials is shown.

Kinetics of Coil-to-Globule Transition of Dansyl-Labeled Poly(N-sopropylacrylamide) Chains in Aqueous Solution

Science.gov (United States)

Li, Chun-liang; Ye, Xiao-dong; Ding, Yan-wei; Liu, Shi-lin

2012-08-01

The coil-to-globule transition of thermally sensitive linear poly(N-isopropylacrylamide) (PNIPAM) labeled with dansyl group is induced by 1.54 μm laser pulses (width≈10 ns). The dansyl group is used to follow the transition kinetics because its fluorescence intensity is very sensitive to its micro-environment. As the molar ratio of NIPAM monomer to dansyl group increases from 110 to 300, the effect of covalently attached dansyl fluorophores on the transition decreases. In agreement with our previous study in which we used 8-anilino-1-naphthalensulfonic acid ammonium salt free in water as a fluorescent probe, the current study reveals that the transition has two distinct stages with two characteristic times, namely, τfast≈0.1 ms, which can be attributed to the nucleation and formation of some “pearls" (locally contracting segments) on the chain, and τslow≈0.5 ms, which is related to the merging and coarsening of the “pearls". τfast is independent of the PNIPAM chain length over a wide range (Mw=2.8×106-4.2×107 g/mol). On the other hand, τslow only slightly increases with the chain length.

Entrappment of alkaline protease and β-galactosidase in radiation stitched together poly-N-vinylcaprolactam

International Nuclear Information System (INIS)

Davidenko, T.I.; Kravchenko, I.A.

1996-01-01

The gel formations by poly-N-vinylcaprolactam upon its γ-irradiation by the 20-25 kGy dose as a results of partial polymer stitching together is shown, which is confirmed by the CD-and thermogravimetric data. By the alkaline protease and β-galactosidase entrapment in poly-N- vinylcaprolactam stitched together by γ-irradiation, the active preparations are obtained with 90-98 % and 30-35 % activity retained for alkaline protease and β-galactosidase, respectively. The increased stability of alkaline protease at acidic pH values and higher temperature was noted, and for β-galactosidase - the possibility of repeated use of the obtained preparation for lactose hydrolysis

Poly (ethylene oxide)-block-poly (n-butyl acrylate)-blockpoly (acrylic acid) triblock terpolymers with highly asymmetric hydrophilic blocks: synthesis and aqueous solution properties

OpenAIRE

Petrov, P. (Petar); Yoncheva, K. (Krassimira); Mokreva, P. (Pavlina); Konstantinov, S. (Spiro); Irache, J.M. (Juan Manuel); Müller, A.H.E. (Axel H.E.)

2013-01-01

The synthesis and aggregation behaviour in aqueous media of novel amphiphilic poly(ethylene oxide)- block-poly(n-butyl acrylate)-block-poly(acrylic acid) (PEO–PnBA–PAA) triblock terpolymers were studied. Terpolymers composed of two highly asymmetric hydrophilic PEO (113 monomer units) and PAA (10–17 units) blocks, and a longer soft hydrophobic PnBA block (163 or 223 units) were synthesized by atom transfer radical polymerisation (ATRP) of n-butyl acrylate and tert-butyl acrylate ...

Self-Assembled Core-Shell CdTe/Poly(3-hexylthiophene) Nanoensembles as Novel Donor-Acceptor Light-Harvesting Systems.

Science.gov (United States)

Istif, Emin; Kagkoura, Antonia; Hernandez-Ferrer, Javier; Stergiou, Anastasios; Skaltsas, Theodosis; Arenal, Raul; Benito, Ana M; Maser, Wolfgang K; Tagmatarchis, Nikos

2017-12-27

The self-assembly of novel core-shell nanoensembles consisting of regioregular poly(3-hexylthiophene) nanoparticles (P3HT NPs ) of 100 nm as core and semiconducting CdTe quantum dots (CdTe QDs ) as shell with a thickness of a few tens of nanometers was accomplished by employing a reprecipitation approach. The structure, morphology, and composition of CdTe QDs /P3HT NPs nanoensembles were confirmed by high-resolution scanning transmission microscopy and dynamic light-scattering studies. Intimate interface contact between the CdTe QDs shell and the P3HT NPs core leads to the stabilization of the CdTe QDs /P3HT NPs nanoensemble as probed by the steady-state absorption spectroscopy. Effective quenching of the characteristic photoluminescence of CdTe QDs at 555 nm, accompanied by simultaneous increase in emission of P3HT NPs at 660 and 720 nm, reveals photoinduced charge-transfer processes. Probing the redox properties of films of CdTe QDs /P3HT NPs further proves the formation of a stabilized core-shell system in the solid state. Photoelectrochemical assays on CdTe QDs /P3HT NPs films show a reversible on-off photoresponse at a bias voltage of +0.8 V with a 3 times increased photocurrent compared to CdTe QDs . The improved charge separation is directly related to the unique core-shell configuration, in which the outer CdTe QDs shell forces the P3HT NPs core to effectively act as electron acceptor. The creation of novel donor-acceptor core-shell hybrid materials via self-assembly is transferable to other types of conjugated polymers and semiconducting nanoparticles. This work, therefore, opens new pathways for the design of improved optoelectronic devices.

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

Science.gov (United States)

Sangeetha, P.; Jeganathan, K.; Ramakrishnan, V.

2013-06-01

The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E2 (high) and A1 (LO) phonon mode of InN core at 490 and 590 cm-1 respectively and E2 (high) phonon mode of GaN shell at 573 cm-1. The free carrier concentration of InN core is found to be low in the order ˜ 1016 cm-3 due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of ˜15 nm. The phonon-life time of core-shell nanowire structure is estimated to be ˜0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E2 (high) phonon mode of GaN shell at 573 cm-1 as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111 substrate

Directory of Open Access Journals (Sweden)

P. Sangeetha

2013-06-01

Full Text Available The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE on Si (111 substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E2 (high and A1 (LO phonon mode of InN core at 490 and 590 cm−1 respectively and E2 (high phonon mode of GaN shell at 573 cm−1. The free carrier concentration of InN core is found to be low in the order ∼ 1016 cm−3 due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of ∼15 nm. The phonon-life time of core-shell nanowire structure is estimated to be ∼0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E2 (high phonon mode of GaN shell at 573 cm−1 as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

International Nuclear Information System (INIS)

Sangeetha, P.; Ramakrishnan, V.; Jeganathan, K.

2013-01-01

The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E 2 (high) and A 1 (LO) phonon mode of InN core at 490 and 590 cm −1 respectively and E 2 (high) phonon mode of GaN shell at 573 cm −1 . The free carrier concentration of InN core is found to be low in the order ∼ 10 16 cm −3 due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of ∼15 nm. The phonon-life time of core-shell nanowire structure is estimated to be ∼0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E 2 (high) phonon mode of GaN shell at 573 cm −1 as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

Novel elastomeric fibrous networks produced from poly(xylitol sebacate)2:5 by core/shell electrospinning: fabrication and mechanical properties.

Science.gov (United States)

Li, Yuan; Thouas, George A; Chen, Qizhi

2014-12-01

Fabrication of nonlinear elastic materials that resemble biological tissues remains a challenge in biomaterials research. Here, a new fabrication protocol to produce elastomeric fibrous scaffolds was established, using the core/shell electrospinning technique. A prepolymer of poly(xylitol sebacate) with a 2:5mol ratio of xylitol:sebacic acid (PXS2:5) was first formulated, then co-electrospun with polyvinyl alcohol (PVA - 95,000Mw). After cross-linking of core polymer PXS2:5, the PVA shells were rinsed off in water, leaving a porous elastomeric network of PXS2:5 fibres. Under aqueous conditions, the PXS2:5 fibrous scaffolds exhibited stable, nonlinear J-shaped stress-strain curves, with large average rupture elongation (76%) and Young׳s modulus (~1.0MPa), which were in the range of muscle tissue. Rupture elongation of PXS2:5 was also much higher when electrospun, compared to 2D solid sheets (45%). In direct contact with cell monolayers under physiological conditions, PXS2:5 scaffolds were as biocompatible as those made of poly-l-lactic acid (PLLA), with improvements over culture medium alone. In conclusion, the newly developed porous PXS2:5 scaffolds show tissue-like mechanical properties and excellent biocompatibility, making them very promising for bioengineering of soft tissues and organs. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Synthesis and characterization of core-shell gold nanoparticles with poly(vinyl pyrrolidone) from a new precursor salt

Science.gov (United States)

Behera, M.; Ram, S.

2013-02-01

In this article, we report a facile one-step chemical synthesis of gold (Au) nanoparticles (GNPs) from a new precursor salt i.e., gold hydroxide in the presence of poly(vinyl pyrrolidone) (PVP) polymer. The non-aqueous dispersion of GNPs was comprehensively characterized by UV-Visible, FTIR, zeta potential, and transmission electron microscope (TEM). A strong surface plasmon resonance band at 529 nm in the UV-Visible spectrum confirms the formation of GNPs in the Au colloid. The FTIR spectroscopic results showed that PVP molecules get chemisorbed onto the surface of GNP via O-atom of carbonyl group. A negative zeta potential of (-)16 mV reveals accumulation of nonbonding electrons of O-atom of carbonyl group of PVP molecules on the nanosurface of GNP. TEM images demonstrate a core-shell nanostructure with an Au-crystalline core covered by a thin amorphous PVP-shell. PVP-capped GNPs could be a potential candidate for bio-sensing, catalysis, and other applications.

Poly (N-isopropylacrylamide)-functionalized dendrimer as a thermosensitive nanoplatform for delivering malloapelta B against HepG2 cancer cell proliferation

Science.gov (United States)

Ngan Le, Phung; Chuong Pham, Dinh; Hai Nguyen, Dai; Quyen Tran, Ngoc; Dimitrov, Vladimir; Ivanov, Petko; Nguyen Xuan, Cuong; Nguyen, Hoai Nam; Khoa Nguyen, Cuu

2017-06-01

In recent years, nanocarriers have emerged as effective platforms for delivering several kinds of herbal medicine and naturally bioactive compounds. In this study we developed an outstanding thermosensitive dendritic nanocarrier to efficiently deliver malloapelta B (Mall B), which is a water insoluble bioactive compound isolated from leaves of Mallotus apelta—Vietnamese medicinal plant. The thermosensitive poly(N-isopropylacrylamide) (PNIPAM) polymer-conjugated polyamidoamine (PAMAM) dendrimer copolymer was prepared via Michael reaction. The copolymer structures were confirmed by proton nuclear magnectic resonance (1H NMR). Morphology of the nanocarrier was observered around 70-120 nm by transmission electron microscopy (TEM). Size distributions were measured by dynamic light scattering (DLS) of the nanocarrier and its Mall B-loaded performed at 146.8 nm and 194.5 nm, respectively. The PNIPAM-g-PAMAM-based nanocarrier exhibited higher Mall B loading efficiency (DL  =  59.93  ±  0.19%) and entrapment efficiency (EE  =  89.98  ±  2.06%) as compared to PNIPAM (DL  =  52.54  ±  0.45% and EE  =  66.45  ±  2.78%). In vitro release indicated that approximately 30% amount of the loaded Mall B released at pH 5.5 after 54 h tracking. At the same time, 12.5% amount of the molecules released at pH 7.4.Cytotoxicity assay results showed that the Mall B-loaded nanocarrier significantly inhibited HepG2 cancer cell proliferation. These obtained results indicated that the nanocarrier could solve hydrophobic property of Mall B for further medicine applications.

Poly(N-isopropyl acrylamide)-block-poly(n-butyl acrylate) thermoresponsive amphiphilic copolymers: synthesis, characterization and self-assembly behavior in aqueous solutions

Czech Academy of Sciences Publication Activity Database

Škvarla, J.; Zedník, J.; Šlouf, Miroslav; Pispas, S.; Štěpánek, M.

2014-01-01

Roč. 61, December (2014), s. 124-132 ISSN 0014-3057 R&D Projects: GA TA ČR TE01020118 Institutional support: RVO:61389013 Keywords : thermoresponsive block copolymers * poly(N-isopropyl acrylamide) * light scattering Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.005, year: 2014

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

Energy Technology Data Exchange (ETDEWEB)

Sangeetha, P.; Ramakrishnan, V. [Department of Laser Studies, School of Physics, Madurai Kamaraj University, Madurai-625 021 (India); Jeganathan, K. [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli-620 024 (India)

2013-06-15

The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E{sub 2} (high) and A{sub 1} (LO) phonon mode of InN core at 490 and 590 cm{sup -1} respectively and E{sub 2} (high) phonon mode of GaN shell at 573 cm{sup -1}. The free carrier concentration of InN core is found to be low in the order {approx} 10{sup 16} cm{sup -3} due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of {approx}15 nm. The phonon-life time of core-shell nanowire structure is estimated to be {approx}0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E{sub 2} (high) phonon mode of GaN shell at 573 cm{sup -1} as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

Core-shell architectures as nano-size transporters

International Nuclear Information System (INIS)

Adeli, M.; Zarnegar, Z.; Kabiri, R.; Salimi, F.; Dadkah, A.

2006-01-01

Core-shell architectures containing poly (ethylene imine) (PEI) as a core and poly (lactide) (PLA) as arms were prepared. PEI was used as macro initiator for ring opening polymerization of lactide. PEI-PLA core-shell architectures were able to encapsulate guest molecules. Size of the core-shell architectures was between 10- 100 nm, hence they can be considered as nano carriers to transport the guest molecules. Transport capacity of nano carriers depends on their nano-environments and type of self-assembly in solvent. In solid state nano carriers self-assemble as long structures with nano-size diameter or they form network structures. Aggregations type depends on the concentration of nano carriers in solution. Effect of the shell thickness and aggregation type on the release rate are also investigated

Poly(glycidyl methacrylate)—A soft template for the facile preparation of poly(glycidyl methacrylate) core-copper nanoparticle shell nanocomposite

International Nuclear Information System (INIS)

Mohammed Safiullah, S.; Abdul Wasi, K.; Anver Basha, K.

2015-01-01

Graphical abstract: - Highlights: • PGMA/Cu nanohybrids have been synthesized by Surface deposition method. • The CuNPs were deposited on the PGMA surface without surface modification. • CuNP deposition on PGMA has a significant effect on morphology and thermal stability. - Abstract: Poly(glycidyl methacrylate) core/copper nanoparticle shell nanocomposite (PGMA/Cu nanohybrid) was prepared by simple two step method (i) The synthesis of poly(glycidyl methacrylate) (PGMA) beads by free radical suspension polymerization followed by (ii) direct deposition of copper nanoparticles (CuNPs) on activated PGMA beads. The PGMA beads were used as a soft template to host the CuNPs without surface modification of it. In this method the CuNPs were formed by chemical reduction of copper salts using sodium borohydride in water medium and deposited directly on the activated PGMA. Two different concentrations of copper salts were employed to know the effect of concentration on the shape and size of nanoparticles. The results showed that, the different sizes and shapes of CuNPs were deposited on the PGMA matrix. The X-ray Diffraction study results showed that the CuNPs were embedded on the surface of the PGMA matrix. The scanning electron microscopic images revealed that the fabrication of CuNPs on the PGMA matrix possess different shapes and changes the morphology and nature of PGMA beads significantly. The fluorescent micrograph also confirmed that the CuNPs were doped on the PGMA surface. The thermal studies have demonstrated that the CuNPs deposition on the surface of PGMA beads had a significant effect.

Poly(glycidyl methacrylate)—A soft template for the facile preparation of poly(glycidyl methacrylate) core-copper nanoparticle shell nanocomposite

Energy Technology Data Exchange (ETDEWEB)

Mohammed Safiullah, S., E-mail: safichem@gmail.com [Department of Chemistry, C. Abdul Hakeem College of Engineering & Technology, Melvisharam, Vellore District, Tamil Nadu 632509 (India); P.G. & Research Department of Chemistry, C. Abdul Hakeem College, Melvisharam, Vellore District, Tamil Nadu 632509 (India); Abdul Wasi, K. [P.G. & Research Department of Chemistry, C. Abdul Hakeem College, Melvisharam, Vellore District, Tamil Nadu 632509 (India); Anver Basha, K., E-mail: kanverbasha@gmail.com [P.G. & Research Department of Chemistry, C. Abdul Hakeem College, Melvisharam, Vellore District, Tamil Nadu 632509 (India)

2015-12-01

Graphical abstract: - Highlights: • PGMA/Cu nanohybrids have been synthesized by Surface deposition method. • The CuNPs were deposited on the PGMA surface without surface modification. • CuNP deposition on PGMA has a significant effect on morphology and thermal stability. - Abstract: Poly(glycidyl methacrylate) core/copper nanoparticle shell nanocomposite (PGMA/Cu nanohybrid) was prepared by simple two step method (i) The synthesis of poly(glycidyl methacrylate) (PGMA) beads by free radical suspension polymerization followed by (ii) direct deposition of copper nanoparticles (CuNPs) on activated PGMA beads. The PGMA beads were used as a soft template to host the CuNPs without surface modification of it. In this method the CuNPs were formed by chemical reduction of copper salts using sodium borohydride in water medium and deposited directly on the activated PGMA. Two different concentrations of copper salts were employed to know the effect of concentration on the shape and size of nanoparticles. The results showed that, the different sizes and shapes of CuNPs were deposited on the PGMA matrix. The X-ray Diffraction study results showed that the CuNPs were embedded on the surface of the PGMA matrix. The scanning electron microscopic images revealed that the fabrication of CuNPs on the PGMA matrix possess different shapes and changes the morphology and nature of PGMA beads significantly. The fluorescent micrograph also confirmed that the CuNPs were doped on the PGMA surface. The thermal studies have demonstrated that the CuNPs deposition on the surface of PGMA beads had a significant effect.

Monolithic Composite “Pressure + Acceleration + Temperature + Infrared” Sensor Using a Versatile Single-Sided “SiN/Poly-Si/Al” Process-Module

Directory of Open Access Journals (Sweden)

Xinxin Li

2013-01-01

Full Text Available We report a newly developed design/fabrication module with low-cost single-sided “low-stress-silicon-nitride (LS-SiN/polysilicon (poly-Si/Al” process for monolithic integration of composite sensors for sensing-network-node applications. A front-side surface-/bulk-micromachining process on a conventional Si-substrate is developed, featuring a multifunctional SiN/poly-Si/Al layer design for diverse sensing functions. The first “pressure + acceleration + temperature + infrared” (PATIR composite sensor with the chip size of 2.5 mm × 2.5 mm is demonstrated. Systematic theoretical design and analysis methods are developed. The diverse sensing components include a piezoresistive absolute-pressure sensor (up to 700 kPa, with a sensitivity of 49 mV/MPa under 3.3 V supplied voltage, a piezoresistive accelerometer (±10 g, with a sensitivity of 66 μV/g under 3.3 V and a −3 dB bandwidth of 780 Hz, a thermoelectric infrared detector (with a responsivity of 45 V/W and detectivity of 3.6 × 107 cm·Hz1/2/W and a thermistor (−25–120 °C. This design/fabrication module concept enables a low-cost monolithically-integrated “multifunctional-library” technique. It can be utilized as a customizable tool for versatile application-specific requirements, which is very useful for small-size, low-cost, large-scale sensing-network node developments.

Mucoadhesive properties of low molecular weight chitosan- or glycol chitosan- and corresponding thiomer-coated poly(isobutylcyanoacrylate) core-shell nanoparticles.

Science.gov (United States)

Palazzo, Claudio; Trapani, Giuseppe; Ponchel, Gilles; Trapani, Adriana; Vauthier, Christine

2017-08-01

The aim of the present work was to evaluate the mucoadhesive properties of poly(isobutyl cyanoacrylate) (PIBCA) nanoparticles (NPs) coated with Low Molecular Weight (LMW) chitosan (CS)- and glycol chitosan (GCS)-based thiomers as well as with the corresponding LMW unmodified polysaccharides. For this purpose, all the CS- and GCS-based thiomers were prepared under simple and mild conditions starting from the LMW unmodified polymers CS and GCS. The resulting NPs were of spherical shape with diameters ranging from 400 to 600nm and 187 to 309nm, for CS- and GCS-based NPs, respectively. The mucoadhesive characteristics of these core shell NPs were studied in Ussing chambers measuring the percentage of NPs stuck on the mucosal of fresh intestinal tissue after 2h of incubation. Moreover, incubation of nanoparticle formulations with the intestinal tissue induced changes in transmucosal electrical resistance which were measured to gain information into the opening of tight junctions and to control the integrity of the mucosa. Thus, it was found that PIBCA NPs coated with the GCS-Glutathione conjugate (GCGPIBCA NPs) possessed the most favorable mucoadhesive performances. Moreover, both GCGPIBCA- and GCS-N-acetyl-cysteine (GCNPIBCA)-core-shell NPs might induced an enlargement of the epithelial cell tight junctions. In conclusion, coating of PIBCA NPs with GCS-based thiomers may be useful for improving the mucoadhesive and permeation properties of these nanocarriers. Copyright © 2017 Elsevier B.V. All rights reserved.

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

OpenAIRE

P. Sangeetha; K. Jeganathan; V. Ramakrishnan

2013-01-01

The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E2 (high) and A1 (LO) phonon mode of InN core at 490 and 590 cm−1 respectively and E2 (high) phonon mode of GaN shell at 573 cm−1. The free carrier concentration of InN core is foun...

Activismo, política y subversión en la literatura niuyorriqueña: del programa poético-político de Miguel Algarín a la poética menor de Tato Laviera

Directory of Open Access Journals (Sweden)

Alejo López

2014-01-01

Full Text Available Este trabajo se propone dar cuenta de la relación entre poesía y política desarrollada por la tradición literaria niuyorriqueña. A partir de un análisis comparativo de las diversas modulaciones a través de las cuales esta relación fundamental se configuró en la obra de un corpus de autores emblemáticos de la primera generación niuyorriqueña, intentaremos demostrar cómo esta relación entre poesía y política oscila entre una modulación agonística de carácter contestatario y otra que sostiene su politicidad a través de la configuración de una literatura menor en su sentido deleuzeano. La poesía niuyorriqueña es definida por sus fundadores (Algarín, Esteves como “una afirmación de lucha política” , entendida esta como la oposición confrontativa contra las fuerzas sociales que recluyen a la comunidad a una posición marginal. Sin embargo figuras como las de Víctor Hernández Cruz o Tato Laviera pre- sentan una modulación diferente de esta articulación agonística entre literatura y política, especialmente Laviera, en cuya obra no encontramos una articulación entre poesía y política en tanto praxis diferenciadas, sino que ambas se hallan integradas en un mismo nivel a través de la configuración de una lengua y una identidad inasimilables e indómitas, en tanto instru- mentos de resistencia frente a los sistemas de asimilación y marginalización, lo que deviene, finalmente, en la constitución de una “literatura menor” , un tipo de literatura cuya potencia política surge del trabajo contrahegemónico de una lengua menor dentro de otra mayor.

Probing the structural dependence of carbon space lengths of poly(N-hydroxyalkyl acrylamide)-based brushes on antifouling performance.

Science.gov (United States)

Yang, Jintao; Zhang, Mingzhen; Chen, Hong; Chang, Yung; Chen, Zhan; Zheng, Jie

2014-08-11

Numerous biocompatible antifouling polymers have been developed for a wide variety of fundamental and practical applications in drug delivery, biosensors, marine coatings, and many other areas. Several antifouling mechanisms have been proposed, but the exact relationship among molecular structure, surface hydration property, and antifouling performance of antifouling polymers still remains elusive. Here this work strives to provide a better understanding of the structure-property relationship of poly(N-hydroxyalkyl acrylamide)-based materials. We have designed, synthesized, and characterized a series of polyHAAA brushes of various carbon spacer lengths (CSLs), that is, poly(N-hydroxymethyl acrylamide) (polyHMAA), poly(N-(2-hydroxyethyl)acrylamide) (polyHEAA), poly(N-(3-hydroxypropyl)acrylamide) (polyHPAA), and poly(N-(5-hydroxypentyl)acrylamide) (polyHPenAA), to study the structural dependence of CSLs on their antifouling performance. HMAA, HEAA, HPAA, and HPenAA monomers contained one, two, three, and five methylene groups between hydroxyl and amide groups, while the other groups in polymer backbones were the same as each other. The relation of such small structural differences of polymer brushes to their surface hydration and antifouling performance was studied by combined experimental and computational methods including surface plasmon resonance sensors, sum frequency generation (SFG) vibrational spectroscopy, cell adhesion assay, and molecular simulations. Antifouling results showed that all polyHAAA-based brushes were highly surface resistant to protein adsorption from single protein solutions, undiluted blood serum and plasma, as well as cell adhesion up to 7 days. In particular, polyHMAA and polyHEAA with the shorter CSLs exhibited higher surface hydration and better antifouling ability than polyHPMA and polyHPenAA. SFG and molecular simulations further revealed that the variation of CSLs changed the ratio of hydrophobicity/hydrophilicity of polymers

Thermal analysis of polyaniline poly(N-vinylpyrrolidone)-stabilized dispersions

Czech Academy of Sciences Publication Activity Database

Peřinka, N.; Držková, M.; Hajná, Milena; Jašúrek, B.; Šulcová, P.; Syrový, T.; Kaplanová, M.; Stejskal, Jaroslav

2014-01-01

Roč. 116, č. 2 (2014), s. 589-595 ISSN 1388-6150 R&D Projects: GA TA ČR TE01020022 Institutional support: RVO:61389013 Keywords : polyaniline * poly(N-vinylpyrrolidone) * dispersion Subject RIV: CG - Electrochemistry Impact factor: 2.042, year: 2014

Synthesis of amphiphilic poly(ε-caprolactone)-b-poly( N-vinylcaprolactam) block copolymers via the combination of RAFT polymerization and click chemistry

International Nuclear Information System (INIS)

Assis, Paulo Henrique; Aguiar, Graziele Aparecida de Jesus; Moraes, Rodolfo Minto de; Medeiros, Simone de Fatima; Santos, Amilton Martins

2016-01-01

Full text: In recent years, well-defined block copolymers composed of a hydrophilic and hydrophobic segments have gained much interest as drug carriers, because of their enhanced solubility and sustained release of the drug in controlled delivery systems [1]. The development of strategies to obtain block copolymers has attracted considerable attention, due to the possibility to combine characteristic properties of the homopolymers. A wide variety of well-defined block copolymers have been successfully synthesized by combining the efficiency and selectivity of click chemistry with the powerful RAFT polymerization mechanism. In the present work, well-defined amphiphilic, biocompatible, partially biodegradable, and thermosensitive poly(ε-caprolactone)-b-poly(N-vinylcaprolactam) (PCL-b-PNVCL) block copolymers were synthesized by combining ring opening polymerization (ROP), reversible addition-fragmentation chain transfer (RAFT) polymerization and subsequent click chemistry reaction. Alkyne-terminated poly(ε-caprolactone) (alkyne-PCL) was obtained by the ring opening polymerization of ε-caprolactone (ε-CL) using propargyl alcohol as initiator and stannous-2-ethylhexanoate [Sn(Oct) 2 ] as catalyst. The azide end-capped-poly(N-vinylcaprolactam) (PNVCL-N 3 ) was synthesized by reversible addition-fragmentation chain transfer/macromolecular design via interchange of xanthates (RAFT/MADIX) polymerization of the N-vinylcaprolactam (NVCL) mediated by a novel chain transfer agent comprising an azide function , 2-azidoethyl[(ethoxycarbonothioyl)thio](phenyl)acetate. These functionalized homopolymers, alkyne-PCL and PNVCL-N 3 , were coupled by the 1,3 dipolar cycloaddition reaction in order to obtain the corresponding block copolymers. These (co)polymers were characterized by FTIR, 1 H NMR and GPC measurements. Reference: 1. RAMESH, K., SINGH, S., MITRA, K., CHATTOPADHYAY, D., MISRA, N., & RAY, B. (2015). Colloid and Polymer Science, 1-9. (author)

Controllable dielectric and electrical performance of polymer composites with novel core/shell-structured conductive particles through biomimetic method

International Nuclear Information System (INIS)

Yang, Dan; Tian, Ming; Wang, Wencai; Li, Dongdong; Li, Runyuan; Liu, Haoliang; Zhang, Liqun

2013-01-01

Highlights: ► Conductive core/shell-structured particles were synthesized by biomimetic method. ► These particles with silica/poly(dopamine)/silver core and poly(dopamine) shell. ► Dielectric composites were prepared with resulted particles and silicone elastomer. ► The dielectric properties of the composites can be controlled by shell thickness. ► This biomimetic method is simple, nontoxic, efficient and easy to control. - Abstract: Novel silica/poly(dopamine)/silver (from inner to outer) (denoted as SiO 2 /PDA/Ag) conductive micro-particles were first synthesized by biomimetic poly(dopamine) coating. These micro-particles were then coated with a poly(dopamine) layer to form core/shell-structured particles, with silica/poly(dopamine)/silver core and poly(dopamine) shell (denoted as SiO 2 /PDA/Ag/PDA). This multilayer core/shell micro-particles were confirmed by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscope. Polymer composites were then prepared by mechanical blending of poly(dimethyl siloxane) and the core/shell-structured particles. It was found that the silver layer and the poly(dopamine) shell had good adhesion with substrate and they kept intact even under violent shearing stress during mechanical mixing. The effect of the thickness of outermost poly(dopamine) shell as well as the loading amount of this filler on the dielectric and electrical properties of the composites was further studied. The results showed that the dielectric constant, dielectric loss, and conductivity of the composites decreased with increasing shell thickness (10–53 nm) at the same loading level. And the maximal dielectric constant of composites was achieved in the composites filled with SiO 2 /PDA/Ag/PDA (with 10–15 nm PDA shell) particles, which was much larger than that of the composite filled with SiO 2 /PDA/Ag particles without insulative PDA shell. At the same time, the composites can change

Hole drift mobility in poly(hexylphenylsilane)

International Nuclear Information System (INIS)

Kunimi, Y.; Seki, S.; Tagawa, S.

2000-01-01

Poly(n-alkylphenylsilane)s in which n-alkyl were changed from methyl to octyl were polymerized. Hole transport properties of poly(alkyllphenylsilane)s were systematically studied by the DC time-of-flight (TOF) technique. While the hole drift mobility of poly(methylphenylsilane) increased monotonously in entire field, those of poly(hexylphenylsilane) and poly(octylphenylsilane) decreased with increase in the field strength. Temperature dependence of hole drift mobility in those polymers was small. On the basis of Baessler's disorder formalism the mobility was analyzed quantitatively to disserve complex contributions of charge transport. The analyzed results indicated that with increase in the length of n-alkyl side-groups, the energetic disorder of hopping sites became smaller and the disorder of distance between hopping sites became larger. These results were supported by the results obtained by UV absorption measurement and positron annihilation life-time spectroscopy measurement. (author)

Preparation and characterization of emulsifier-free polyphenylsilsesquioxane-poly (styrene–butyl acrylate) hybrid particles

Energy Technology Data Exchange (ETDEWEB)

Bai, Ruiqin; Qiu, Teng, E-mail: qiuteng@mail.buct.edu.cn; Han, Feng; He, Lifan; Li, Xiaoyu, E-mail: lixy@mail.buct.edu.cn

2013-10-01

The core–shell polyphenylsilsesquioxane-poly (styrene–butyl acrylate) hybrid latex paticles with polyphenylsilsesquioxane as core and poly (styrene–butyl acrylate) as shell were successfully synthesized by seeded emulsion polymerization using polyphenylsisesquioxane (PPSQ) latex particles as seeds. X-ray diffraction (XRD) indicated that the polyphenylsilsesquioxane (PPSQ) had ladder structure, and PPSQ had incorporated into the hybrid latex particles. Transmission electron microscopy (TEM) confirmed that the resultant hybrid latex particles had the core–shell structure. TEM and dynamic light scattering (DLS) analysis indicated that the polyphenylsisesquioxane latex particles and obtained core–shell hybrid latex particles were uniform and possessed narrow size distributions. X-ray photoelectron spectroscopy (XPS) analysis also indicated that the PPSQ core particles were enwrapped by the polymer shell. In addition, compared with pure poly (styrene–butyl acrylate) latex film, the polyphenylsilsesquioxane-poly (styrene–butyl acrylate) hybrid latex film exhibited lower water uptake, higher pencil hardness and better thermal stability.

Síntesis y almacenamiento de carga de la nueva aleación polipirrol/poli(ácido maleico-olefina

Directory of Open Access Journals (Sweden)

D´eramo, F.

2000-06-01

Full Text Available The influence that the electrosynthesis conditions of the polypyrrole/poly(maleic acid-co-olefin blend have on the charge storage ability (amount of electrical charge stored (mC per unit mass (mg of electrogenerated polymer has been analysed. This is the initial step for the optimisation, pyrrole and poly (maleic acid-co-olefin concentrations and the polymerisation temperature have been the studied parameters. Optimising these ones, we could obtain materials with average storage charge of 120mc.mg-1.

Se ha analizado la influencia de diversas variables de síntesis sobre la capacidad de almacenamiento de carga (mC de carga almacenada / mg de polímero electrogenerado de aleaciones poliméricas de polipirrol/poli(ácido maléico-co-olefina, como paso inicial para la optimación de este material para su aplicación en baterías todo orgánicas. Las variables de estudio han sido: el potencial y el tiempo de polimerización, las concentraciones de pirrol y poli(ácido maléico-co-olefina y la temperatura de la solución de polimerización. Optimando estos parámetros se ha logrado sintetizar materiales con una capacidad promedio de almacenamiento de carga de 120 mC. mg-1.

In vivo non-invasive optical imaging of temperature-sensitive co-polymeric nanohydrogel

Science.gov (United States)

Chen, Haiyan; Zhang, Jian; Qian, Zhiyu; Liu, Fei; Chen, Xinyang; Hu, Yuzhu; Gu, Yueqing

2008-05-01

Assessment of hyperthermia in pathological tissue is a promising strategy for earlier diagnosis of malignant tumors. In this study, temperature-sensitive co-polymeric nanohydrogel poly(N-isopropylacrylamide-co-acrylic acid) (PNIPA-co-AA) was successfully synthesized by the precipitation polymerization method. The diameters of nanohydrogels were controlled to be less than 100 nm. Also the lower critical solution temperature (LCST, 40 °C) was manipulated above physiological temperature after integration of near-infrared (NIR) organic dye (heptamethine cyanine dye, HMCD) within its interior cores. NIR laser light (765 nm), together with sensitive charge coupled device (CCD) cameras, were designed to construct an NIR imaging system. The dynamic behaviors of PNIPA-co-AA-HMCD composites in denuded mice with or without local hyperthermia treatment were real-time monitored by an NIR imager. The results showed that the PNIPA-co-AA-HMCD composites accumulated in the leg treated with local heating and diffused much slower than that in the other leg without heating. The results demonstrated that the temperature-responsive PNIPA-co-AA-HMCD composites combining with an NIR imaging system could be an effective temperature mapping technique, which provides a promising prospect for earlier tumor diagnosis and thermally related therapeutic assessment.

In vivo non-invasive optical imaging of temperature-sensitive co-polymeric nanohydrogel

International Nuclear Information System (INIS)

Chen Haiyan; Hu Yuzhu; Zhang Jian; Liu Fei; Chen Xinyang; Gu Yueqing; Qian Zhiyu

2008-01-01

Assessment of hyperthermia in pathological tissue is a promising strategy for earlier diagnosis of malignant tumors. In this study, temperature-sensitive co-polymeric nanohydrogel poly(N-isopropylacrylamide-co-acrylic acid) (PNIPA-co-AA) was successfully synthesized by the precipitation polymerization method. The diameters of nanohydrogels were controlled to be less than 100 nm. Also the lower critical solution temperature (LCST, 40 deg. C) was manipulated above physiological temperature after integration of near-infrared (NIR) organic dye (heptamethine cyanine dye, HMCD) within its interior cores. NIR laser light (765 nm), together with sensitive charge coupled device (CCD) cameras, were designed to construct an NIR imaging system. The dynamic behaviors of PNIPA-co-AA-HMCD composites in denuded mice with or without local hyperthermia treatment were real-time monitored by an NIR imager. The results showed that the PNIPA-co-AA-HMCD composites accumulated in the leg treated with local heating and diffused much slower than that in the other leg without heating. The results demonstrated that the temperature-responsive PNIPA-co-AA-HMCD composites combining with an NIR imaging system could be an effective temperature mapping technique, which provides a promising prospect for earlier tumor diagnosis and thermally related therapeutic assessment

Synthesis and characterization of poly[N-isopropylacrylamide-co-1-(N,N-bis-carboxymethyl)amino-3-allylglycerol] grafted to magnetic nano-particles for the extraction and determination of fluvoxamine in biological and pharmaceutical samples.

Science.gov (United States)

Panahi, Homayon Ahmad; Tavanaei, Yasamin; Moniri, Elham; Keshmirizadeh, Elham

2014-06-06

In this research, a novel method is reported for the surface grafting of N-isopropylacrylamide as a thermosensitive agent and 1-(N,N-bis-carboxymethyl)amino-3-allylglycerol with an affinity toward fluvoxamine onto magnetic nano-particles modified by 3-mercaptopropyltrimethoxysilane. The grafted nano-particles were characterized by Fourier transform infrared spectroscopy, elemental analysis, and thermogravimetric analysis. The surface morphology was studied with scanning electron microscopy and transmission electron microscopy. The resulting grafted nano-particles were used in solid phase extraction and determining of trace fluvoxamine in biological human fluids and pharmaceutical samples. The profile of the fluvoxamine uptake by the modified magnetic nano-particles indicated good accessibility of the active sites in the grafted copolymer. It was found that the adsorption behavior could be fitted by the Freundlich adsorption isotherm model. It was observed that a maximum amount of fluvoxamine was released at a temperature above the lower critical solution temperature of the polymer. Copyright © 2014 Elsevier B.V. All rights reserved.

Initiated chemical vapor deposition of thermoresponsive poly(N-vinylcaprolactam) thin films for cell sheet engineering.

Science.gov (United States)

Lee, Bora; Jiao, Alex; Yu, Seungjung; You, Jae Bem; Kim, Deok-Ho; Im, Sung Gap

2013-08-01

Poly(N-vinylcaprolactam) (PNVCL) is a thermoresponsive polymer known to be nontoxic, water soluble and biocompatible. Here, PNVCL homopolymer was successfully synthesized for the first time by use of a one-step vapor-phase process, termed initiated chemical vapor deposition (iCVD). Fourier transform infrared spectroscopy results showed that radical polymerization took place from N-vinylcaprolactam monomers without damaging the functional caprolactam ring. A sharp lower critical solution temperature transition was observed at 31°C from the iCVD poly(N-vinylcaprolactam) (PNVCL) film. The thermoresponsive PNVCL surface exhibited a hydrophilic/hydrophobic alteration with external temperature change, which enabled the thermally modulated attachment and detachment of cells. The conformal coverage of PNVCL film on various substrates with complex topography, including fabrics and nanopatterns, was successfully demonstrated, which can further be utilized to fabricate cell sheets with aligned cell morphology. The advantage of this system is that cells cultured on such thermoresponsive surfaces could be recovered as an intact cell sheet by simply lowering the temperature, eliminating the need for conventional enzymatic treatments. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Synthesis of Poly(N-vinyl-2-pyrrolidone-co-methyl methacrylate by Maghnite-H+ a Non-toxic Catalyst

Directory of Open Access Journals (Sweden)

Mohamed Benadda

2014-10-01

Full Text Available In the present work poly (N-vinyl-2-pyrrolidone-co-methyl methacrylate copolymers were prepared successfully and cleanly by a one step process via cationic copolymerization of N-vinyl-2-pyrrolidone (NVP with methyl methacrylate (MMA, in heterogeneous phase using “Maghnite-H+” (Mag-H+ as catalyst in bulk, Maghnite is a montmorillonite sheet silicate clay exchanged with protons to produce Maghnite-H+. Temperature is varied between 20 and 80 °C. The effects of reaction temperature, amount of Mag-H+ on the yield and the intrinsic viscosity (η were investigated. A typical reaction product of poly (NVP-co- MMA was analyzed by infra red spectroscopy (FTIR and 1H-NMR, 13C-NMR spectroscopy as well as by viscosimetry. © 2014 BCREC UNDIP. All rights reservedReceived: 24th November 2013; Revised: 30th June 2014; Accepted: 8th July 2014How to Cite: Benadda, M., Ferrahi, M.I., Belbachir, M. (2014. Synthesis of Poly(N-vinyl-2-pyrrolidone-co-methyl methacrylate by Maghnite-H+ a Non-toxic Catalyst. Bulletin of Chemical Reaction Engineering & Catalysis, 9 (3: 201-206. (doi: 10.9767/bcrec.9.3.5743.201-206Permalink/DOI: http://dx.doi.org/10.9767/bcrec.9.3.5743.201-206

Raman study of magnesium induced conversion of polyU·polyA duplexes to polyU·polyA·polyU triplexes

OpenAIRE

Herrera, S. J. Espinoza; Štepánek, J.

2010-01-01

Raman titration experiment with magnesium salt added gradually to aqueous solution of duplexes formed by RNA homopolynucleotides polyU and polyA was performed to reveal its effect on homopolynucleotide complexes. Statistical analysis of obtained spectral set has confirmed the effect already found by less structurally sensitive methods [Nucleic Acids Res. 31(17) (2003), 5101–5107] that at sufficiently high concentrations magnesium causes transformation of polyU·polyA duplexes to polyU·polyA·po...

Pt silicide/poly-Si Schottky diodes as temperature sensors for bolometers

Energy Technology Data Exchange (ETDEWEB)

Yuryev, V. A., E-mail: vyuryev@kapella.gpi.ru; Chizh, K. V.; Chapnin, V. A.; Mironov, S. A.; Dubkov, V. P.; Uvarov, O. V.; Kalinushkin, V. P. [A. M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov Street, Moscow 119991 (Russian Federation); Senkov, V. M. [P. N. Lebedev Physical Institute of the Russian Academy of Sciences, 53 Leninskiy Avenue, Moscow 119991 (Russian Federation); Nalivaiko, O. Y. [JSC “Integral” – “Integral” Holding Management Company, 121A, Kazintsa I. P. Street, Minsk 220108 (Belarus); Novikau, A. G.; Gaiduk, P. I. [Belarusian State University, 4 Nezavisimosti Avenue, 220030 Minsk (Belarus)

2015-05-28

Platinum silicide Schottky diodes formed on films of polycrystalline Si doped by phosphorus are demonstrated to be efficient and manufacturable CMOS-compatible temperature sensors for microbolometer detectors of radiation. Thin-film platinum silicide/poly-Si diodes have been produced by a CMOS-compatible process on artificial Si{sub 3}N{sub 4}/SiO{sub 2}/Si(001) substrates simulating the bolometer cells. Layer structure and phase composition of the original Pt/poly-Si films and the Pt silicide/poly-Si films synthesized by a low-temperature process have been studied by means of the scanning transmission electron microscopy; they have also been explored by means of the two-wavelength X-ray structural phase analysis and the X-ray photoelectron spectroscopy. Temperature coefficient of voltage for the forward current of a single diode is shown to reach the value of about −2%/ °C in the temperature interval from 25 to 50 °C.

Phase behavior of polystyrene-block-poly(n-alkyl methacrylate) copolymers investigated by SANS, SAXS, and temperature-dependent FTIR spectroscopy

International Nuclear Information System (INIS)

Ryu, Du Yeol; Lee, Dong Hyun; Kim, Hye Jeong; Kim, Jin Kon; Jung, Y. M.; Kim, S. B.

2005-01-01

The phase behavior of polystyrene-block -poly(n-alkyl methacrylate) (PS-PnAMA) copolymer were investigated by Small-Angle Neutron Scattering (SANS), Small-Angle X-ray Scattering (SAXS), and temperature-dependent Fourier Transform Infrared (FTIR) spectroscopy. Also, the effect of hydrostatic pressure on the transition temperatures was studied by using SANS with pressure controller. Phase behavior was changed significantly with the change of alkyl number (n). For n = 2∼4, only Lower Disordered-to-Order Tansition (LDOT) was observed, whereas the Ordered-to-Disorder (ODT) was found for n =1 and n =6. Finally, a closed-loop phase behavior was found for n =5. Using incompressible random phase approximation, the segmental interactions (χ) between PS and PnAMA for all n values were obtained. The standard expression of χ = a + b/T (where T is the absolute temperature) was valid only for n =1 and n =6. But, this relationship was not valid any more for n = 2∼4. For n =5, a more complex behavior of χ upon temperature was observed. We investigated, by using temperature-dependent FTIR, the mechanism why as closed loop phase behavior was observed for n =5. Interestingly, the conformation of C-C-O stretching band of the PnPMA chain (n=5) (and thus the directional enthapic gain) was different in the two disordered states, and, therefore, the driving force to induce the disordered state at lower temperatures was different from that at higher temperatures

MOVPE growth of position-controlled InGaN / GaN core-shell nanorods

Energy Technology Data Exchange (ETDEWEB)

Mandl, Martin [Osram Opto Semiconductors GmbH, Regensburg (Germany); Institut fuer Halbleitertechnik, TU Braunschweig (Germany); Schimpke, Tilman; Binder, Michael; Galler, Bastian; Lugauer, Hans-Juergen; Strassburg, Martin [Osram Opto Semiconductors GmbH, Regensburg (Germany); Wang, Xue; Ledig, Johannes; Ehrenburg, Milena; Wehmann, Hergo-Heinrich; Waag, Andreas [Institut fuer Halbleitertechnik, TU Braunschweig (Germany); Kong, Xiang; Trampert, Achim [Paul-Drude-Institut fuer Festkoerperelektronik, Berlin (Germany)

2013-07-01

Core-shell group III-nitride nano- and microrods (NAMs) enable a significant increase of the active layer area by exploiting the non-polar side facets (m-planes) and thus can potentially contribute to mitigating the so-called efficiency droop in LEDs. GaN NAMs exhibiting high aspect ratios were grown in a production-type MOVPE system. Low V/III ratio, hydrogen-rich carrier gas mixture and surfactants supported the 3D growth of the pencil-shape n-type GaN core. Desired narrow distributions of shape, diameter and height were achieved. The arrangement of the NAMs was controlled by patterns etched into SiO{sub 2} masks deposited on GaN templates. The active layer (InGaN/GaN SQW and MQWs) and the layer for the p-side were deposited with 2D-like conditions wrapped around the core. The crystalline quality of the NAMs, shell growth rates and the Indium distribution were investigated by high resolution transmission electron microscopy. Furthermore, optical emission was studied using density-dependent photoluminescence spectroscopy.

Reinforcement of Natural Rubber with Core-Shell Structure Silica-Poly(Methyl Methacrylate Nanoparticles

Directory of Open Access Journals (Sweden)

Qinghuang Wang

2012-01-01

Full Text Available A highly performing natural rubber/silica (NR/SiO2 nanocomposite with a SiO2 loading of 2 wt% was prepared by combining similar dissolve mutually theory with latex compounding techniques. Before polymerization, double bonds were introduced onto the surface of the SiO2 particles with the silane-coupling agent. The core-shell structure silica-poly(methyl methacrylate, SiO2-PMMA, nanoparticles were formed by grafting polymerization of MMA on the surface of the modified SiO2 particles via in situ emulsion, and then NR/SiO2 nanocomposite was prepared by blending SiO2-PMMA and PMMA-modified NR (NR-PMMA. The Fourier transform infrared spectroscopy results show that PMMA has been successfully introduced onto the surface of SiO2, which can be well dispersed in NR matrix and present good interfacial adhesion with NR phase. Compared with those of pure NR, the thermal resistance and tensile properties of NR/SiO2 nanocomposite are significantly improved.

The Melting Behavior and Thermal Stability of Green Poly(L-lactic acid) with N, N, N, N'-Tetra(benzoyl) Ethylene Diamine Tetraacetic Acid Dihydrazide

International Nuclear Information System (INIS)

Cai, Y.; Qiang Xu, Q.; Ren, L.; Zhao, L.

2015-01-01

The thermal properties of green poly(L-lactic acid) (PLLA) with N, N, N, N'-tetra(benzoyl) ethylene diamine tetraacetic acid dihydrazide (NA) at different conditions were investigated. The melting behavior of PLLA/NA sample after isothermal crystallization at 100 degree C showed that the low-temperature melting peak shifted to high temperature with increasing of crystallization time. However, the high-temperature melting peak did not show any change. Meantime, the melting enthalpy of cold crystallization was higher than that of hot crystallization, and the difference between cold crystallization and hot crystallization increased from 0.31 J/g to 0.89 J/g with increasing of crystallization time. Heating or cooling rate affected the melting behavior of PLLA, the low-temperature and high-temperature melting peak shifted to low temperature with increasing of rate, and the ratio of melting peak area between low-temperature melting peak and high-temperature melting peak decreased. Thermal stability of PLLA/NA indicated that PLLA/NA only exhibited one decomposition stage as decomposition of PLLA. (author)

Temperature-sensitive porous membrane production through radiation co-grafting of NIPAAm on/in PVDF porous membrane

International Nuclear Information System (INIS)

Liu Qi; Zhu Zhiyong; Yang Xiaomin; Chen Xiliang; Song Yufeng

2007-01-01

N-isopropylacrylamide (NIPAAm) monomer was grafted on and in poly(vinylidene fluoride) (PVDF) micro-pore membrane by γ-irradiation. The influence of irradiation and reaction conditions on the grafting yield was investigated in detail. The chemical structure of NIPAAm-grafted PVDF (NIPAAm-g-PVDF) membrane was characterized by Fourier transform infrared spectra and X-ray photoelectron spectra measurements. The morphology of the sample surface as well as the cross-section before and after grafting was characterized by scanning electron microscope. The temperature sensitive properties of the membrane were monitored by measuring the conductance as well as the water flux through the sample thickness. The results show that the membrane exhibits clearly temperature-sensitive permeability to water as expected, i.e. the permeability of water changes dramatically as the temperature goes over the lower critical solution temperature of NIPAAm

Self-assembly of graft polyurethanes having both crystallizable poly({epsilon}-caprolactone) blocks and soft poly(n-butyl acrylate) segments

Energy Technology Data Exchange (ETDEWEB)

Ibarboure, E.; Baron, A.; Papon, E. [Laboratoire de Chimie des Polymeres Organiques (LCPO), CNRS, Universite Bordeaux I. 16, Avenue Pey Berland, 33607, Pessac-Cedex (France); Rodriguez-Hernandez, J., E-mail: jrodriguez@enscpb.f [Laboratoire de Chimie des Polymeres Organiques (LCPO), CNRS, Universite Bordeaux I. 16, Avenue Pey Berland, 33607, Pessac-Cedex (France)

2009-04-02

We report the self-assembly behavior of graft polyurethanes combining in its structure soft lateral poly(n-butyl acrylate) (PnBuA) chains with rigid and crystallizable polycaprolactone (PCL) segments. Segmented polyurethanes microphase separated into high-glass transition temperature PCL hard and low-glass transition temperature PnBuA soft domains. The variation of the microstructure as a function of the hard segment content (ratio hard to soft segments) within the structure has been studied by using atomic force microscopy. Additionally, the crystallization mechanism appeared to be directly related to the properties of the substrates forming parallel lamellar structures on hydrophilic substrates and perpendicular lamellae with hydrophobic substrates.

Direct correlations of structural and optical properties of three-dimensional GaN/InGaN core/shell micro-light emitting diodes

Science.gov (United States)

Sadat Mohajerani, Matin; Müller, Marcus; Hartmann, Jana; Zhou, Hao; Wehmann, Hergo-H.; Veit, Peter; Bertram, Frank; Christen, Jürgen; Waag, Andreas

2016-05-01

Three-dimensional (3D) InGaN/GaN quantum-well (QW) core-shell light emitting diodes (LEDs) are a promising candidate for the future solid state lighting. In this contribution, we study direct correlations of structural and optical properties of the core-shell LEDs using highly spatially-resolved cathodoluminescence spectroscopy (CL) in combination with scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). Temperature-dependent resonant photoluminescence (PL) spectroscopy has been performed to understand recombination mechanisms and to estimate the internal quantum efficiency (IQE).

Poly(ethylene oxide) surfactant polymers

OpenAIRE

VACHEETHASANEE, KATANCHALEE; WANG, SHUWU; QIU, YONGXING; MARCHANT, ROGER E.

2004-01-01

We report on a series of structurally well-defined surfactant polymers that undergo surface-induced self-assembly on hydrophobic biomaterial surfaces. The surfactant polymers consist of a poly(vinyl amine) backbone with poly(ethylene oxide) and hexanal pendant groups. The poly(vinyl amine) (PVAm) was synthesized by hydrolysis of poly(N-vinyl formamide) following free radical polymerization of N-vinyl formamide. Hexanal and aldehyde-terminated poly (ethyleneoxide) (PEO) were simultaneously att...

Study of poly(N,N-dimethylacrylamide)/CdS nanocomposite organic/inorganic gels.

Science.gov (United States)

Bekiari, Vlasoula; Pagonis, Konstantinos; Bokias, Georgios; Lianos, Panagiotis

2004-09-14

CdS nanoparticles have been synthesized and stabilized in poly(N,N-dimethylacrylamide) hydrogels. The properties of the composite material have been characterized by UV-vis spectroscopy, scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, and steady-state and time-resolved luminescence spectroscopy. This material can be obtained in three different states: swollen, shrunk, and freeze-dried. The swollen and the freeze-dried states correspond to a nanocomposite organic/inorganic (wet or dry) gel containing CdS nanoparticles of approximately 50 nm diameter while the shrunk state is a two-phase system containing CdS crystals, which precipitate forming interesting geometrical shapes.

Determination of the optical properties of PNIPAAm gels used in biological applications

CSIR Research Space (South Africa)

Singh, A

2009-07-01

Full Text Available Poly(N-isopropylacrylamide) that is PNIPAAm is a temperature sensitive smart material which displays a lower critical solution temperature (LCST) at 33-35oC. At the lower critical solution temperature, the gel changes from hydrophilic to hydrophobic...

Generation and thermally adjustable catalysis of silver nanoparticle immobilized temperature-sensitive nanocomposite

Science.gov (United States)

Xu, Jun; Zhou, Tao; Jia, Lei; Shen, Xiaoke; Li, Xiaohui; Li, Huijun; Xu, Zhouqing; Cao, Jianliang

2017-03-01

The rise in environmental issues due to the catalytic degradation of pollutants in water has received much attention. In this report, a facile method was developed for the generation of a novel thermosensitive Ag-decorated catalyst, SiO2@PNIPAM@Ag (the average particle size is around 540 nm), through atom transfer radical polymerization (ATRP) and mild reducing reactions. First, poly(N-isopropylacrylamide) (PNIPAM) was used to create a shell around mercapto-silica spheres that allowed for enhanced catalyst support dispersion into water. Second, through a mild reducing reaction, these Ag nanoparticles (NPs) were then anchored to the surface of SiO2@PNIPAM spheres. The resulting catalyst revealed catalytic activity to degrade various nitrobenzenes and organic dyes in an aqueous solution with sodium borohydride (NaBH4) at ambient temperature. The catalytic activity can be adjusted in different temperatures through the aggregation or dispersion of Ag catalyst on the polymer supporters, which is due to the thermosensitive PNIPAM shell. The ease of preparation and efficient catalytic activity of the catalyst can make it a promising candidate for the use in degrading organic pollutants for environmental remediation.

Generation and thermally adjustable catalysis of silver nanoparticle immobilized temperature-sensitive nanocomposite

Energy Technology Data Exchange (ETDEWEB)

Xu, Jun; Zhou, Tao; Jia, Lei, E-mail: jlxj@hpu.edu.cn; Shen, Xiaoke; Li, Xiaohui; Li, Huijun; Xu, Zhouqing; Cao, Jianliang, E-mail: caojianliang@hpu.edu.cn [Henan Polytechnic University, College of Chemistry and Chemical Engineering (China)

2017-03-15

The rise in environmental issues due to the catalytic degradation of pollutants in water has received much attention. In this report, a facile method was developed for the generation of a novel thermosensitive Ag-decorated catalyst, SiO{sub 2}@PNIPAM@Ag (the average particle size is around 540 nm), through atom transfer radical polymerization (ATRP) and mild reducing reactions. First, poly(N-isopropylacrylamide) (PNIPAM) was used to create a shell around mercapto-silica spheres that allowed for enhanced catalyst support dispersion into water. Second, through a mild reducing reaction, these Ag nanoparticles (NPs) were then anchored to the surface of SiO{sub 2}@PNIPAM spheres. The resulting catalyst revealed catalytic activity to degrade various nitrobenzenes and organic dyes in an aqueous solution with sodium borohydride (NaBH{sub 4}) at ambient temperature. The catalytic activity can be adjusted in different temperatures through the aggregation or dispersion of Ag catalyst on the polymer supporters, which is due to the thermosensitive PNIPAM shell. The ease of preparation and efficient catalytic activity of the catalyst can make it a promising candidate for the use in degrading organic pollutants for environmental remediation.

Microfluidic Fabrication of Morphology-Controlled Polymeric Microspheres of Blends of Poly(4-butyltriphenylamine and Poly(methyl methacrylate

Directory of Open Access Journals (Sweden)

Saki Yoshida

2018-04-01

Full Text Available Multicomponent polymer particles with specific morphology are promising materials exhibiting novel functionality which cannot be obtained with single-component polymer particles. Particularly, the preparation of such kinds of polymer particles involving electrically or optically active conjugated polymers with uniform size is a challenging subject due to their intense demands. Here, microspheres of binary polymer blend consisting of poly(4-butyltriphenylamine (PBTPA/poly(methyl methacrylate (PMMA (1:1 in weight were produced via a microfluidic emulsification with a Y-shaped microreactor, and a subsequent solvent evaporation method. The flow rate of the dispersed phase (polymer solution was fixed to 7 µL/min, and 140 or 700 µL/min of the flow rate of the continuous phase (aqueous 0.6 wt % of poly(vinyl alcohol (PVA solution was utilized to produce the dispersion with different diameter. The concentration of dispersed phase was adjusted to 0.1 or 1.0 w/v%. Core-shell, Janus and dumbbell type microspheres were obtained dependent on the flow rate of continuous phase. Incomplete core-shell type microspheres were produced for the blend involving low molecular weight PMMA. Complex Janus and core-shell type microspheres were fabricated by the addition of sodium dodecyl sulfate (SDS to continuous phase. It is found that final morphologies are strongly dependent on the initial conditions of dispersion including the particle size suggesting that the morphologies are governed by the kinetical factors together with the conventionally accepted thermodynamic ones.

Polymer electrolytes: an investigation of some poly (N-propylaziridine)/lithium salt compositions

Energy Technology Data Exchange (ETDEWEB)

Baldwin, K R; Golder, A J; Knight, J

1984-04-01

Poly (N-propylaziridine)/lithium salt compositions were synthesized and their electrical conductivities were measured to assess their suitability as electrolytes in safe, leakproof, high energy-density lithium batteries operating at ambient temperature. The effects on conductivity of temperature, and the nature and concentration of the salt were studied. The salts markedly improve conductivity of the compositions over that of the undoped polymer but they are insufficiently conducting to be considered as battery electrolytes, due possibly to ion pairing. Their creep resistance is also low. Less fluid compositions containing higher molecular weight polymers better able to promote ion separation are more suitable. (ESA)

Activismo, política y subversión en la literatura niuyorriqueña: del programa poético-político de Miguel Algarín a la poética menor de Tato Laviera

OpenAIRE

Alejo López

2014-01-01

Este trabajo se propone dar cuenta de la relación entre poesía y política desarrollada por la tradición literaria niuyorriqueña. A partir de un análisis comparativo de las diversas modulaciones a través de las cuales esta relación fundamental se configuró en la obra de un corpus de autores emblemáticos de la primera generación niuyorriqueña, intentaremos demostrar cómo esta relación entre poesía y política oscila entre una modulación agonística de carácter contestatario y o...

Biodegradable flocculants based on polyacrylamide and poly(N,N-dimethylacrylamide) grafted amylopectin.

Science.gov (United States)

Kolya, Haradhan; Tripathy, Tridib

2014-09-01

Synthesis of amylopectin grafted polyacrylamide (AP-g-PAM) and poly(N,N-dimethylacrylamide) (AP-g-PDMA) was carried out by Ce4+ in water medium. The reaction conditions for maximum grafting was optimized by varying the reaction variables, including the concentration of monomers, ceric ammonium nitrate (CAN), amylopectin, reaction time and temperature. The graft copolymers were characterized by FTIR spectroscopy, NMR (both 1H and 13C) spectroscopy, molecular weight determination and molecular weight distribution by using size exclusion chromatography (SEC), thermal analysis (TGA), SEM studies. Biodegradation of the graft copolymers was carried out by enzyme hydrolysis. Flocculation performances of the graft copolymers were evaluated in 1.0 wt% coal and 1.0 wt% silica suspensions. A comparative study of the flocculation performances of AP-g-PDMA and AP-g-PAM was also made. It shows that the flocculation performance of AP-g-PDMA was better than that of AP-g-PAM. AP-g-PDMA performed best when compared with other commercial flocculants in the same suspensions. Copyright © 2014 Elsevier B.V. All rights reserved.

Participación política y violencia de género en América Latina

Directory of Open Access Journals (Sweden)

Laura Albaine

2014-07-01

Full Text Available Este artículo reflexiona a través del análisis de fac- tores socioculturales e institucionales sobre uno de los obstáculos más graves que condicionan la participación política de las mujeres en América Latina: El acoso y vio- lencia política en razón de género. Esta problemática es una nueva expresión que ha adoptado la violencia de gé- nero en la arena política que restringe el ejercicio de los derechos políticos de las mujeres y el derecho a vivir una vida libre de violencia. El acoso y violencia política se manifiesta más allá de los avances normativos logrados en la región orientados a generar condiciones de igualdad en términos de género en la participación política. En consecuencia, a las nor- mas que promueven el acceso de las mujeres a cargos de decisión, tales como cuotas o paridad, deben sumársele cuerpos legales que garanticen, además de sus derechos políticos, su seguridad y sus derechos humanos. AbstractThis paper focuses on a reflection and analysis of socio-cultural and institutional factors that affect wom- en’s political participation Latin America, such as gen- der-based harassment and violence. This problem is a new expression that has adopted gender-based violence in political arena, restricting not only the exercise of women’s political rights but also their right to live a life free of violence. Despite Latin American countries have enacted laws to create conditions in terms of gender equality in polit- ical participation, political harassment and violence still occurs. However, these policy actions are not enough to ensure women’s access to decision-making positions, such as quotas or parity; it must also be legal bodies to ensure, in addition to their political rights, their personal safety and human rights. 

TiN/VN composites with core/shell structure for supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Dong, Shanmu; Chen, Xiao [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Gu, Lin [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 9808577 (Japan); Zhou, Xinhong [Qingdao University of Science and Technology, Qingdao 266101 (China); Wang, Haibo; Liu, Zhihong; Han, Pengxian; Yao, Jianhua; Wang, Li [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Cui, Guanglei, E-mail: cuigl@qibebt.ac.cn [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Chen, Liquan [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)

2011-06-15

Research highlights: {yields} Vanadium and titanium nitride nanocomposite with core-shell structure was prepared. {yields} TiN/VN composites with different V:Ti molar ratios were obtained. {yields} TiN/VN composites can provide promising electronic conductivity and favorable capacity storage. -- Abstract: TiN/VN core-shell composites are prepared by a two-step strategy involving coating of commercial TiN nanoparticles with V{sub 2}O{sub 5}.nH{sub 2}O sols followed by ammonia reduction. The highest specific capacitance of 170 F g{sup -1} is obtained when scanned at 2 mV s{sup -1} and a promising rate capacity performance is maintained at higher voltage sweep rates. These results indicate that these composites with good electronic conductivity can deliver a favorable capacity performance.

Poly(mono/diethylene glycol n-tetradecyl ether vinyl ethers with Various Molecular Weights as Phase Change Materials

Directory of Open Access Journals (Sweden)

Dongfang Pei

2018-02-01

Full Text Available At present, research on the relationship of comb-like polymer phase change material structures and their heat storage performance is scarce. Therefore, this relationship from both micro and macro perspectives will be studied in this paper. In order to achieve a high phase change enthalpy, ethylene glycol segments were introduced between the vinyl and the alkyl side chains. A series of poly(mono/diethylene glycol n-tetradecyl ether vinyl ethers (PC14EnVEs (n = 1, 2 with various molecular weights were polymerized by living cationic polymerization. The results of PC14E1VE and PC14E2VE showed that the minimum number of carbon atoms required for side-chain crystallization were 7.7 and 7.2, which were lower than that reported in the literature. The phase change enthalpy 89 J/g (for poly(mono ethylene glycol n-tetradecyl ether vinyl ethers and 86 J/g (for poly(hexadecyl acrylate were approximately equal. With the increase of molecular weight, the melting temperature, the melting enthalpy, and the initial thermal decomposition temperature of PC14E1VE changed from 27.0 to 28.0 °C, from 95 to 89 J/g, and from 264 to 287 °C, respectively. When the number average molar mass of PC14EnVEs exceeded 20,000, the enthalpy values remained basically unchanged. The introduction of the ethylene glycol chain was conducive to the crystallization of alkyl side chains.

Synthesis of core-fluorescent four-armed star and dicyclic 8-shaped poly(THF)s by electrostatic self-assembly and covalent fixation (ESA–CF) protocol

KAUST Repository

Fujiwara, Susumu; Yamamoto, Takuya; Tezuka, Yasuyuki; Habuchi, Satoshi

2013-01-01

A pair of four-armed star and dicyclic 8-shaped poly(tetrahydrofuran)s, poly(THF)s, possessing a perylene diimide group at the core position (Ia and Ib, respectively) were synthesized by means of an electrostatic self-assembly and covalent fixation (ESA–CF) protocol. Mono- and bifunctional poly(THF)s having N-phenylpiperidinium salt end groups accompanying a perylene diimide tetracarboxylate as a counteranion were prepared by the ion-exchange reaction, and the subsequent covalent conversion by reflux in toluene afforded the corresponding core-fluorescent four-armed star and dicyclic 8-shaped poly(THF)s, (Ia and Ib, respectively) for the use of single-molecule fluorescence microscopy measurements.

Synthesis of core-fluorescent four-armed star and dicyclic 8-shaped poly(THF)s by electrostatic self-assembly and covalent fixation (ESA–CF) protocol

KAUST Repository

Fujiwara, Susumu

2013-12-07

A pair of four-armed star and dicyclic 8-shaped poly(tetrahydrofuran)s, poly(THF)s, possessing a perylene diimide group at the core position (Ia and Ib, respectively) were synthesized by means of an electrostatic self-assembly and covalent fixation (ESA–CF) protocol. Mono- and bifunctional poly(THF)s having N-phenylpiperidinium salt end groups accompanying a perylene diimide tetracarboxylate as a counteranion were prepared by the ion-exchange reaction, and the subsequent covalent conversion by reflux in toluene afforded the corresponding core-fluorescent four-armed star and dicyclic 8-shaped poly(THF)s, (Ia and Ib, respectively) for the use of single-molecule fluorescence microscopy measurements.

Hyaluronic acid/poly(lactic-co-glycolic acid) core/shell fiber meshes loaded with epigallocatechin-3-O-gallate as skin tissue engineering scaffolds.

Science.gov (United States)

Lee, Eun Ji; Lee, Jong Ho; Jin, Linhua; Jin, Oh Seong; Shin, Yong Cheol; Sang, Jin Oh; Lee, Jaebeom; Hyon, Suong-Hyu; Han, Dong-Wook

2014-11-01

In this study, hyaluronic acid (HA)/poly(lactic-co-glycolic acid, PLGA) core/shell fiber meshes loaded with epigallocatechin-3-O-gallate (EGCG) (HA/PLGA-E) for application to tissue engineering scaffolds for skin regeneration were prepared via coaxial electrospinning. Physicochemical properties of HA/PLGA-E core/shell fiber meshes were characterized by SEM, Raman spectroscopy, contact angle, EGCG release profiling and in vitro degradation. Biomechanical properties of HA/PLGA-E meshes were also investigated by a tensile strength test. SEM images showed that HA/PLGA-E fiber meshes had a three-dimensional interconnected pore structure with an average fiber diameter of about 1270 nm. Raman spectra revealed that EGCG was uniformly dispersed in the PLGA shell of meshes. HA/PLGA-E meshes showed sustained EGCG release patterns by controlled diffusion and PLGA degradation over 4 weeks. EGCG loading did not adversely affect the tensile strength and elastic modulus of HA/PLGA meshes, while increased their hydrophilicity and surface energy. Attachment of human dermal fibroblasts on HA/PLGA-E meshes was appreciably increased and their proliferation was steadily retained during the culture period. These results suggest that HA/PLGA-E core/shell fiber meshes can be potentially used as scaffolds supporting skin regeneration.

Synthesis of bi-phase dispersible core-shell FeAu@ZnO magneto-opto-fluorescent nanoparticles

Science.gov (United States)

Li, Xue-Mei; Liu, Hong-Ling; Liu, Xiao; Fang, Ning; Wang, Xian-Hong; Wu, Jun-Hua

2015-11-01

Bi-phase dispersible core-shell FeAu@ZnO magneto-opto-fluorescent nanoparticles were synthesized by a modified nanoemulsion process using poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO) as the surfactant. The morphology and crystal structure of the nanoparticles were studied by TEM/HRTEM and XRD. The nanoparticles manifest soft ferromagnetic and/or near superparamagnetic behavior with a small coercivity of ~19 Oe at room temperature. The corresponding magnetic hysteresis curves were elucidated by the modified Langevin equation. The FTIR study confirms the PEO-PPO-PEO molecules on the surface of the nanoparticles. The UV-vis and PL results reveal the well-behaved absorption bands including surface plasmon resonance and multiple visible fingerprint photoluminescent emissions of the nanoparticles dispersed in both hydrophilic and hydrophobic solvents. Moreover, the processes of solvent dispersion-collection of the nanoparticles were demonstrated for application readiness of such core-shell nanostructures.

Shear-Induced Phase Separation in Aqueous Polymer Solutions: Temperature-Sensitive Microgels and Linear Polymer Chains

NARCIS (Netherlands)

Stieger, M.A.; Richtering, W.

2003-01-01

The influence of shear flow on the phase separation of aqueous poly(N-isopropylacrylamide) (PNiPAM) microgel suspensions was investigated by means of rheo-turbidity and rheo-small angle neutron scattering (rheo-SANS) and compared to the behavior of linear PNiPAM macromolecules. The rheological

Crystal morphology modification by the addition of tailor-made stereocontrolled poly(N-isopropyl acrylamide)

DEFF Research Database (Denmark)

Munk, Tommy; Baldursdottir, Stefania; Hietala, Sami

2012-01-01

. One such additive is the thermosensitive polymer poly(N-isopropyl acrylamide) (PNIPAM). The use of PNIPAM as a crystallization additive provides a possibility to affect viscosity at separation temperatures and nucleation and growth rates at higher temperatures. In this study, novel PNIPAM derivatives......; the morphology of crystals changed from needle to dendritic shape. Additionally, the amphiphilic nature of PNIPAM increased the solubility of nitrofurantoin in water. PNIPAMs with varying molecular weights and stereoregularities resulted in similar changes in the crystal habit of the drug regardless of whether...

Lower critical solution temperature behavior of alpha-substituted poly(acrylic acids)s, cyclopolymerization of N-vinylformamido-methylacrylates, and use of the World-Wide Web in polymer science education

Science.gov (United States)

Michalovic, Mark Stephen

A series of alpha-substituted poly(acrylic acid)s was synthesized and characterized. Their aqueous solution properties were investigated with respect to lower critical solution temperature (LCST) behavior. Poly(alpha-methoxymethylacrylic acid) was found to have a lower critical solution temperature (LCST) of 46°C, poly(alpha-methoxyethoxymethylacrylic acid) showed an LCST of 26.5°C and poly(alpha-methoxyethoxyethoxymethylacrylic acid) showed an LCST of 66°C. The cloud points of the solutions of these polymers were found to be sensitive to pH, and to concentrations of additives such as urea, salts, and surfactants. Because of low molecular weight due to chain transfer, high molecular weight analogs of the ether-linked polymers were synthesized in which ester linkages joined the oligo-oxyethylene segment to the acrylate moiety. Poly(alpha-methoxyethoxyacetoxymethylacrylic acid) was the only one of this series to give an LCST with a value of 52.5°C. Copolymers of t-butyl alpha-methoxymethylacrylate (tBMMA) with alpha-(1H,1H- perfluorooctyloxymethyl)acrylic acid (PFOMA) were synthesized, deprotected and their lower critical solution temperatures (LCSTs) evaluated. At PFOMA feed ratios of 0.25 mol % or less, no observable change in the LCST was observed, while at PFOMA feed ratios of above 0.25 mol % to 1.125 mol %, a large linear decrease in the LCST was observed with increasing fluorocarbon content. t-Butyl alpha-(N-vinylformamidomethyl)acrylate (tBVFA) and ethyl alpha-(N-vinylformamidomethyl)acrylate (EVFA) were synthesized from t-butyl alpha-bromomethylacrylate and ethyl alpha-chloromethylacrylate, respectively. tBVFA was found to cyclopolymerize at 120°C in DMF, DMSO, and 1,2-dichlorobenzene at solvent:monomer ratios of 10:1 vol:wt. Molecular weights for poly(tBVFA) ranged from 10,000 to 13,000 as estimated by size-exclusion chromatography. At lower solvent monomer ratio (1:1), and at lower temperature (71°C), crosslinking occurred. EVFA was found to

Efficiency of poly-generating high temperature fuel cells

Energy Technology Data Exchange (ETDEWEB)

Margalef, Pere; Brown, Tim; Brouwer, Jacob; Samuelsen, Scott [National Fuel Cell Research Center (NFCRC), University of California, Irvine, CA 92697-3550 (United States)

2011-02-15

High temperature fuel cells can be designed and operated to poly-generate electricity, heat, and useful chemicals (e.g., hydrogen) in a variety of configurations. The highly integrated and synergistic nature of poly-generating high temperature fuel cells, however, precludes a simple definition of efficiency for analysis and comparison of performance to traditional methods. There is a need to develop and define a methodology to calculate each of the co-product efficiencies that is useful for comparative analyses. Methodologies for calculating poly-generation efficiencies are defined and discussed. The methodologies are applied to analysis of a Hydrogen Energy Station (H{sub 2}ES) showing that high conversion efficiency can be achieved for poly-generation of electricity and hydrogen. (author)

Controlled-release and preserved bioactivity of proteins from (self-assembled core-shell double-walled microspheres

Directory of Open Access Journals (Sweden)

Yuan W

2012-01-01

Full Text Available Weien Yuan1,2, Zhenguo Liu11Department of Neurology, Xinhua Hospital, affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 2School of Pharmacy, Shanghai Jiao Tong University, Shanghai, People’s Republic of ChinaAbstract: In order to address preserved protein bioactivities and protein sustained-release problems, a method for preparing double-walled microspheres with a core (protein-loaded nanoparticles with a polymer-suspended granule system-formed core and a second shell (a polymer-formed shell for controlled drug release and preserved protein bioactivities has been developed using (solid-in-oil phase-in-hydrophilic oil-in-water (S/O/Oh/W phases. The method, based on our previous microsphere preparation method (solid-in-oil phase-in-hydrophilic oil-in-water (S/O/Oh/W, employs different concentric poly(D,L-lactide-co-glycolide, poly(D,L-lactide, and protein-loaded nanoparticles to produce a suspended liquid which then self-assembles to form shell-core microspheres in the hydrophilic oil phase, which are then solidified in the water phase. Variations in the preparation parameters allowed complete encapsulation by the shell phase, including the efficient formation of a poly(D,L-lactide shell encapsulating a protein-loaded nanoparticle-based poly(D,L-lactide-co-glycolide core. This method produces core-shell double-walled microspheres that show controlled protein release and preserved protein bioactivities for 60 days. Based upon these results, we concluded that the core-shell double-walled microspheres might be applied for tissue engineering and therapy for chronic diseases, etc.Keywords: protein delivery, protein stability, core-shell microspheres, dextran nanoparticles

Position-controlled MOVPE growth and electro-optical characterization of core-shell InGaN/GaN microrod LEDs

Science.gov (United States)

Schimpke, Tilman; Lugauer, H.-J.; Avramescu, A.; Varghese, T.; Koller, A.; Hartmann, J.; Ledig, J.; Waag, A.; Strassburg, M.

2016-03-01

Today's InGaN-based white LEDs still suffer from a significant efficiency reduction at elevated current densities, the so-called "Droop". Core-shell microrods, with quantum wells (QWs) covering their entire surface, enable a tremendous increase in active area scaling with the rod's aspect ratio. Enlarging the active area on a given footprint area is a viable and cost effective route to mitigate the droop by effectively reducing the local current density. Microrods were grown in a large volume metal-organic vapor phase epitaxy (MOVPE) reactor on GaN-on-sapphire substrates with a thin, patterned SiO2 mask for position control. Out of the mask openings, pencil-shaped n-doped GaN microrod cores were grown under conditions favoring 3D growth. In a second growth step, these cores are covered with a shell containing a quantum well and a p-n junction to form LED structures. The emission from the QWs on the different facets was studied using resonant temperature-dependent photoluminescence (PL) and cathodoluminescence (CL) measurements. The crystal quality of the structures was investigated by transmission electron microscopy (TEM) showing the absence of extended defects like threading dislocations in the 3D core. In order to fabricate LED chips, dedicated processes were developed to accommodate for the special requirements of the 3D geometry. The electrical and optical properties of ensembles of tens of thousands microrods connected in parallel are discussed.

N-Isopropylacrylamide-co-glycidylmethacrylate as a Thermoresponsive Substrate for Corneal Endothelial Cell Sheet Engineering

Directory of Open Access Journals (Sweden)

Bernadette K. Madathil

2014-01-01

Full Text Available Endothelial keratoplasty is a recent shift in the surgical treatment of corneal endothelial dystrophies, where the dysfunctional endothelium is replaced whilst retaining the unaffected corneal layers. To overcome the limitation of donor corneal shortage, alternative use of tissue engineered constructs is being researched. Tissue constructs with intact extracellular matrix are generated using stimuli responsive polymers. In this study we evaluated the feasibility of using the thermoresponsive poly(N-isopropylacrylamide-co-glycidylmethacrylate polymer as a culture surface to harvest viable corneal endothelial cell sheets. Incubation below the lower critical solution temperature of the polymer allowed the detachment of the intact endothelial cell sheet. Phase contrast and scanning electron microscopy revealed the intact architecture, cobble stone morphology, and cell-to-cell contact in the retrieved cell sheet. Strong extracellular matrix deposition was also observed. The RT-PCR analysis confirmed functionally active endothelial cells in the cell sheet as evidenced by the positive expression of aquaporin 1, collagen IV, Na+-K+ ATPase, and FLK-1. Na+-K+ ATPase protein expression was also visualized by immunofluorescence staining. These results suggest that the in-house developed thermoresponsive culture dish is a suitable substrate for the generation of intact corneal endothelial cell sheet towards transplantation for endothelial keratoplasty.

Synthesis and properties of new cationic polymers on 2-[(methacryloyloxy)ethyl]trimethyl ammonium chloride and N-isopropylacrylamidet base

International Nuclear Information System (INIS)

Sergaziev, A.; Khutoryanskij, V.; Bajzhumanova, T.; Fefelova, N.; Nurkeeva, Z.

2003-01-01

New water-soluble cationic polyelectrolytes were synthesized by γ-radiation copolymerization of 2-[(methacryloyloxy)ethyl]trimethyl ammonium chloride and N-isopropylacrylamide. The phase transition of aqueous solutions of copolymers was studied with temperature increase in presence and absence of inorganic salts. The copolymers complexation with potassium hexacyano ferrates (II, III) was investigated. It was shown that the poly-complexes solubility depends on concentration of interacting reagents and temperature. (author)

Core-Shell-Structured Copolyaniline-Coated Polymeric Nanoparticle Suspension and Its Viscoelastic Response under Various Electric Fields

Directory of Open Access Journals (Sweden)

Il-Jae Moon

2015-08-01

Full Text Available Semi-conducting poly(n-methylaniline (PNMA-coated poly(methyl methacrylate (PMMA composite nanoparticles were synthesized using cross-linked and grafted PMMA particles as a core, and then, the PNMA shell was coated via chemical oxidative polymerization on the surface of modified PMMA nanoparticles. Their electroresponsive electrorheological characteristics when dispersed in silicone were confirmed under applied electric fields using a rotational rheometer, focusing on their viscoelastic response. Using a frequency sweep test, the frequency dependence of both the storage and loss moduli was confirmed to increase upon increasing the electric field, with a stable plateau regime over the entire angular frequency range.

Polymerization of N-isopropylacrylamide under magnetic levitation

International Nuclear Information System (INIS)

Fujiwara, Y; Katsumoto, Y; Ohishi, Y; Koyama, M; Ohno, K; Akita, M; Inoue, K; Tanimoto, Y

2006-01-01

A study of an effect of the magnetic levitation on polymerization of N-isopropylacrylamide at room temperature was carried out. The magnetic levitation environment, which is created by strong and upward magnetic force counterbalanced with the downward gravitational force, is multiple environment consisting of both the microgravity and the strong magnetic field which is lacking in a space vehicle orbiting around the earth. In this work, the effect was evaluated from the viewpoint of the number-average molecular weight (M n ) and the polydispersity (the index of the molecular weight distribution) of the synthesized polymer. A small extent (∼10 %) of the effect was observed on both the parameters. When the polymer was synthesized under the magnetic levitation environment, M n increased while the polydispersity decreased as compared with those of the polymer synthesized under the gravity

Synthesis and characterization of thermally stable poly(amide-imide-montmorillonite nanocomposites based on bis(4-carboxyphenyl-N,N'-pyromellitimide acid

Directory of Open Access Journals (Sweden)

M. Hajibeygi

2013-04-01

Full Text Available Two new poly(amide-imide-montmorillonite reinforced nanocomposites containing bis(4-carboxyphenyl-N,N'-pyromellitimide acid moiety in the main chain were synthesized by a convenient solution intercalation technique. Poly(amide-imide (PAI as a source of polymer matrix was synthesized by the direct polycondensation reaction of bis(4-carboxyphenyl-N,N'-pyromellitimide acid with 4,4'-diamino diphenyl sulfone in the presence of triphenyl phosphite (TPP, CaCl2, pyridine and N-methyl-2-pyrrolidone (NMP. Morphology and structure of the resulting PAI-nanocomposite films with 10 and 20% silicate particles were characterized by FT-IR spectroscopy, X-ray diffraction (XRD and scanning electron microscopy (SEM. The effect of clay dispersion and the interaction between clay and polymeric chains on the properties of nanocomposites films were investigated by using UV-Vis spectroscopy, thermal gravimetry analysis (TGA and water uptake measurements.DOI: http://dx.doi.org/10.4314/bcse.v27i1.10

Temperature tunable micellization of polystyrene-block-poly(2-vinylpyridine) at Si-ionic liquid interface.

Science.gov (United States)

Lu, Haiyun; Lee, Dong Hyun; Russell, Thomas P

2010-11-16

Highly ordered and stable micelles formed from both symmetric and asymmetric block copolymers of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) at the Si-ionic liquid (IL) interface have been investigated by scanning force microscopy (SFM) and transmission electron microscopy (TEM). The 1-butyl-3-methylimidazolium trifluoromethanesulfonate IL, a selective and temperature-tunable solvent for the P2VP block, was used and gave rise to block copolymer micelles having different morphologies that strongly depended on the annealing temperature. The effects of film thickness, molecular weight of block copolymers, and experimental conditions, such as preannealing, rinsing, and substrate properties, on the morphologies of block copolymer micelles were also studied. In addition, spherical micelles consisting of PS core and P2VP shell could also be obtained by core-corona inversion by annealing the as-coated micellar film in the IL at high temperatures. The possible mechanism for micelle formation is discussed.

Study on the crystallization of multiarm stars with a poly(ethyleneimine) core and poly(ϵ-caprolactone) arms of different length

Energy Technology Data Exchange (ETDEWEB)

Díaz, Angélica; Bacaicoa, Anna; Casas, Maria Teresa; Franco, Lourdes [Departament d’Enginyeria Química, Universitat Politècnica de Catalunya, Av. Diagonal 647, Barcelona E-08028 (Spain); Serra, Angels [Departament de Química Analítica i Química Orgànica, Universitat Rovira i Virgili. C. Marcel.lí Domingo, s/n. Campus Sescelades, Tarragona 43007 (Spain); Puiggalí, Jordi, E-mail: Jordi.Puiggali@upc.edu [Departament d’Enginyeria Química, Universitat Politècnica de Catalunya, Av. Diagonal 647, Barcelona E-08028 (Spain)

2015-05-10

Highlights: • Isothermal crystallization kinetics of multiarm stars. • Influence of the length of poly(ϵ-caprolactone) arms on crystallization kinetics. • Influence of the length of poly(ϵ-caprolactone) arms on secondary nucleation constant. • Crystallization of mixtures of stars having different arm lengths. - Abstract: Crystallization of multiarm star systems constituted by a core of poly(ethyleneimine) (PEI) and arms of poly(ϵ-caprolactone) (PCL) was studied by transmission electron microscopy, calorimetry and optical microscopy techniques. Three systems differing on the degree of polymerization of PCL were studied as well as binary mixtures constituted by systems differing on the length of PCL arms. Samples were able to crystallize from both diluted solutions and the melt state giving rise to well-formed lamellae and spherulites, respectively. Lamellae of samples with large PCL arms were highly regular and corresponded to elongated hexagonal crystals with an aspect ratio that decreased with the length of PCL arms. A significant decrease on equilibrium melting temperatures, degree of crystallinity and glass transition temperature was detected for samples having short PCL arms. Crystallization kinetics were also highly influenced by the length of PCL arms, being both nucleation density and secondary nucleation constant increased as the length of PCL arms decreased. Crystallization of star mixtures having different PCL lengths was determined by the larger arms since they initiated the process and subsequently shorter arms were progressively incorporated. A thermal nucleation was characteristic of multiarm star mixtures due to the different crystallization temperature ranges of samples with large and short PCL arms, whereas samples with a homogeneous arm length rendered an athermal nucleation.

Non-equilibrium effects evidenced by vibrational spectra during the coil-to-globule transition in poly(N-isopropylacrylamide) subjected to an ultrafast heating-cooling cycle.

Science.gov (United States)

Deshmukh, Sanket A; Kamath, Ganesh; Suthar, Kamlesh J; Mancini, Derrick C; Sankaranarayanan, Subramanian K R S

2014-03-14

Molecular dynamics simulations in conjunction with finite element calculations are used to explore the conformational dynamics of a thermo-sensitive oligomer, namely poly(N-isopropylacrylamide) (PNIPAM), subjected to an ultra-fast heating-cooling cycle. Finite element (FE) calculations were used to predict the temperature profile resulting from laser-induced heating of the polymer-aqueous system. The heating rate (∼0.6 K ps(-1)) deduced from FE calculations was used to heat an aqueous solution of PNIPAM consisting of 30 monomeric units (30-mer) from 285 K to 315 K. Non-equilibrium effects arising from the ultra-fast heating-cooling cycle results in a hysteresis during the coil-to-globule transition. The corresponding atomic scale conformations were characterized by monitoring the changes in the vibrational spectra, which provided a reliable metric to study the coil-to-globule transition in PNIPAM and vice-versa across the LCST. The vibrational spectra of bonds involving atoms from the oligomer backbone and the various side-groups (amide I, amide II, and the isopropyl group of PNIPAM) of the oligomers were analyzed to study the conformational changes in the oligomer corresponding to the observed hysteresis. The differences in the vibrational spectra calculated at various temperatures during heating and cooling cycles were used to understand the coil-to-globule and globule-to-coil transitions in the PNIPAM oligomer and identify the changes in the relative interactions between various atoms in the backbone and in the side groups of the oligomer with water. The shifts in the computed vibrational spectral peaks and the changes in the intensity of peaks for the different regions of PNIPAM, seen across the LCST during the heating cycle, are in good agreement with previous experimental studies. The changes in the radius of gyration (Rg) and vibrational spectra for amide I and amide II regions of PNIPAM suggest a clear coil-to-globule transition at ∼301 K during the

Por un sistema de interpretación de los procesos de regionalización e integración andina desde el análisis de políticas publicas

Directory of Open Access Journals (Sweden)

Catalina Toro Pérez

2007-01-01

Full Text Available En Colombia son mas bien recientes, los estudios de investigación sobre el proceso de integración andina y latinoamericana, en tiempos donde, sus relaciones internacionales, oscilan entre una inserción subordinada a los Estados Unidos y su aislamiento frente a los países vecinos, en una solitaria cruzada de por el restablecimiento del mito de la seguridad nacional, la autoridad y el orden en una sociedad que parece, al mismo tiempo, desintegrarse y fragmentarse cada día mas. Sin embargo, mientras el proceso de integración de la Comunidad Andina languidece, un nuevo tipo de regionalización política suramericana, se abre paso, impulsado por movimientos sociales y gobiernos alternativos de Ecuador, Venezuela, Bolivia, Argentina, y Brasil quienes en medio de grandes contradicciones, comienzan a constituir un frente común, contra las políticas de regionalización impuestas por los Estados Unidos, en materia de seguridad, defensa y comercio en el área andina. En un contexto de desintegración andina y de fractura social interna, como abordar la historia de los procesos de integración andina, sus conflictos y sus alternativas de construcción de practicas políticas comunes? Con el fin de aportar a la construcción de un marco de interpretación de los Procesos de Regionalización e Integración Andina, recogemos la contribución reciente de investigadores europeos que desde el campo de la sociología de la acción pública, abordan el análisis de la experiencia comunitaria europea. Luego a partir de diversas aproximaciones a los procesos de Integración andina en particular y latinoamericana en general, arrojamos una primera propuesta de interpretación desde el campo del análisis de las Políticas Publicas.

Homogeneous synthesis of cellulose acrylate-g-poly (n-alkyl acrylate) solid-solid phase change materials via free radical polymerization.

Science.gov (United States)

Qian, Yong-Qiang; Han, Na; Bo, Yi-Wen; Tan, Lin-Li; Zhang, Long-Fei; Zhang, Xing-Xiang

2018-08-01

A novel solid-solid phase change materials, namely, cellulose acrylate-g-poly (n-alkyl acrylate) (CA-g-PAn) (n = 14, 16 and 18) were successfully synthesized by free radical polymerization in N, N-dimethylacetamide (DMAc). The successful grafting was confirmed by fourier transform infrared spectra (FT-IR) and nuclear magnetic resonance (NMR). The properties of the CA-g-PAn copolymers were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA). The phase change temperatures and the melting enthalpies of CA-g-PAn copolymers are in the range of 10.1-53.2 °C and 15-95 J/g, respectively. It can be adjusted by the contents of poly (n-alkyl acrylate) and the length of alkyl side-chain. The thermal resistant temperatures of CA-g-PA14, 16 and 18 copolymers are 308 °C, 292 °C and 273 °C, respectively. It show that all of grafting materials exhibit good thermal stability and shape stability. Therefore, it is expected to be applied in the cellulose-based thermos-regulating field. Copyright © 2018 Elsevier Ltd. All rights reserved.

Core-shell particle composition by liquid phase infrared spectroscopy

International Nuclear Information System (INIS)

Ribeiro, Luiz F.B.; Machado, Ricardo A.F.; Goncalves, Odinei H.; Bona, Evandro

2011-01-01

Polymeric particles with core-shell morphology can offer advantages over conventional particles improving properties like mechanical and chemical resistance. However, particle composition must be known due to its influence on the final properties. In this work liquid phase infrared spectroscopy was used to determine the overall composition of core-shell particles composed by polystyrene (core) and poly(methyl methacrylate) (shell). Results were in agreement with those obtained with H 1 Nuclear Magnetic Resonance data (Goncalves et al, 2008). (author)

Tacticities study of high poly-α-olefins, from poly-1-hexene to poly-1-octadecene, obtained with metallocenes catalysts

International Nuclear Information System (INIS)

Silva, Luciano F. da; Galland, Griselda B.

2003-01-01

High poly-α-olefins such as poly-1-hexene, poly-1-octene, poly-1-decene, poly-1-dodecene, poly-1-tetradecene, poly-1-hexadecene and poly-1-octadecene were obtained with the homogeneous iso specific catalyst rac-Et[Ind]ZrCl 2 /MAO and with the homogeneous syndiospecific catalyst Me 2 C[Cp(9-Flu)]ZrCl 2 /MAO at the polymerization temperatures of 0 deg C, 30 deg C and 60 deg C. The polymers were analyzed by 13 C NMR to study the influence of the α - olefins sizes, the catalysts type and the polymerization temperatures in their tacticities. The stereospecific control of both catalytic systems decreased with the increase of the reaction temperature and with the α-olefin size. (author)

Synthesis, characterization and photo behavior of new poly(amide-imide/montmorillonite nanocomposite containing N,N'-pyrromellitoyl-bis-L-alanine

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M. Hajibeygi

2013-09-01

Full Text Available Two new samples of poly(amide-imide-nanocomposites were synthesized by insertion nano silicate particles in poly(amide-imide (PAI chains using a convenient solution intercalation technique. PAI as a source of polymer matrix was synthesized by the direct polycondensation reaction of N,N'-pyrromelitoyl-bis-L-alanine with 4,4'-diamino diphenyl ether in the presence of triphenyl phosphite (TPP, CaCl2, pyridine and N-methyl-2-pyrrolidone (NMP. Morphology and structure of the resulting PAI-nanocomposite films with 5 and 10% silicate particles were characterized by FTIR spectroscopy, X-ray diffraction (XRD and scanning electron microscopy (SEM. The effect of clay dispersion and the interaction between clay and polymeric chains on the properties of nanocomposites films were investigated by using UV-Vis spectroscopy, thermogravimetric analysis (TGA and water uptake measurements.DOI: http://dx.doi.org/10.4314/bcse.v27i3.15

Intracellular ion monitoring using a gold-core polymer-shell nanosensor architecture

Energy Technology Data Exchange (ETDEWEB)

Stanca, S E; Cranfield, C G; Biskup, C [Biomolecular Photonics Group, University Hospital Jena, Teichgraben 8, 07743 Jena (Germany); Nietzsche, S [Centre for Electron Microscopy, University Hospital Jena, Ziegel-muehlenweg 1, 07743 Jena (Germany); Fritzsche, W, E-mail: sarmiza.stanca@mti.uni-jena.de, E-mail: charles.cranfield@mti.uni-jena.de, E-mail: christoph.biskup@mti.uni-jena.de [Institute of Photonic Technology, Albert-Einstein-Strasse 9, 07745 Jena (Germany)

2010-02-05

In this study, we describe the design of new ratiometric fluorescent nanosensors, whose architecture is based on a gold core surrounded by a poly(vinyl alcohol)-polyacetal shell. To the gold core, indicator dyes and reference dyes are attached via a cysteine linker. This nanosensor architecture is flexible with regards to the number and types of fluorophore linkages possible. The robust poly(vinyl alcohol)-polyacetal shell protects the fluorophores linked to the core from non-specific interactions with intracellular proteins. The nanosensors developed in this way are biocompatible and can be easily incorporated into mammalian cells without the use of transfection agents. Here, we show the application of these nanosensors for intracellular pH and sodium ion measurements.

Efficient simultaneous removal of U(VI) and Cu(II) from aqueous solution using core-shell nZVI@SA/CMC-Ca beads

International Nuclear Information System (INIS)

Shuhong Hu; Xiaoyan Lin; Wenhui Zhao; Ministry of Education, Sichuan; Xuegang Luo

2018-01-01

Core-shell nanoscale zero-valent iron@alginate/carboxymethyl cellulose sodium composite loaded with calcium (nZVI@SA/CMC-Ca) beads were synthesized in this study using coaxial electronic injection method. The adsorbent structure was characterized via FT-IR, SEM, EDX and XPS. The adsorption behavior of U(VI) and Cu(II) on core-shell nZVI@SA/CMC-Ca beads was studied under various experimental parameters like pH, contact time and temperature. The isotherm and the kinetic data, pertaining to the adsorption of U(VI) and Cu(II) by core-shell nZVI@SA/CMC-Ca beads obeyed both the Langmuir and Freundlich isotherms model and the pseudo-second-order kinetics model, respectively. The thermodynamic parameters revealed the spontaneous and endothermic nature of the adsorption. The experiment of regeneration and reusability suggested core-shell nZVI@SA/CMC-Ca bead was a regenerated material. (author)

The influence of MOVPE growth conditions on the shell of core-shell GaN microrod structures

Science.gov (United States)

Schimpke, Tilman; Avramescu, Adrian; Koller, Andreas; Fernando-Saavedra, Amalia; Hartmann, Jana; Ledig, Johannes; Waag, Andreas; Strassburg, Martin; Lugauer, Hans-Jürgen

2017-05-01

A core-shell geometry is employed for most next-generation, three-dimensional opto-electric devices based on III-V semiconductors and grown by metal organic vapor phase epitaxy (MOVPE). Controlling the shape of the shell layers is fundamental for device optimization, however no detailed analysis of the influence of growth conditions has been published to date. We study homogeneous arrays of gallium nitride core-shell microrods with height and diameter in the micrometer range and grown in a two-step selective area MOVPE process. Changes in shell shape and homogeneity effected by deliberately altered shell growth conditions were accurately assessed by digital analysis of high-resolution scanning electron microscope images. Most notably, two temperature regimes could be established, which show a significantly different behavior with regard to material distribution. Above 900 °C of wafer carrier temperature, the shell thickness along the growth axis of the rods was very homogeneous, however variations between vicinal rods increase. In contrast, below 830 °C the shell thickness is higher close to the microrod tip than at the base of the rods, while the lateral homogeneity between neighboring microrods is very uniform. This temperature effect could be either amplified or attenuated by changing the remaining growth parameters such as reactor pressure, structure distance, gallium precursor, carrier gas composition and dopant materials. Possible reasons for these findings are discussed with respect to GaN decomposition as well as the surface and gas phase diffusion of growth species, leading to an improved control of the functional layers in next-generation 3D V-III devices.

Microwave based synthesis and spectral characterization of thermo-sensitive poly(N,N-diethylacrylamide) grafted pectin copolymer.

Science.gov (United States)

Işıklan, Nuran; Tokmak, Şeyma

2018-07-01

The functionalization of polysaccharides with synthetic polymers has attracted great attention owing to its application in many industrial fields. The aim of this work was to study the impact of pectin functionalization with N,N-diethylacrylamide (DEAAm). Pectin was modified via microwave-induced graft copolymerization of DEAAm using ceric ammonium nitrate (CAN) and N,N,N',N'-tetramethylethylenediamine (TEMED). FTIR, 13 C NMR, DSC/TGA, XRD, and SEM techniques were used to verify the structure of graft copolymers. Various reaction conditions such as microwave irradiation time, temperature, microwave power, monomer, initiator, and TEMED concentrations were investigated to get a maximum grafting yield of 192%. Lower critical solution temperatures (LCST) of graft copolymers were determined by UV spectroscopy. Graft copolymers were found to be thermo-sensitive, with LCST of 31°C and high thermal resistance. Biocompatibility test of copolymers showed that copolymers were not cytotoxic to L929 fibroblasts cells and can be used as a biomaterial. Copyright © 2018 Elsevier B.V. All rights reserved.

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,

Temperature Induced Solubility Transitions of Various Poly(2-oxazolines in Ethanol-Water Solvent Mixtures

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Hanneke M. L. Lambermont-Thijs

2010-08-01

Full Text Available The solution behavior of a series of poly(2-oxazolines with different side chains, namely methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, pentyl, hexyl, heptyl, octyl, nonyl, phenyl and benzyl, are reported in ethanol-water solvent mixtures based on turbidimetry investigations. The LCST transitions of poly(2-oxazolines with propyl side chains and the UCST transitions of the poly(2-oxazolines with more hydrophobic side chains are discussed in relation to the ethanol-water solvent composition and structure. The poly(2-alkyl-2-oxazolines with side chains longer than propyl only dissolved during the first heating run, which is discussed and correlated to the melting transition of the polymers.

Mechanistic analysis of temperature-dependent current conduction through thin tunnel oxide in n+-polySi/SiO2/n+-Si structures

Science.gov (United States)

Samanta, Piyas

2017-09-01

We present a detailed investigation on temperature-dependent current conduction through thin tunnel oxides grown on degenerately doped n-type silicon (n+-Si) under positive bias ( VG ) on heavily doped n-type polycrystalline silicon (n+-polySi) gate in metal-oxide-semiconductor devices. The leakage current measured between 298 and 573 K and at oxide fields ranging from 6 to 10 MV/cm is primarily attributed to Poole-Frenkel (PF) emission of trapped electrons from the neutral electron traps located in the silicon dioxide (SiO2) band gap in addition to Fowler-Nordheim (FN) tunneling of electrons from n+-Si acting as the drain node in FLOating gate Tunnel OXide Electrically Erasable Programmable Read-Only Memory devices. Process-induced neutral electron traps are located at 0.18 eV and 0.9 eV below the SiO2 conduction band. Throughout the temperature range studied here, PF emission current IPF dominates FN electron tunneling current IFN at oxide electric fields Eox between 6 and 10 MV/cm. A physics based new analytical formula has been developed for FN tunneling of electrons from the accumulation layer of degenerate semiconductors at a wide range of temperatures incorporating the image force barrier rounding effect. FN tunneling has been formulated in the framework of Wentzel-Kramers-Brilloiun taking into account the correction factor due to abrupt variation of the energy barrier at the cathode/oxide interface. The effect of interfacial and near-interfacial trapped-oxide charges on FN tunneling has also been investigated in detail at positive VG . The mechanism of leakage current conduction through SiO2 films plays a crucial role in simulation of time-dependent dielectric breakdown of the memory devices and to precisely predict the normal operating field or applied floating gate (FG) voltage for lifetime projection of the devices. In addition, we present theoretical results showing the effect of drain doping concentration on the FG leakage current.

Microencapsulation of Epoxidized Linseed Oil Liquid Cross-Linker in Poly(N-vinyl-pyrrolidone): Optimization by a Design-of-Experiments Approach

NARCIS (Netherlands)

Senatore, D.; Laven, J.; Benthem, van R.A.T.M.; La Camera, D.; With, de G.

2010-01-01

A liquid cross-linker, epoxidized linseed oil (ELO), was encapsulated in a plastic with a high glass transition temperature (poly(N-vinyl-2-pyrrolidone); PVP). The process parameters of the spray-drying employed were optimized by a Design-of-Experiments (DoE) approach. Three factors concerning both

Synthesis and thermal behavior of new organometallic poly ketones and co-poly ketones based on diferrocenylidene piperidone

International Nuclear Information System (INIS)

Aly, K.I.

2005-01-01

A new interesting category of organometallic poly ketones and copolyketones were synthesized via Friedel - Crafts reaction through the polymerization of 2,6-[Bis (2-ferrocenyl )methylene] N-methylpiperidone (II) with different diacid chlorides. The model compound was synthesized by reacting the monomer (II) with benzoyl chloride and characterized by HNMR, IR and elemental analyses. The poly ketones and copolyketones were insoluble in most organic solvents but soluble easily in protic solvents. The thermal properties of these poly ketones and copolyketones were evaluated and correlated to their structural units by TGA and DSC measurements, and had inherent viscosity 0.34-0.52 dl g-1. Moreover, the electrical conductivity of one of the poly ketones, as selected example, Va and copolyketone VI were investigated above the temperature range (300-500 K) and showed that it followed an Arrhenius equation with activation energy 2.09 eV, also the morphological properties of selected examples of poly-and copolyketones were detected by SEM

Poly(vinyl-alcohol)/poly(ethylene-glycol)/poly(ethylene-imine) blend membranes - structure and CO2 facilitated transport

International Nuclear Information System (INIS)

Ben Hamouda, S.; Quang, Trong Nguyen; Langevin, D.; Sadok, Roudeslic

2010-01-01

Poly(vinyl-alcohol) (PVA)/poly(ethylene-imine) (PEI)/poly(ethylene-glycol) (PEG) blend membranes were prepared by solution casting followed by solvent evaporation. The effects of the blend polymer composition on the membrane structure and CO 2 /N 2 permeation characteristics were investigated. IR spectroscopy evidenced strong hydrogen bonding interactions between amorphous PVA and PEI, and weaker interactions between PVA and PEG. DSC studies showed that PVA crystallization was partially inhibited by the interactions between amorphous PVA and PEI blend, in which PEG separated into nodules. The CO 2 permeability decreased with an increase in CO 2 partial pressure in feed gas, while the N 2 permeability remained constant. This result indicated that only CO 2 was transported by the facilitated transport mechanism. The CO 2 and N 2 permeabilities increased monotonically with the PEI content in the blend membranes, whereas the ideal selectivity of CO 2 to N 2 transport showed a maximum. When CO 2 is humidified, its permeability through the blend membranes is much higher than that of dry CO 2 , but the change in permeability due to the presence of humidity is reversible. (authors)

Synthesis of a pH- and Thermo- Responsive Binary Copolymer Poly(N-vinylimidazole-co-N-vinylcaprolactam Grafted onto Silicone Films

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Ángela Obando-Mora

2015-10-01

Full Text Available This work focuses on the effects of gamma-ray irradiation conditions on the stimuli-responsiveness of silicone rubber (SR substrates grafted with N-vinylcaprolactam (NVCL and N-vinylimidazole (NVIM, modified by the simultaneously polymerization and grafting method, which is expected to result in valuable new applications in the near future. The modification of silicone rubber was carried out via γ-ray radiation in order to graft a binary copolymer, poly(N-vinylimidazole-co-N-vinylcaprolactam, by the pre-irradiation method, to obtain pH- and thermo-responsive materials. The grafting yield was found to be directly proportional to the dose and monomers concentration. The biomaterials were characterized by using Fourier-transform infrared attenuated total reflection (FTIR-ATR, differential scanning calorimetry (DSC, thermogravimetric analysis (TGA, and swelling; and their stimuli behavior was evaluated by lower critical solution temperature (LCST and pH critical studies.

Electrochemical n-doping of poly(dithienylvinylene). A comparison of cyclovoltammetric and conductive properties in n- and p-doping

Energy Technology Data Exchange (ETDEWEB)

Zotti, G. (Ist. di Polarografia ed Elettrochimica Preparative, Consiglio Nazionale delle Ricerche, Padua (Italy)); Schiavon, G. (Ist. di Polarografia ed Elettrochimica Preparative, Consiglio Nazionale delle Ricerche, Padua (Italy))

1994-03-15

Electrochemical n-doping of poly(dithienylvinylene) has been performed in AN+0.1 M N(C[sub n]H[sub 2n+1])[sub 4][sup +]ClO[sub 4][sup -] (n=1,2,3,4 and 6) and compared with p-doping. Cyclic voltammetry, in situ ESR and UV-Vis spectroelectrochemistry show that radical anions produced in n-doping are moderately unstable towards disproportionation whereas, in p-doping, radical cations are stabilized by [pi]-dimerization. In situ conductivity of n-doped polymer decreases as the size of the dopant cation increases, suggesting charge transport control by interchain hopping. The different conductivities of n- and p-doped polymers are due to the different sizes of the counterions. (orig.)

Nanostructured poly(benzimidazole membranes by N-alkylation

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J. Weber

2014-01-01

Full Text Available Modification of poly(benzimidazole (PBI by N-alkylation leads to polymers capable of undergoing microphase separation. Polymers with different amounts of C18 alkyl chains have been prepared. The polymers were analyzed by spectroscopy, thermal analysis, electron microscopy and X-ray scattering. The impact of the amount of alkyl chains on the observed microphase separation was analyzed. Membranes prepared from the polymers do show microphase separation, as evidenced by scattering experiments. While no clear morphology could be derived for the domains in the native state, evidence for the formation of lamellar morphologies upon doping with phosphoric acid is provided. Finally, the proton conductivity of alkyl-modified PBI is compared with that of pure PBI, showing that the introduction of alkyl side chains does not result in significant conductivity changes.

Synthesis and characterization of thermosensitive poly(organophosphazenes) with methoxy-poly(ethylene glycol) and alkylamines as side groups

International Nuclear Information System (INIS)

Lee, Bae Hoon; Song, Soo Chang; Lee, Young Moo; Sohn, Youn Soo

2002-01-01

Thermosensitive poly(organophosphazenes) bearing methoxy-poly(ethylene glycon) (MPEG) and alkylamine as substituents have been synthesized and characterized by elemental analysis, NMR spectroscopy, GPC, and DSC. All the polymers exhibited crystallinity, which was probably induced by the MPEG side chain of the polymers. All the polymers exhibited the lower critical solution temperature (LCSTs) in the range of 28 to 94 .deg. C depending on several factors such as mole ratio of the substituents, kinds of PEG and alkylamines. The higher content of MPEG and shorter chain length of alkylamines of the polymers afforded the higher LCST. The LCSTs of the polymers exhibited almost concentration-independent behavior in the range of 3-30 wt % of the polymers in aqueous solutions. The polymers showed the higher LCSTs in the acidic solutions than in the neutral and basic solutions. The ionic strength of the polymer solution affected the LCST,which decreased with increased NaCl concentration. The polymer bearing almost equimolar substituents with the -N-P-N unit has shown the LCST more sensitive to NaCl and pH than that with the -N-P-O- unit. The polymers were found to degrade in acidic solution but be very stable in alkali solution as well as in the buffer solution of pH 7.4

Si+ and N+ ion implantation for improving blood compatibility of medical poly(methyl methacrylate)

International Nuclear Information System (INIS)

Li, D.J.; Cui, F.Z; Cui, F.Z.

1998-01-01

Si + and N + ion implantation into medical poly(methyl methacrylate) (PMMA) were performed at an energy of 80 keV with fluences ranging from 5x10 12 to 5x10 15 ions/cm 2 at room temperature to improve blood compatibility. The results of the blood contacting measurements in vitro showed that the anticoagulability and anticalcific behaviour on the surface morphology were enhanced after ion implantation. No appreciable change in the surface morphology was detected by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) analysis indicated that ion implantation broke some original chemical bonds on the surface to form some new Si- and N-containing groups. These results were considered responsible for the enhancement in the blood compatibility of PMMA. (author)

"Chameleon" Macromolecules: Synthesis, Structures and Applications of Stimulus Responsive Polymers

NARCIS (Netherlands)

Sui, Xiaofeng

2012-01-01

This thesis describes the preparation and characterization of addressable responsive polymer structures and their versatile applications. Stimuli responsive polymer chains including temperature responsive poly(N-isopropylacrylamide), PNIPAM, pH responsive poly(methacrylic acid), PMAA and redox

Synthesis of N-halamine-functionalized silica-polymer core-shell nanoparticles and their enhanced antibacterial activity

International Nuclear Information System (INIS)

Dong, Alideertu; Wang Tao; Xiao Linghan; Wang Weiwei; Zhao Tianyi; Zheng Xin; Liu Fengqi; Gao Ge; Huang Jinfeng; Chen Yuxin; Lan Shi

2011-01-01

N-halamine-functionalized silica-polymer core-shell nanoparticles with enhanced antibacterial activity were synthesized through the encapsulation of silica nanoparticles as support with polymeric N-halamine. The as-synthesized nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive x-ray spectrometry (EDX), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR). These N-halamine-functionalized silica-polymer core-shell nanoparticles displayed powerful antibacterial performance against both Gram-positive bacteria and Gram-negative bacteria, and their antibacterial activities have been greatly improved compared with their bulk counterparts. Therefore, these N-halamine-functionalized silica-polymer core-shell nanoparticles have the potential for various significant applications such as in medical devices, healthcare products, water purification systems, hospitals, dental office equipment, food packaging, food storage, household sanitation, etc.

Synthesis of N-halamine-functionalized silica-polymer core-shell nanoparticles and their enhanced antibacterial activity

Energy Technology Data Exchange (ETDEWEB)

Dong, Alideertu; Wang Tao; Xiao Linghan; Wang Weiwei; Zhao Tianyi; Zheng Xin; Liu Fengqi; Gao Ge [College of Chemistry, Jilin University and MacDiarmid Laboratory, Changchun 130021 (China); Huang Jinfeng; Chen Yuxin [Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education, Jilin University, Changchun 130012 (China); Lan Shi, E-mail: gaoge@jlu.edu.cn [College of Chemistry and Chemical Engineering, Inner Mongolia University for the Nationalities, Tongliao 028000 (China)

2011-07-22

N-halamine-functionalized silica-polymer core-shell nanoparticles with enhanced antibacterial activity were synthesized through the encapsulation of silica nanoparticles as support with polymeric N-halamine. The as-synthesized nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive x-ray spectrometry (EDX), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR). These N-halamine-functionalized silica-polymer core-shell nanoparticles displayed powerful antibacterial performance against both Gram-positive bacteria and Gram-negative bacteria, and their antibacterial activities have been greatly improved compared with their bulk counterparts. Therefore, these N-halamine-functionalized silica-polymer core-shell nanoparticles have the potential for various significant applications such as in medical devices, healthcare products, water purification systems, hospitals, dental office equipment, food packaging, food storage, household sanitation, etc.

Biocompatibility and intradiscal application of a thermoreversible celecoxib-loaded poly-N-isopropylacrylamide MgFe-layered double hydroxide hydrogel in a canine model.

Science.gov (United States)

Willems, Nicole; Yang, Hsiao-Yin; Langelaan, Marloes L P; Tellegen, Anna R; Grinwis, Guy C M; Kranenburg, Hendrik-Jan C; Riemers, Frank M; Plomp, Saskia G M; Craenmehr, Eric G M; Dhert, Wouter J A; Papen-Botterhuis, Nicole E; Meij, Björn P; Creemers, Laura B; Tryfonidou, Marianna A

2015-08-20

Chronic low back pain due to intervertebral disc (IVD) degeneration is associated with increased levels of inflammatory mediators. Current medical treatment consists of oral anti-inflammatory drugs to alleviate pain. In this study, the efficacy and safety of a novel thermoreversible poly-N-isopropylacrylamide MgFe-layered double hydroxide (pNIPAAM MgFe-LDH) hydrogel was evaluated for intradiscal controlled delivery of the selective cyclooxygenase (COX) 2 inhibitor and anti-inflammatory drug celecoxib (CXB). Degradation, release behavior, and the ability of a CXB-loaded pNIPAAM MgFe-LDH hydrogel to suppress prostaglandin E2 (PGE2) levels in a controlled manner in the presence of a proinflammatory stimulus (TNF-α) were evaluated in vitro. Biocompatibility was evaluated histologically after subcutaneous injection in mice. Safety of intradiscal application of the loaded and unloaded hydrogels was studied in a canine model of spontaneous mild IVD degeneration by histological, biomolecular, and biochemical evaluation. After the hydrogel was shown to be biocompatible and safe, an in vivo dose-response study was performed in order to determine safety and efficacy of the pNIPAAM MgFe-LDH hydrogel for intradiscal controlled delivery of CXB. CXB release correlated to hydrogel degradation in vitro. Furthermore, controlled release from CXB-loaded hydrogels was demonstrated to suppress PGE2 levels in the presence of TNF-α. The hydrogel was shown to exhibit a good biocompatibility upon subcutaneous injection in mice. Upon intradiscal injection in a canine model, the hydrogel exhibited excellent biocompatibility based on histological evaluation of the treated IVDs. Gene expression and biochemical analyses supported the finding that no substantial negative effects of the hydrogel were observed. Safety of application was further confirmed by the absence of clinical symptoms, IVD herniation or progression of degeneration. Controlled release of CXB resulted in a nonsignificant

Prediction of Poly(A Sites by Poly(A Read Mapping.

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Thomas Bonfert

Full Text Available RNA-seq reads containing part of the poly(A tail of transcripts (denoted as poly(A reads provide the most direct evidence for the position of poly(A sites in the genome. However, due to reduced coverage of poly(A tails by reads, poly(A reads are not routinely identified during RNA-seq mapping. Nevertheless, recent studies for several herpesviruses successfully employed mapping of poly(A reads to identify herpesvirus poly(A sites using different strategies and customized programs. To more easily allow such analyses without requiring additional programs, we integrated poly(A read mapping and prediction of poly(A sites into our RNA-seq mapping program ContextMap 2. The implemented approach essentially generalizes previously used poly(A read mapping approaches and combines them with the context-based approach of ContextMap 2 to take into account information provided by other reads aligned to the same location. Poly(A read mapping using ContextMap 2 was evaluated on real-life data from the ENCODE project and compared against a competing approach based on transcriptome assembly (KLEAT. This showed high positive predictive value for our approach, evidenced also by the presence of poly(A signals, and considerably lower runtime than KLEAT. Although sensitivity is low for both methods, we show that this is in part due to a high extent of spurious results in the gold standard set derived from RNA-PET data. Sensitivity improves for poly(A sites of known transcripts or determined with a more specific poly(A sequencing protocol and increases with read coverage on transcript ends. Finally, we illustrate the usefulness of the approach in a high read coverage scenario by a re-analysis of published data for herpes simplex virus 1. Thus, with current trends towards increasing sequencing depth and read length, poly(A read mapping will prove to be increasingly useful and can now be performed automatically during RNA-seq mapping with ContextMap 2.

PH-Sensitive Nanogels Synthesised by Radiation-Induced Cross-Linking of Hydrogen-Bonded Interpolymer Complexes in Aqueous Solution

International Nuclear Information System (INIS)

Ulanski, P.; Kadłubowski, S.; Henke, A.; Olejnik, A.K.; Rokita, B.; Wach, R.; Rosiak, J.M.

2010-01-01

Nanogels, i.e., internally cross-linked hydrophilic polymeric particles of sub-micron sizes, gained much interest over the last years due to their possible application as components of advanced type of medicines, like drug carriers. It is expected that they can facilitate distribution and delivery of different types of biologically active substances (including proteins, peptides and oligonucleotides) in a controlled way within the human body. Nanogels and their bigger analogues – microgels, are mainly synthesised through free-radical cross-linking polymerization of monomers. This synthetic routine can be carried out in solution but more often emulsion techniques are preferred (mini- or microemulsion) due to easier size control and exclusion of the macrogelation process. Additionally, surfactant-free emulsion polymerization (SFEP) is the method of choice for the preparation of temperature-sensitive particles, mainly based on poly(N-isopropylacrylamide).Nanogels were also successfully prepared by intramolecular cross-linking of single macromolecules. More recently, covalent stabilization was utilized to obtain the self-assembled structures like micelles of amphiphilic block copolymers, held by relatively weak physical interactions. Due to low stability of these polymolecular systems against dilution or temperature changes, different chemistry-based strategies to turn them into permanent nanopaticles were proposed in the literature (e.g., independent stabilization of a core or a shell of the micelles)

PH-Sensitive Nanogels Synthesised by Radiation-Induced Cross-Linking of Hydrogen-Bonded Interpolymer Complexes in Aqueous Solution

Energy Technology Data Exchange (ETDEWEB)

Ulanski, P.; Kadłubowski, S.; Henke, A.; Olejnik, A. K.; Rokita, B.; Wach, R.; Rosiak, J.M., E-mail: slawekka@mitr.p.lodz.pl [Technical University of Lodz, Wroblewskiego 15, 93-590 Lodz (Poland)

2010-07-01

Nanogels, i.e., internally cross-linked hydrophilic polymeric particles of sub-micron sizes, gained much interest over the last years due to their possible application as components of advanced type of medicines, like drug carriers. It is expected that they can facilitate distribution and delivery of different types of biologically active substances (including proteins, peptides and oligonucleotides) in a controlled way within the human body. Nanogels and their bigger analogues – microgels, are mainly synthesised through free-radical cross-linking polymerization of monomers. This synthetic routine can be carried out in solution but more often emulsion techniques are preferred (mini- or microemulsion) due to easier size control and exclusion of the macrogelation process. Additionally, surfactant-free emulsion polymerization (SFEP) is the method of choice for the preparation of temperature-sensitive particles, mainly based on poly(N-isopropylacrylamide).Nanogels were also successfully prepared by intramolecular cross-linking of single macromolecules. More recently, covalent stabilization was utilized to obtain the self-assembled structures like micelles of amphiphilic block copolymers, held by relatively weak physical interactions. Due to low stability of these polymolecular systems against dilution or temperature changes, different chemistry-based strategies to turn them into permanent nanopaticles were proposed in the literature (e.g., independent stabilization of a core or a shell of the micelles)

Por un sistema de interpretación de los procesos de regionalización e integración andina desde el análisis de políticas públicas

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Catalina Toro Pérez

2008-07-01

Full Text Available Este artículo pretende abordar la historia reciente de los estudios sobre integración y regionalización andina, desde el campo de análisis de las políticas públicas. Frente a una tradición analítica amparada por el debate entre inter- gubernamentalistas y neo-funcionalistas, los estudios de la “regionalización” coinciden con la consolidación del campo de las políticas públicas y su expansión hacia otras sub-disciplinas de la ciencia política con útiles metodológicos, como el análisis multinivel de la nueva gobernanza, los análisis cognitivos y la acción colectiva, así como los estudios sobre la inserción de redes epistémicas en los procesos de toma de decisión global. Frente esta enorme influencia en el ámbito académico centroeuropeo y anglosajón, América Latina posee una rica e importante tradición analítica a partir de los análisis sobre las transformaciones del rol del Estado y de sus estructuras de poder. A partir de la economía política crítica aporta no solamente una dimensión histórica a los estudios de los procesos de integración actual, sino también una dimensión socio-económica y geopolítica de su contexto en el cambiante sistema capitalista mundial. Desde esta perspectiva, las instituciones regionales andinas, como la CAN, no estarían ausentes de una visión de orden mundial hegemónica, que se expresaría en formas históricas y simbólicas de dominación. Frente a las tendencias de regionalismo abierto y libre comercio y con ellas la emergencia de nuevas coaliciones de actores, asociados a los Estados capitalistas centrales se plantea entonces una perspectiva crítica que permita una construcción alternativa a las propuestas de integración subordinadas a los sistemas de representaciones del “orden mundial”.

Synthesis and characterization of new optically active poly(amide ...

African Journals Online (AJOL)

Synthesis and characterization of new optically active poly(amide-imide)s based on N -trimellitimido- ... Bulletin of the Chemical Society of Ethiopia ... (DMAc), dimethyl sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP) at room temperature.

Polymer electrolytes: an investigation of some poly (n-propylaziridine)/lithium salt compositions. Technical report

Energy Technology Data Exchange (ETDEWEB)

Baldwin, K R; Golder, A J; Knight, J

1984-04-01

Some poly(N-propylaziridine)/lithium salt compositions have been synthesized and their electrical conductivities have been measured in order to assess their suitability as electrolytes in safe, leakproof, high energy-density lithium batteries operating at ambient temperature. The effects on conductivity of temperature, and the nature and concentration of the salt have also been studied. The presence of the salts markedly improved the conductivity of the compositions over that of the undoped polymer but they were insufficiently conducting to be considered as battery electrolytes, due possibly to ion-pairing. Their creep resistance was also low. It was concluded that less fluid compositions containing higher molecular weight polymers better able to promote ion separation would be more suitable.

Polymer Inverse Temperature-Dependent Solubility: A Visual Demonstration of the Importance of "T[Delta]S" in the Gibbs Equation

Science.gov (United States)

Bergbreiter, David E.; Mijalis, Alexander J.; Fu, Hui

2012-01-01

Reversible polymer dehydration and precipitation from water due to the unfavorable entropy of hydration is examined using a melting-point apparatus. The thermoresponsive lower critical solution temperature (LCST) behavior of poly(N-isopropylacrylamide) (PNIPAM) is responsible for these effects. An experiment is described that allows students to…

Green synthesis of antimicrobial and antitumor N,N,N-trimethyl chitosan chloride/poly (acrylic acid)/silver nanocomposites.

Science.gov (United States)

Abu Elella, Mahmoud H; Mohamed, Riham R; Abdel-Aziz, Marwa M; Sabaa, Magdy W

2018-05-01

The present study is imported to solve two critical problems we face in our daily life which are microbial pollution and colon cancer. One pot green synthesis of a water soluble polyelectrolyte complex (PEC) between cationic polysaccharide as N,N,N-trimethyl chitosan chloride (TMC) and anionic polymer as poly (acrylic acid) (PAA) in presence of silver nanoparticles to yield (TMC/PAA/Ag) nanocomposites with different Ag weight ratios. Structure of TMC, PAA and TMC/PAA (PEC) were proved via different analysis tools. TMC/PAA and its Ag nanocomposites are used as antimicrobial agents against different pathogenic bacteria and fungi to solve microbial pollution. TMC/PAA-Silver nanocomposites had the highest antimicrobial activity which increases with increasing Ag %. Cytotoxicity data confirmed also that TMC/PAA/Ag (3%) had the most cytotoxic effect (the less cell viability %) towards colon cancer. TMC/PAA (PEC) was formed through electrostatic interactions between N-quaternized (-N + R 3 ) groups in TMC and carboxylate (-COO - ) groups in PAA. Copyright © 2018 Elsevier B.V. All rights reserved.

Synthesis and Application of Aurophilic Poly(Cysteine and Poly(Cysteine-Containing Copolymers

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David Ulkoski

2017-10-01

Full Text Available The redox capacity, as well as the aurophilicity of the terminal thiol side groups, in poly(Cysteine lend a unique characteristic to this poly(amino acid or polypeptide. There are two major application fields for this polymer: (i biomedical applications in drug delivery and surface modification of biomedical devices and (ii as coating for electrodes to enhance their electrochemical sensitivity. The intended application determines the synthetic route for p(Cysteine. Polymers to be used in biomedical applications are typically polymerized from the cysteine N-carboxyanhydride by a ring-opening polymerization, where the thiol group needs to be protected during the polymerization. Advances in this methodology have led to conditions under which the polymerization progresses as living polymerization, which allows for a strict control of the molecular architecture, molecular weight and polydispersity and the formation of block copolymers, which eventually could display polyphilic properties. Poly(Cysteine used as electrode coating is typically polymerized onto the electrode by cyclic voltammetry, which actually produces a continuous, pinhole-free film on the electrode via the formation of covalent bonds between the amino group of Cysteine and the carbon of the electrode. This resulting coating is chemically very different from the well-defined poly(Cysteine obtained by ring-opening polymerizations. Based on the structure of cysteine a significant degree of cross-linking within the coating deposited by cyclic voltammetry can be assumed. This manuscript provides a detailed discussion of the ring-opening polymerization of cysteine, a brief consideration of the role of glutathione, a key cysteine-containing tripeptide, and examples for the utilization of poly(Cysteine and poly(Cysteine-containing copolymers, in both, the biomedical as well as electrochemical realm.

Polyaniline Coated Core-Shell Typed Stimuli-Responsive Microspheres and Their Electrorheology

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Yu Zhen Dong

2018-03-01

Full Text Available Functional core-shell-structured particles have attracted considerable attention recently. This paper reviews the synthetic methods and morphologies of various electro-stimuli responsive polyaniline (PANI-coated core-shell-type microspheres, including PANI-coated Fe3O4, SiO2, Fe2O3, TiO2, poly(methyl methacrylate, poly(glycidyl methacrylate, and polystyrene along with their electrorheological (ER characteristics when prepared by dispersing these particles in an insulating medium. In addition to the various rheological characteristics and their analysis, such as shear stress and yield stress of their ER fluids, this paper summarizes some of the mechanisms proposed for ER fluids to further understand the responses of ER fluids to an externally applied electric field.

Interpretación en arqueología : piezas de collar de una necrópolis navarra

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Amparo Castiela Rodríguez

2005-01-01

Full Text Available Los restos de ajuar, recuperados en la necrópolis que han seguido el rito de la cremación, nos llegan muy alterados y requieren en ocasiones un esfuerzo especial para su comprensión. En el caso de varias piezas procedentes de La Atalaya, que formaban parte de collares, cuya interpretación ofrecemos

Starch-g-Poly-(N, N-dimethyl acrylamide-co-acrylic acid): an efficient Cr (VI) ion binder.

Science.gov (United States)

Kolya, Haradhan; Roy, Anirban; Tripathy, Tridib

2015-01-01

Synthesis of Starch-g-(Poly N, N-dimethylacrylamide-co-acrylic acid) was carried out by solution polymerization technique using potassium perdisulfate (K(2)S(2)O(8)) as the initiator. The graft copolymer was characterized by measuring molecular weight, using size exclusion chromatography (SEC), FTIR spectroscopy and X-ray diffraction (XRD) studies. The synthetic graft copolymer was used for removal of hexavalent chromium ion [Cr (VI)] from its aqueous solution. Various operating variables affecting the metal sorption such as, the amount of adsorbent, solution pH, contact time, temperature and the Cr (VI) solution concentration were extensively investigated. FTIR and UV-VIS spectroscopy, cyclic voltammetry (CV) were employed to study the metal complexation. The adsorption data could be well described by the pseudo-second-order and Langmuir isotherm model which indicate a chemisorption process. Calculation of the various thermodynamic parameters for the adsorption was also done. The negative value of free energy change (ΔG°) indicates the spontaneous nature of the adsorption. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhancing cisplatin delivery to hepatocellular carcinoma HepG2 cells using dual sensitive smart nanocomposite.

Science.gov (United States)

Salimi, Farzaneh; Dilmaghani, Karim Akbari; Alizadeh, Effat; Akbarzadeh, Abolfazl; Davaran, Soodabeh

2017-07-07

Targeted entrance and accumulation of higher doses of drugs into malignant cells could help in intensification of tumor specific cytotoxicity. A dual-responsive nanogel, poly(N-isopropylacrylamide)-co-poly(N,N-(dimethylamino)ethyl methacrylate) [P(NIPAM-co-DMA)] containing N-isopropylacrylamide (NIPAM) as thermoresponsive monomer and N,N-(dimethylamino)ethyl methacrylate (DMA) as pH-responsive monomer and methylene-bis-acrylamide (MBA) as cross-linking agent, was synthesized by free radical emulsion polymerization. Cisplatin along with magnetic Fe 3 O 4 nanoparticles (MNPs) was loaded into the nanogel by physically embedding the magnetic nanoparticles into hydrogel matrix after gelation to obtain drug-loaded magnetic nanocomposite [P(NIPAM-co-DMA)/Fe 3 O 4 ]. Drug loading efficiencies and drug release profiles of cisplatin-loaded P(NIPAM-co-DMA) nanogel and P(NIPAM-co-DMA)/Fe 3 O 4 nanocomposite were evaluated in vitro for controlled drug delivery in different temperature and pH conditions. Finally, the anticancer activity of P(NIPAM-co-DMA)/Fe 3 O 4 nanocomposite on human liver HepG2 cells was evaluated. Nanogel and nanocomposite showed significantly higher (p < .05) cisplatin release at 40 °C compared to 37 °C and at pH 5.7 compared to pH 7.4, demonstrating their temperature and pH sensitivity, respectively. The cytotoxicity assay of drug free nanogel on HepG2 cell line indicated that the nanogel is biocompatible and suitable as drug carrier. Moreover, MTT assay revealed that the cisplatin-loaded nanocomposite represented significant superior cytotoxicity (p < .05) to HepG2 cells as compared with free cisplatin.

In situ forming poly(ethylene glycol)- Poly(L -lactide) hydrogels via michael addition: Mechanical properties, degradation, and protein release

NARCIS (Netherlands)

Buwalda, S.J.; Dijkstra, Pieter J.; Feijen, Jan

2012-01-01

Chemically crosslinked hydrogels are prepared at remarkably low macromonomer concentrations from 8-arm poly(ethylene glycol)-poly(L-lactide) star block copolymers bearing acrylate end groups (PEG-(PLLAn)8-AC, n = 4 or 12) and multifunctional PEG thiols (PEG-(SH)n, n = 2, 4, or 8) through a

Microesferas poliméricas magnéticas à base de estireno e divinilbenzeno com morfologia casca e núcleo Magnetic polymeric microspheres based on styrene and divinylbenzene with core-shell morphology

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Washington J. F. Formiga

2013-01-01

Full Text Available Microesferas poliméricas com propriedades magnéticas à base de estireno (STY e divinilbenzeno (DVB foram sintetizadas usando a técnica de polimerização em suspensão em duas etapas. Na primeira, foram preparados os núcleos poliméricos à base de STY e DVB e magnetita. Na segunda, os núcleos foram previamente inchados em uma emulsão de STY e DVB e novamente polimerizados para a formação da casca. Foram variados o método de adição da emulsão e o tempo de inchamento. Os materiais obtidos foram caracterizados quanto ao tamanho de partícula por peneiramento, análise termogravimétrica (TGA, microscopia eletrônica de varredura (SEM e magnetometria de amostra vibrante (VSM. Os métodos avaliados na formação da casca de poli(estireno-co-divinilbenzeno produziram partículas com diâmetro médio maior do que o núcleo. Este resultado indica a formação de morfologia casca e núcleo. O controle morfológico só foi obtido com as resinas RR48/1 e RR48/3. O método onde a emulsão de estireno e divinilbenzeno foi adicionada em etapa única, seguida de 48 horas de inchamento do núcleo a 10 °C (RR48/1, forneceu o maior rendimento (64%. Além disso, todas as resinas casca-núcleo foram sensíveis ao estímulo magnético realizado por um ímã, atestando assim que foram produzidas resinas com propriedades magnéticas.Magnetic polymeric microspheres based on styrene (STY and divinylbenzene (DVB were synthesized in two steps. Firstly, the polymeric core, constituted by STY, DVB and magnetite, was prepared by suspension polymerization. Then, the core was swollen in a STY and DVB emulsion. Subsequently, a second suspension polymerization was carried out in order to form a shell. The emulsion addition method and the swelling time were varied. The particle size, morphology, thermal stability and magnetic properties of the microspheres were studied by sieving, thermogravimetric analysis (TGA, scanning electron microscopy (SEM and vibrating

Fabrication and characterization of novel multilayered structures by stereocomplexion of poly(D-lactic acid)/poly(L-lactic acid) and self-assembly of polyelectrolytes

Science.gov (United States)

Yang, Gesheng; Pastorino, Laura

2016-01-01

Summary The enantiomers poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA) were alternately adsorbed directly on calcium carbonate (CaCO3) templates and on poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) multilayer precursors in order to fabricate a novel layer-by-layer (LBL) assembly. A single layer of poly(L-lysine) (PLL) was used as a linker between the (PDLA/PLLA)n stereocomplex and the cores with and without the polymeric (PSS/PAH)n/PLL multilayer precursor (PEM). Nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) were used to characterize the chemical composition and molecular weight of poly(lactic acid) polymers. Both multilayer structures, with and without polymeric precursor, were firstly fabricated and characterized on planar supports. A quartz crystal microbalance (QCM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and ellipsometry were used to evaluate the thickness and mass of the multilayers. Then, hollow, spherical microcapsules were obtained by the removal of the CaCO3 sacrificial template. The chemical composition of the obtained microcapsules was confirmed by differential scanning calorimetry (DSC) and wide X-ray diffraction (WXRD) analyses. The microcapsule morphology was evaluated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements. The experimental results confirm the successful fabrication of this innovative system, and its full biocompatibility makes it worthy of further characterization as a promising drug carrier for sustained release. PMID:26925356

Influence of molar mass of polymer on the solvent activity for binary system of poly N-vinylcaprolactam and water

International Nuclear Information System (INIS)

Foruotan, Masumeh; Zarrabi, Mona

2009-01-01

The water activity in aqueous solution of poly N-vinyl caprolactam with different molecular weights is measured by isopiestic method at T = 308.15 K. The results show that water activity and vapour pressure of poly N-vinylcaprolactam solution increases with increasing the molecular weight. The Flory-Huggins model, the modified Flory-Huggins model and Freed Flory-Huggins equation + NRTL model are used for correlation of the experimental solvent activity. It is found that the Freed Flory-Huggins + NRTL model is better than the others

Synthesis and application of solar cells of poly (3-decylthiophene/N/titanium dioxide hybrid

Directory of Open Access Journals (Sweden)

2011-05-01

Full Text Available An organic-inorganic nanocomposite material of poly (3-decylthiophene and titanium dioxide doped with N (P3DT/N/TiO2 were synthesized. Structures were characterized using X-ray diffraction (XRD, infrared spectroscopy (IR, transmission electron microscopy (TEM, and X-ray photoelectron spectroscopy (XPS. Optical and electrochemical properties were determined using UV-visible spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. These tests indicated that P3DT/N/TiO2 was a new p-n semiconductor photoelectric material, and the solar cell prepared with P3DT/N/TiO2 performed well.

Síntesis de poli ácido láctico y poli ricinoleato empleando calentamiento por microondas y su utilización en la producción de termoplasticos de poliuretano Synthesis of poly lactic acid and poly ricinoleate using microwave heating and their use in the production of polyurethane thermoplastic

Directory of Open Access Journals (Sweden)

Paula Mazo

2011-01-01

Full Text Available En este trabajo se realiza la síntesis de poliuretano termoplástico (TPU utilizando oligómeros sintetizados a partir de ácido DL Láctico y ácido ricinoléico. Estos polioles fueron obtenidos desde fuentes renovables, mediante la policondensación de los monómeros sin catalizador. Se evalúo el efecto de las microondas en las reacciones, donde se encuentraron efectos no térmicos que disminuyen la energía de activación y aumentan la constante de velocidad, en una cinética de tercer orden; el seguimiento y la caracterización de los productos intermedios se realiza mediante la cuantificación de valor ácido por titulación (ASTM D4662 - 03 y número de hidroxilos (ASTM D4274 - 05. Los termoplásticos obtenidos se caracterizan mediante las siguientes pruebas: resistencia tensil y % elongación (ASTM D882-97, análisis de calorimetría diferencial de barrido (DSC, espectroscopía infrarroja (IR y microscopía de fuerza atómica (AFM. Los TPU se obtuvieron con un porcentaje de segmentos suaves del 50%, todos presentan morfología segmentada y segregación de fases. Las formulaciones con poli(DL ácido Láctico y Difenilmetanodiisocianato (MDI presentan la mayor rigidez y temperatura de transición vítrea (Tg.In this paper we report on the synthesis of thermoplastic polyurethane (TPU using oligomers synthesized from DL Lactic acid and ricinoleic acid. These polyols were obtained from renewable sources by polycondensation of monomers without catalysts. The effect of microwaves on the reactions was evaluated, where non-thermal effects were found to lower the activation energy and increase the rate constant in a third-order kinetics. The monitoring and characterization of intermediate products was done by quantification of acid value by titration (ASTM D4662 - 03 and hydroxyl number (ASTM D4274 - 05. Thermoplastics obtained are characterized by the following tests: tensile strength and elongation percentage (ASTM D882-97, analysis of

Poly(ethylene oxide) surfactant polymers.

Science.gov (United States)

Vacheethasanee, Katanchalee; Wang, Shuwu; Qiu, Yongxing; Marchant, Roger E

2004-01-01

We report on a series of structurally well-defined surfactant polymers that undergo surface-induced self-assembly on hydrophobic biomaterial surfaces. The surfactant polymers consist of a poly(vinyl amine) backbone with poly(ethylene oxide) and hexanal pendant groups. The poly(vinyl amine) (PVAm) was synthesized by hydrolysis of poly(N-vinyl formamide) following free radical polymerization of N-vinyl formamide. Hexanal and aldehyde-terminated poly(ethylene oxide) (PEO) were simultaneously attached to PVAm via reductive amination. Surfactant polymers with different PEO:hexanal ratios and hydrophilic/hydrophobic balances were prepared, and characterized by FT-IR, 1H-NMR and XPS spectroscopies. Surface active properties at the air/water interface were determined by surface tension measurements. Surface activity at a solid surface/water interface was demonstrated by atomic force microscopy, showing epitaxially molecular alignment for surfactant polymers adsorbed on highly oriented pyrolytic graphite. The surfactant polymers described in this report can be adapted for simple non-covalent surface modification of biomaterials and hydrophobic surfaces to provide highly hydrated interfaces.

Thermoresponsive polymer system based on poly(N-vinylcaprolactam) intended for local radiotherapy applications

Czech Academy of Sciences Publication Activity Database

Černoch, Peter; Černochová, Zulfiya; Kučka, Jan; Hrubý, Martin; Petrova, Svetlana; Štěpánek, Petr

2015-01-01

Roč. 98, April (2015), s. 7-12 ISSN 0969-8043 R&D Projects: GA MPO FR-TI4/625; GA MŠk(CZ) LH14079 Grant - others:AV ČR(CZ) M200501201 Program:M Institutional support: RVO:61389013 Keywords : poly(N-vinylcaprolactam) * tumor * brachytherapy Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.136, year: 2015

Synthesis and characterization of poly aniline/wood and poly aniline/carbon composites

International Nuclear Information System (INIS)

Kanwal, F.; Siddiqi, S.A.; Tasleem, S.

2009-01-01

Conducting polymers have shown many applications in the field of nano science, nano technology and nuclear science. Poly aniline (PAN I) is the most studied conducting polymer due to its environmental stability, easy availability of its raw materials, and simple synthesis. We have synthesized poly aniline and two of its conducting composites i.e., poly aniline-carbon and poly aniline-wood in acidic medium (HCI) using K/sub 2/Cr/sub 2/O/sub 7/ as oxidizing agent. All samples were characterized by FTIR and four-probe d.c. conductivity methods The synthesis was carried out at two different temperatures (0 degree C and -5 degree C) and it was found that the yield and conductivity were maximum at lower temperature (-5 degree C). The poly aniline-carbon composites showed enhanced conductivity whereas poly aniline-wood composites showed reduced conductivity when compared with the conductivity of pure poly aniline. (author)

Preparation and Properties of PTFE-PMMA Core-Shell Nanoparticles and Nanocomposites

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Diego Antonioli

2012-01-01

Full Text Available The preparation of polytetrafluoroethylene-poly(methyl methacrylate (PTFE-PMMA core-shell particles was described, featuring controlled size and narrow size distribution over a wide compositional range, through a seeded emulsion polymerization starting from a PTFE seed of 26 nanometers. Over the entire MMA/PTFE range, the particle size increases as the MMA/PTFE ratio increases. A very precise control over the particle size can be exerted by properly adjusting the ratio between the monomer and the PTFE seed. Particles in the 80–240 nm range can be prepared with uniformity indexes suited to build 2D and 3D colloidal crystals. These core-shell particles were employed to prepare nanocomposites with different compositions, through an annealing procedure at a temperature higher than the glass transition temperature of the shell forming polymer. A perfect dispersion of the PTFE particles within the PMMA matrix was obtained and optically transparent nanocomposites were prepared containing a very high PTFE amount.

Mechanical properties of a waterborne pressure-sensitive adhesive with a percolating poly(acrylic acid)-based diblock copolymer network: effect of pH.

Science.gov (United States)

Gurney, Robert S; Morse, Andrew; Siband, Elodie; Dupin, Damien; Armes, Steven P; Keddie, Joseph L

2015-06-15

Copolymerizing an acrylic acid comonomer is often beneficial for the adhesive properties of waterborne pressure-sensitive adhesives (PSAs). Here, we demonstrate a new strategy in which poly(acrylic acid) (PAA) is distributed as a percolating network within a PSA film formed from a polymer colloid. A diblock copolymer composed of PAA and poly(n-butyl acrylate) (PBA) blocks was synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization and adsorbed onto soft acrylic latex particles prior to their film formation. The thin adsorbed shells on the particles create a percolating network that raises the elastic modulus, creep resistance and tensile strength of the final film. When the film formation occurs at pH 10, ionomeric crosslinking occurs, and high tack adhesion is obtained in combination with high creep resistance. The results show that the addition of an amphiphilic PAA-b-PBA diblock copolymer (2.0 wt.%) to a soft latex provides a simple yet effective means of adjusting the mechanical and adhesive properties of the resulting composite film. Copyright © 2015 Elsevier Inc. All rights reserved.

Luminescence and efficiency optimization of InGaN/GaN core-shell nanowire LEDs by numerical modelling

Science.gov (United States)

Römer, Friedhard; Deppner, Marcus; Andreev, Zhelio; Kölper, Christopher; Sabathil, Matthias; Strassburg, Martin; Ledig, Johannes; Li, Shunfeng; Waag, Andreas; Witzigmann, Bernd

2012-02-01

We present a computational study on the anisotropic luminescence and the efficiency of a core-shell type nanowire LED based on GaN with InGaN active quantum wells. The physical simulator used for analyzing this device integrates a multidimensional drift-diffusion transport solver and a k . p Schrödinger problem solver for quantization effects and luminescence. The solution of both problems is coupled to achieve self-consistency. Using this solver we investigate the effect of dimensions, design of quantum wells, and current injection on the efficiency and luminescence of the core-shell nanowire LED. The anisotropy of the luminescence and re-absorption is analyzed with respect to the external efficiency of the LED. From the results we derive strategies for design optimization.

Preparation of Cotton-Wool-Like Poly(lactic acid-Based Composites Consisting of Core-Shell-Type Fibers

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Jian Wang

2015-11-01

Full Text Available In previous works, we reported the fabrication of cotton-wool-like composites consisting of siloxane-doped vaterite and poly(l-lactic acid (SiVPCs. Various irregularly shaped bone voids can be filled with the composite, which effectively supplies calcium and silicate ions, enhancing the bone formation by stimulating the cells. The composites, however, were brittle and showed an initial burst release of ions. In the present work, to improve the mechanical flexibility and ion release, the composite fiber was coated with a soft, thin layer consisting of poly(d,l-lactic-co-glycolic acid (PLGA. A coaxial electrospinning technique was used to prepare a cotton-wool-like material comprising “core-shell”-type fibers with a diameter of ~12 µm. The fibers, which consisted of SiVPC coated with a ~2-µm-thick PLGA layer, were mechanically flexible; even under a uniaxial compressive load of 1.5 kPa, the cotton-wool-like material did not exhibit fracture of the fibers and, after removing the load, showed a ~60% recovery. In Tris buffer solution, the initial burst release of calcium and silicate ions from the “core-shell”-type fibers was effectively controlled, and the ions were slowly released after one day. Thus, the mechanical flexibility and ion-release behavior of the composites were drastically improved by the thin PLGA coating.

Study of shallow trench isolation technology with a poly-Si sidewall buffer layer

International Nuclear Information System (INIS)

Juang, M H; Chen, C L; Jang, S L

2008-01-01

Shallow trench isolation (STI) technology with a poly-Si buffer layer at the trench sidewall has been studied. At the densification temperature of 950 °C, for the samples without using a poly-Si buffer layer, the resulting junction shows a leakage of about 700 nA cm −2 for a diode area of 100 × 100 µm 2 , primarily due to large peripheral junction leakage. The large leakage is ascribed to the defect generation caused by a thermally induced stress near the trench sidewall. The usage of a poly-Si buffer layer in the trench sidewall is found to significantly improve the junction characteristics. As a result, when a 40 nm poly-Si buffer layer is sandwiched between the Si substrate and the trench-fill silicon oxide, the resultant junctions show a leakage of only about 8 nA cm −2 . This result may reflect the considerably reduced thermally induced stress near the trench sidewall. Furthermore, at the densification temperature of 1100 °C, the usage of a poly-Si buffer layer can help to achieve excellent junctions with a leakage smaller than 5 nA cm −2 for a diode area of 100 × 100 µm 2

The thermal degradation of poly(iso-butyl methacrylate and poly(sec-butyl methacrylate

Directory of Open Access Journals (Sweden)

IVANKA G. POPOVIC

2000-12-01

Full Text Available The non-oxidative thermal degradation of poly(iso-butyl methacrylate and poly(sec-butyl methacrylate was investigated by studying changes in the polymer residue. Due to the different number of b-hydrogens in their ester substituents, these two polymeric isomers behave differently when subjected to elevated temperatures. Poly(iso-butyl methacrylate degrades quantitatively by depolymerisation with zip lengths of the same order of magnitude as those of poly(methyl methacrylate. Poly(sec-butyl methacrylate degrades by a combined degradation mechanism of depolymerisation and de-esterification. De-esterification becomes a significant thermolysis route at temperatures higher than 240°C.

Gate current for p+-poly PMOS devices under gate injection conditions

NARCIS (Netherlands)

Hof, A.J.; Holleman, J.; Woerlee, P.H.

2001-01-01

In current CMOS processing both n+-poly and p+-poly gates are used. The I-V –relationship and reliability of n+-poly devices are widely studied and well understood. Gate currents and reliability for p+-poly PMOS devices under gate injection conditions are not well understood. In this paper, the

Time-resolved small-angle neutron scattering study on soap-free emulsion polymerization

Energy Technology Data Exchange (ETDEWEB)

Motokawa, Ryuhei [Research Group of Soft Matter and Neutron Scattering, Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Koizumi, Satoshi [Research Group of Soft Matter and Neutron Scattering, Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan)]. E-mail: koizumi@neutrons.tokai.jaeri.go.jp; Hashimoto, Takeji [Research Group of Soft Matter and Neutron Scattering, Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Nakahira, Takayuki [Department of Applied Chemistry and Biotechnology, Chiba University, Chiba-shi, Chiba 263-8522 (Japan); Annaka, Masahiko [Department of Chemistry, Kyushu University, Fukuoka 812-8581 (Japan)

2006-11-15

We investigated an aqueous soap-free emulsion polymerization process of Poly(N-isopropylacrylamide)-block-poly(ethylene glycol) by ultra-small-angle and time-resolved small-angle neutron scattering methods. The results indicate that the compartmentalization of chain end radicals into solid-like micelle cores crucially leads to the quasi-living behavior of the radical polymerization by prohibiting recombination process.

Effect of Isotacticity of Linear Poly(N-isopropylacrylamide) on its ...

Indian Academy of Sciences (India)

decreased with the increase in the isotacticity of the polymer. Gelation ... microscopy (SEM), differential scanning calorimetry ... The gap between two paral- ... sidering degree of polymerization, x = 6) with benzyl ..... Apart from the blue shift, the absorbance value grad- ..... for Bethe lattice, n should have the value equal to.

Polaron Hopping in Nano-scale Poly(dA–Poly(dT DNA

Directory of Open Access Journals (Sweden)

Singh Mahi

2010-01-01

Full Text Available Abstract We investigate the current–voltage relationship and the temperature-dependent conductance of nano-scale samples of poly(dA–poly(dT DNA molecules. A polaron hopping model has been used to calculate the I–V characteristic of nano-scale samples of DNA. This model agrees with the data for current versus voltage at temperatures greater than 100 K. The quantities G 0 , i 0 , and T 1d are determined empirically, and the conductivity is estimated for samples of poly(dA–poly(dT.

Synthesis and characterization of foldable and magnetic field-sensitive, freestanding poly(vinyl acetate)/poly(vinyl chloride)/polyfuran composite and nanocomposite films

Energy Technology Data Exchange (ETDEWEB)

Sarıtaş, Sevilay; Eşsiz, Serpil; Sarı, Bekir, E-mail: bsari@gazi.edu.tr

2017-07-01

Highlights: • In this study, ternary composite/nanocomposite films were synthesized. • Magnetic field-sensitive folding films were prepared without any elastomer. • Morphological studies show that all composite films have a smooth surface. • The ternary composites/nanocomposite show improved thermal stability compared to the pure PF. - Abstract: In this study, polyfuran and poly(vinyl acetate)/poly(vinyl chloride)/polyfuran ternary composites were synthesized via the chemical polymerization method. The temperature and magnetic field–sensitive novel composites and the nanocomposite were obtained in the form of powders and films. It was observed that the prepared novel conductive films have superior properties at a certain temperature range (25–50 °C) such as bending and folding. The structural properties, thermal behavior, surface morphology, internal structure, and surface roughness of the prepared samples were investigated by various characterization techniques. The conductivities of the samples were measured at room temperature and different temperatures by the four-point technique. X-ray Diffraction analysis results demonstrated that the PF and composites have an amorphous structure, whereas the nanocomposite is in crystalline form. The saturation magnetization (Ms) values of the magnetite and nanocomposite were found to be 58.9 and 5.3 emu g{sup −1}, respectively. It was found that magnetite-doped nanocomposite has superparamagnetic properties at room temperature.

Self-assembly in poly(dimethylsiloxane)-poly(ethylene oxide) block copolymer template directed synthesis of Linde type A zeolite.

Science.gov (United States)

Bonaccorsi, Lucio; Calandra, Pietro; Kiselev, Mikhail A; Amenitsch, Heinz; Proverbio, Edoardo; Lombardo, Domenico

2013-06-11

We describe the hydrothermal synthesis of zeolite Linde type A (LTA) submicrometer particles using a water-soluble amphiphilic block copolymer of poly(dimethylsiloxane)-b-poly(ethylene oxide) as a template. The formation and growth of the intermediate aggregates in the presence of the diblock copolymer have been monitored by small-angle X-ray scattering (SAXS) above the critical micellar concentration at a constant temperature of 45 °C. The early stage of the growth process was characterized by the incorporation of the zeolite LTA components into the surface of the block copolymer micellar aggregates with the formation of primary units of 4.8 nm with a core-shell morphology. During this period, restricted to an initial time of 1-3 h, the core-shell structure of the particles does not show significant changes, while a subsequent aggregation process among these primary units takes place. A shape transition of the SAXS profile at the late stage of the synthesis has been connected with an aggregation process among primary units that leads to the formation of large clusters with fractal characteristics. The formation of large supramolecular assemblies was finally verified by scanning electron microscopy, which evidenced the presence of submicrometer aggregates with size ranging between 100 and 300 nm, while X-ray diffraction confirmed the presence of crystalline zeolite LTA. The main finding of our results gives novel insight into the mechanism of formation of organic-inorganic mesoporous materials based on the use of a soft interacting nanotemplate as well as stimulates the investigation of alternative protocols for the synthesis of novel hybrid materials with new characteristics and properties.

Control of in vivo disposition and immunogenicity of polymeric micelles by adjusting poly(sarcosine) chain lengths on surface

Science.gov (United States)

Kurihara, Kensuke; Ueda, Motoki; Hara, Isao; Ozeki, Eiichi; Togashi, Kaori; Kimura, Shunsaku

2017-07-01

Four kinds of A3B-type amphiphilic polydepsipeptides, (poly(sarcosine))3- b-poly( l-lactic acid) (the degree of polymerization of poly(sarcosine) are 10, 33, 55, and 85; S10 3 , S33 3 , S55 3 , and S85 3 ) were synthesized to prepare core-shell type polymeric micelles. Their in vivo dispositions and stimulations to trigger immune system to produce IgM upon multiple administrations to mice were examined. With increasing poly(sarcosine) chain lengths, the hydrophilic shell became thicker and the surface density at the most outer surface decreased on the basis of dynamic and static light scattering measurements. These two physical elements of polymeric micelles elicited opposite effects on the immune response in light of the chain length therefore to show an optimized poly(sarcosine) chain length existing between 33mer and 55mer to suppress the accelerated blood clearance phenomenon associated with polymeric micelles.

A broadening temperature sensitivity range with a core-shell YbEr@YbNd double ratiometric optical nanothermometer

Science.gov (United States)

Marciniak, L.; Prorok, K.; Francés-Soriano, L.; Pérez-Prieto, J.; Bednarkiewicz, A.

2016-02-01

The chemical architecture of lanthanide doped core-shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ~980 to the more relevant ~808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb-Er co-doped core nanoparticles with the Yb-Nd co-doped shell, we have intentionally combined temperature dependent Er up-conversion together with temperature dependent Nd --> Yb energy transfer, and thus have expanded the temperature response range ΔT of a single nanoparticle based optical nano-thermometer under single ~808 nm wavelength photo-excitation from around ΔT = 150 K to over ΔT = 300 K (150-450 K). Such engineered nanocrystals are suitable for remote optical temperature measurements in technology and biotechnology at the sub-micron scale.The chemical architecture of lanthanide doped core-shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ~980 to the more relevant ~808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb-Er co-doped core nanoparticles with the Yb-Nd co-doped shell, we have intentionally combined temperature dependent Er up-conversion together with temperature dependent Nd --> Yb energy transfer, and thus have expanded the temperature response range ΔT of a single nanoparticle

New Poly(amide-imide)/Nanocomposites Reinforced Silicate Nanoparticles Based on N-pyromellitimido-L-phenyl Alanine Containing Ether Moieties

Science.gov (United States)

Faghihi, Khalil; Shabanian, Meisam; Dadfar, Ehsan

2012-02-01

A series of Poly(amide-imide)/montmorillonite nanocomposites containing N-pyromellitimido-L-phenyl alanine moiety in the main chain were synthesized by a convenient solution intercalation technique. Poly(amide-imide) (PAI) 5 as a source of polymer matrix was synthesized by the direct polycondensation reaction of N-pyromellitimido-L-phenyl alanine 3 with 4,4'-diamino diphenyl ether 4 in the presence of triphenyl phosphite (TPP), CaCl2, pyridine and N-methyl-2-pyrrolidone (NMP). The resulting nanocomposite films were characterized by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The results showed that organo-modified clay was dispersed homogeneously in PAI matrix. TGA indicated an enhancement of thermal stability of new nanocomposites compared with the pure polymer.

The Influence of Preparation Conditions on the Electrical Conductivity of Poly N-Methyl-pyrrole Films

DEFF Research Database (Denmark)

Vidanapathirana, K.; Careem, M.A.; Skaarup, Steen

1999-01-01

on the electrical conductivity has been investigated. The conductivity was measured by the in situ method using a specially prepared two-band microelectrode. The current density used during the polymerization has a considerable influence on the conductivity, as earlier observed for polypyrrole in non......Electro-active poly-N-methylpyrrole (PNMP) films have been galvanostatically polymerized under a range of conditions. The influence of the conditions used in electropolymerization, such as electrolyte concentration, current density, type of doping anion. and temperature during polymerization......-aqueous electrolytes. The conductivity changes with the size of the anion and the concentration of the electrolyte as well as on the temperature at which the polymerization was carried out. Polymer films formed at relatively higher temperatures had lower conductivities and were not able to insert as many counterions...

Preparation of Ca-alginate coated nZVI core shell beads for uranium (VI) removal from aqueous solution

International Nuclear Information System (INIS)

Shuhong Hu; Xiaoyan Lin; Yahui Zhang; Meiling Shi

2017-01-01

In this study, the core-shell nanoscale zero-valent iron (nZVI)@Alg-Ca beads were synthesized by coaxial electronic injection method for removal of U (VI) from aqueous solution, and characterized by SEM, EDX and XPS. The results showed that the pseudo-second-order models and the Langmuir isotherm model fitted well with the data obtained. The removal mechanism may include both physical adsorption of U (VI) on the surface or inside of core-shell nZVI@Alg-Ca beads and subsequent reduction of U (VI) to U (IV). Therefore, the core-shell nZVI@Alg-Ca beads would have an application prospect in effective removal of U (VI) contamination from aqueous solution. (author)

Antiresonant guiding in a poly(methyl-methacrylate) hollow-core optical fiber

DEFF Research Database (Denmark)

Markos, Christos; Nielsen, Kristian; Bang, Ole

2015-01-01

Strong antiresonant reflecting optical waveguiding is demonstrated in a novel poly (methyl-methacrylate) (PMMA) hollow-core fiber. The transmission spectrum of the fiber was characterized using a supercontinuum source and it revealed distinct resonances with resonant dips as strong as ~20 d......B in the wavelength range 480-900 nm, where PMMA has low absorption. The total propagation loss of the fiber was measured to have a minimum of ~45 dB m-1 at around 500 nm. The thermal sensitivity of the fiber is 256 ± 16 pm °C-1, defined as the red-shift of the resonances per °C, which is three times higher than...... the sensitivity of polymer fiber Bragg gratings....

Soft microgel particles at fluid interfaces

NARCIS (Netherlands)

Deshmukh, Omkar

2015-01-01

We investigate the use of soft microgel particles based on a thermosensitive poly- mer, poly-N-isopropylacrylamide (PNIPAM) to stabilize a fluid interface. We also study the effect of temperature on the adsorption kinetics and the interfacial behaviour of these particles on air-water and oil-water

Poly(ethylene oxide)–Poly(propylene oxide)-Based Copolymers for ...

African Journals Online (AJOL)

Amphiphilic poly(ethylene oxide)–poly(propylene oxide) (PEO–PPO)-based copolymers are thermoresponsive materials having aggregation properties in aqueous medium. As hydrosolubilizers of poorly water-soluble drugs and improved stability of sensitive agents, these materials have been investigated for improvement ...

Electron mobility limited by optical phonons in wurtzite InGaN/GaN core-shell nanowires

Science.gov (United States)

Liu, W. H.; Qu, Y.; Ban, S. L.

2017-09-01

Based on the force-balance and energy-balance equations, the optical phonon-limited electron mobility in InxGa1-xN/GaN core-shell nanowires (CSNWs) is discussed. It is found that the electrons tend to distribute in the core of the CSNWs due to the strong quantum confinement. Thus, the scattering from first kind of the quasi-confined optical (CO) phonons is more important than that from the interface (IF) and propagating (PR) optical phonons. Ternary mixed crystal and size effects on the electron mobility are also investigated. The results show that the PR phonons exist while the IF phonons disappear when the indium composition x < 0.047, and vice versa. Accordingly, the total electron mobility μ first increases and then decreases with indium composition x, and reaches a peak value of approximately 3700 cm2/(V.s) when x = 0.047. The results also show that the mobility μ increases as increasing the core radius of CSNWs due to the weakened interaction between the electrons and CO phonons. The total electron mobility limited by the optical phonons exhibits an obvious enhancement as decreasing temperature or increasing line electron density. Our theoretical results are expected to be helpful to develop electronic devices based on CSNWs.

Gold Nanoparticles Size Design and Control by Poly(N,N′-diethylaminoethyl methacrylate)

OpenAIRE

Cortez-Lemus, Norma A.; Licea-Claverie, Angel; Paraguay-Delgado, Francisco; Alonso-Nuñez, Gabriel

2015-01-01

Poly(N,N′-diethylaminoethyl methacrylate) (PDEAEM) with different molecular weights was used to stabilize gold nanoparticles (AuNPs) obtained by in situ reduction of tetrachloroauric acid using citrates under acidic conditions and in organic/alcoholic medium. The influence of the pH value on gold nanoparticle size in the presence of PDEAEM was investigated. Results show that the pH of the reacting mixture has a dramatic effect on the size, polydispersity, and morphology of the resulting AuNPs...

Poly (ADP-ribose) metabolism in alkylated mouse L5178Y cells

International Nuclear Information System (INIS)

Boyle, J.M.

1985-01-01

Poly ADP-ribosylation of two mouse lymphoma cell lines, L5178Y (LS) and the radiation and alkylating agent resistant derivative AII, was investigated by uptake of [ 3 H]NAD by permeabilised cells into acid-precipitable material that was sensitive to phosphodiesterase but insensitive to DNase and RNase. Basal activities in both lymphoma lines were 3-4-fold greater than in mouse L1210 leukaemia cells. However, total endogenous poly (ADP-R) polymerase activity in both L5178Y cell lines, stimulated by a large excess of DNase in the presence of Triton X-100, was less than half the activity in L1210 cells. Doses of N-methyl-N-nitrosourea (MNU) that produced 20-50% survival of colony-forming units increased poly (ADP-R) in both lymphoma lines by only 25% compared with 377% in L1210 cells when synthesis was measured immediately after a 30-min exposure of MNU. Concentrations of 3-aminobenzamide (3AB) above 2.5 mM inhibited colony-forming ability of lymphoma cells and equally inhibited uptake of [ 14 C]formate into protein, RNA and DNA indicating that 3AB behaves as a general metabolic poison. Non-toxic concentrations of 3AB potentiated cell killing by MNU to a similar degree in both lymphoma cell lines. In conclusion, the authors have found little evidence to support the hypothesis that the differential sensitivity of LS and AII is related to poly ADP-ribosylation. Compared with other mouse cells, L5178Y cells appear deficient in poly (ADP-R) polymerase and poly (ADP-R) glycohydrolase activities

PLGA-lecithin-PEG core-shell nanoparticles for controlled drug delivery.

Science.gov (United States)

Chan, Juliana M; Zhang, Liangfang; Yuet, Kai P; Liao, Grace; Rhee, June-Wha; Langer, Robert; Farokhzad, Omid C

2009-03-01

Current approaches to encapsulate and deliver therapeutic compounds have focused on developing liposomal and biodegradable polymeric nanoparticles (NPs), resulting in clinically approved therapeutics such as Doxil/Caelyx and Genexol-PM, respectively. Our group recently reported the development of biodegradable core-shell NP systems that combined the beneficial properties of liposomal and polymeric NPs for controlled drug delivery. Herein we report the parameters that alter the biological and physicochemical characteristics, stability, drug release properties and cytotoxicity of these core-shell NPs. We further define scalable processes for the formulation of these NPs in a reproducible manner. These core-shell NPs consist of (i) a poly(D,L-lactide-co-glycolide) hydrophobic core, (ii) a soybean lecithin monolayer, and (iii) a poly(ethylene glycol) shell, and were synthesized by a modified nanoprecipitation method combined with self-assembly. Preparation of the NPs showed that various formulation parameters such as the lipid/polymer mass ratio and lipid/lipid-PEG molar ratio controlled NP physical stability and size. We encapsulated a model chemotherapy drug, docetaxel, in the NPs and showed that the amount of lipid coverage affected its drug release kinetics. Next, we demonstrated a potentially scalable process for the formulation, purification, and storage of NPs. Finally, we tested the cytotoxicity using MTT assays on two model human cell lines, HeLa and HepG2, and demonstrated the biocompatibility of these particles in vitro. Our data suggest that the PLGA-lecithin-PEG core-shell NPs may be a useful new controlled release drug delivery system.

pH- and thermo-responsive microcontainers as potential drug delivery systems: Morphological characteristic, release and cytotoxicity studies.

Science.gov (United States)

Efthimiadou, Eleni K; Tapeinos, Christos; Tziveleka, Leto-Aikaterini; Boukos, Nikos; Kordas, George

2014-04-01

Polymeric pH- and thermo-sensitive microcontainers (MCs) were developed as a potential drug delivery system for cancer therapy. It is well known that cancer cells exhibit notable characteristics such as acidic pH due to glycolytic cycle and higher temperature due to their higher proliferation rate. Based on these characteristics, we constructed a dual pH- and thermo-sensitive material for specific drug release on the pathological tissue. The MC's fabrication is based on a two-step procedure, in which, the first step involves the core synthesis and the second one is related to the shell formation. The core consists of poly(methyl methacrylate (PMMA), while the shell consists of PMMA, poly(isopropylacrylamide), poly(acrylic acid) and poly(divinylbenzene). Three different types of MCs were synthesized based on the seed polymerization method. The synthesized MCs were characterized structurally by Fourier transform infrared and morphologically by scanning electron microscopy. Dynamic light scattering was also used to study their behavior in aqueous solution under different pH and temperature conditions. For the loading and release study, the anthracycline drug daunorubicin (DNR) was used as a model drug, and its release properties were evaluated under different pH and thermo-conditions. Cytotoxicity studies were also carried out against MCF-7 breast cancer and 3T3 mouse embryonic fibroblast cells. According to our results, the synthesized microcontainers present desired pH and thermo behavior and can be applied in drug delivery systems. It is worth mentioning that the synthesized microcontainers which incorporated the drug DNR exhibit higher toxicity than the free drug. Copyright © 2014 Elsevier B.V. All rights reserved.

UV and γ-ray resistance of poly(N-methylmaleimide-alt-isobutene) and poly(diisopropyl fumarate) as transparent polymer films

Science.gov (United States)

Imaizumi, Ryota; Furuta, Masakazu; Okamura, Haruyuki; Matsumoto, Akikazu

2017-09-01

UV and γ-ray resistance of transparent polymers obtained by radical polymerization of maleic and fumaric acid derivatives, i.e., an alternating copolymer of N-methylmaleimide and isobutene (PMI) and poly(diisopropyl fumarate) (PDiPF), was investigated. Transmittance in UV and visible regions of these polymers were examined after UV irradiation and compared with the results for poly(methyl methacrylate) (PMMA) and polycarbonate (PC) as conventional transparent polymers. The order of stability toward UV irradiation was PMMA≈PDiPF>PMI>>PC, deduced from changes in the transmittance of 380 nm light. Tensile mechanical properties, such as elastic modulus, maximum strength, and elongation values of PMI, PDiPF, and PMMA were also investigated after UV and γ-radiation. UV irradiation induced the side chain scission of PMI and PDiPF via Norrish I type reaction as well as crosslinking by combination between formed polymer radicals, leading to deterioration in their optical and mechanical properties. γ-radiation induced significant changes in molecular weight and mechanical properties of the polymers. In conclusion, PMI exhibited unchanged mechanical properties and PDiPF maintained its high transparency under various irradiation conditions.

Bonding at Compatible and Incompatible Amorphous Interfaces of Polystyrene and Poly(Methyl Methacrylate) Below the Glass Transition Temperature

DEFF Research Database (Denmark)

Boiko, Yuri M.; Lyngaae-Jørgensen, Jørgen

2004-01-01

Films of high-molecular-weight amorphous polystyrene (PS, M-w = 225 kg/mol, M-w/M-n = 3, T-g-bulk = 97degreesC, where T-g-bulk is the glass transition temperature of the bulk sample) and poly(methyl methacrylate) (PMMA, M-w = 87 kg/mol, M-w/M-n = 2, Tg-bulk = 109degreesC) were brought into contact...

Synthesis and Characterization of Microencapsulated Phase Change Materials with Poly(urea-urethane) Shells Containing Cellulose Nanocrystals.

Science.gov (United States)

Yoo, Youngman; Martinez, Carlos; Youngblood, Jeffrey P

2017-09-20

The main objective of this study is to develop microencapsulation technology for thermal energy storage incorporating a phase change material (PCM) in a composite wall shell, which can be used to create a stable environment and allow the PCM to undergo phase change without any outside influence. Surface modification of cellulose nanocrystals (CNCs) was conducted by grafting poly(lactic acid) oligomers and oleic acid to improve the dispersion of nanoparticles in a polymeric shell. A microencapsulated phase change material (methyl laurate) with poly(urea-urethane) (PU) composite shells containing the hydrophobized cellulose nanocrystals (hCNCs) was fabricated using an in situ emulsion interfacial polymerization process. The encapsulation process of the PCMs with subsequent interfacial hCNC-PU to form composite microcapsules as well as their morphology, composition, thermal properties, and release rates was examined in this study. Oil soluble Sudan II dye solution in methyl laurate was used as a model hydrophobic fill, representing other latent fills with low partition coefficients, and their encapsulation efficiency as well as dye release rates were measured spectroscopically in a water medium. The influence of polyol content in the PU polymer matrix of microcapsules was investigated. An increase in polyol contents leads to an increase in the mean size of microcapsules but a decrease in the gel content (degree of cross-linking density) and permeability of their shell structure. The encapsulated PCMs for thermal energy storage demonstrated here exhibited promising performance for possible use in building or paving materials in terms of released heat, desired phase transformation temperature, chemical and physical stability, and concrete durability during placement.

Synthesis and Characterization of pH and Thermo Dual-Responsive Hydrogels with a Semi-IPN Structure Based on N-Isopropylacrylamide and Itaconamic Acid.

Science.gov (United States)

Rwei, Syang-Peng; Tuan, Huynh Nguyen Anh; Chiang, Whe-Yi; Way, Tun-Fun

2018-04-28

A series of semi-interpenetrating polymer network (semi-IPN) hydrogels were synthesized and investigated in this study. Linear copolymer poly( N -isopropylacrylamide-co-itaconamic acid) p(NIPAM-co-IAM), which is formed by copolymerization of N -isopropylacrylamide (NIPAM) and itaconamic acid (IAM, 4-amino-2-ethylene-4-oxobutanoic acid), was introduced into a solution of NIPAM to form a series of pH and thermo dual-responsive p(NIPAM-co-IAM)/pNIPAM semi-IPN hydrogels by free radical polymerization. The structural, morphological, chemical, and physical properties of the linear copolymer and semi-IPN hydrogels were investigated. The semi-IPN hydrogel showed high thermal stability according to thermal gravimetric analyzer (TGA). Scanning electronic microscopy (SEM) images showed that the pore size was in the range of 119~297 µm and could be controlled by the addition ratio of the linear copolymer in the semi-IPN structure. The addition of linear copolymer increased the fracture strain from 57.5 ± 2.9% to 91.1 ± 4.9% depending on the added amount, while the compressive modulus decreased as the addition increased. Moreover, the pH and thermo dual-responsive properties were investigated using differential scanning calorimetry (DSC) and monitoring the swelling behavior of the hydrogels. In deionized (DI) water, the equilibrium swelling ratio of the hydrogels decreased as the temperature increased from 20 °C to 50 °C, while it varied in various pH buffer solutions. In addition, the swelling and deswelling rates of the hydrogels also significantly increased. The results indicate that the novel pH-thermo dual-responsive semi-IPN hydrogels were synthesized successfully and may be a potential material for biomedical, drug delivery, or absorption application.

Drug-Induced Morphology Switch in Drug Delivery Systems Based on Poly(2-oxazoline)s

Science.gov (United States)

2015-01-01

Defined aggregates of polymers such as polymeric micelles are of great importance in the development of pharmaceutical formulations. The amount of drug that can be formulated by a drug delivery system is an important issue, and most drug delivery systems suffer from their relatively low drug-loading capacity. However, as the loading capacities increase, i.e., promoted by good drug–polymer interactions, the drug may affect the morphology and stability of the micellar system. We investigated this effect in a prominent system with very high capacity for hydrophobic drugs and found extraordinary stability as well as a profound morphology change upon incorporation of paclitaxel into micelles of amphiphilic ABA poly(2-oxazoline) triblock copolymers. The hydrophilic blocks A comprised poly(2-methyl-2-oxazoline), while the middle blocks B were either just barely hydrophobic poly(2-n-butyl-2-oxazoline) or highly hydrophobic poly(2-n-nonyl-2-oxazoline). The aggregation behavior of both polymers and their formulations with varying paclitaxel contents were investigated by means of dynamic light scattering, atomic force microscopy, (cryogenic) transmission electron microscopy, and small-angle neutron scattering. While without drug, wormlike micelles were present, after incorporation of small amounts of drugs only spherical morphologies remained. Furthermore, the much more hydrophobic poly(2-n-nonyl-2-oxazoline)-containing triblock copolymer exhibited only half the capacity for paclitaxel than the poly(2-n-butyl-2-oxazoline)-containing copolymer along with a lower stability. In the latter, contents of paclitaxel of 8 wt % or higher resulted in a raspberry-like micellar core. PMID:24548260

Poly(styrene-co-N-methacryloyl-l-phenylalanine methyl ester)-functionalized magnetic nanoparticles as sorbents for the analysis of sodium benzoate in beverages.

Science.gov (United States)

Ji, Shilei; Li, Nan; Qi, Li; Wang, Minglin

2017-01-01

In this study, poly(styrene-co-N-methacryloyl-l-phenylalanine methyl ester)-functionalized magnetic nanoparticles were constructed and used as magnetic solid-phase extraction sorbents for analysis of food preservatives in beverages. To prepare the poly(amino acid)-based sorbents, N-methacryloyl-l-phenylalanine methyl ester, and styrene served as the functional monomers and modified onto the magnetic nanoparticles via free radical polymerization. Interestingly, compared with propylparaben and potassium sorbate, the proposed poly(amino acid)-based sorbents showed a good selectivity to sodium benzoate. The adsorption capacity of the sorbents to sodium benzoate was 6.08 ± 0.31 mg/g. Moreover, the fast adsorption equilibrium could be reached within 5 min. Further, the resultant poly(amino acid)-based sorbents were applied in the analysis of sodium benzoate in real beverage samples. The results proved that the proposed magnetic solid-phase extraction sorbents have a great potential for the analysis of preservatives in food samples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of carbon nanospheres by the pyrolysis of polyacrylonitrile–poly(methyl methacrylate core–shell composite nanoparticles

Directory of Open Access Journals (Sweden)

Dafu Wei

2017-09-01

Full Text Available Carbon nanospheres with a high Brunauer–Emmett–Teller (BET specific surface area were fabricated via the pyrolysis of polyacrylonitrile–poly(methyl methacrylate (PAN–PMMA core–shell nanoparticles. Firstly, PAN–PMMA nanoparticles at high concentration and low surfactant content were controllably synthesized by a two-stage azobisisobutyronitrile (AIBN-initiated semicontinuous emulsion polymerization. The carbon nanospheres were obtained after the PAN core domain was converted into carbon and the PMMA shell was sacrificed via the subsequent heat treatment steps. The thickness of the PMMA shell can be easily adjusted by changing the feeding volume ratio (FVR of methyl methacrylate (MMA to acrylonitrile (AN. At an FVR of 1.6, the coarse PAN cores were completely buried in the PMMA shells, and the surface of the obtained PAN–PMMA nanoparticles became smooth. The thick PMMA shell can inhibit the adhesion between carbon nanospheres caused by cyclization reactions during heat treatment. The carbon nanospheres with a diameter of 35–65 nm and a high BET specific surface area of 612.8 m2/g were obtained from the PAN–PMMA nanoparticles synthesized at an FVR of 1.6. The carbon nanospheres exhibited a large adsorption capacity of 190.0 mg/g for methylene blue, thus making them excellent adsorbents for the removal of organic pollutants from water.

Entre la literatura y la práctica política. Una aproximación a la Venezuela de Rómulo Gallegos

Directory of Open Access Journals (Sweden)

Lisandro Angelini

2014-01-01

Full Text Available La trayectoria de Rómulo Gallegos, reflejada en sus obras literarias, así como en su rol intelectual y político, resulta una opción pertinente para el análisis del pensamiento de este autor durante el período de consolidación del modelo de Estado-Nación venezolano moderno. Así, el objetivo general de este trabajo es determinar la interacción entre la producción literaria de Rómulo Gallegos y el pro- ceso de construcción del Estado-Nación, teniendo como referencia las condiciones sociales, culturales y políticas del espacio venezolano y el contexto latinoamericano del siglo XX. En tanto que como objetivos específicos se persigue, en primer lugar, identificar el rol intelectual de Gallegos y princi- palmente el impacto de su obra durante la primera mitad del siglo XX. En segundo lugar, analizar las preocupaciones políticas del autor, y el modo en que estas condicionan y contribuyen al contenido de sus narraciones literarias. Respecto al abordaje metodológico de la investigación, este se ha planteado en términos cuali- tativos, debido al carácter del problema y los objetivos definidos. Se ha realizado paralelamente una lectura profunda de las fuentes obtenidas, así como de la bibliografía en general, procediendo a su recolección y organización de las mismas siguiendo la lógica de los objetivos propuestos. Los resultados a los que nos ha conducido el relevamiento de las fuentes y la bibliografía, po- nen de manifiesto que el intento de reconfigurar el relato fundacional venezolano desde la ficción literaria, por un lado, y el objetivo de consolidar un proyecto político renovador, por otro, si bien gozaron de una amplia difusión editorial, no pudieron verse materializados desde la práctica polí- tica, ya que un golpe de Estado, que alejó a Gallegos tempranamente del poder ejecutivo, reinstauró en Venezuela una visión republicana tradicional y un gobierno elitista y autoritario.

Morphological, dielectric and electric conductivity characteristics of clay-containing nanohybrids of Poly(N-Vinyl Carbazole) and Polypyrrole

CSIR Research Space (South Africa)

Haldar, I

2012-10-01

Full Text Available Poly(N-vinyl carbazole) (PNVC) and polypyrrole (PPY)-montmorillonite (MMT) clay hybrids were prepared by mechanical grinding of the respective monomers with MMT followed by subsequent standard processing methods. Fourier transform infrared...

Eco-friendly synthesis of core-shell structured (TiO2/Li2CO3) nanomaterials for low cost dye-sensitized solar cells.

Science.gov (United States)

Karuppuchamy, S; Brundha, C

2016-12-01

Core-shell structured TiO 2 /Li 2 CO 3 electrode was successfully synthesized by eco-friendly solution growth technique. TiO 2 /Li 2 CO 3 electrodes were characterized using X-ray Diffractometer (XRD), Scanning electron microscopy (SEM) and photocurrent-voltage measurements. The synthesized core-shell electrode material was sensitized with tetrabutylammonium cis-di(thiocyanato)-N,N'-bis(4-carboxylato-4'-carboxylic acid-2,2'-bipyridine)ruthenate(II) (N-719). The performance of dye-sensitized solar cells (DSCs) based on N719 dye modified TiO 2 /Li 2 CO 3 electrodes was investigated. The effect of various shell thickness on the photovoltaic performance of the core-shell structured electrode is also investigated. We found that Li 2 CO 3 shells of all thicknesses perform as inert barriers which improve open-circuit voltage (V oc ) of the DSCs. The energy conversion efficiency was greatly dependent on the thickness of Li 2 CO 3 on TiO 2 film, and the highest efficiency of 3.7% was achieved at the optimum Li 2 CO 3 shell layer. Copyright © 2015 Elsevier Inc. All rights reserved.

Surface mobility and structural transitions of poly(n-alkyl methacrylates) probed by dynamic contact angle measurements

NARCIS (Netherlands)

van Damme, H.S.; Hogt, A.H.; Feijen, Jan

1986-01-01

Dynamic contact angles and contact-angle hysteresis of a series of poly(n-alkyl methacrylates) (PAMA) were investigated using the Wilhelmy plate technique. The mobility of polymer surface chains, segments, and side groups affected the measured contact angles and their hysteresis. A model is

Room-temperature fabrication of core-shell nano-ZnO/pollen grain biocomposite for adsorptive removal of organic dye from water

International Nuclear Information System (INIS)

Tzvetkov, George; Kaneva, Nina; Spassov, Tony

2017-01-01

Highlights: • Meso-/macro-porous nano-ZnO covered pollen grains are prepared at room temperature. • A possible formation mechanism of the core-shell microparticles was proposed. • Adsorptive removal of Malachite Green from water by the biocomposite is studied. - Abstract: A new core-shell nano-ZnO/pollen grain (n-ZnO/PG) biocomposite has been successfully synthesized via simple and low-temperature two-step liquid precipitation method. The synthetic strategy consists of grafting the surface of pine pollen grains (PG) with Zn"2"+-organic complexes followed by a treatment in Zn(CH_3COO)_2/NaOH solution, thus producing a closed n-ZnO shell around the organic core, with a thickness of ∼450 nm. Scanning electron microscopy, X-ray diffraction, FTIR, XPS and UV–vis spectroscopy measurements along with N_2 adsorption/desorption were used to characterize the resulting n-ZnO/PG biocomposite. The as-prepared core-shell microparticles are meso-/macro-porous with BET surface area of 25 m"2 g"−"1 and total pore volume of 0.26 cm"3 g"−"1. The adsorption properties of n-ZnO/PG were evaluated through adsorption of Malachite Green (MG) from aqueous medium at room temperature (25 °C). For the sake of comparison, the physico-chemical and adsorptive properties of the raw PG and pure n-ZnO were also examined. Results indicate that n-ZnO/PG is the most favorable for the adsorption of MG under the conditions used in this study. The adsorption kinetic data for PG, n-ZnO and n-ZnO/PG follow the pseudo-second order equation and the maximum adsorption capacity follows an order of n-ZnO/PG > n-ZnO > PG. For n-ZnO/PG an adsorption uptake up to 145.9 mg g"−"1 is observed. The as-prepared core-shell biocomposite material is a promising cost-effective and environmentally friendly adsorbent due to its textural properties, surface chemistry, adsorption capacity and recyclability.

Smart stimuli sensitive nanogels in cancer drug delivery and imaging: a review.

Science.gov (United States)

Maya, S; Sarmento, Bruno; Nair, Amrita; Rejinold, N Sanoj; Nair, Shantikumar V; Jayakumar, R

2013-01-01

Nanogels are nanosized hydrogel particles formed by physical or chemical cross-linked polymer networks. The advantageous properties of nanogels related to the ability of retaining considerable amount of water, the biocompatibility of the polymers used, the ability to encapsulate and protect a large quantity of payload drugs within the nanogel matrix, the high stability in aqueous media, their stimuli responsively behavior potential, and the versatility in release drugs in a controlled manner make them very attractive for use in the area of drug delivery. The materials used for the preparation of nanogels ranged from natural polymers like ovalbumin, pullulan, hyaluronic acid, methacrylated chondroitin sulfate and chitosan, to synthetic polymers like poly (N-isopropylacrylamide), poly (Nisopropylacrylamide- co-acrylic acid) and poly (ethylene glycol)-b-poly (methacrylic acid). The porous nanogels have been finding application as anti-cancer drug and imaging agent reservoirs. Smart nanogels responding to external stimuli such as temperature, pH etc can be designed for diverse therapeutic and diagnostic applications. The nanogels have also been surface functionalized with specific ligands aiding in targeted drug delivery. This review focus on stimuli-sensitive, multi-responsive, magnetic and targeted nanogels providing a brief insight on the application of nanogels in cancer drug delivery and imaging in detail.

Poly(vinyl alcohol)/poly(acrylic acid)/TiO2/graphene oxide nanocomposite hydrogels for pH-sensitive photocatalytic degradation of organic pollutants

International Nuclear Information System (INIS)

Moon, Young-E; Jung, Gowun; Yun, Jumi; Kim, Hyung-Il

2013-01-01

Graphical abstract: The photocatalytic removal of pollutants was improved by the two-step mechanism based on the adsorption of pollutants by hydrogel and the effective decomposition by combination of TiO 2 and graphene oxide. -- Highlights: • pH sensitive PVA/PAAc hydrogels were prepared by radical polymerization and condensation reaction. • PVA/PAAc/TiO 2 /graphene oxide nanocomposite hydrogels were used for treatment of basic waste water. • Photocatalytic acitivity of TiO 2 was improved by incorporation of graphene oxide. • Photocatalytic decomposition by nanocomposite hydrogel was improved by increasing pH. -- Abstract: Poly(vinyl alcohol)/poly(acrylic acid)/TiO 2 /graphene oxide nanocomposite hydrogels were prepared using radical polymerization and condensation reaction for the photocatalytic treatment of waste water. Graphene oxide was used as an additive to improve the photocatalytic activity of poly(vinyl alcohol)/poly(acrylic acid)/TiO 2 nanocomposite hydrogels. Both TiO 2 and graphene oxide were immobilized in poly(vinyl alcohol)/poly(acrylic acid) hydrogel matrix for an easier recovery after the waste water treatment. The photocatalytic activity of poly(vinyl alcohol)/poly(acrylic acid)/TiO 2 /graphene oxide nanocomposite hydrogels was evaluated on the base of the degradation of pollutants by using UV spectrometer. The improved removal of pollutants was due to the two-step mechanism based on the adsorption of pollutants by nanocomposite hydrogel and the effective decomposition of pollutants by TiO 2 and graphene oxide. The highest swelling of nanocomposite hydrogel was observed at pH 10 indicating that poly(vinyl alcohol)/poly(acrylic acid)/TiO 2 /graphene oxide nanocomposite hydrogels were suitable as a promising system for the treatment of basic waste water

a-Axis GaN/AlN/AlGaN Core-Shell Heterojunction Microwires as Normally Off High Electron Mobility Transistors.

Science.gov (United States)

Song, Weidong; Wang, Rupeng; Wang, Xingfu; Guo, Dexiao; Chen, Hang; Zhu, Yuntao; Liu, Liu; Zhou, Yu; Sun, Qian; Wang, Li; Li, Shuti

2017-11-29

Micro/nanowire-based devices have been envisioned as a promising new route toward improved electronic and optoelectronic applications, which attracts considerable research interests. However, suffering from applicable strategies to synthesize uniform core-shell structures to meet the requirement for the investigations of electrical transport behaviors along the length direction or high electron mobility transistor (HEMT) devices, heterojunction wire-based electronics have been explored limitedly. In the present work, GaN/AlN/AlGaN core-shell heterojunction microwires on patterned Si substrates were synthesized without any catalyst via metalorganic chemical vapor deposition. The as-synthesized microwires had low dislocation, sharp, and uniform heterojunction interfaces. Electrical transport performances were evaluated by fabricating HEMTs on the heterojunction microwire channels. Results demonstrated that a normally off operation was achieved with a threshold voltage of 1.4 V, a high on/off current ratio of 10 8 , a transconductance of 165 mS/mm, and a low subthreshold swing of 81 mV/dec. The normally off operation may attribute to the weak polarization along semipolar facets of the heterojunction, which leads to weak constrain of 2DEG.

Antiresonant guiding in a poly(methyl-methacrylate) hollow-core optical fiber

International Nuclear Information System (INIS)

Markos, Christos; Nielsen, Kristian; Bang, Ole

2015-01-01

Strong antiresonant reflecting optical waveguiding is demonstrated in a novel poly (methyl-methacrylate) (PMMA) hollow-core fiber. The transmission spectrum of the fiber was characterized using a supercontinuum source and it revealed distinct resonances with resonant dips as strong as ∼20 dB in the wavelength range 480–900 nm, where PMMA has low absorption. The total propagation loss of the fiber was measured to have a minimum of ∼45 dB m −1 at around 500 nm. The thermal sensitivity of the fiber is 256 ± 16 pm °C −1 , defined as the red-shift of the resonances per °C, which is three times higher than the sensitivity of polymer fiber Bragg gratings. (paper)

The involvement of poly(ADP-ribose) polymerase in the degradation of NAD caused by γ-radiation and N-methyl-N-nitrosourea

International Nuclear Information System (INIS)

Skidmore, C.J.; Davies, M.I.; Goodwin, P.M.; Halldorsson, H.; Lewis, P.J.; Shall, S.; Zia'ee, A.

1979-01-01

Both N-methyl-N-nitrosourea and γ-radiation lower cellular NAD in mouse leukaemia cells (L1210) in a dose-dependent way. The minimum NAD level is reached 2 h after a brief exposure to N-methyl-N-nitrosourea, but within 15 min of γ-irradiation. The cells remain metabolically active; they are able to recover their control NAD levels and are impermeable to trypan blue. Several inhibitors of poly(ADP-ribose) polymerase inhibit the drop in cellular NAD caused by these two agents: 2 mM 5-methylnicotinamide, 1 mM theophylline or 1 mM theobromine inhibit the effect of N-methyl-N-nitrosourea on cellular NAD level; 200 μM thymidine, 500 μM 5-methylnicotinaminde, 500 μM thephylline and 500 μM theobromine prevent the lowering of cellular NAD by γ-irradiation. The extent to which the drop in cellular NAD is inhibited is dependent on both the concentration of cytotoxic agent and of polymerase inhibitor. Caffeine will inhibit the drop in NAD but only at 10 mM, while nicotonic acid is ineffictive even at this dose. The activity of poly(ADP-ribose) polymerase is permeabilized cells immediately after γ-radiation increases with dose up to 12 krad, giving a maximal 3.4-fold stimulation of the enzyme activity, whereas the degradation of NAD under conditions optimal for NAD glycohydrolase does not change. The activity of the polymerase shows a close temporal correlation with the NAD drop following both γ-radiation and N-methyl-N-nitrosourea. The enzyme activity is maximal when the NAD content. (orig./AJ) 891 AJ/orig.- 892 HIS [de

De la autoformación como práctica instituyente en las metrópolis postfordistas

OpenAIRE

Miquel Bartual, María José

2013-01-01

A través de un recorrido teórico- práctico, nos proponemos investigar cómo, en el contexto de las metrópolis postfordistas, determinados procesos de autoformación pueden llevar a transformaciones sociales en el ámbito político. En esta premisa, analizaremos previamente si la autoformación constituye en sí un cuestionamiento de los lugares asignados en la redistribución de los saberes, vinculada a procesos de cooperación social y resistencia, así como a la generación de instituciones del comú...

Undoped and doped poly(tetraphenylbenzidine) as sensitive material for an impedimetric nitrogen dioxide gas dosimeter

Energy Technology Data Exchange (ETDEWEB)

Marr, I.; Moos, R., E-mail: functional.materials@uni-bayreuth.de [Department of Functional Materials, University of Bayreuth, Bayreuth 95440 (Germany); Neumann, K.; Thelakkat, M. [Department of Macromolecular Chemistry I, Applied Functional Polymers, University of Bayreuth, Bayreuth 95440 (Germany)

2014-09-29

This article presents a nitrogen dioxide (NO{sub 2}) detecting gas dosimeter based on poly(tetraphenylbenzidine) poly(TPD) as nitrogen oxide (NO{sub x}) sensitive layer. Gas dosimeters are suitable devices to determine reliably low levels of analytes over a long period of time. During NO{sub x} exposure, the analyte molecules are accumulated irreversibly in the sensing layer of the dosimeter enhancing the conductivity of the hole conducting poly(TPD), which can be measured by impedance spectroscopy. Due to their possibility for low cost production by simple printing techniques and very good physical, photochemical, and electrochemical properties, poly(TPD)s are suitable for application in gas dosimeters operated at room temperature. We studied the effect of doping with a Co(III)-complex in combination with a conducting salt on the dosimeter behavior. Compared to the undoped material, a strong influence of the doping can be observed: the conductivity of the sensing material increases significantly, the noise of the signal decreases and an unwanted recovery of the sensor signal can be prevented, leading to a NO{sub x} detection limit <10 ppm.

Evaluation of peritoneal adhesions formation and tissue response to polypropylene - poli (2-hydroxyethyl methacrylate-(polyHEMA implant on rats' abdominal wall Avaliação da formação de aderências peritoneais e da resposta tecidual ao implante de poli (2-hidroxietil dimetacrilato-(poliHEMA na parede abdominal de ratos

Directory of Open Access Journals (Sweden)

Neusa Margarida Paulo

2010-08-01

Full Text Available PURPOSE: To verify if the composit poli (2-hydroxyethyl methacrylate-PolyHEMA/polypropylene mesh implanted in the female rat's abdominal wall could be suitable for the prevention of peritoneal adhesions, and for the evaluation of the tecidual response produced by this biomaterial. METHODS: Polypropylene meshes (Group PP, n=20 and polypropylene meshes coated with a layer of poli (2-hydroxyethyl methacrylate-PolyHEMA (Group PH, n=20 were implanted on the abdominal wall of Wistar female rats. Ten animals from each group were submitted to euthanasia at 15 and 30 days of the postoperative period. RESULTS: The animals from the group PP presented visceral adhesions on the mesh surface, which was not observed in the ones from group PH. At the histopathological examination foreign body response was observed in both groups, whilst there was a greater intensity of inflammatory response in group PH on both moments. CONCLUSION: The poli (2-hydroxyethyl methacrylate polyHEMA hydrogel associated to polypropylene mesh reduces visceral adhesion formation in rats, although it may be associated to greater inflammatory reaction.OBJETIVO: Verificar se compósito poli 2-hidroxietil dimetacrilato (PoliHEMA / tela de polipropileno implantado na parede abdominal de ratas seria adequado para prevenção de aderências peritoneais e avaliar a resposta tecidual desencadeada por este biomaterial. MÉTODOS: Foram implantadas telas de polipropileno - Grupo PP (n=20 e telas de polipropileno revestidas por uma camada de poli 2 (hidroxietil dimetacrilato-PolyHEMA - Grupo PH (n=20 na parede abdominal de ratas da linhagem Wistar. Dez animais de cada grupo foram submetidos à eutanásia aos 15 e 30 dias de pós-operatório. RESULTADOS: Os animais do grupo PP apresentaram aderências viscerais na superfície da tela, o que não foi observado nos do grupo PH. Observou-se no exame histopatológico resposta tipo corpo estranho nos dois grupos sendo que no grupo PH houve maior

Caracterización del material compuesto mármol-poliéster

OpenAIRE

Corpas Iglesias, F. A.; Iglesias Godino, F. J.; Codina Sánchez, S.; Ruiz Román, J. M.; Ruiz Prieto, J. M.; Alonso Santos, C.

2002-01-01

En este trabajo, caracterizamos un nuevo material compuesto, formado con una mezcla de poliéster y de mármol blanco triturado. El propósito final es doble: por un lado obtener un material para aplicaciones lo suficientemente competitivas como para que se pueda iniciar un estudio económico de viabilidad, aumentando el rendimiento de la materia prima y mejorando las salidas laborales de las comarcas extractoras. Para la caracterización del material se ha determinado el porcentaje adecuado de...

Characterization of poly-aniline/silicon heterojunction for gamma dosimetry

International Nuclear Information System (INIS)

Laranjeira, Jane M.G.; Khoury, Helen J.; Azevedo, Walter M.; Silva Junior, Eronides F. da; Vasconcelos, Elder A.

2000-01-01

In this work, we have developed and characterized poly-aniline/silicon heterojunction diodes for dosimetry applications. The poly-aniline thin film (thickness in order of microns) was deposited on n-type Si (1 Ωcm) by spin-coating technique from soluble poly-aniline. Al electrode was evaporated on the back side of Si wafer and a circular gold electrode with an area of 0,0036 cm 2 was evaporated on the poly-aniline film. The UV-visible and infrared characterization of the poly-aniline solution and the poly-aniline film has also been done. The heterojunction presents good rectifying behavior at room temperature and the rectification ratio were found to be 51664 ±1,0 V under ambient conditions. The saturation current densities are of the order of 1,4 μA/cm 2 at -1,0 V. The forward current correspond to the negative polarity on the aluminum electrode side and the ideality factor of diodes was approximately 2. The rectifying characteristics of diodes was changed after interaction with gamma radiation ( 60 Co) and the results shows that this devices has potential for applications in dosimetry for doses in range of 0 to 4000 Gy. (author)

Preparation of poly(N-vinylpyrrolidone-stabilized ZnO colloid nanoparticles

Directory of Open Access Journals (Sweden)

Tatyana Gutul

2014-04-01

Full Text Available We propose a method for the synthesis of a colloidal ZnO solution with poly(N-vinylpyrrolidone (PVP as stabilizer. Stable colloidal solutions with good luminescence properties are obtained by using PVP as stabilizer in the synthesis of ZnO nanoparticles by a sol–gel method assisted by ultrasound. Nanoparticles with sizes of 30–40 nm in a PVP matrix are produced as a solid product. The colloidal ZnO/PVP/methanol solution, apart from the most intense PL band at 356 nm coming from the PVP, exhibits a strong PL band at 376 nm (3.30 eV which corresponds to the emission of the free exciton recombination in ZnO nanoparticles.

Highly sensitive and ultrafast response surface acoustic wave humidity sensor based on electrospun polyaniline/poly(vinyl butyral) nanofibers

International Nuclear Information System (INIS)

Lin Qianqian; Li Yang; Yang Mujie

2012-01-01

Highlights: ► Polyanline/poly(vinyl butyral) nanofibers are prepared by electrospinning. ► Nanofiber-based SAW humidity sensor show high sensitivity and ultrafast response. ► The SAW sensor can detect very low humidity. - Abstract: Polyaniline (PANi) composite nanofibers were deposited on surface acoustic wave (SAW) resonator with a central frequency of 433 MHz to construct humidity sensors. Electrospun nanofibers of poly(methyl methacrylate), poly(vinyl pyrrolidone), poly(ethylene oxide), poly(vinylidene fluoride), poly(vinyl butyral) (PVB) were characterized by scanning electron microscopy, and humidity response of corresponding SAW humidity sensors were investigated. The results indicated that PVB was suitable as a matrix to form nanofibers with PANi by electrospinning (ES). Electrospun PANi/PVB nanofibers exhibited a core–sheath structure as revealed by transmittance electron microscopy. Effects of ES collection time on humidity response of SAW sensor based on PANi/PVB nanofibers were examined at room temperature. The composite nanofiber sensor exhibited very high sensitivity of ∼75 kHz/%RH from 20 to 90%RH, ultrafast response (1 s and 2 s for humidification and desiccation, respectively) and good sensing linearity. Furthermore, the sensor could detect humidity as low as 0.5%RH, suggesting its potentials for low humidity detection. Attempts were done to explain the attractive humidity sensing performance of the sensor by considering conductivity, hydrophilicity, viscoelasticity and morphology of the polymer composite nanofibers.

Morphology and growing of nanometric multilayered films formed by alternated layers of poly(3,4-ethylenedioxythiophene) and poly(N-methylpyrrole)

Energy Technology Data Exchange (ETDEWEB)

Aradilla, David [Departament d' Enginyeria Quimica, E. T. S. d' Enginyers Industrials, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain); Center for Research in Nano-Engineering, Universitat Politecnica de Catalunya, Campus Sud, Edifici C' , C/Pasqual i Vila s/n, Barcelona E-08028 (Spain); Estrany, Francesc, E-mail: francesc.estrany@upc.ed [Center for Research in Nano-Engineering, Universitat Politecnica de Catalunya, Campus Sud, Edifici C' , C/Pasqual i Vila s/n, Barcelona E-08028 (Spain); Unitat de Quimica Industrial, Escola Universitaria d' Enginyeria Tecnica Industrial de Barcelona, Universitat Politecnica de Catalunya, Comte d' Urgell 187, 08036 Barcelona (Spain); Armelin, Elaine [Departament d' Enginyeria Quimica, E. T. S. d' Enginyers Industrials, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain); Center for Research in Nano-Engineering, Universitat Politecnica de Catalunya, Campus Sud, Edifici C' , C/Pasqual i Vila s/n, Barcelona E-08028 (Spain); Aleman, Carlos, E-mail: carlos.aleman@upc.ed [Departament d' Enginyeria Quimica, E. T. S. d' Enginyers Industrials, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain); Center for Research in Nano-Engineering, Universitat Politecnica de Catalunya, Campus Sud, Edifici C' , C/Pasqual i Vila s/n, Barcelona E-08028 (Spain)

2010-05-31

Multilayered nanometric films formed by alternated layers of conducting poly(3,4-ethylenedioxythiophene) and poly(N-methylpyrrole) doped with perchlorate anions (ml-PEDOT/PNMPy) have been prepared using a layer-by-layer electrodeposition technique combined with a very small polymerization time. The mechanisms of formation and growth of the resulting multilayered systems have been investigated using Atomic Force Microscopy (AFM), and compared with those obtained for the corresponding homopolymers, which were prepared using identical experimental conditions. Furthermore, the local conductivity, electroactivity and electrostability have been also examined. Analyses of the morphology, topography and roughness of the surfaces indicate that the formation and growth of the multilayered films strongly depend on the number of layers as well as on the chemical nature of the conducting polymer. Interestingly, AFM reflects that the formation and growth of the ml-PEDOT/PNMPy films are significantly different from those of PEDOT and PNMPy homopolymers. The electrical and electrochemical properties of the systems under study are fully consistent with the proposed mechanisms. Results evidenced that multilayered systems formed by two conducting polymers are more advantageous from a technological point of view than the corresponding copolymers.

Morphology and growing of nanometric multilayered films formed by alternated layers of poly(3,4-ethylenedioxythiophene) and poly(N-methylpyrrole)

International Nuclear Information System (INIS)

Aradilla, David; Estrany, Francesc; Armelin, Elaine; Aleman, Carlos

2010-01-01

Multilayered nanometric films formed by alternated layers of conducting poly(3,4-ethylenedioxythiophene) and poly(N-methylpyrrole) doped with perchlorate anions (ml-PEDOT/PNMPy) have been prepared using a layer-by-layer electrodeposition technique combined with a very small polymerization time. The mechanisms of formation and growth of the resulting multilayered systems have been investigated using Atomic Force Microscopy (AFM), and compared with those obtained for the corresponding homopolymers, which were prepared using identical experimental conditions. Furthermore, the local conductivity, electroactivity and electrostability have been also examined. Analyses of the morphology, topography and roughness of the surfaces indicate that the formation and growth of the multilayered films strongly depend on the number of layers as well as on the chemical nature of the conducting polymer. Interestingly, AFM reflects that the formation and growth of the ml-PEDOT/PNMPy films are significantly different from those of PEDOT and PNMPy homopolymers. The electrical and electrochemical properties of the systems under study are fully consistent with the proposed mechanisms. Results evidenced that multilayered systems formed by two conducting polymers are more advantageous from a technological point of view than the corresponding copolymers.

Thermoresponsive magnetic composite nanomaterials for multimodal cancer therapy.

Science.gov (United States)

Purushotham, S; Ramanujan, R V

2010-02-01

The synthesis, characterization and property evaluation of drug-loaded polymer-coated magnetic nanoparticles (MNPs) relevant to multimodal cancer therapy has been studied. The hyperthermia and controlled drug release characteristics of these particles was examined. Magnetite (Fe(3)O(4))-poly-n-(isopropylacrylamide) (PNIPAM) composite MNPs were synthesized in a core-shell morphology by dispersion polymerization of n-(isopropylacrylamide) chains in the presence of a magnetite ferrofluid. These core-shell composite particles, with a core diameter of approximately 13nm, were loaded with the anti-cancer drug doxorubicin (dox), and the resulting composite nanoparticles (CNPs) exhibit thermoresponsive properties. The magnetic properties of the composite particles are close to those of the uncoated magnetic particles. In an alternating magnetic field (AMF), composite particles loaded with 4.15 wt.% dox exhibit excellent heating properties as well as simultaneous drug release. Drug release testing confirmed that release was much higher above the lower critical solution temperature (LCST) of the CNP, with a release of up to 78.1% of bound dox in 29h. Controlled drug release testing of the particles reveals that the thermoresponsive property can act as an on/off switch by blocking drug release below the LCST. Our work suggests that these dox-loaded polymer-coated MNPs show excellent in vitro hyperthermia and drug release behavior, with the ability to release drugs in the presence of AMF, and the potential to act as agents for combined targeting, hyperthermia and controlled drug release treatment of cancer.

Infraestructuras y políticas internacionales de desarrollo para gestión de los datos de investigación

Directory of Open Access Journals (Sweden)

Fabiano Couto Corrêa da Silva

2016-07-01

Full Text Available Existen enormes carencias de desarrollo tecnológico para acometer con éxito la tarea de disponer acceso, mediante la investigación y la generación de conocimiento, los datos oriundos de la investigación científica. Han surgido como una respuesta de las instituciones, en especial las académicas, repositorios que sirven para preservar y poner a disposición de su comunidad académica e investigadora, los datos de investigación que hacen parte de su patrimonio intelectual. Por lo tanto, la adopción de formatos de intercambio de datos y padronización de los mecanismos de almacenamiento son necesarias para disponer la ciencia internamente en el país y en nivel internacional. Nuestra investigación constituye un análisis de infraestructuras y políticas de desarrollo para gestión de los datos de investigación teniendo en cuenta los mecanismos adoptados para la gestión de los datos de investigación en nível internacional.

Evidence of a low temperature dynamical transition in concentrated PNIPAM microgels

OpenAIRE

Zanatta, Marco; Tavagnacco, Letizia; Buratti, Elena; Bertoldo, Monica; Natali, Francesca; Chiessi, Ester; Orecchini, Andrea; Zaccarelli, Emanuela

2018-01-01

The occurrence of a dynamical transition at low temperature has been reported in a large number of different proteins. Here we provide the first observation of a "protein-like" dynamical transition in a non-biological aqueous environment. To this aim we exploit the popular colloidal system of poly-N-isopropylacrylamide (PNIPAM) microgels, extending their investigation to unprecedentedly high concentrations. Thanks to the heterogeneous polymeric architecture of the microgels, water crystalliza...

Voltammetric sensing of bisphenol A based on a single-walled carbon nanotubes/poly{3-butyl-1-[3-(N-pyrrolyl)propyl] imidazolium ionic liquid} composite film modified electrode

International Nuclear Information System (INIS)

Chen, Xuemin; Ren, Tongqing; Ma, Ming; Wang, Zhengguo; Zhan, Guoqing; Li, Chunya

2013-01-01

Highlights: • Single-walled carbon nanotubes (SWCNTs)-ionic liquid (IL) nanocomposite fabrication. • SWCNTs-Poly-IL film modified electrode was prepared and characterized. • Voltammetric behaviors of bisphenol A were investigated thoroughly. • Sensitive voltammetric method for bisphenol A determination was developed. -- Abstract: Using carboxylic acid-functionalized single walled carbon nanotubes (SWCNTs-COO − ) as an anion and 3-butyl-1-[3-(N-pyrrolyl)propyl]imidazolium as a cation, a novel SWCNTs-COO-ionic liquid (SWCNTs-COO-IL) nanocomposite was fabricated successfully. The as-prepared SWCNTs-COO-IL nanocomposite was confirmed with transmission electron microscopy, X-ray photoelectron spectroscopy, UV–vis, FTIR and Raman spectroscopy. The SWCNTs-COO-IL nanocomposite was coated onto a glassy carbon electrode surface followed by cyclic voltammetric scanning to fabricate a SWCNTs/poly{3-butyl-1-[3-(N-pyrrolyl)propyl] imidazolium ionic liquid} composite film modified electrode (SWCNTs/Poly-IL/GCE). Scanning electron microscope and electrochemical impedance spectroscopy were used to characterize SWCNTs/Poly-IL/GCE. Electrochemical behaviors of bisphenol A (BPA) at the SWCNTs/Poly-IL/GCE were investigated thoroughly. It was found that an obvious oxidation peak appeared without reduction peak in the reverse scanning, indicating an irreversible electrochemical process. The oxidation peak currents of BPA were linearly related to scan rate in the range of 20–300 mV s −1 , suggesting an adsorption controlled process rather than a diffusion controlled process. Differential pulse voltammetry was employed for the voltammetric sensing of BPA. Experimental conditions such as film thickness, pH value, accumulation potential and time that influence the analytical performance of the SWCNTs/Poly-IL/GCE were optimized. Under optimal conditions, the oxidation peak current was linearly related to BPA concentration in the range of 5.0 × 10 −9 to 3.0 × 10 −5 mol L

Poly(N-4-vinylbenzyl-1,4,7-triazacyclononane Copper Complex Grafted Solid Catalyst for Oxidative Polymerization of 2,6-Dimethylphenol

Directory of Open Access Journals (Sweden)

Kei Saito

2016-01-01

Full Text Available A new solid phase catalyst, poly(N-4-vinylbenzyl-1,4,7-triazacyclononane copper(I complex, grafted onto polystyrene particles, has been employed for the oxidative polymerization of 2,6-dimethylphenol using an aqueous biphasic (water/toluene solvent system. The solid catalyst was synthesized by first grafting N-(4-vinylbenzyl-1,4,7-triaza-cyclononane onto polystyrene particles using a radical mediated polymerization method and next by creating the polymer-metal complex of copper-triazacyclononane with these modified particles. Poly(2,6-dimethyl-1,4-phenylene oxide was successfully obtained from the polymerization of 2,6-dimethylphenol using this new metal-organic solid phase catalyst.

Synthesis, Characterization, and Acute Oral Toxicity Evaluation of pH-Sensitive Hydrogel Based on MPEG, Poly(ε-caprolactone, and Itaconic Acid

Directory of Open Access Journals (Sweden)

Liwei Tan

2013-01-01

Full Text Available A kind of chemically cross-linked pH-sensitive hydrogels based on methoxyl poly(ethylene glycol-poly(caprolactone-acryloyl chloride (MPEG-PCL-AC, PECA, poly(ethylene glycol methyl ether methacrylate (MPEGMA, MEG, N,N-methylenebisacrylamide (BIS, and itaconic acid (IA were prepared without using any organic solvent by heat-initiated free radical method. The obtained macromonomers and hydrogels were characterized by 1H NMR and FT-IR, respectively. Morphology study of hydrogels was also investigated in this paper, and it showed that the hydrogels had good pH-sensitivity. The acute toxicity test and histopathological study were conducted in BALB/c mice. The results indicated that the maximum tolerance dose of the hydrogel was higher than 10000 mg/kg body weight. No morality or signs of toxicity were observed during the whole 7-day observation period. Compared to the control groups, there were no important adverse effects in the variables of hematology routine test and serum chemistry analysis both in male or female treatment group. Histopathological study also did not show any significant lesions, including heart, liver, lung, spleen, kidney, stomach, intestine, and testis. All the results demonstrated that this hydrogel was nontoxic after gavage. Thus, the hydrogel might be the biocompatible potential candidate for oral drug delivery system.

Analysis of poly(styrene-co-methyl acrylate) and poly(styrene-co-butyl acrylate) by high-performance liquid chromatography

NARCIS (Netherlands)

Sparidans, R.W.; Claessens, H.A.; van Doremaele, G.H.J.; Herk, van A.M.

1990-01-01

Poly(styrene—co-methyl acrylate) and poly(styrene—co-butyl acrylate) were separated according to their chemical composition by gradient elution. The chromatographic separation on silica was optimized for a gradient ranging from n-heptane as a non-solvent to dichloromethane containing a small amount

The measurement of electrostatic potentials in core/shell GaN nanowires using off-axis electron holography

DEFF Research Database (Denmark)

Yazdi, Sadegh; Kasama, Takeshi; Ciechonski, R

2013-01-01

Core-shell GaN nanowires are expected to be building blocks of future light emitting devices. Here we apply off-axis electron holography to map the electrostatic potential distributions in such nanowires. To access the cross-section of selected individual nanowires, focused ion beam (FIB) milling...... is used. Furthermore, to assess the influence of FIB damage, the dopant potential measured from an intact NW is compared with a FIB prepared one. It is shown that in addition to the built-in potential between the p-type shell and unintentionally n-type under-layer there is a potential barrier between...... the core and under-layer which are both unintentionally n-type doped....

Miscibility and specific interactions in blends of poly(n-vinyl-2-pyrrolidone) and acid functional polyester resins.

NARCIS (Netherlands)

Senatore, D.; Berix, M.J.A.; Laven, J.; Benthem, van R.A.T.M.; With, de G.; Mezari, B.; Magusin, P.C.M.M.

2008-01-01

Miscibility and intermol. interactions of novel blends of poly(N-vinyl-2-pyrrolidone) (PVP) and acid functional polyester resins (APE) were studied by use of Differential Scanning Calorimetry (DSC), Attenuated Total Reflectance Fourier Transform IR (ATR-FTIR), Cross-Polarization Magic Angle Spinning

Polyester kumaşların indigo boyar maddeleri ile boyanabilirliğinin geliştirilmesi için poli(Vinil Alkol) ve modifiye poli(Vinil Alkol) polimerleri ile modifiye edilmesi

OpenAIRE

KALKAN ERDOĞAN, Meryem

2017-01-01

Bu çalışmada, tekstil sanayiinde önemli sentetik liflerden olan poli(etilen teraftalat) (PET) esaslı polyester (PES) kumaşların, indigo boyarmaddesi ile pamuklu denim (kot) kumaşlara benzer şekilde yüzeysel ve kesintisiz olarak soğukta boyanabilmesi amacıyla, poli(vinil alkol) (PVA) ve farklı bileşimlerde sentezlenen modifiye PVA (M-PVA) polimerlerini kullanarak fiziksel ve kimyasal yöntemler ile modifikasyonu gerçekleştirildi. M-PVA polimerleri, PVA varlığında glisidil metakrilat (G...

A ferrocene functionalized polymer: Poly [N-(ferrocenylmethyl)-o-phenylenediamine]. Electrochemical production and spectroelectroelectrochemical investigation in acetonitrile medium

International Nuclear Information System (INIS)

Gülce, Handan; Yetkin, Ahmet; Akgül, Eda; Gülce, Ahmet

2013-01-01

An electroactive and conductive polymer having pendant ferrocene units was prepared from the electrochemical polymerization of the synthesized monomer, N-(ferrocenylmethyl)-o-phenylenediamine in 0.1 M tetrabuthylammonium perchlorate/acetonitrile medium. The poly-N-(ferrocenylmethyl)-o-phenylenediamine (poly-FMOPD) was generated potentiodynamically or potentiostatically at both of indium tin oxide coated glass substrate and Pt electrodes. The poly-FMOPD film was characterized by cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy, dry conductivity measurements, ultraviolet–visible absorption spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy. The electrical conductivity of polymer films was determined as 1.0 × 10 −1 and 4 × 10 −2 S cm −1 depending on the potential scanning range during electropolymerization. The electroactivity of the polymer film retained even after hundreds cycles between their reduced and oxidized states. The spectroelectrochemical analysis demonstrated that the polymer film reveals a reversible cycling with distinctive color changes between neutral and reduced/oxidized forms. For the polymer film, the maximum optical contrasts (ΔT%) were measured as 18% at and 37% at 480 nm by step the potential between (0.00 V)-(1.20 V) and (− 0.50 V)-(− 1.70 V), respectively. The optical energy band gaps as the onset energy for the π–π* transitions are calculated as 1.89 eV, 1.85 eV and 1.88 eV for the neutral, reduced and oxidized states of poly-FMOPD. - Highlights: • The ferrocene functionalized monomer and its polymer were synthesized electrochemically. • Spectroelectrochemical investigations were performed. • The polymer film showed reversible color changes between different redox forms. • It was found that the polymer film is conductive

Preparation of thermo and pH-responsive polymer@Au/Fe{sub 3}O{sub 4} core/shell nanoparticles as a carrier for delivery of anticancer agent

Energy Technology Data Exchange (ETDEWEB)

Ghorbani, Marjan [University of Tabriz, Laboratory of Polymer, Faculty of Chemistry (Iran, Islamic Republic of); Hamishehkar, Hamed, E-mail: hamishehkarh@tbzmed.ac.ir [Tabriz University of Medical Sciences, Drug Applied Research Center (Iran, Islamic Republic of); Arsalani, Naser; Entezami, Ali Akbar, E-mail: aentezami@tabrizu.ac.ir [University of Tabriz, Laboratory of Polymer, Faculty of Chemistry (Iran, Islamic Republic of)

2015-07-15

In this work, a thermo and pH-responsive poly-N-isopropylacrylamide-co-itaconic acid containing thiol side groups were successfully synthesized to prepare Doxorubicin-loaded polymer@Au/Fe{sub 3}O{sub 4} core/shell nanoparticles (DOX-NPs). Copolymer and NPs were fully characterized by FT-IR, HNMR, photo-correlation spectroscopy, SEM, X-ray diffraction, vibrating-sample magnetometer, thermal gravimetric analysis, and UV–Vis spectroscopy. The stimuli-responsive characteristics of NPs were evaluated by in vitro release study in simulated cancerous environment. The biocompatibility and cytotoxic properties of NPs and DOX-NPs are explored by MTT method. The prepared NPs with the size of 50 nm showed paramagnetic characteristics with suitable and stable dispersion at physiological medium and high loading capacity (up to 55 %) of DOX. DOX-NPs yielded a pH- and temperature-triggered release of entrapped drugs at tumor tissue environment (59 % of DOX release) compared to physiological condition (20 % of DOX release) during 48 h. In vitro cytotoxicity studies indicated that the NPs showed no cytotoxicity on A549 cells at different amounts after incubation for 72 h confirming its suitability as a drug carrier. DOX-NPs, on the other hand, caused an efficient anticancer performance as verified by MTT assay test. It was concluded that developed NPs by us in this study may open the possibilities for targeted delivery of DOX to the cancerous tissues.

Thermally reversible cross-linked poly(ether-urethanes

Directory of Open Access Journals (Sweden)

V. Gaina

2013-07-01

Full Text Available Cross-linked poly(ether-urethanes were prepared by Diels-Alder (DA reaction of the furan-containing poly(ether-urethane to bismaleimides and showed thermal reversibility evidenced by differential scanning calorimetry and attenuated total reflectance in conjunction with Fourier transform infrared spectroscopy (ATR-FTIR. The furan-containing poly(ether-urethanes were synthesized by the polyaddition reaction of 1,6-hexamethylene diisocyanate (HMDI or 4,4'- dibenzyl diisocyanate (DBDI to poly(tetramethylene ether glycol (PTMEG having Mn = 250, 650, 1000, 1500 and 2000 and 2-[N,N-bis(2-methyl-2-hydroxyethylamino]furfuryl as chain extender by the solution prepolymer method. The molar ratio of isocyanate: PTMEG:chain extender varied from 2:1:1 to 4:1:3, which produces a molar concentration of furyl group ranging between 3.65•10–4 and 1.25•10–3 mol/g.

Determination of thermodynamic properties of poly(cyclohexyl methacrylate)by inverse gas chromatography

Institute of Scientific and Technical Information of China (English)

Ismet KAYA; Cigdem Yigit PALA

2014-01-01

In this work,some thermodynamic properties of poly( cyclohexyl methacrylate)were studied by inverse gas chromatography( IGC). For this purpose,the polymeric substance was coated on Chromosorb W and which was filled into a glass column. The retention times(tr)of the probes were determined from the interactions of poly(cyclohexyl methacrylate)with n-pentane,n-hexane,n-heptane,n-octane,n-decane, methanol,ethanol,2-propanol,butanol,acetone,ethyl methyl ketone,benzene,toluene and o-xylene by IGC technique. Then,the specific volume(V0g)was determined for each probe molecule. By using(1/T;lnV0g) graphics,the glass transition temperature of poly( cyclohexyl methacrylate)was found to be 373 K. The adsorp-tion heat under the glass transition temperature(ΔH a ),and partial molar heat of sorption above the glass tran-sition(ΔHS1 ),partial molar free energy of sorption(ΔGS1 )and partial molar entropy of sorption(ΔSS1 )belong-ing to sorption for every probe were calculated. The partial molar heat of mixing at infinite dilution(ΔH∞1 ), partial molar free energy of mixing at infinite dilution(ΔG∞1 ),Flory-Huggins interaction parameter(χ∞12 )and weight fraction activity coefficient(a1/w1)∞ values of polymer-solute systems were calculated at different col-umn temperatures. The solubility parameters(δ2 )of the polymer were obtained by IGC technique.

Determination of thermodynamic properties of poly (cyclohexyl methacrylate) by inverse gas chromatography.

Science.gov (United States)

Kaya, Ismet; Pala, Cigdem Yigit

2014-07-01

In this work, some thermodynamic properties of poly (cyclohexyl methacrylate) were studied by inverse gas chromatography (IGC). For this purpose, the polymeric substance was coated on Chromosorb W and which was filled into a glass column. The retention times (t(r)) of the probes were determined from the interactions of poly (cyclohexyl methacrylate) with n-pentane, n-hexane, n-heptane, n-octane, n-decane, methanol, ethanol, 2-propanol, butanol, acetone, ethyl methyl ketone, benzene, toluene and o-xylene by IGC technique. Then, the specific volume (Vg(0)) was determined for each probe molecule. By using (1/T; lnVg(0)) graphics, the glass transition temperature of poly (cyclohexyl methacrylate) was found to be 373 K. The adsorption heat under the glass transition temperature (deltaH(a)), and partial molar heat of sorption above the glass transition (deltaH1(S)), partial molar free energy of sorption (deltaG1(S)) and partial molar entropy of sorption (deltaS1(S)) belonging to sorption for every probe were calculated. The partial molar heat of mixing at infinite dilution (deltaH1(infinity)), partial molar free energy of mixing at infinite dilution (deltaG1(infinity)), Flory-Huggins interaction parameter (chi12(infinity)) and weight fraction activity coefficient (a1/w1)(infinity) values of polymer-solute systems were calculated at different column temperatures. The solubility parameters (delta2) of the polymer were obtained by IGC technique.

Man and «polis»; the gordian knot of education in Aristotle Hombre y «polis»: el nudo gordiano de la educación en Aristóteles

Directory of Open Access Journals (Sweden)

Concepción NAVAL

2013-09-01

Full Text Available Education is better seen as a help in order to grow in freedom and dignity, inside a society. Aristotle helps us to better understand this question. He gives us suggestive insights of the concepts of man, and education, very much related to the polis. The social dimesion of education is always present in the Greek tradition, but in Aristotle there is also a genuine knowledge of the individual. There is no educative problem separeted to the social and political roots.La educación se puede ver como una ayuda para crecer en libertad y dignidad. Será educativo aquello que favorezca la perfección de la persona; y por eso, cuando se habla de la educación como un factor de reproducción social, se intentará referir unos factores externos a la propia persona, y determinarlos según la armonía personal. Esta cuestión de plena actualidad tienen un planteamiento sugerente en Aristóteles quien nos ofrece una visión del hombre y de la educación, en estrecha relación con la polis, que son de interés. El carácter social de la educación está siempre presente en la tradición y pensamiento griego, puesto que el hombre es un animal político. Sin embargo, también está vivo en este autor el conocimiento del valor individual. No existía un problema educativo separado del aspecto político y moral.

Synthesis of thermoplastic poly(ester-olefin elastomers

Directory of Open Access Journals (Sweden)

Tanasijević Branka

2004-01-01

Full Text Available A series of thermoplastic poly(ester-olefin elastomers, based on poly(ethylene-stat-butylene, HO-PEB-OH, as the soft segment and poly (butylene terephthalate, PBT, as the hard segment, were synthesized by a catalyzed transesterification reaction in solution. The incorporation of soft hydrogenated poly(butadiene segments into the copolyester backbone was accomplished by the polycondensation of α, ω-dihydroxyl telechelic HO-PEB-OH, (PEB Mn = 3092 g/mol with 1,4-butanediol (BD and dimethyl terephthalate (DMT in the presence of a 50 wt-% high boiling solvent i.e., 1,2,4-trichlorobenzene. The molar ratio of the starting comonomers was selected to result in a constant hard to soft weight ratio of 60:40. The synthesis was optimized in terms of both the concentration of catalyst, tetra-n-butyl-titanate (Ti(OBu4, and stabilizer, N,N'-diphenyl-p-phenylenediamine (DPPD, as well as the reaction time. It was found that the optimal catalyst concentration (Ti(OBu4 for the synthesis of these thermoplastic elastomers was 1.0 mmol/mol ester and the optimal DPPD concentration was 1.0 wt-%. The extent of the reaction was followed by measuring the inherent viscosity of the reaction mixture. The effectiveness of the incorporation of the soft segments into the copolymer chains was proved by Soxhlet extraction with chloroform. The molecular structures, composition and the size of the synthesized poly(ester-butylenes were verified by 1H NMR spectroscopy, viscometry of dilute solutions and the complex dynamic melt viscosity. The thermal properties of poly(ester-olefins were investigated by differential scanning calorimetry (DSC. The degree of crystallinity was also determined by DSC. The thermal and thermo-oxidative stability were investigated by thermogravimetric analysis (TGA. The rheological properties of poly(ester-olefins were investigated by dynamic mechanical spectroscopy in the melt and solid state.

Fluorescently Labeled Branched Polymers and Thermal Responsive Nanoparticles for Live Cell Imaging

NARCIS (Netherlands)

Zhou, D.; Ma, Y.; Poot, Andreas A.; Dijkstra, Pieter J.; Feijen, Jan

2012-01-01

Branched poly(methoxy-PEG acrylate) and thermally responsive poly(methoxy-PEG acrylate)-block-poly(N-isopropylacrylamide) are synthesized by RAFT polymerization. After reduction, these polymers are fluorescently labeled by reacting the free thiol groups with N-(5-fluoresceinyl)maleimide. As shown by

PRODUCCIÓN DE POLI-β -HIDROXIBUTIRATO (PHB β POR Ralstonia eutropha ATCC 17697

Directory of Open Access Journals (Sweden)

Barbosa Marcela

2005-06-01

Full Text Available Ralstonia eutropha es la bacteria más utilizada en la producción de poli-β-hidroxibutirato (PHB por su capacidad de acumular polímero hasta en un 80% de su peso seco. En el presente trabajo se realizaron fermentaciones por lote alimentado en dos etapas a escala 3 litros usando tres concentraciones de fructosa (5, 10 y 15 g/l. En la primera etapa, manteniendo constante la relación carbono-nitrógeno en 6.85 g C/g N, se buscó obtener una alta concentración celular; en la segunda etapa las células obtenidas se limitaron en la fuente de nitrógeno para permitir la acumulación del biopolímero. La mejor concentración para producir el material es 5 g/l en la cual se obtuvo un porcentaje de acumulación del 66.2%, una velocidad de crecimiento específico inicial de 0.5171 h-1 y una productividad de 0.1245 g PHB/ l h.

Room-temperature fabrication of core-shell nano-ZnO/pollen grain biocomposite for adsorptive removal of organic dye from water

Energy Technology Data Exchange (ETDEWEB)

Tzvetkov, George, E-mail: george.tzvetkov@gmail.com; Kaneva, Nina; Spassov, Tony

2017-04-01

Highlights: • Meso-/macro-porous nano-ZnO covered pollen grains are prepared at room temperature. • A possible formation mechanism of the core-shell microparticles was proposed. • Adsorptive removal of Malachite Green from water by the biocomposite is studied. - Abstract: A new core-shell nano-ZnO/pollen grain (n-ZnO/PG) biocomposite has been successfully synthesized via simple and low-temperature two-step liquid precipitation method. The synthetic strategy consists of grafting the surface of pine pollen grains (PG) with Zn{sup 2+}-organic complexes followed by a treatment in Zn(CH{sub 3}COO){sub 2}/NaOH solution, thus producing a closed n-ZnO shell around the organic core, with a thickness of ∼450 nm. Scanning electron microscopy, X-ray diffraction, FTIR, XPS and UV–vis spectroscopy measurements along with N{sub 2} adsorption/desorption were used to characterize the resulting n-ZnO/PG biocomposite. The as-prepared core-shell microparticles are meso-/macro-porous with BET surface area of 25 m{sup 2} g{sup −1} and total pore volume of 0.26 cm{sup 3} g{sup −1}. The adsorption properties of n-ZnO/PG were evaluated through adsorption of Malachite Green (MG) from aqueous medium at room temperature (25 °C). For the sake of comparison, the physico-chemical and adsorptive properties of the raw PG and pure n-ZnO were also examined. Results indicate that n-ZnO/PG is the most favorable for the adsorption of MG under the conditions used in this study. The adsorption kinetic data for PG, n-ZnO and n-ZnO/PG follow the pseudo-second order equation and the maximum adsorption capacity follows an order of n-ZnO/PG > n-ZnO > PG. For n-ZnO/PG an adsorption uptake up to 145.9 mg g{sup −1} is observed. The as-prepared core-shell biocomposite material is a promising cost-effective and environmentally friendly adsorbent due to its textural properties, surface chemistry, adsorption capacity and recyclability.

Synthesis of low polydisperse isotactic poly(N-isopropylacrylamide)s ...

Indian Academy of Sciences (India)

environment-friendly and less toxic methanol-water mixtures by RAFT polymerization ... effect on the LCST of the obtained water soluble polymers. 2. Experimental. 2.1 Materials ... at room temperature by comparing the integration of.

Application of polyacrylic acid-poly-N,N-dimethyldiallylammonium chloride polyelectrolyte complexes for structuring of polluted soil of Semipalatinsk nuclear test site

International Nuclear Information System (INIS)

Sabantseva, T.; Bashenova, A.; Orazzhanova, L.K.; Yashkarova, M.G.; Bimendina, L.A.

2002-01-01

The present communication is devoted to investigation of structuring efficiency of polyacrylic acid-poly-N,N-dimethyldiallylammonium chloride (PAA-PDMDAACI) polyelectrolyte complexes. The granulometric analysis of selected soil samples before and after the treatment of aqueous solution of PAA, PDMDAACI and PAA-PDMDAACI complexes at different molar ratio of polymer components and polymer concentrations was carried out. Analysis shows that nonstoichiometric polyelectrolyte complex [PAA]:[PDMDAACI]=3:1 possesses the best structuring effect. But this result is worse than in the case using of [PAA]:[polyethylene glycol]=1:1 inter-polymer complex

Preparation of new series of poly(amide-imide) reinforced layer silicate nano composite containing N-trimellitimide-L-alanine

International Nuclear Information System (INIS)

Faghihi, K.; Soleimani, M.; Shabanian, M.

2011-01-01

A new poly(amide-imide)-montmorillonite series were generated through solution intercalation technique. Cloisite 20A was used as a modified montmorillonite for ample compatibility with the poly(amide-imide) (PAI) matrix. The PAI 5 chains were synthesized by the direct polycondensation reaction of N-trimellitylimido-L-alanine (3) with 4,4'-diamino diphenyl ether (4) in the presence of tryphenyl phosphites (TPP), CaCl 2 , pyridine and N-methyl-2-pyrrolidone (NMP). Morphology and structure of the resulting PAI-nano composite films 5a-5d with (5-20 Wt%) silicate particles were characterized by Ftir spectroscopy, X-ray diffraction and scanning electron microscopy. The effect of clay dispersion and the interaction between clay and polymeric chains on the properties of nano composites films were investigated by using UV-Vis spectroscopy, thermogravimetric analysis and water uptake measurements. (Author)

Preparation of new series of poly(amide-imide) reinforced layer silicate nano composite containing N-trimellitimide-L-alanine

Energy Technology Data Exchange (ETDEWEB)

Faghihi, K.; Soleimani, M. [Polymer Research Laboratory, Department of Chemistry, Faculty of Science, Islamic Azad University, Arak Branch, Arak (Iran, Islamic Republic of); Shabanian, M., E-mail: k-faghihi@araku.ac.ir [Young Researches Club, Islamic Azad University, Arak Branch, Arak (Iran, Islamic Republic of)

2011-07-01

A new poly(amide-imide)-montmorillonite series were generated through solution intercalation technique. Cloisite 20A was used as a modified montmorillonite for ample compatibility with the poly(amide-imide) (PAI) matrix. The PAI 5 chains were synthesized by the direct polycondensation reaction of N-trimellitylimido-L-alanine (3) with 4,4'-diamino diphenyl ether (4) in the presence of tryphenyl phosphites (TPP), CaCl{sub 2}, pyridine and N-methyl-2-pyrrolidone (NMP). Morphology and structure of the resulting PAI-nano composite films 5a-5d with (5-20 Wt%) silicate particles were characterized by Ftir spectroscopy, X-ray diffraction and scanning electron microscopy. The effect of clay dispersion and the interaction between clay and polymeric chains on the properties of nano composites films were investigated by using UV-Vis spectroscopy, thermogravimetric analysis and water uptake measurements. (Author)

Development of AC-coupled, poly-silicon biased, p-on-n silicon strip detectors in India for HEP experiments

Science.gov (United States)

Jain, Geetika; Dalal, Ranjeet; Bhardwaj, Ashutosh; Ranjan, Kirti; Dierlamm, Alexander; Hartmann, Frank; Eber, Robert; Demarteau, Marcel

2018-02-01

P-on-n silicon strip sensors having multiple guard-ring structures have been developed for High Energy Physics applications. The study constitutes the optimization of the sensor design, and fabrication of AC-coupled, poly-silicon biased sensors of strip width of 30 μm and strip pitch of 55 μm. The silicon wafers used for the fabrication are of 4 inch n-type, having an average resistivity of 2-5 k Ω cm, with a thickness of 300 μm. The electrical characterization of these detectors comprises of: (a) global measurements of total leakage current, and backplane capacitance; (b) strip and voltage scans of strip leakage current, poly-silicon resistance, interstrip capacitance, interstrip resistance, coupling capacitance, and dielectric current; and (c) charge collection measurements using ALiBaVa setup. The results of the same are reported here.

Modificación estructural de Poli(Acido Láctico) (PLA) mediante extrusión reactiva: estudio preliminar en mezclador interno escala laboratorio

OpenAIRE

Espejo, Lucas

2011-01-01

Doble titulació Este proyecto, realizado en Centro Catalá del Plástico y por lo tanto implicado en el dominio de los polímeros, pretende preparar y caracterizar sistemas de Acido Poli(Láctico) (PLA) con extensores de cadena (CE) que serían adecuados y eficientes para el sector de los envases. Los procesos tal la Inyección y/o Extrusión empleando el PLA en este campo se enfrentan a la pérdida de las propiedades termo-mecánicas. Es el resultado de la degradación térmica y h...

Effect of acid on the aggregation of poly(ethylene xide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers.

Science.gov (United States)

Yang, Bin; Guo, Chen; Chen, Shu; Ma, Junhe; Wang, Jing; Liang, Xiangfeng; Zheng, Lily; Liu, Huizhou

2006-11-23

The acid effect on the aggregation of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers EO(20)PO(70)EO(20) has been investigated by transmission electron microscopy (TEM), particle size analyzer (PSA), Fourier transformed infrared, and fluorescence spectroscopy. The critical micellization temperature for Pluronic P123 in different HCl aqueous solutions increases with the increase of acid concentration. Additionally, the hydrolysis degradation of PEO blocks is observed in strong acid concentrations at higher temperatures. When the acid concentration is low, TEM and PSA show the increase of the micelle mean diameter and the decrease of the micelle polydispersity at room temperature, which demonstrate the extension of EO corona and tendency of uniform micelle size because of the charge repulsion. When under strong acid conditions, the aggregation of micelles through the protonated water bridges was observed.

Macrochain configuration, stucture of free volume and transport properties of poly(1-trimethylsilyl-1-propyne) and poly(1-trimethylgermyl-1-propyne)

KAUST Repository

Matson, Samira M.; Rä tzke, Klaus; Shaikh, Muhammad Qasim; Litvinova, Elena G.; Shishatskiy, Sergey M.; Peinemann, Klaus-Viktor; Khotimskiy, Valeriy S.

2012-01-01

The relationship between poly(1-trimethylsilyl-1-propyne) (PTMSP) and poly(1-trimethylger- myl-1-propyne) (PTMGP) microstructure, gas permeability and structure of free volume is reported. n-Butane/methane mixed-gas permeation properties of PTMSP

Safety and complications of absorbable threads made of poly-L-lactic acid and poly lactide/glycolide: Experience with 148 consecutive patients.

Science.gov (United States)

Sarigul Guduk, Sukran; Karaca, Nezih

2018-04-01

Thread lifting is a minimally invasive procedure for lifting and repositioning tissues. Few articles with absorbable sutures exist in the literature. Furthermore there is no study focusing on complications of absorbable sutures. To describe complications of thread lifting using a totally absorbable suture composed of poly-L-lactic acid affixed with poly lactide/glycolide cones. Data regarding complications were analyzed retrospectively for 148 patients underwent thread lifting between June 2014 and February 2017. A total of 321 pairs of sutures used in the 148 patients studied. Overall 40 (27%) patients had complications regarded as minimal or moderate without permanent sequela. The most common complication was skin dimpling and irregularity (n = 17, 11.4%) followed by ecchymosis (n = 12, 8.1%), suture extrusion (n = 4, 2.7%), and pain (n = 4, 2.7%) Except one patient, dimpling, and irregularity resolved in all patients after 3-7 days spontaneously. Suture migration was observed in 2 (1.35%) patients. Hematoma and infection were seen in 2 patients one for each. The procedure using sutures made of absorbable poly-L-lactic acid and poly lactide/glycolide is a relatively safe procedure without major complications. © 2018 Wiley Periodicals, Inc.

Studies on biodegradable and crosslinkable poly(castor oil fumarate)/poly(propylene fumarate) composite adhesive as a potential injectable biomaterial.

Science.gov (United States)

Mitha, M K; Jayabalan, M

2009-12-01

Biodegradable hydroxyl terminated-poly(castor oil fumarate) (HT-PCF) and poly(propylene fumarate) (HT-PPF) resins were synthesized as an injectable and in situ-cross linkable polyester resins for orthopedic applications. An injectable adhesive formulation containing this resin blend, N-vinyl pyrrolidone (NVP), hydroxy apatite, free radical initiator and accelerator was developed. The Composite adhesives containing the ratio of resin blend and NVP, 2.1:1.5, 2.1:1.2 and 2.1:1.0 set fast with tolerable exothermic temperature as a three dimensionally cross linked toughened material. Crosslink density and mechanical properties of the crosslinked composite increase with increase of NVP. The present crosslinked composite has hydrophilic character and cytocompatibility with L929 fibroblast cells.

Control the wettability of poly(n-isopropylacrylamide-co-1-adamantan-1-ylmethyl acrylate) modified surfaces: the more Ada, the bigger impact?

Science.gov (United States)

Shi, Xiu-Juan; Chen, Gao-Jian; Wang, Yan-Wei; Yuan, Lin; Zhang, Qiang; Haddleton, David M; Chen, Hong

2013-11-19

Surface-initiated SET-LRP was used to synthesize polymer brush containing N-isopropylacrylamide and adamantyl acrylate using Cu(I)Cl/Me6-TREN as precursor catalyst and isopropanol/H2O as solvent. Different reaction conditions were explored to investigate the influence of different parameters (reaction time, catalyst concentration, monomer concentration) on the polymerization. Copolymers with variable 1-adamantan-1-ylmethyl acrylate (Ada) content and comparable thickness were synthesized onto silicon surfaces. Furthermore, the hydrophilic and bioactive molecule β-cyclodextrin-(mannose)7 (CDm) was synthesized and complexed with adamantane via host-guest interaction. The effect of adamantane alone and the effect of CDm together with adamantane on the wettability and thermoresponsive property of surface were investigated in detail. Experimental and molecular structure analysis showed that Ada at certain content together with CDm has the greatest impact on surface wettability. When Ada content was high (20%), copolymer-CDm surfaces showed almost no CDm complexed with Ada as the result of steric hindrance.

The study on grafting comonomer of n-butyl acrylate and styrene onto poly(ethylene terephthalate) film by gamma-ray induced graft copolymerization

Energy Technology Data Exchange (ETDEWEB)

Ping Xiang; Wang Mozhen [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China); Ge Xuewu, E-mail: xwge@ustc.edu.c [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2010-09-15

Poly(ethylene terephthalate) (PET) film was successfully grafted with n-butyl acrylate and styrene comonomer through gamma-ray induced graft copolymerization. The degree of grafting (DG) and the composition of grafted side chain were characterized by {sup 1}H NMR. It was found that St can inhibit the homopolymerization of BA effectively and increase the DG when the concentration of comonomer mixture is kept constant. The proportion of St to BA in grafted side chain has a positive dependence on the feed ratio of St, which ultimately approaches the feed ratio. The thermal properties of poly(ethylene terephthalate)-graft-poly(n-butyl acrylate-co-styrene) (PET-g-P(BA-co-St)) films were investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The T{sub g} of PET decreases with the DG, indicating that the grafted P(BA-co-St) copolymer has good compatibility with PET backbone.

Hacia la gestión ambiental de residuos sólidos en las metrópolis de América Latina

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Luz Ángela Rodríguez Escobar

2002-11-01

Full Text Available La contaminación generada por la acumulación de residuos sólidos está presente en todas las metrópolis de América Latina, afectando el ecosistema. Dicha contaminación es causada por la población y su aglomeración en zonas urbanas. Los datos estadísticos de las metrópolis latinoamericanas permiten establecer una relación directa entre población y acumulación de residuos sólidos y también entre nivel de ingresos y generación de residuos, mostrando que la relación población-residuos sólidos está mediada por variables económicas y culturales. La información de generación de basura por persona y su respectivo nivel socioeconómico permite establecer diferencias de cantidad y calidad de los residuos generados por individuos de distinto nivel socioeconómico, que a su vez se asocian a diferentes estilos de vida y patrones de consumo. Así, la producción de basura es potenciada por la dinámica de producción y consumo y por la dinámica demográfica, siendo un efecto no esperado de ambas, que convierte los residuos sólidos en un subproducto del modelo de desarrollo y la dinámica demográfica. En el escenario planteado, el problema ambiental de los residuos sólidos en .las metrópolis de América Latina aparece como irresoluto y la decisión de resolverlo de manera fundamental pasa por cambiar el modelo de desarrollo y el comportamiento de la sociedad. Una solución menos extrema consiste en hacer un manejo integral de los residuos sólidos a través de políticas de gestión integral.

Minimally invasive injectable short nanofibers of poly(glycerol sebacate) for cardiac tissue engineering

International Nuclear Information System (INIS)

Ravichandran, Rajeswari; Venugopal, Jayarama Reddy; Sundarrajan, Subramanian; Mukherjee, Shayanti; Sridhar, Radhakrishnan; Ramakrishna, Seeram

2012-01-01

Myocardial tissue lacks the ability to appreciably regenerate itself following myocardial infarction (MI) which ultimately results in heart failure. Current therapies can only retard the progression of disease and hence tissue engineering strategies are required to facilitate the engineering of a suitable biomaterial to repair MI. The aim of this study was to investigate the in vitro properties of an injectable biomaterial for the regeneration of infarcted myocardium. Fabrication of core/shell fibers was by co-axial electrospinning, with poly(glycerol sebacate) (PGS) as core material and poly-l-lactic acid (PLLA) as shell material. The PLLA was removed by treatment of the PGS/PLLA core/shell fibers with DCM:hexane (2:1) to obtain PGS short fibers. These PGS short fibers offer the advantage of providing a minimally invasive injectable technique for the regeneration of infarcted myocardium. The scaffolds were characterized by SEM, FTIR and contact angle and cell–scaffold interactions using cardiomyocytes. The results showed that the cardiac marker proteins actinin, troponin, myosin heavy chain and connexin 43 were expressed more on short PGS fibers compared to PLLA nanofibers. We hypothesized that the injection of cells along with short PGS fibers would increase cell transplant retention and survival within the infarct, compared to the standard cell injection system. (paper)

Gold Nanoparticles Size Design and Control by Poly(N,N′-diethylaminoethyl methacrylate

Directory of Open Access Journals (Sweden)

Norma A. Cortez-Lemus

2015-01-01

Full Text Available Poly(N,N′-diethylaminoethyl methacrylate (PDEAEM with different molecular weights was used to stabilize gold nanoparticles (AuNPs obtained by in situ reduction of tetrachloroauric acid using citrates under acidic conditions and in organic/alcoholic medium. The influence of the pH value on gold nanoparticle size in the presence of PDEAEM was investigated. Results show that the pH of the reacting mixture has a dramatic effect on the size, polydispersity, and morphology of the resulting AuNPs. Moreover, the size of the nanoparticles (NPs may be modified by changing the solution’s pH or by changing the solvent type. Electron microscope images showed that the sizes of AuNPs coated with PDEAEM were not sensitive to the variation of the polymer molecular weight in the range between 9000 and 29300 g/mol; however their aggregation behavior depended strongly on the polymer molecular weight as revealed by dynamic light scattering studies. AuNPs stabilized with PDEAEM (AuNP@PDEAEM are stable in water at acidic pH and in organic polar solvents.

Características de adhesión entre fibras de queratina y poliéster insaturado

Directory of Open Access Journals (Sweden)

Marco Paniagua

2008-01-01

Full Text Available En este trabajo se presentan los métodos y resultados utilizados para determinar las características de adhesión entre fibras de queratina y una matriz de poliéster insaturado. Las fibras fueron preparadas con varios tratamientos superficiales para determinar el efecto de estos en la adhesión a la matriz mediante: i pruebas de desgarre de monofilamento, pull-out, como método directo de medición y ii pruebas de tensión en laminados como método indirecto para estudiar, mediante microscopía electrónica SEM, la adhesión fibra matriz en la zona de fractura.

Association of DNA with poly(N-vinylpyrrolidone)-C sub 6 sub 0 complex in D sub 2 O

CERN Document Server

Toeroek, G; Lebedev, V T; Orlova, D N; Kaboev, O K; Sibilev, A I; Sibileva, M A; Zgonnik, V N; Melenevskaya, E Y; Vinogradova, L V

2002-01-01

The interaction of DNA with a poly(N-vinylpyrrolidone)-C sub 6 sub 0 complex in D sub 2 O has been studied by SANS at physiological temperatures T=20 C and 40 C. On increasing the concentration of the complex (C=0.1-1.0 wt. %) at a constant DNA content (C sup * =0.1 wt. %), we observed a progressive complex association with DNA, while the PVP revealed the opposite behaviour (maximum association at C=0.5 wt. %). Complexes clustering with DNA (gyration radius of the associates R sub G propor to 15-30 nm) are more pronounced at 40 C. (orig.)

Graphene-poly aniline by oxidative electro polymerization

International Nuclear Information System (INIS)

Pa-a, Jonathan E.; Enriquez, Erwin P.

2013-01-01

In this work , the photochemically synthesized NH 2 - graphene is doped with poly aniline through oxidative electro polymerization to form the NH 2 -graphene/poly aniline composites. These composites with varying amounts of NH 2 -graphene are investigated using Fourier Transform-infrared (FTIR) spectroscopy, ultraviolet-visible (UV)absorption spectroscopy , scanning electron microscopy (SEM-EDX), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and electrochemical measurements. FTIR analysis strongly suggests incorporation of NH 2 -graphene sheets on poly aniline via imine (C=N) formation. UV/visible analysis of composites containing varying amounts of NH 2 -graphene in PANI shows different extent of modification on the oxidation state of the emeraldine base form to leuco emeraldine form of the PANI chain segments with possible formation of imine (C=N) units at other positions of the aniline ring in the composite, Time evolution UV/visible spectra by UV-irradiation of composites tend to proceed further with imine and phenazine-like microstructure formation. TEM and SEM images show patterns on aggregation of regular to deformed fibers surrounding planar surfaces which may indicate interior surface of NH 2 -graphene sheets not being grafted with polymers. Improved thermal stability of poly aniline in the presence of minimum amount of NH 2 -graphene sheets further confirms structural transformation within the microstructures. Electrochemical measurements by cyclic voltammetry show enhanced capacitive behavior relative to pure poly aniline. The route of synthesis using NH 2 -graphene and poly aniline offers a simple but controlled synthetic route for electrochemical doping and welding of N-containing heterocyclic structures onto pristine graphene sheets for possible use in sensing and energy storage applications. (author)

A smart core-sheath nanofiber that captures and releases red blood cells from the blood

Science.gov (United States)

Shi, Q.; Hou, J.; Zhao, C.; Xin, Z.; Jin, J.; Li, C.; Wong, S.-C.; Yin, J.

2016-01-01

A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from the blood above phase-transition temperature of PNIPAAm. Meanwhile, the captured RBCs are readily released from the nanofibers with temperature stimuli in an undamaged manner. The release efficiency of up to 100% is obtained while maintaining cellular integrity and function. This work presents promising nanofibers to effectively capture non-adherent cells and release for subsequent molecular analysis and diagnosis of single cells.A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from

Suzuki coupling reactions catalyzed by poly(N-ethyl-4-vinylpyridinium bromide stabilized palladium nanoparticles in aqueous solution

Directory of Open Access Journals (Sweden)

2008-04-01

Full Text Available InIn this work, it was investigated to use of poly(N-ethyl-4-vinylpyridinium bromide stabilized palladium nanoparticles in the Suzuki reaction between phenylboronic acid and aryl halides in aqueous solution. The nanoparticles were isolated and re-used several times with low loss of activity.

Preparation of poly(acrylamide-co-acrylic acid)-grafted gum and its flocculation and biodegradation studies.

Science.gov (United States)

Mittal, H; Mishra, Shivani B; Mishra, A K; Kaith, B S; Jindal, R; Kalia, S

2013-10-15

Biodegradation studies of Gum ghatti (Gg) and acrylamide-co-acrylic acid based flocculants [Gg-cl-poly(AAm-co-AA)] have been reported using the soil composting method. Gg-cl-poly(AAm-co-AA) was found to degrade 89.76% within 60 days. The progress of biodegradation at each stage was monitored through FT-IR and SEM. Polymer was synthesized under pressure using potassium persulphate-ascorbic acid as a redox initiator and N,N'-methylene-bis-acrylamide as a crosslinker. Synthesized polymer was found to show pH, temperature and ionic strength of the cations dependent swelling behavior. Gg-cl-poly(AAm-co-AA) was utilized for the selective absorption of saline from different petroleum fraction-saline emulsions. The flocculation efficiency of the polymer was studied as a function of polymer dose, temperature and pH of the solution. Gg-cl-poly(AAm-co-AA) showed maximum flocculation efficiency with 20 mol L(-1) polymer dose in acidic medium at 50 °C. Copyright © 2013. Published by Elsevier Ltd.

Poly(tetramethyleneterephthalate) crosslinked by irradiation

International Nuclear Information System (INIS)

Nyberg, D.D.

1978-01-01

Crosslinking, e.g., by irradiation, of a polymer comprising poly(tetramethyleneterephthalate) is made possible by the addition of a member selected from the group consisting of triallyl cyanurate and N,N'-m-phenylenedimaleimide. The resulting crosslinked modified polymer may be rendered heat recoverable

Synthesis and characterization of antifouling poly(N-acryloylaminoethoxyethanol) with ultralow protein adsorption and cell attachment.

Science.gov (United States)

Chen, Hong; Zhang, Mingzhen; Yang, Jintao; Zhao, Chao; Hu, Rundong; Chen, Qiang; Chang, Yung; Zheng, Jie

2014-09-02

Rational design of effective antifouling polymers is challenging but important for many fundamental and applied applications. Herein we synthesize and characterize an N-acryloylaminoethoxyethanol (AAEE) monomer, which integrates three hydrophilic groups of hydroxyl, amide, and ethylene glycol in the same material. AAEE monomers were further grafted and polymerized on gold substrates to form polyAAEE brushes with well-controlled thickness via surface-initiated atomic transfer radical polymerization (SI-ATRP), with particular attention to a better understanding of the molecular structure-antifouling property relationship of hydroxyl-acrylic-based polymers. The surface hydrophilicity and antifouling properties of polyAAEE brushes as a function of film thickness are studied by combined experimental and computational methods including surface plasmon resonance (SPR) sensors, atomic force microscopy (AFM), cell adhesion assay, and molecular dynamics (MD) simulations. With the optimal polymer film thicknesses (∼10-40 nm), polyAAEE-grafted surfaces can effectively resist protein adsorption from single-protein solutions and undiluted human blood plasma and serum to a nonfouling level (i.e., antifouling properties. The molecular structure-antifouling properties relationship of a series of hydroxyl-acrylic-based polymers is also discussed. This work hopefully provides a promising structural motif for the design of new effective antifouling materials beyond traditional ethylene glycol-based antifouling materials.

Dynamic crossovers and activated regimes in a narrow distribution poly(n-butyl acrylate): an ESR study

Energy Technology Data Exchange (ETDEWEB)

Andreozzi, Laura; Autiero, Ciro; Faetti, Massimo; Giordano, Marco; Zulli, Fabio [Department of Physics ' E Fermi' , University of Pisa, largo Pontecorvo 3, 56127 Pisa (Italy); polyLAB-CNR, largo Pontecorvo 3, 56127 Pisa (Italy)

2006-07-19

The rotational dynamics of the spin probe cholestane dissolved in a narrow distribution poly(n-butyl acrylate) sample has been investigated via electron spin resonance (ESR) spectroscopy. The measurements were carried out in a wide temperature range: different dynamic regions have been recognized, and the coupling of the probe dynamics to the {alpha} and secondary relaxations has been revealed. In particular, the coupling with the structural relaxation is ruled by two fractionary Vogel-Fulcher laws (VF). The crossover from one VF region to the other occurs at the temperature T{sub C} = 1.17T{sub g}, signalling the onset of the cooperativity in the dynamics and confirming a behaviour previously observed in ESR studies carried out on polymeric glass-formers. Furthermore, in this work we discuss the activated regime at the highest temperatures and show that the activation energy does not depend on the length of the polymer main- and side-chains, while its onset temperature linearly depends on the chain length.

Dynamic crossovers and activated regimes in a narrow distribution poly(n-butyl acrylate): an ESR study

International Nuclear Information System (INIS)

Andreozzi, Laura; Autiero, Ciro; Faetti, Massimo; Giordano, Marco; Zulli, Fabio

2006-01-01

The rotational dynamics of the spin probe cholestane dissolved in a narrow distribution poly(n-butyl acrylate) sample has been investigated via electron spin resonance (ESR) spectroscopy. The measurements were carried out in a wide temperature range: different dynamic regions have been recognized, and the coupling of the probe dynamics to the α and secondary relaxations has been revealed. In particular, the coupling with the structural relaxation is ruled by two fractionary Vogel-Fulcher laws (VF). The crossover from one VF region to the other occurs at the temperature T C = 1.17T g , signalling the onset of the cooperativity in the dynamics and confirming a behaviour previously observed in ESR studies carried out on polymeric glass-formers. Furthermore, in this work we discuss the activated regime at the highest temperatures and show that the activation energy does not depend on the length of the polymer main- and side-chains, while its onset temperature linearly depends on the chain length

Studies on the structure and thermal behaviour of poly(N-alkyl sesqui oxanes) base silicon resins; Estudos da estrutura e do comportamento termico de resinas de silicona a base de poli(N-alquilsilsesquioxanos)

Energy Technology Data Exchange (ETDEWEB)

Prado, Luis Antonio Sanchez de Almeida; Yoshida, Inez Valeria Pagotto [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Inst. de Quimica], e-mail: valeria@iqm.unicamp.br

2000-07-01

In this work, T, T{sup A}D{sup L} and T{sup A}D{sup C} silicone resins were obtained by the sol-gel process. Poly(dimethylsiloxane) and tetramethyl diethoxydisiloxane were used as sources of D{sup L} and D{sup C} units, respectively, while n-octyltriethoxysilane and n-dodecyltriethoxysilane were employed as precursors for T{sup A} units. The molecular structure and the composition were investigated by FT-IR and {sup 29}Si MAS NMR spectra. A partial loss of TMDES was observed during the curing of the resins. TGA traces indicated good thermal stability for all resins prepared. DSC curves showed the presence of a glass-transition and first-order transition for the resins containing n-octyl and n-dodecyl groups, respectively. The presence of the last transition could be attributed to the fusion of nano domains constituted by n-dodecyl groups. (author)

Epoxy/anhydride thermosets modified with end-capped star polymers with poly(ethyleneimine cores of different molecular weight and poly(ε–caprolactone arms

Directory of Open Access Journals (Sweden)

C. Acebo

2015-09-01

Full Text Available Multiarm star polymers, with a hyperbranched poly(ethyleneimine (PEI core and poly(ε-caprolactone (PCL arms end-capped with acetyl groups were synthesized by ring-opening polymerization of ε-caprolactone from PEI cores of different molecular weight. These star polymers were used as toughening agents for epoxy/anhydride thermosets. The curing process was studied by calorimetry, thermomechanical analysis and infrared spectroscopy. The final properties of the resulting materials were determined by thermal and mechanical tests. The addition of the star polymers led to an improvement up to 130% on impact strength and a reduction in the thermal stresses up to 55%. The structure and molecular weight of the modifier used affected the morphology of the resulting materials. Electron microscopy showed phase-separated morphologies with nano-sized fine particles well adhered to the epoxy/anhydride matrix when the higher molecular weight modifier was used.

Constructing Asymmetric Polyion Complex Vesicles via Template Assembling Strategy: Formulation Control and Tunable Permeability

Directory of Open Access Journals (Sweden)

Junbo Li

2017-11-01

Full Text Available A strategy for constructing polyion complex vesicles (PICsomes with asymmetric structure is described. Poly(methylacrylic acid-block-poly(N-isopropylacrylamide modified gold nanoparticles (PMAA-b-PNIPAm-@-Au NPs were prepared and then assembled with poly(ethylene glycol-block-poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine] (PEG-b-PMMPImB via polyion complex of PMMA and PMMPImB. After removing the Au NPs template, asymmetric PICsomes composed of a PNIPAm inner-shell, PIC wall, and PEG outer-corona were obtained. These PICsomes have low protein absorption and thermally tunable permeability, provided by the PEG outer-corona and the PNIPAm inner-shell, respectively. Moreover, PICsome size can be tailored by using templates of predetermined sizes. This novel strategy for constructing asymmetric PICsomes with well-defined properties and controllable size is valuable for applications such as drug delivery, catalysis and monitoring of chemical reactions, and biomimetics.

All-Polymer Photovoltaic Devices of Poly(3-(4- n -octyl)-phenylthiophene) from Grignard Metathesis (GRIM) Polymerization

KAUST Repository

Holcombe, Thomas W.

2009-10-14

(Graph Presented) The synthesis of poly[3-(4-n-octyl)-phenylthiophene] (POPT) from Grignard Metathesis (GRIM) is reported. GRIM POPT is found to have favorable electronic, optical, and processing properties for organic photovoltaics (OPVs). Space-charge limited current and field effect transistor measurements for POPT yielded hole mobilities of 1 × 10-4 cm2/(V s) and 0.05 cm2/(V s), respectively. Spincasting GRIM POPT from chlorobenzene yields a thin film with a 1.8 eV band gap, and PC61BM:POPT bulk heterojection devices provide a peak performance of 3.1%. Additionally, an efficiency of 2.0% is achieved in an all-polymer, bilayer OPV using poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-(1-cyanovinylene) phenylene] (CNPPV) as an acceptor. This state-of-the-art all-polymer device is analyzed in comparison to the analogous poly(3-hexylthiophene) (P3HT)/CNPPV device. Counter to expectations based on more favorable energy level alignment, greater active layer light absorption, and similar hole mobility, P3HT/CNPPV devices perform less well than POPT/CNPPV devices with a peak efficiency of 0.93%. © 2009 American Chemical Society.

All-Polymer Photovoltaic Devices of Poly(3-(4- n -octyl)-phenylthiophene) from Grignard Metathesis (GRIM) Polymerization

KAUST Repository

Holcombe, Thomas W.; Woo, Claire H.; Kavulak, David F.J.; Thompson, Barry C.; Fréchet, Jean M. J.

2009-01-01

(Graph Presented) The synthesis of poly[3-(4-n-octyl)-phenylthiophene] (POPT) from Grignard Metathesis (GRIM) is reported. GRIM POPT is found to have favorable electronic, optical, and processing properties for organic photovoltaics (OPVs). Space-charge limited current and field effect transistor measurements for POPT yielded hole mobilities of 1 × 10-4 cm2/(V s) and 0.05 cm2/(V s), respectively. Spincasting GRIM POPT from chlorobenzene yields a thin film with a 1.8 eV band gap, and PC61BM:POPT bulk heterojection devices provide a peak performance of 3.1%. Additionally, an efficiency of 2.0% is achieved in an all-polymer, bilayer OPV using poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-(1-cyanovinylene) phenylene] (CNPPV) as an acceptor. This state-of-the-art all-polymer device is analyzed in comparison to the analogous poly(3-hexylthiophene) (P3HT)/CNPPV device. Counter to expectations based on more favorable energy level alignment, greater active layer light absorption, and similar hole mobility, P3HT/CNPPV devices perform less well than POPT/CNPPV devices with a peak efficiency of 0.93%. © 2009 American Chemical Society.

Temperature effects on the stability of gold nanoparticles in the presence of a cationic thermoresponsive copolymer

Energy Technology Data Exchange (ETDEWEB)

Pamies, Ramón [Technical University of Cartagena, Department of Material Engineering and Manufacturing (Spain); Zhu, Kaizheng [University of Oslo, Department of Chemistry (Norway); Kjøniksen, Anna-Lena, E-mail: anna.l.kjoniksen@hiof.no [Østfold University College, Faculty of Engineering (Norway); Nyström, Bo [University of Oslo, Department of Chemistry (Norway)

2016-11-15

New hybrid complexes composed by a thermoresponsive copolymer and gold nanoparticles (R{sub h} = 22 nm) have been characterized by dynamic light scattering (DLS) and UV-visible spectroscopy. A cationic thermoresponsive triblock copolymer, methoxy-poly(ethylene glycol)-block-poly(N-isopropylacrylamide)-block-poly((3-acrylamidopropyl) trimethyl ammonium chloride), abbreviated as MPEG-b-PNIPAAM-b-PN(+), has been synthesized by atom transfer radical polymerization (ATRP). We have evaluated the thermal response at low concentrations of this triblock copolymer in bulk solution and the effect of concentration on the interaction between this thermosensitive copolymer and the gold nanoparticles (AuNPs) to form new hybrid complexes (60–1000 nm) at different temperatures. The thermosensitive nature of the copolymer causes both aggregation and contraction of the aggregates at elevated temperatures. The AuNPs were found to be separately embedded in the hybrid complexes. Interestingly, the AuNPs prevent macroscopic phase separation of the system at high temperatures.

TEMPLATE POLYMERIZATION OF N-VINYLIMIDAZOLE ALONG POLY(METHACRYLIC ACID) IN WATER .2. KINETICS OF THE TEMPLATE POLYMERIZATION

NARCIS (Netherlands)

VANDEGRAMPEL, HT; TAN, YY; CHALLA, G

1991-01-01

The template polymerization of N-vinylimidazole (VIm) along poly(methacrylic acid) (PMAA) in water at 50-degrees-C with 2,2'-azobis(2-amidinopropane).2HCl (AAP) as initiator was studied by using variable initiator and monomer concentrations at constant [PMAA]/[VIm]0. From the order in [VIm] it was

Core-shell polymer nanoparticles for prevention of GSH drug detoxification and cisplatin delivery to breast cancer cells

Science.gov (United States)

Surnar, Bapurao; Sharma, Kavita; Jayakannan, Manickam

2015-10-01

Platinum drug delivery against the detoxification of cytoplasmic thiols is urgently required for achieving efficacy in breast cancer treatment that is over expressed by glutathione (GSH, thiol-oligopeptide). GSH-resistant polymer-cisplatin core-shell nanoparticles were custom designed based on biodegradable carboxylic functional polycaprolactone (PCL)-block-poly(ethylene glycol) diblock copolymers. The core of the nanoparticle was fixed as 100 carboxylic units and the shell part was varied using various molecular weight poly(ethylene glycol) monomethyl ethers (MW of PEGs = 100-5000 g mol-1) as initiator in the ring-opening polymerization. The complexation of cisplatin aquo species with the diblocks produced core-shell nanoparticles of 75 nm core with precise size control the particles up to 190 nm. The core-shell nanoparticles were found to be stable in saline solution and PBS and they exhibited enhanced stability with increase in the PEG shell thickness at the periphery. The hydrophobic PCL layer on the periphery of the cisplatin core behaved as a protecting layer against the cytoplasmic thiol residues (GSH and cysteine) and exhibited embryonic fibroblast cells (Wt-MEFs), and breast cancer (MCF-7) and cervical cancer (HeLa) cell lines. Free cisplatin and polymer drug core-shell nanoparticles showed similar cytotoxicity effects in the HeLa cells. In MCF-7 cells, the free cisplatin drug exhibited 50% cell death whereas complete cell death (100%) was accomplished by the polymer-cisplatin core-shell nanoparticles. Confocal microscopic images confirmed that the core-shell nanoparticles were taken up by the MCF-7 and HeLa cells and they were accumulated both at the cytoplasm as well at peri-nuclear environments. The present investigation lays a new foundation for the polymer-based core-shell nanoparticles approach for overcoming detoxification in platinum drugs for the treatment of GSH over-expressed breast cancer cells.Platinum drug delivery against the detoxification

Phase behavior of poly(dimethylsiloxane)-poly(ethylene oxide) amphiphilic block and graft copolymers in compressed carbon dioxide

International Nuclear Information System (INIS)

Stoychev, Ivan; Peters, Felix; Kleiner, Matthias; Sadowski, Gabriele; Clerc, Sebastien; Ganachaud, Francois; Chirat, Mathieu; Lacroix-Desmazes, Patrick; Fournel, Bruno

2012-01-01

The phase behavior of triblock and graft-type poly(dimethylsiloxane) (PDMS)-poly(ethylene oxide) (PEO) copolymer surfactants has been investigated in compressed carbon dioxide (CO 2 ). For this purpose, cloud-point pressures have been measured in the pressure and temperature range from P=10 to 40 MPa and from T= 293 to 338 K. The Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state (EoS) has been applied to model the experimental data in order to better understand the influence of the structure of the copolymers on the phase behavior of the system. The pure-component parameters for PDMS have been fitted originally to PDMS/n-pentane system. These parameters are successfully applied for PDMS in CO 2 by adjusting a temperature-dependent binary interaction parameter. The phase behavior of the triblock copolymers was successfully predicted by PC-SAFT. In contrast, the phase behavior of the graft copolymers was difficult to predict accurately at this stage. (authors)

Ionic core–shell dendrimers with a polycationic core: structural aspects and host–guest binding properties

NARCIS (Netherlands)

van de Coevering, R.; Bruijnincx, P.C.A.; Lutz, M.; Spek, A.L.; van Koten, G.; Klein Gebbink, R.J.M.

2007-01-01

The structural aspects and host–guest binding properties of ionic core–shell dendrimers [1]Br8 and [2]Br4, which bear a polycationic core and a neutral shell of Fréchet-type poly(benzyl aryl ether) dendrons, have been investigated by means of dendritic wedges [3]Br2 and [4]Br, that resemble one of

Adsorção de poli(acrilamida-b-N,N-dihexilacrilamida sobre arenito: determinação das condições para se atingir o equilíbrio real Poly(acrylamide-b-N,N-dihexylacrylamide adsorption on sandstone: determination of the conditions to reach the real equilibrium

Directory of Open Access Journals (Sweden)

Ana Maria S. Maia

2007-03-01

Full Text Available Durante as últimas décadas, o interesse em polímeros anfifílicos tem aumentado continuamente. Neste trabalho, o comportamento do copolímero hidrofílico/hidrofóbico poli(acrilamida-b-N,N-dihexilacrilamida (PADHA na interface sólido/líquido foi estudado para se quantificar a adsorção quando o equilíbrio do sistema é atingido. Na interface água/arenito, a isoterma de adsorção para a PADHA mostrou uma forma incomum, caracterizada pela ausência de uma região de patamar e um aumento contínuo na quantidade adsorvida com a concentração polimérica. Esta forma de adsorção particular poderia ser explicada pela formação de múltiplas camadas devido a associações hidrofóbicas, através das quais as camadas adsorvidas seriam formadas, em parte, por algumas cadeias que não estão diretamente em contato com a superfície sólida.During the last few decades, interest in amphiphilic polymers has increased steadily. In this work, the behavior of the hydrophilic/hydrophobic copolymer poly(acrylamide-b-N,N-dihexylacrylamide (PADHA at a solid/liquid interface has been studied to quantify adsorption at equilibrium. At the water/sandstone interface, the adsorption isotherm for PADHA show an unusual profile, characterized by the absence of a "plateau" region and a monotonic increase in the adsorbed amount with polymer concentration in the bulk. This particular adsorption profile could be explained by the formation of multiple layers caused by hydrophobic associations, the adsorbed layers being partly formed by chains that are not directly in contact with the surface.

Biphasic Equilibrium Dialysis of Poly(N-Isopropyl Acrylamide Nanogels Synthesized at Decreased Temperatures for Targeted Delivery of Thermosensitive Bioactives

Directory of Open Access Journals (Sweden)

Witold Musial

2013-01-01

Full Text Available Hydrogel nanoparticles, referred to also as nanogels, are of special interest for medical and pharmaceutical applications. Due to small size in the range below the diameter of the capillaries, they are proposed as drug delivery carriers. The aim of the study was to estimate the influence of composition and reaction conditions during synthesis of poly-N-isopropyl acrylamide cross-linked by polyethylene glycol diacrylate on the purification rates of the polymer. Six types of thermosensitive nanogels were prepared by surfactant-free dispersion polymerization and assessed in terms of process yield, composition, and size at temperatures below and over volume phase temperature. During the diffusion of impurities, in the course of dialysis, assessed by the conductometric method, the remarkable influence of temperature and initiator concentration on the process was revealed. The release rates varied in the range between 9.63 · 10−2 and 1.39 · 10−1 h−1 in the first stage of the process, whereas in the second stage they were between 2.09 · 10−2 and 6.28 · 10−2 h−1. The evaluated time to obtain acceptable purity of the preparation was estimated to be in the range of 18 days. More detailed research should be directed towards the influence of the structure of obtained material on the purification process.

Covalent bonding of PMMA, PBMA, and poly(HEMA) to hydroxyapatite particles

NARCIS (Netherlands)

Liu, Q.; de Wijn, J.R.; van Blitterswijk, Clemens

1998-01-01

In our earlier study, we showed that the surface hydroxyl groups of hydroxyapatite have the ability to react with organic isocyanate groups. In this study, the feasibility of grafting poly(methyl methacrylate) (PMMA), poly(n-butyl methacrylate) (PBMA), and Poly(hydroxyethyl methacrylate)

Cinética de cristalización del poliéster secuencial derivado del ácido glicólico y ácido 4-hidroxibutírico

OpenAIRE

Casanova Rodríguez, Mireya

2007-01-01

El objetivo principal de este Proyecto Final de Carrera es el estudio de la cinética de cristalización del poliéster secuencial poli[ácido 4-hidroxibutírico)-alt-(ácido glicólico)]. El polímero estudiado es un nuevo material que presenta interés como material biodegradable para aplicaciones en biomedicina, como por ejemplo su utilización como sistema liberador de fármacos. Mediante calorimetría se determinan los parámetros térmicos importantes como son la temperatura fusión,...

Further evidence for poly-ADP-ribosylated histones as DNA suppressors

International Nuclear Information System (INIS)

Yu, F.L.; Geronimo, I.H.; Bender, W.; Meginniss, K.E.

1986-01-01

For many years histones have been considered to be the gene suppressors in eukaryotic cells. Recently, the authors have found strong evidence indicating that poly-ADP-ribosylated histones, rather than histones, are the potent inhibitors of DNA-dependent RNA synthesis. They now report additional evidence for this concept: 1) using histone inhibitor isolated directly from nuclei, the authors are able to confirm their earlier findings that the inhibitor substances are sensitive to pronase, snake venom phosphodiesterase digestion and 0.1N KOH hydrolysis, and are resistant to DNase I and RNase A digestion, 2) the O.D. 260/O.D.280 ratio of the histone inhibitor is between pure protein and nuclei acid, suggesting the inhibitor substance is a nucleoprotein hybrid. This result directly supports the fact that the isolated histone inhibitor is radioactive poly (ADP-ribose) labeled, 3) commercial histones show big differences in inhibitor activity. The authors believe this reflects the variation in poly-ADP-ribosylation among commercial histones, and 4) 0.1N KOH hydrolysis eliminates the poly (ADP-ribose) radioactivity from the acceptor proteins as well as histone inhibitor activity. Yet, on gel, the inhibitor shows identical histone bands and stain intensity before and after hydrolysis, indicating the histones per se are qualitatively and quantitatively unaffected by alkaline treatment. This result strongly suggests that histones themselves are not capable of inhibiting DNA-dependent RNA synthesis

Temperature responsive hydrogel magnetic nanocomposites for hyperthermia and metal extraction applications

Energy Technology Data Exchange (ETDEWEB)

Reddy, N. Narayana, E-mail: nagireddynarayana@gmail.com [Center for Advanced Biomaterials for Healthcare, Istituto Italiano di Tecnologia@CRIB, Largo Barsanti e Matteucci 53, 80125 Napoli (Italy); Ravindra, S. [Department of Physics, College of Science, Engineering and Technology, University of South Africa, Johannesburg 1709 (South Africa); Reddy, N. Madhava [Department of Environmental Science, Gates Institute of Technology, NH-7, Gooty, Anantapuram, Andhra Pradesh (India); Rajinikanth, V. [Department of Physics, College of Science, Engineering and Technology, University of South Africa, Johannesburg 1709 (South Africa); Raju, K. Mohana [Synthetic Polymer Laboratory, Department of Polymer Science & Technology, S.K. University, Anantapuram, Andhra Pradesh (India); Vallabhapurapu, Vijaya Srinivasu [Department of Physics, College of Science, Engineering and Technology, University of South Africa, Johannesburg 1709 (South Africa)

2015-11-15

The present work deals with the development of temperature and magnetic responsive hydrogel networks based on poly (N-isopropylacrylamide)/acrylamido propane sulfonic acid. The hydrogel matrices are synthesized by polymerizing N-isopropylacrylamide (NIPAM) monomer in the presence of acrylamido propane sulphonicacid (AMPS) using a cross-linker (N,N-methylenebisacrylamide, MBA) and redox initiating system [ammonium persulphate (APS)/tetramethylethylenediamine (TMEDA)]. The magnetic nanoparticles are generated throughout the hydrogel networks using in situ method by incorporating iron ions and subsequent treatment with ammonia. A series of hydrogel-magnetic nanocomposites (HGMNC) are developed by varying AMPS composition. The synthesized hydrogel magnetic nanocomposites (HGMNC) are characterized by using Fourier Transform Infrared (FTIR) Spectroscopy, X-ray diffraction (XRD), Thermal Analyses and Electron Microscopy analysis (Scanning and Transmission Electron Microscope). The metal extraction capacities of the prepared hydrogel (HG) and hydrogel magnetic nanocomposites (HGMNC) were studied at different temperatures. The results suggest that HGMNCs have higher extraction capacity compared to HG and HG loaded iron ions. This data also reveals that the extraction of metals by hydrogel magnetic nanocomposites (HGMNCs) is higher at higher temperatures than room temperature. The prepared HGMNCs are also subjected to hyperthermia (cancer therapy) studies. - Highlights: • We have developed temperature responsive hydrogel magnetic nanocomposites. • Addition of AMPS monomer to this magnetic hydrogel enhances the temperature sensitivity to 40–43 °C. • Similarly the sulfonic groups present in the AMPS units enhances the swelling ratio of magnetic hydrogels. • AMPS acts as good stabilizing agent for nanoparticles in the magnetic nanogel.

Temperature responsive hydrogel magnetic nanocomposites for hyperthermia and metal extraction applications

International Nuclear Information System (INIS)

Reddy, N. Narayana; Ravindra, S.; Reddy, N. Madhava; Rajinikanth, V.; Raju, K. Mohana; Vallabhapurapu, Vijaya Srinivasu

2015-01-01

The present work deals with the development of temperature and magnetic responsive hydrogel networks based on poly (N-isopropylacrylamide)/acrylamido propane sulfonic acid. The hydrogel matrices are synthesized by polymerizing N-isopropylacrylamide (NIPAM) monomer in the presence of acrylamido propane sulphonicacid (AMPS) using a cross-linker (N,N-methylenebisacrylamide, MBA) and redox initiating system [ammonium persulphate (APS)/tetramethylethylenediamine (TMEDA)]. The magnetic nanoparticles are generated throughout the hydrogel networks using in situ method by incorporating iron ions and subsequent treatment with ammonia. A series of hydrogel-magnetic nanocomposites (HGMNC) are developed by varying AMPS composition. The synthesized hydrogel magnetic nanocomposites (HGMNC) are characterized by using Fourier Transform Infrared (FTIR) Spectroscopy, X-ray diffraction (XRD), Thermal Analyses and Electron Microscopy analysis (Scanning and Transmission Electron Microscope). The metal extraction capacities of the prepared hydrogel (HG) and hydrogel magnetic nanocomposites (HGMNC) were studied at different temperatures. The results suggest that HGMNCs have higher extraction capacity compared to HG and HG loaded iron ions. This data also reveals that the extraction of metals by hydrogel magnetic nanocomposites (HGMNCs) is higher at higher temperatures than room temperature. The prepared HGMNCs are also subjected to hyperthermia (cancer therapy) studies. - Highlights: • We have developed temperature responsive hydrogel magnetic nanocomposites. • Addition of AMPS monomer to this magnetic hydrogel enhances the temperature sensitivity to 40–43 °C. • Similarly the sulfonic groups present in the AMPS units enhances the swelling ratio of magnetic hydrogels. • AMPS acts as good stabilizing agent for nanoparticles in the magnetic nanogel

Stereocomplexed 8-armed poly(ethylene glycol)-poly(lactide) star block copolymer hydrogels: Gelation mechanism, mechanical properties and degradation behavior

NARCIS (Netherlands)

Buwalda, S.J.; Calucci, L.; Forte, C.; Dijkstra, Pieter J.; Feijen, Jan

2012-01-01

Mixing aqueous poly(ethylene glycol)-poly(d-lactide) and poly(ethylene glycol)-poly(l-lactide) star block copolymer solutions resulted in the formation of stereocomplexed hydrogels within 1 min. A study towards the mechanism of the temperature dependent formation of stereocomplexes in the hydrogels

Tunable Temperature Response of a Thermochromic Photonic Gel Sensor Containing N-Isopropylacrylamide and 4-Acryloyilmorpholine

Directory of Open Access Journals (Sweden)

Hwanam Kye

2017-06-01

Full Text Available In this study, thermochromic photonic gels were fabricated using 2-hydroxyethyl methacrylate (HEMA as a hydrogel building block, and 4-Acryloyl morpholine (ACMO and N-isopropylacrylamide (NIPAAM as thermoresponsive monomers with different critical solution temperature behaviors. Rapid photopolymerization of opal-templated monomer mixtures of varying ACMO contents formed five individual thermochromic inverse opal photonic gels integrated on a single substrate. With temperature variation from 10 °C to 80 °C, the changes in reflective colors and reflectance spectra of the respective thermochromic gels were noted, and λpeak changes were plotted. Because NIPAAM exhibits a lower critical solution temperature (LCST at 33 °C, the NIPAAM-only gel showed a steep slope for dλpeak/dT below 40 °C, whereas the slope became flatter at high temperatures. As the ACMO content increased in the thermochromic gel, the curve of dλpeak/dT turned out to be gradual within the investigated temperature range, exhibiting the entire visible range of colors. The incorporation of ACMO in NIPAAM-based thermochromic gels therefore enabled a better control of color changes at a relatively high-temperature regime compared to a NIPAAM-only gel. In addition, ACMO-containing thermochromic gels exhibited a smaller hysteresis of λpeak for the heating and cooling cycle.

Thermodynamics of poly(7-methoxy-2-acetylbenzofurane methyl methacrylate-co-styrene) and poly(2-acetylbenzofurane methyl methacrylate-co-styrene)-probe interactions at different temperatures by inverse gas chromatography

International Nuclear Information System (INIS)

İlter, Zülfiye; Demir, Abdullah; Kaya, İsmet

2016-01-01

Highlights: • Thermodynamic of methacrylate-co-styrene polymers were studied by the inverse gas chromatography. • The sorption parameters of polymer-solute systems were determined under glass transition temperature of polymers. • The solubility parameter (δ 2 ) of the polymer was obtained from the slope and intercepts. • Flory-Huggins interaction parameter (χ 12 ∞ ) were determined for polymer-solute systems. - Abstract: In this study, some thermodynamic properties of poly(7-methoxy-2-acetylbenzofurane methyl methacrylate-co-styrene) Poly(MABMM-co-St) and poly(2-acetylbenzofurane methyl methacrylate-co-styrene) Poly(ABMM-co-St) were studied by the inverse gas chromatography (IGC) technique. The retention times (t r ) of selected organic probes were determined from the interactions with Poly(MABMM-co-St) and Poly(ABMM-co-St) of four groups of solvents with different chemical natures and polarities. Then, specific volume (V g 0 ) values of probes were calculated at different column temperatures. The glass transition temperatures (T g ) of Poly(MABMM-co-St) and Poly(ABMM-co-St) were found as 393, 413 K from inverse gas chromatography measurements, respectively. Under the glass transition temperatures adsorption heat (ΔH a ) and above the glass transition molar heat (ΔH 1 S ), free energies (ΔG 1 S ) and entropies (ΔS 1 S ) belonging to sorption for every probe were calculated from inverse gas chromatography measurements. The partial molar heat (ΔH 1 ∞ ), partial molar free energy (ΔG 1 ∞ ), Flory-Huggins interaction parameter (χ 12 ∞ ) and weight fraction activity coefficient (a 1 /w 1 ) ∞ , values for infinite dilute solutions were calculated for polymer-probe systems. The solubility parameter (δ 2 ) of the polymer was obtained from the slope and intercepts of Flory-Huggins interaction parameter (χ 12 ∞ ) graphs with solubility parameters (δ 1 ) of probes.

A novel multi-responsive polyampholyte composite hydrogel with excellent mechanical strength and rapid shrinking rate.

Science.gov (United States)

Xu, Kun; Tan, Ying; Chen, Qiang; An, Huiyong; Li, Wenbo; Dong, Lisong; Wang, Pixin

2010-05-15

Series of hydrophilic core-shell microgels with cross-linked poly(N-isopropylacrylamide) (PNIPAAm) as core and poly(vinyl amine) (PVAm) as shell are synthesized via surfactant-free emulsion polymerization. Then, the microgels are treated with a small amount of potassium persulfate (KPS) to generate free radicals on the amine nitrogens of PVAm, which subsequently initiate the graft copolymerization of acrylic acid (AA), acryloyloxyethyl trimethyl ammonium chloride (DAC), and acrylamide (AAm) onto microgels to prepare multi-responsive composite hydrogels. The composite hydrogels consist of cross-linked ungrafted polyampholyte chains as the first network and microgels with grafted polyampholyte chains as graft point and second network and show surprising mechanical strength and rapid response rate. The investigation shows the compress strength of composite hydrogels is up to 17-30 MPa, which is 60-100 times higher than that of the hydrogel matrix. The composite hydrogel shows reversible switch of transmittance when traveling the lowest critical temperature (LCST) of microgels. When the composite hydrogel swollen in pH 2.86 solution at ambient condition is immersed into the pH 7.00 solution at 45 °C, a rapid dynamic shrinking can be observed. And the character time (τ) of shrinking dynamic of composite hydrogel is 251.9 min, which is less than that of hydrogel matrix (τ=2273.7 min). Copyright © 2010 Elsevier Inc. All rights reserved.

Interfacial electrostatics of poly(vinylamine hydrochloride), poly(diallyldimethylammonium chloride), poly-l-lysine, and poly-l-arginine interacting with lipid bilayers.

Science.gov (United States)

McGeachy, A C; Dalchand, N; Caudill, E R; Li, T; Doğangün, M; Olenick, L L; Chang, H; Pedersen, J A; Geiger, F M

2018-04-25

Charge densities of cationic polymers adsorbed to lipid bilayers are estimated from second harmonic generation (SHG) spectroscopy and quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. The systems surveyed included poly(vinylamine hydrochloride) (PVAm), poly(diallyldimethylammonium chloride) (PDADMAC), poly-l-lysine (PLL), and poly-l-arginine (PLR), as well as polyalcohol controls. Upon accounting for the number of positive charges associated with each polyelectrolyte, the binding constants and apparent free energies of adsorption as estimated from SHG data are comparable despite differences in molecular masses and molecular structure, with ΔGads values of -61 ± 2, -58 ± 2, -57 ± 1, -52 ± 2, -52 ± 1 kJ mol-1 for PDADMAC400, PDADMAC100, PVAm, PLL, and PLR, respectively. Moreover, we find charge densities for polymer adlayers of approximately 0.3 C m-2 for poly(diallyldimethylammonium chloride) while those of poly(vinylamine) hydrochloride, poly-l-lysine, and poly-l-arginine are approximately 0.2 C m-2. Time-dependent studies indicate that polycation adsorption to supported lipid bilayers is only partially reversible for most of the polymers explored. Poly(diallyldimethylammonium chloride) does not demonstrate reversible binding even over long timescales (>8 hours).

Polarity and temperature-dependent properties of poly(N-isopropylacrylamide) and poly(N,N-diethylacryl-amide) hydrogels studied by liquid chromatography

Czech Academy of Sciences Publication Activity Database

Hradil, Jiří; Macková, Hana; Horák, Daniel

2009-01-01

Roč. 281, č. 1 (2009), s. 142-149 ISSN 1022-1360. [Microsymposium on Polymer Colloids: From Design to Biomedical and Industrial Applications /48./. Praha, 20.07.2008-24.07.2008] R&D Projects: GA AV ČR KAN200200651 Institutional research plan: CEZ:AV0Z40500505 Keywords : polymers * behavior * bioseparation Subject RIV: CD - Macromolecular Chemistry

Facile fabrication and characterization of poly(tetrafluoroethylene)@polypyrrole/nano-silver composite membranes with conducting and antibacterial property

Science.gov (United States)

Shi, Zhiquan; Zhou, Hui; Qing, Xutang; Dai, Tingyang; Lu, Yun

2012-06-01

Porous poly(tetrafluoroethylene) (PTFE) membranes play an important role in air purification and separation engineering. To achieve the bi-functionality of conducting and antibacterial property, two kinds of poly(tetrafluoroethylene)@ polypyrrole/nano-silver composite membranes have been prepared. One involves hydrophobic polypyrrole/nano-silver composite with hollow capsule nanostructures immobilized on the surface of the PTFE membranes. The other is a type of composite membranes with polypyrrole/nano-silver composite wholly packed on the fibrils of the expand PTFE membrane to form core/shell coaxial cable structures. The structure and morphology of the two kinds of composite membranes have been characterized by FTIR, UV-vis, XRD, TGA and SEM measurements. Possible formation mechanisms of the hollow capsules and the core/shell nanocable structures have been discussed in detail. The antibacterial effects of composite membranes are also briefly investigated.

Design and characterization of dexamethasone-loaded poly (glycerol sebacate)-poly caprolactone/gelatin scaffold by coaxial electro spinning for soft tissue engineering.

Science.gov (United States)

Nadim, Afsaneh; Khorasani, Saied Nouri; Kharaziha, Mahshid; Davoodi, Seyyed Mohammadreza

2017-09-01

The aim of this research was to fabricate dexamethasone (Dex)-loaded poly (glycerol sebacate) (PGS)-poly (caprolactone) (PCL)/gelatin (Gt) (PGS-PCL/Gt-Dex) fibrous scaffolds in the form of core/shell structure which have potential application in soft tissues. In this regard, after synthesize and characterizations of PGS, PGS-PCL and gelatin fibrous scaffolds were separately developed in order to optimize the electrospinning parameters. In the next step, coaxial electrospun fibrous scaffold of PGS-PCL/Gt fibrous scaffold with PGS-PCL as core and Gt as shell was developed and its mechanical, physical and chemical properties were characterized. Moreover, degradability, hydrophilicity and biocompatibility of PGS-PCL/Gt fibrous scaffold were evaluated. In addition, Dex was encapsulated in PGS-PCL/Gt fibrous scaffold and drug release was assessed for tissue engineering application. Results demonstrated the formation of coaxial fibrous scaffold with average porosity of 79% and average fiber size of 294nm. Moreover, PGS-PCL/Gt fibrous scaffold revealed lower elastic modulus, ultimate tensile and ultimate elongation than those of PGS-PCL scaffold and more close to mechanical properties of natural tissue. Furthermore, lower contact angle of PGS-PCL/Gt than that of PGS-PCL demonstrated improved surface hydrophilicity of scaffold. DEX release was sustained over a period time of 30days from the scaffolds via three steps consisting of an initial burst release, secondary linear phase release pattern with slower rate over 20days followed by an apparent zero-order release phase. MTT observations demonstrated that there was no evidence of toxicity in the samples with and without Dex. Our findings indicated that core/shell PGS-PCL/Gt-Dex fibrous could be used as a carrier for the sustained release of drugs relevant for tissue engineering which makes it appropriate for soft tissue engineering. Copyright © 2017 Elsevier B.V. All rights reserved.

A silicone rubber based composites using n-octadecane/poly (styrene-methyl methacrylate microcapsules as energy storage particle

Directory of Open Access Journals (Sweden)

W.L. Wu

Full Text Available A phase-change energy-storage material, silicone rubber (SR coated n-octadecane/poly (styrene-methyl methacrylate (SR/OD/P(St-MMA microcapsule composites, was prepared by mixing SR and OD/P(St-MMA microcapsules. The microcapsule content and silicone rubber coated method were investigated. The morphology and thermal properties of the composites were characterized by scanning electron microscopy (SEM, thermogravimetric analysis (TG, differential scanning calorimetry (DSC and heat storage properties. The results showed that the thermal and mechanical properties of SR/OD/P(St-MMA composites were excellent when the microcapsules were coated with room temperature vulcanized silicone rubber (RTVSR, of which content was 2 phr (per hundred rubber. The enthalpy value of the composites was 67.6 J g−1 and the composites were found to have good energy storage function. Keywords: n-Octadecane, Silicone rubber, Microcapsule, Energy-storage, Composites

Synthesis and self-assembly of amphiphilic poly(acrylicacid)-poly(ɛ-caprolactone)-poly(acrylicacid) block copolymer as novel carrier for 7-ethyl-10-hydroxy camptothecin.

Science.gov (United States)

Djurdjic, Beti; Dimchevska, Simona; Geskovski, Nikola; Petrusevska, Marija; Gancheva, Valerya; Georgiev, Georgi; Petrov, Petar; Goracinova, Katerina

2015-01-01

The process of molecular self-assembly plays a crucial role in formulation of polymeric nanoparticulated drug delivery carriers as it creates the possibility for enhanced drug encapsulation and carrier surface engineering. This study aimed to develop a novel self-assembled polymeric micelles for targeted delivery in tumor cells in order to overcome not only various drawbacks of 7-ethyl-10-hydroxy camptothecin (SN-38) but also various reported limitations of other drug delivery systems, especially low drug loading and premature release. Custom synthesized amphiphilic triblock copolymer poly(acrylic acid)-poly(ɛ-caprolactone)-poly(acrylic acid) (PAA(13)-PCL(35)-PAA(13)) was used to prepare kinetically stable micelles by nanoprecipitation and modified nanoprecipitation procedure. Core-shell micelles with diameter of 120-140 nm, negative zeta potential and satisfactory drug loading were produced. The prepared formulations were stable in pH range of 3-12 and in media with NaCl concentration calorimetry analyses confirmed the entrapment of the active substance into the micelles. The kinetic analysis of dissolution studies revealed that the main mechanism of drug release from the prepared formulations is Fickian diffusion. Growth inhibition studies as well as DNA fragmentation assay performed on SW-480 cell lines clearly demonstrated increased growth inhibition effect and presence of fragmented DNA in cells treated with loaded micelles compared to SN-38 solution. Altogether, these results point out to potential biomedical and clinical application of PAA-PCL-PAA systems in the future. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Longitudinal acoustic properties of poly(lactic acid) and poly(lactic-co-glycolic acid)

International Nuclear Information System (INIS)

Parker, N G; Povey, M J W; Mather, M L; Morgan, S P

2010-01-01

Acoustics offers rich possibilities for characterizing and monitoring the biopolymer structures being employed in the field of biomedical engineering. Here we explore the rudimentary acoustic properties of two common biodegradable polymers: poly(lactic acid) and poly(lactic-co-glycolic acid). A pulse-echo technique is developed to reveal the bulk speed of sound, acoustic impedance and acoustic attenuation of small samples of the polymer across a pertinent temperature range of 0-70 0 C. The glass transition appears markedly as both a discontinuity in the first derivative of the speed of sound and a sharp increase in the acoustic attenuation. We further extend our analysis to consider the role of ethanol, whose presence is observed to dramatically modify the acoustic properties and reduce the glass transition temperature of the polymers. Our results highlight the sensitivity of acoustic properties to a range of bulk properties, including visco-elasticity, molecular weight, co-polymer ratio, crystallinity and the presence of plasticizers.

Significantly Enhanced Dielectric Performances and High Thermal Conductivity in Poly(vinylidene fluoride)-Based Composites Enabled by SiC@SiO2 Core-Shell Whiskers Alignment.

Science.gov (United States)

He, Dalong; Wang, Yao; Song, Silong; Liu, Song; Deng, Yuan

2017-12-27

Design of composites with ordered fillers arrangement results in anisotropic performances with greatly enhanced properties along a specific direction, which is a powerful tool to optimize physical properties of composites. Well-aligned core-shell SiC@SiO 2 whiskers in poly(vinylidene fluoride) (PVDF) matrix has been achieved via a modified spinning approach. Because of the high aspect ratio of SiC whiskers, strong anisotropy and significant enhancement in dielectric constant were observed with permittivity 854 along the parallel direction versus 71 along the perpendicular direction at 20 vol % SiC@SiO 2 loading, while little increase in dielectric loss was found due to the highly insulating SiO 2 shell. The anisotropic dielectric behavior of the composite is perfectly understood macroscopically to have originated from anisotropic intensity of interfacial polarization based on an equivalent circuit model of two parallel RC circuits connected in series. Furthermore, finite element simulations on the three-dimensional distribution of local electric field, polarization, and leakage current density in oriented SiC@SiO 2 /PVDF composites under different applied electrical field directions unambiguously revealed that aligned core-shell SiC@SiO 2 whiskers with a high aspect ratio significantly improved dielectric performances. Importantly, the thermal conductivity of the composite was synchronously enhanced over 7 times as compared to that of PVDF matrix along the parallel direction at 20 vol % SiC@SiO 2 whiskers loading. This study highlights an effective strategy to achieve excellent comprehensive properties for high-k dielectrics.