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.

Thermoresponsive behaviour of terpolymers containing poly(ethylene oxide), poly(2-ethyl-2-oxazoline) and poly(.epsilon.-caprolactone) blocks in aqueous solutions: an NMR study

Czech Academy of Sciences Publication Activity Database

Konefal, Rafal; Spěváček, Jiří; Jäger, Eliezer; Petrova, Svetlana

2016-01-01

Roč. 294, č. 11 (2016), s. 1717-1726 ISSN 0303-402X R&D Projects: GA ČR(CZ) GA15-13853S; GA MŠk(CZ) 7F14009 Institutional support: RVO:61389013 Keywords : thermoresponsive polymer * terpolymer containing poly(ethylene oxide), poly(2-ethyl-2-oxazoline) and poly(epsilon-caprolactone) blocks * nanoparticles Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.723, year: 2016

Thermo-responsive, UV-active poly(phenyl acrylate-b-poly(diethyl acrylamide block copolymers

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M. Maric

2013-12-01

Full Text Available The homopolymerization of phenyl acrylate (PA was investigated for the first time by nitroxide mediated polymerization (NMP with the succinimidyl form of the SG1-based unimolecular initiator 2-[N-tert-butyl-2,2-(dimethylpropyl-aminooxy]propionic acid (BlocBuilder MA. The control of PPA homopolymerization was improved by the use of 15 mol% additional free nitroxide SG1 ([tert-butyl[1-(diethoxyphosphoryl-2,2-dimethylpropyl]amino]oxidanyl and dispersities, Mw/Mn, of around 1.2 were achieved. A PPA homopolymer was then successfully chain-extended with diethyl acrylamide (DEAAm to form a block copolymer of PPA-b-PDEAAm where the PDEAAm segment is thermo-responsive, while the PPA block is potentially UV-active. The thermo-responsive behavior of the block copolymer in 0.5 wt% aqueous solution was studied by UV-Vis spectrometry and dynamic light scattering (DLS, indicating cloud point temperatures of 26–30°C, close to that reported for PDEAAm homopolymers.

A Fluorescent Thermometer Based on a Pyrene-Labeled Thermoresponsive Polymer

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Ulrich S. Schubert

2010-08-01

Full Text Available Thermoresponsive polymers that undergo a solubility transition by variation of the temperature are important materials for the development of ‘smart’ materials. In this contribution we exploit the solubility phase transition of poly(methoxy diethylene glycol methacrylate, which is accompanied by a transition from hydrophilic to hydrophobic, for the development of a fluorescent thermometer. To translate the polymer phase transition into a fluorescent response, the polymer was functionalized with pyrene resulting in a change of the emission based on the microenvironment. This approach led to a soluble polymeric fluorescent thermometer with a temperature range from 11 °C to 21 °C. The polymer phase transition that occurs during sensing is studied in detail by dynamic light scattering.

Aggregation behavior of doubly thermoresponsive polysulfobetaine-b-poly(N-isopropylacrylamide) diblock copolymers

Czech Academy of Sciences Publication Activity Database

Vishnevetskaya, N. S.; Hildebrand, V.; Niebuur, B.-J.; Grillo, I.; Filippov, Sergey K.; Laschewsky, A.; Müller-Buschbaum, P.; Papadakis, C. M.

2016-01-01

Roč. 49, č. 17 (2016), s. 6655-6668 ISSN 0024-9297 R&D Projects: GA ČR(CZ) GC15-10527J Institutional support: RVO:61389013 Keywords : polymer * thermoresponsive * block copolymer Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.835, year: 2016

Thermo-responsive cell culture carrier: Effects on macrophage functionality and detachment efficiency.

Science.gov (United States)

Rennert, Knut; Nitschke, Mirko; Wallert, Maria; Keune, Natalie; Raasch, Martin; Lorkowski, Stefan; Mosig, Alexander S

2017-01-01

Harvesting cultivated macrophages for tissue engineering purposes by enzymatic digestion of cell adhesion molecules can potentially result in unintended activation, altered function, or behavior of these cells. Thermo-responsive polymer is a promising tool that allows for gentle macrophage detachment without artificial activation prior to subculture within engineered tissue constructs. We therefore characterized different species of thermo-responsive polymers for their suitability as cell substrate and to mediate gentle macrophage detachment by temperature shift. Primary human monocyte- and THP-1-derived macrophages were cultured on thermo-responsive polymers and characterized for phagocytosis and cytokine secretion in response to lipopolysaccharide stimulation. We found that both cell types differentially respond in dependence of culture and stimulation on thermo-responsive polymers. In contrast to THP-1 macrophages, primary monocyte-derived macrophages showed no signs of impaired viability, artificial activation, or altered functionality due to culture on thermo-responsive polymers compared to conventional cell culture. Our study demonstrates that along with commercially available UpCell carriers, two other thermo-responsive polymers based on poly(vinyl methyl ether) blends are attractive candidates for differentiation and gentle detachment of primary monocyte-derived macrophages. In summary, we observed similar functionality and viability of primary monocyte-derived macrophages cultured on thermo-responsive polymers compared to standard cell culture surfaces. While this first generation of custom-made thermo-responsive polymers does not yet outperform standard culture approaches, our results are very promising and provide the basis for exploiting the unique advantages offered by custom-made thermo-responsive polymers to further improve macrophage culture and recovery in the future, including the covalent binding of signaling molecules and the reduction of

Thermoresponsive Supramolecular Chemotherapy by "V"-Shaped Armed β-Cyclodextrin Star Polymer to Overcome Drug Resistance.

Science.gov (United States)

Fan, Xiaoshan; Cheng, Hongwei; Wang, Xiaoyuan; Ye, Enyi; Loh, Xian Jun; Wu, Yun-Long; Li, Zibiao

2018-04-01

Pump mediated drug efflux is the key reason to result in the failure of chemotherapy. Herein, a novel star polymer β-CD-v-(PEG-β-PNIPAAm) 7 consisting of a β-CD core, grafted with thermo-responsive poly(N-isopropylacrylamide) (PNIPAAm) and biocompatible poly(ethylene glycol) (PEG) in the multiple "V"-shaped arms is designed and further fabricated into supramolecular nanocarriers for drug resistant cancer therapy. The star polymer could encapsulate chemotherapeutics between β-cyclodextrin and anti-cancer drug via inclusion complex (IC). Furthermore, the temperature induced chain association of PNIPAAm segments facilitated the IC to form supramolecular nanoparticles at 37 °C, whereas the presence of PEG impart great stability to the self-assemblies. When incubated with MDR-1 membrane pump regulated drug resistant tumor cells, much higher and faster cellular uptake of the supramolecular nanoparticles were detected, and the enhanced intracellular retention of drugs could lead to significant inhibition of cell growth. Further in vivo evaluation showed high therapeutic efficacy in suppressing drug resistant tumor growth without a significant impact on the normal functions of main organs. This work signifies thermo-responsive supramolecular chemotherapy is promising in combating pump mediated drug resistance in both in vitro and in vivo models, which may be encouraging for the advanced drug delivery platform design to overcome drug resistant cancer. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermoresponsive Hydrogels and Their Biomedical Applications: Special Insight into Their Applications in Textile Based Transdermal Therapy

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Sudipta Chatterjee

2018-04-01

Full Text Available Various natural and synthetic polymers are capable of showing thermoresponsive properties and their hydrogels are finding a wide range of biomedical applications including drug delivery, tissue engineering and wound healing. Thermoresponsive hydrogels use temperature as external stimulus to show sol-gel transition and most of the thermoresponsive polymers can form hydrogels around body temperature. The availability of natural thermoresponsive polymers and multiple preparation methods of synthetic polymers, simple preparation method and high functionality of thermoresponsive hydrogels offer many advantages for developing drug delivery systems based on thermoresponsive hydrogels. In textile field applications of thermoresponsive hydrogels, textile based transdermal therapy is currently being applied using drug loaded thermoresponsive hydrogels. The current review focuses on the preparation, physico-chemical properties and various biomedical applications of thermoresponsive hydrogels based on natural and synthetic polymers and especially, their applications in developing functionalized textiles for transdermal therapies. Finally, future prospects of dual responsive (pH/temperature hydrogels made by these polymers for textile based transdermal treatments are mentioned in this review.

Methacrylic Zwitterionic, Thermoresponsive, and Hydrophilic (Co)Polymers via Cu(0)-Polymerization: The Importance of Halide Salt Additives.

Science.gov (United States)

Simula, Alexandre; Anastasaki, Athina; Haddleton, David M

2016-02-01

The synthesis of hydrophilic, thermoresponsive, and zwitterionic polymethacrylates is reported by Cu(0)-mediated reversible deactivation radical polymerization in water and/or water/alcohol mixtures. The predisproportionation of [Cu(I) (PMDETA)Cl] in water prior to initiator and monomer addition is exploited to yield well-defined polymethacrylates with full monomer conversions in 30 min. The addition of supplementary halide salts (NaCl) enables the synthesis of various molecular weight poly[poly(ethylene glycol) methyl ether methacrylate] (PEGMA475) (DPn = 10-80, Mn ≈ 10,000-40 000 g mol(-1)) with full monomer conversion and narrow molecular weight distributions attained in all cases (Đ ≈ 1.20-1.30). A bifunctional PEG initiator (average Mn ≈ 1000 g mol(-1)) is utilized for the polymerization of a wide range of methacrylates including 2-dimethylaminoethyl methacrylate, 2-morpholinoethyl methacrylate, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, and 2-methacryloyloxyethyl phosphorylcholine. Despite the high water content, high end group fidelity is demonstrated by in situ chain extensions and block copolymerizations with PEGMA475 yielding well-defined functional telechelic pentablock copolymers within 2.5 h. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of thermo-responsive PNIPAAm-g-ETFE for cell culture dishes by pre-irradiation grafting

Science.gov (United States)

Yamahara, Yumi; Nagasawa, Naotsugu; Taguchi, Mitsumasa; Oshima, Akihiro; Washio, Masakazu

2018-01-01

Thermo-responsive templates for the cell cultivation based on Poly(tetrafluoroethylene-co-ethylene) (ETFE) were fabricated by pre-irradiation grafting of N-isoproplyacrylamide (NIPAAm) monomer by electron beam (EB) irradiation under nitrogen gas atmosphere at room temperature, and their characteristic properties were studied. The detachment of cultured HeLa cells from fabricated thermo-responsive templates were attempted. Furthermore, the reaction mechanism is proposed using ESR spectroscopy and FT-IR spectroscopy. It is confirmed that the cultured HeLa cells were detached from fabricated thermo-responsive templates at 20 °C. Water contact angle analysis indicated that obtained templates had thermo-response around 30 °C. It is suggested that the grafted polymer chains would mainly react with peroxy radicals (-CF2-CF(OO･)-) on tetrafluoroethylene unit in ETFE.

Fluorescent, thermo-responsive biotin-P(NIPAAm-co-NDAPM)- b-PCL micelles for cell-tracking and drug delivery

International Nuclear Information System (INIS)

Li Yongyong; Zhang Xianzheng; Cheng Han; Zhu Jingling; Li Unnam; Cheng Sixue; Zhuo Renxi

2007-01-01

An amphiphilic, biotinylated poly(N-isopropylacrylamide-co-N-(3-dimethylamino propyl)methacrylamide)-block- poly(ε-caprolactone) (biotin-P(NIPAAm-co-NDAPM)- b-PCL) block copolymer was synthesized. The cytotoxicity study showed that the copolymer exhibited no apparent cytotoxicity. In aqueous solution, biotin-P(NIPAAm-co-NDAPM)- b-PCL copolymer was able to self-assemble into micelles of around 60 nm in diameter with a critical micellar concentration (CMC) of 36 mg l -1 . Biotin-P(NIPAAm- co-NDAPM)-b-PCL micelles were thermo-responsive and the cloud point temperature was at 36.5 deg. C. The fluorescent group, fluorescein isothiocyanate (FITC) was further introduced to label the biotin-P(NIPAAm-co-NDAPM)- b-PCL copolymer. A cell internalization experiment was conducted and it was found that the fluorescent micelles could be internalized into the cells. The drug release behavior of drug-loading micelles was also examined and the drug-loaded biotin-P(NIPAAm-co-NDAPM)- b-PCL micelles showed slow drug release at 27 deg. C and fast drug release at 37 deg. C

Effect of block composition on thermal properties and melt viscosity of poly[2-(dimethylaminoethyl methacrylate], poly(ethylene oxide and poly(propylene oxide block co-polymers

Directory of Open Access Journals (Sweden)

2011-09-01

Full Text Available To modify the rheological properties of certain commercial polymers, a set of block copolymers were synthesized through oxyanionic polymerization of 2-(dimethylaminoethyl methacrylate to the chain ends of commercial prepolymers, namely poly(ethylene oxide (PEO, poly(ethylene oxide-block-poly(propylene oxide-block-poly(ethylene oxide (PEO-PPO-PEO, and poly(propylene oxide (PPO. The formed block copolymers were analysed with size exclusion chromatography and nuclear magnetic resonance spectroscopy in order to confirm block formation. Thermal characterization of the resulting polymers was done with differential scanning calorimetry. Thermal transition points were also confirmed with rotational rheometry, which was primarily used to measure melt strength properties of the resulting block co-polymers. It was observed that the synthesised poly[2-(dimethylaminoethyl methacrylate]-block (PDM affected slightly the thermal transition points of crystalline PEO-block but the influence was stronger on amorphous PPO-blocks. Frequency sweeps measured above the melting temperatures for the materials confirmed that the pre-polymers (PEO and PEO-PPO-PEO behave as Newtonian fluids whereas polymers with a PDM block structure exhibit clear shear thinning behaviour. In addition, the PDM block increased the melt viscosity when compared with that one of the pre-polymer. As a final result, it became obvious that pre-polymers modified with PDM were in entangled form, in the melted state as well in the solidified form.

Controlled Sol-Gel Transitions of a Thermoresponsive Polymer in a Photoswitchable Azobenzene Ionic Liquid as a Molecular Trigger.

Science.gov (United States)

Wang, Caihong; Hashimoto, Kei; Tamate, Ryota; Kokubo, Hisashi; Watanabe, Masayoshi

2018-01-02

Producing ionic liquids (ILs) that function as molecular trigger for macroscopic change is a challenging issue. Photoisomerization of an azobenzene IL at the molecular level evokes a macroscopic response (light-controlled mechanical sol-gel transitions) for ABA triblock copolymer solutions. The A endblocks, poly(2-phenylethyl methacrylate), show a lower critical solution temperature in the IL mixture containing azobenzene, while the B midblock, poly(methyl methacrylate), is compatible with the mixture. In a concentrated polymer solution, different gelation temperatures were observed in it under dark and UV conditions. Light-controlled sol-gel transitions were achieved by a photoresponsive solubility change of the A endblocks upon photoisomerization of the azobenzene IL. Therefore, an azobenzene IL as a molecular switch can tune the self-assembly of a thermoresponsive polymer, leading to macroscopic light-controlled sol-gel transitions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

π-Conjugated polymer anisotropic organogel nanofibrous assemblies for thermoresponsive photonic switches.

Science.gov (United States)

Narasimha, Karnati; Jayakannan, Manickam

2014-11-12

The present work demonstrates one of the first examples of π-conjugated photonic switches (or photonic wave plates) based on the tailor-made π-conjugated polymer anisotropic organogel. New semicrystalline segmented π-conjugated polymers are designed with rigid aromatic oligophenylenevinylene π-core and flexible alkyl chain along the polymer backbone. These polymers are found to be self-assembled as semicrystalline or amorphous with respect to the number of carbon atoms in the alkyl units. These semicrystalline polymers produce organogels having nanofibrous morphology of 20 nm thickness with length up to 5 μm. The polymer organogel is aligned in a narrow glass capillary, and this anisotropic gel device is further demonstrated as photonic switches. The glass capillary device behaves as typical λ/4 photonic wave plates upon the illumination of the plane polarized light. The λ/4 photonic switching ability is found to be maximum at θ = 45° angle under the cross polarizers. The orthogonal arrangements of the gel capillaries produce dark and bright spots as on-and-off optical switches. Thermoreversibility of the polymer organogel (also its xerogel) was exploited to construct thermoresponsive photonic switches for the temperature window starting from 25 to 160 °C. The organic photonic switch concept can be adapted to large number of other π-conjugated materials for optical communication and storage.

Thermoresponsive Poly(2-Oxazoline) Molecular Brushes by Living Ionic Polymerization: Modulation of the Cloud Point by Random and Block Copolymer Pendant Chains

KAUST Repository

Zhang, Ning

2012-08-10

Molecular brushes (MBs) of poly(2-oxazoline)s were prepared by living anionic polymerization of 2-isopropenyl-2-oxazoline to form the backbone and living cationic ring-opening polymerization of 2-n-propyl-2-oxazoline and 2-methyl-2-oxazoline to form random and block copolymers. Their aqueous solutions displayed a distinct thermoresponsive behavior as a function of the side-chain composition and sequence. The cloud point (CP) of MBs with random copolymer side chains is a linear function of the hydrophilic monomer content and can be modulated in a wide range. For MBs with block copolymer side chains, it was found that the block sequence had a strong and surprising effect on the CP. While MBs with a distal hydrophobic block had a CP at 70 °C, MBs with hydrophilic outer blocks already precipitated at 32 °C. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Directory of Open Access Journals (Sweden)

Sushilkumar A. Jadhav

2017-05-01

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

Transfer of fibroblast sheets cultured on thermoresponsive dishes with membranes.

Science.gov (United States)

Kawecki, Marek; Kraut, Małgorzata; Klama-Baryła, Agnieszka; Łabuś, Wojciech; Kitala, Diana; Nowak, Mariusz; Glik, Justyna; Sieroń, Aleksander L; Utrata-Wesołek, Alicja; Trzebicka, Barbara; Dworak, Andrzej; Szweda, Dawid

2016-06-01

In cell or tissue engineering, it is essential to develop a support for cell-to-cell adhesion, which leads to the generation of cell sheets connected by extracellular matrix. Such supports must be hydrophobic and should result in a detachable cell sheet. A thermoresponsive support that enables the cultured cell sheet to detach using only a change in temperature could be an interesting alternative in regenerative medicine. The aim of this study was to evaluate plates covered with thermoresponsive polymers as supports for the formation of fibroblast sheets and to develop a damage-free procedure for cell sheet transfer with the use of membranes as transfer tools. Human skin fibroblasts were seeded on supports coated with a thermoresponsive polymer: commercial UpCell™ dishes (NUNC™) coated with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and dishes coated with thermoresponsive poly(tri(ethylene glycol) monoethyl ether methacrylate) (P(TEGMA-EE)). Confluent fibroblast sheets were effectively cultured and harvested from both commercial PNIPAM-coated dishes and laboratory P(TEGMA-EE)-coated dishes. To transfer a detached cell sheet, two membranes, Immobilon-P(®) and SUPRATHEL(®), were examined. The use of SUPRATHEL for relocating the cell sheets opens a new possibility for the clinical treatment of wounds. This study established the background for implementing thermoresponsive supports for transplanting in vitro cultured fibroblasts.

Blending of styrene-block-butadiene-block-styrene copolymer with sulfonated vinyl aromatic polymers

NARCIS (Netherlands)

Ruggeri, Giacomo; Passaglia, Elisa; Giorgi, Ivan; Picchioni, Francesco; Aglietto, Mauro

2001-01-01

Different polymers containing sulfonic groups attached to the phenyl rings were prepared by sulfonation of polystyrene (PS) and styrene-block-(ethylene-co-1-butene)-block-styrene (SEBS). The sulfonation degree (SD) was varied between 1 and 20 mol% of the styrene units. Polyphase materials containing

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.

Thermoresponsive Poly(2-Oxazoline) Molecular Brushes by Living Ionic Polymerization: Modulation of the Cloud Point by Random and Block Copolymer Pendant Chains

KAUST Repository

Zhang, Ning; Luxenhofer, Robert; Jordan, Rainer

2012-01-01

random and block copolymers. Their aqueous solutions displayed a distinct thermoresponsive behavior as a function of the side-chain composition and sequence. The cloud point (CP) of MBs with random copolymer side chains is a linear function

Thermoresponsive behavior of block copolymers of PEO and PNIPAm with different architecture in aqueous solutions: a study by NMR, FTIR, DSC and quantum-chemical calculations

Czech Academy of Sciences Publication Activity Database

Spěváček, Jiří; Konefal, Rafal; Dybal, Jiří; Čadová, Eva; Kovářová, Jana

2017-01-01

Roč. 94, September (2017), s. 471-483 ISSN 0014-3057 R&D Projects: GA ČR(CZ) GA15-13853S Institutional support: RVO:61389013 Keywords : thermoresponsive polymer * diblock copolymer PEO-b-PNIPAm * y-shape triblock copolymer PEO-b-(PNIPAm)2 Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 3.531, year: 2016

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

Bioactive thermoresponsive polyblend nanofiber formulations for wound healing

Energy Technology Data Exchange (ETDEWEB)

Pawar, Mahesh D. [Polymer Science and Engineering, National Chemical Laboratory, Homi Bhabha Road, Pashan, Pune 411008 (India); MAEER' s Maharashtra Institute of Pharmacy S. No. 124, MIT Campus Paud Road, Kothrud, Pune 411 038 (India); Rathna, G.V.N., E-mail: rv.gundloori@ncl.res.in [Polymer Science and Engineering, National Chemical Laboratory, Homi Bhabha Road, Pashan, Pune 411008 (India); Agrawal, Shubhang [Polymer Science and Engineering, National Chemical Laboratory, Homi Bhabha Road, Pashan, Pune 411008 (India); Kuchekar, Bhanudas S. [MAEER' s Maharashtra Institute of Pharmacy S. No. 124, MIT Campus Paud Road, Kothrud, Pune 411 038 (India)

2015-03-01

The rationale of this work is to develop new bioactive thermoresponsive polyblend nanofiber formulations for wound healing (topical). Various polymer compositions of thermoresponsive, poly(N-isopropylacrylamide), egg albumen and poly(ε-caprolactone) blend solutions with and without a drug [gatifloxacin hydrochloride, Gati] were prepared. Non-woven nanofibers of various compositions were fabricated using an electrospinning technique. The morphology of the nanofibers was analyzed by an environmental scanning electron microscope. The morphology was influenced by the concentration of polymer, drug, and polymer blend composition. Fourier transform infrared spectroscopy analysis showed the shift in bands due to hydrogen ion interactions between polymers and drug. Thermogram of PNIPAM/PCL/EA with Gati recorded a shift in lower critical solution temperature (LCST) and glass transition temperature (T{sub g}) of PNIPAM. Similarly T{sub g} and melting temperature (T{sub m}) of PCL were shifted. X-ray diffraction patterns recorded a decrease in the crystalline state of PCL nanofibers and transformed crystalline drug to an amorphous state. In vitro release study of nanofibers with Gati showed initial rapid release up to 10 h, followed by slow and controlled release for 696 h (29 days). Nanofiber mats with Gati exhibited antibacterial properties to Staphylococcus aureus, supported suitable controlled drug release with in vitro cell viability and in vivo wound healing. - Highlights: • Thermoresponsive and bioactive nanofiber blends of PNIPAM/EA/PCL were fabricated. • Nanofiber blends favored initial rapid release, followed by controlled release. • In vitro cell viability of pure polymers and nanofiber blends was least toxic. • In vivo studies of drug loaded nanofiber mats recorded faster tissue regeneration.

A temperature-dependent coarse-grained model for the thermoresponsive polymer poly(N-isopropylacrylamide)

Energy Technology Data Exchange (ETDEWEB)

Abbott, Lauren J.; Stevens, Mark J., E-mail: msteve@sandia.gov [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2015-12-28

A coarse-grained (CG) model is developed for the thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAM), using a hybrid top-down and bottom-up approach. Nonbonded parameters are fit to experimental thermodynamic data following the procedures of the SDK (Shinoda, DeVane, and Klein) CG force field, with minor adjustments to provide better agreement with radial distribution functions from atomistic simulations. Bonded parameters are fit to probability distributions from atomistic simulations using multi-centered Gaussian-based potentials. The temperature-dependent potentials derived for the PNIPAM CG model in this work properly capture the coil–globule transition of PNIPAM single chains and yield a chain-length dependence consistent with atomistic simulations.

Polymers for bimodal immunoradiotherapy - are they able to promote immune system?

International Nuclear Information System (INIS)

Loukotova, L.; Kucka, J.; Rabyk, M.; Hoecherl, A.; Venclikova, K.; Janouskova, O.; Konefal, R.; Stepanek, P.; Hruby, M.; Kolarova, V.; Sefc, L.

2017-01-01

The conceptually new bimodal treatment is demonstrated with radiolabeled thermoresponsive β-glucan-graft-poly(2- isopropyl-2-oxazoline-co-2-butyl-2-oxazoline). The thermoresponsive polymer behavior in aqueous solutions has been studied showing appropriate cloud point temperature. The in vitro studies have been performed, the polymer has been found to be non-toxic and actively uptaken by cancer cells and macrophages. Moreover, oxidative burst assay has shown the immunostimulatory properties of prepared polymer. The polymer has been radiolabeled with 90 Y 3+ and used in antitumor efficiency in vivo experiment on mice bearing EL4 lymphoma. The in vivo experiment demonstrates the synergic effect of immunoradiotherapy compared to only immunotherapy and radiotherapy. (authors)

A temperature-dependent coarse-grained model for the thermoresponsive polymer poly(N-isopropylacrylamide)

International Nuclear Information System (INIS)

Abbott, Lauren J.; Stevens, Mark J.

2015-01-01

In this study, a coarse-grained (CG) model is developed for the thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAM), using a hybrid top-down and bottom-up approach. Nonbonded parameters are fit to experimental thermodynamic data following the procedures of the SDK (Shinoda, DeVane, and Klein) CG force field, with minor adjustments to provide better agreement with radial distribution functions from atomistic simulations. Bonded parameters are fit to probability distributions from atomistic simulations using multi-centered Gaussian-based potentials. The temperature-dependent potentials derived for the PNIPAM CG model in this work properly capture the coil-globule transition of PNIPAM single chains and yield a chain-length dependence consistent with atomistic simulations

A flexible thermoresponsive cell culture substrate for direct transfer of keratinocyte cell sheets.

Science.gov (United States)

Praveen, Wulligundam; Madathil, Bernadette K; Sajin Raj, R S; Kumary, T V; Anil Kumar, P R

2017-10-25

Most cell sheet engineering systems require a support or carrier to handle the harvested cell sheets. In this study, polyethylene terephthalate-based overhead projection transparency sheets (OHPS) were subjected to surface hydrolysis by alkali treatment to increase pliability and hydrophilicity and enable poly(N-isopropylacrylamide-co-glycidylmethacrylate) copolymer (NGMA) coating to impart thermoresponsiveness. NGMA was applied on the modified OHPS by the technique of spin coating using an indigenously designed spin coater. The spin coating had the advantage of using low volumes of the polymer and a reduced coating time. The surface chemistry and thermoresponsive coating was analyzed by Fourier transform infrared spectroscopy and water contact angle. Human keratinocyte cells were cultured on the spin coated surface and scaffold-free cell sheets were successfully harvested by simple variation of temperature. These cell sheets were found to be viable, exhibited epithelial characteristic and cell-cell contact as confirmed by positive immunostaining for ZO-1. The integrity and morphology of the cell sheet was confirmed by stereomicroscopy and E-SEM. These results highlight the potential of the NGMA spin coated modified OHPS to serve as a thermoresponsive culture surface-cum-flexible transfer tool.

Effect of solvent quality and chain density on normal and frictional forces between electrostatically anchored thermoresponsive diblock copolymer layers

DEFF Research Database (Denmark)

An, Junxue; Liu, Xiaoyan; Dedinaite, Andra

2017-01-01

and a thermoresponsive block of poly(2-isopropyl-2-oxazoline), PIPOZ. We find that at a given temperature different polymer chain densities at the silica surface are achieved depending on the previous temperature history. We explore how this affects surface and friction forces between such layers using the atomic force......Equilibration in adsorbing polymer systems can be very slow, leading to different physical properties at a given condition depending on the pathway that was used to reach this state. Here we explore this phenomenon using a diblock copolymer consisting of a cationic anchor block....... The friction forces decrease in the cooling stage due to rehydration of the PIPOZ chain. A consequence of the adsorption hysteresis is that the friction forces measured at 25 °C are significantly lower after exposure to a temperature of 40 °C than prior to heating, which is due to higher polymer chain density...

ε-Polylysine-based thermo-responsive adsorbents for immunoglobulin adsorption-desorption under mild conditions.

Science.gov (United States)

Maruyama, Masashi; Shibuya, Keisuke

2017-08-22

Thermo-responsive adsorbents for immunoglobulin G (IgG) employing ε-polylysine (EPL) as a polymer backbone were developed. The introduction of mercaptoethylpyridine (MEP) as an IgG-binding ligand and hydrophobization of side chains afforded thermo-responsive IgG adsorbents, whose thermo-responsive IgG desorption ratio was up to 88% (EPL/MEP derivative 3m). The changes in surface densities of active MEP groups, which are caused by thermal conformational changes of the adsorbents, play key roles for IgG desorption. Although a trade-off of IgG adsorption capacity and IgG desorption ratio was observed, the present study offers a novel molecular design for thermo-responsive adsorbents with high synthetic accessibility and potentially low toxicity.

Preparation of thermo-responsive graft copolymer by using a novel macro-RAFT agent and its application for drug delivery

International Nuclear Information System (INIS)

Song, Cunfeng; Yu, Shirong; Liu, Cheng; Deng, Yuanming; Xu, Yiting; Chen, Xiaoling; Dai, Lizong

2016-01-01

A methodology to prepare thermo-responsive graft copolymer by using a novel macro-RAFT agent was proposed. The macro-RAFT agent with pendant dithioester (ZC(S)SR) was facilely prepared via the combination of RAFT polymerization and esterification reaction. By means of ZC(S)SR-initiated RAFT polymerization, the thermo-responsive graft copolymer consisting of poly(methyl methacrylate-co-hydroxylethyl methacrylate) (P(MMA-co-HEMA)) backbone and hydrophilic poly(N-isopropylacrylamide) (PNIPAAm) side chains was constructed through the “grafting from” approach. The chemical compositions and molecular weight distributions of the synthesized polymers were respectively characterized by "1H nuclear magnetic resonance ("1H NMR) and gel permeation chromatography (GPC). Self-assembly behavior of the amphiphilic graft copolymers (P(MMA-co-HEMA)-g-PNIPAAm) was studied by transmission electron microscopy (TEM), dynamic light scattering (DLS) and spectrofluorimeter. The critical micelle concentration (CMC) value was 0.052 mg mL"−"1. These micelles have thermo-responsibility and a low critical solution temperature (LCST) of 33.5 °C. Further investigation indicated that the guest molecule release property of these micelles, which can be well described by a first-order kinetic model, was significantly affected by temperature. Besides, the micelles exhibited excellent biocompatibility and cellular uptake property. Hence, these micelles are considered to have potential application in controlled drug delivery. - Highlights: • A novel macro-RAFT agent with ZC(S)SR was used for preparing graft copolymer. • P(MMA-co-HEMA)-g-PNIPAAm was successful prepared via the “grafting from” approach. • Thermo-responsibility of the P(MMA-co-HEMA)-g-PNIPAAm micelles was investigated. • The drug release behavior of the P(MMA-co-HEMA)-g-PNIPAAm micelles was studied. • These micelles exhibited excellent biocompatibility and cellular uptake property.

Preparation of thermo-responsive graft copolymer by using a novel macro-RAFT agent and its application for drug delivery

Energy Technology Data Exchange (ETDEWEB)

Song, Cunfeng; Yu, Shirong [Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005 (China); Liu, Cheng; Deng, Yuanming; Xu, Yiting [Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005 (China); Fujian Provincial Key Laboratory of Fire Retardant Materials, Xiamen University, Xiamen 361005 (China); Chen, Xiaoling, E-mail: tinachen0628@163.com [Department of Endodontics, Xiamen Stomatology Hospital, Teaching Hospital of Fujian Medical University, Xiamen 361003 (China); Dai, Lizong, E-mail: lzdai@xmu.edu.cn [Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005 (China); Fujian Provincial Key Laboratory of Fire Retardant Materials, Xiamen University, Xiamen 361005 (China)

2016-05-01

A methodology to prepare thermo-responsive graft copolymer by using a novel macro-RAFT agent was proposed. The macro-RAFT agent with pendant dithioester (ZC(S)SR) was facilely prepared via the combination of RAFT polymerization and esterification reaction. By means of ZC(S)SR-initiated RAFT polymerization, the thermo-responsive graft copolymer consisting of poly(methyl methacrylate-co-hydroxylethyl methacrylate) (P(MMA-co-HEMA)) backbone and hydrophilic poly(N-isopropylacrylamide) (PNIPAAm) side chains was constructed through the “grafting from” approach. The chemical compositions and molecular weight distributions of the synthesized polymers were respectively characterized by {sup 1}H nuclear magnetic resonance ({sup 1}H NMR) and gel permeation chromatography (GPC). Self-assembly behavior of the amphiphilic graft copolymers (P(MMA-co-HEMA)-g-PNIPAAm) was studied by transmission electron microscopy (TEM), dynamic light scattering (DLS) and spectrofluorimeter. The critical micelle concentration (CMC) value was 0.052 mg mL{sup −1}. These micelles have thermo-responsibility and a low critical solution temperature (LCST) of 33.5 °C. Further investigation indicated that the guest molecule release property of these micelles, which can be well described by a first-order kinetic model, was significantly affected by temperature. Besides, the micelles exhibited excellent biocompatibility and cellular uptake property. Hence, these micelles are considered to have potential application in controlled drug delivery. - Highlights: • A novel macro-RAFT agent with ZC(S)SR was used for preparing graft copolymer. • P(MMA-co-HEMA)-g-PNIPAAm was successful prepared via the “grafting from” approach. • Thermo-responsibility of the P(MMA-co-HEMA)-g-PNIPAAm micelles was investigated. • The drug release behavior of the P(MMA-co-HEMA)-g-PNIPAAm micelles was studied. • These micelles exhibited excellent biocompatibility and cellular uptake property.

Thermoresponsive Polymers and Inverse Opal Hydrogels for the Detection of Diols.

Science.gov (United States)

Couturier, Jean-Philippe; Wischerhoff, Erik; Bernin, Robert; Hettrich, Cornelia; Koetz, Joachim; Sütterlin, Martin; Tiersch, Brigitte; Laschewsky, André

2016-05-03

Responsive inverse opal hydrogels functionalized by boroxole moieties were synthesized and explored as sensor platforms for various low molar mass as well as polymeric diols and polyols, including saccharides, glycopolymers and catechols, by exploiting the diol induced modulation of their structural color. The underlying thermoresponsive water-soluble copolymers and hydrogels exhibit a coil-to-globule or volume phase transition, respectively, of the LCST-type. They were prepared from oligoethylene oxide methacrylate (macro)monomers and functionalized via copolymerization to bear benzoboroxole moieties. The resulting copolymers represent weak polyacids, which can bind specifically to diols within an appropriate pH window. Due to the resulting modulation of the overall hydrophilicity of the systems and the consequent shift of their phase transition temperature, the usefulness of such systems for indicating the presence of catechols, saccharides, and glycopolymers was studied, exploiting the diol/polyol induced shifts of the soluble polymers' cloud point, or the induced changes of the hydrogels' swelling. In particular, the increased acidity of benzoboroxoles compared to standard phenylboronic acids allowed performing the studies in PBS buffer (phosphate buffered saline) at the physiologically relevant pH of 7.4. The inverse opals constructed of these thermo- and analyte-responsive hydrogels enabled following the binding of specific diols by the induced shift of the optical stop band. Their highly porous structure enabled the facile and specific optical detection of not only low molar mass but also of high molar mass diol/polyol analytes such as glycopolymers. Accordingly, such thermoresponsive inverse opal systems functionalized with recognition units represent attractive and promising platforms for the facile sensing of even rather big analytes by simple optical means, or even by the bare eye.

Surface interaction forces of cellulose nanocrystals grafted with thermoresponsive polymer brushes.

Science.gov (United States)

Zoppe, Justin O; Osterberg, Monika; Venditti, Richard A; Laine, Janne; Rojas, Orlando J

2011-07-11

The colloidal stability and thermoresponsive behavior of poly(N-isopropylacrylamide) brushes grafted from cellulose nanocrystals (CNCs) of varying graft densities and molecular weights was investigated. Indication of the grafted polymer brushes was obtained after AFM imaging of CNCs adsorbed on silica. Also, aggregation of the nanoparticles carrying grafts of high degree of polymerization was observed. The responsiveness of grafted CNCs in aqueous dispersions and as an ultrathin film was evaluated by using light scattering, viscosimetry, and colloidal probe microscopy (CPM). Light transmittance measurements showed temperature-dependent aggregation originating from the different graft densities and molecular weights. The lower critical solution temperature (LCST) of grafted poly(NiPAAm) brushes was found to decrease with the ionic strength, as is the case for free poly(NiPAAm) in aqueous solution. Thermal responsive behavior of grafted CNCs in aqueous dispersions was observed by a sharp increase in dispersion viscosity as the temperature approached the LCST. CPM in liquid media for asymmetric systems consisting of ultrathin films of CNCs and a colloidal silica probe showed the distinctive effects of the grafted polymer brushes on interaction and adhesive forces. The origin of such forces was found to be mainly electrostatic and steric in the case of bare and grafted CNCs, respectively. A decrease in the onset of attractive and adhesion forces of grafted CNCs films were observed with the ionic strength of the aqueous solution. The decreased mobility of polymer brushes upon partial collapse and decreased availability of hydrogen bonding sites with higher electrolyte concentration were hypothesized as the main reasons for the less prominent polymer bridging between interacting surfaces.

Thermo-responsive polymeric nanoparticles for enhancing neuronal differentiation of human induced pluripotent stem cells.

Science.gov (United States)

Seo, Hye In; Cho, Ann-Na; Jang, Jiho; Kim, Dong-Wook; Cho, Seung-Woo; Chung, Bong Geun

2015-10-01

We report thermo-responsive retinoic acid (RA)-loaded poly(N-isopropylacrylamide)-co-acrylamide (PNIPAM-co-Am) nanoparticles for directing human induced pluripotent stem cell (hiPSC) fate. Fourier transform infrared spectroscopy and (1)H nuclear magnetic resonance analysis confirmed that RA was efficiently incorporated into PNIAPM-co-Am nanoparticles (PCANs). The size of PCANs dropped with increasing temperatures (300-400 nm at room temperature, 80-90 nm at 37°C) due to its phase transition from hydrophilic to hydrophobic. Due to particle shrinkage caused by this thermo-responsive property of PCANs, RA could be released from nanoparticles in the cells upon cellular uptake. Immunocytochemistry and quantitative real-time polymerase chain reaction analysis demonstrated that neuronal differentiation of hiPSC-derived neuronal precursors was enhanced after treatment with 1-2 μg/ml RA-loaded PCANs. Therefore, we propose that this PCAN could be a potentially powerful carrier for effective RA delivery to direct hiPSC fate to neuronal lineage. The use of induced pluripotent stem cells (iPSCs) has been at the forefront of research in the field of regenerative medicine, as these cells have the potential to differentiate into various terminal cell types. In this article, the authors utilized a thermo-responsive polymer, Poly(N-isopropylacrylamide) (PNIPAM), as a delivery platform for retinoic acid. It was shown that neuronal differentiation could be enhanced in hiPSC-derived neuronal precursor cells. This method may pave a way for future treatment of neuronal diseases. Copyright © 2015 Elsevier Inc. All rights reserved.

EUV lithographic radiation grafting of thermo-responsive hydrogel nanostructures

International Nuclear Information System (INIS)

Farquet, Patrick; Padeste, Celestino; Solak, Harun H.; Guersel, Selmiye Alkan; Scherer, Guenther G.; Wokaun, Alexander

2007-01-01

Nanostructures of the thermoresponsive poly(N-isopropyl acrylamide) (PNIPAAm) and of PNIPAAm-block-poly(acrylic acid) copolymers were produced on poly(tetrafluoroethylene-co-ethyelene) (ETFE) films using extreme ultraviolet (EUV) lithographic exposure with subsequent graft-polymerization. The phase transition of PNIPAAm nanostructures at the low critical solution temperature (LCST) at 32 deg. C was imaged by atomic force microscopy (AFM) phase contrast measurements in pure water. Results show a higher phase contrast for samples measured below the LCST temperature than for samples above the LCST, proving that the soft PNIPAAm hydrogel transforms into a much more compact conformation above the LCST. EUV lithographic exposures were combined with the reversible addition-fragment chain transfer (RAFT)-mediated polymerization using cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agent to synthesize PNIPAAm block-copolymer nanostructures

Thermo-responsive hydrogels for intravitreal injection and biomolecule release

Science.gov (United States)

Drapala, Pawel

In this dissertation, we develop an injectable polymer system to enable localized and prolonged release of therapeutic biomolecules for improved treatment of Age-Related Macular Degeneration (AMD). Thermo-responsive hydrogels derived from N-isopropylacrylamide (NIPAAm) and cross-linked with poly(ethylene glycol) (PEG) poly(L-Lactic acid) (PLLA) copolymer were synthesized via free-radical polymerization. These materials were investigated for (a) phase change behavior, (b) in-vitro degradation, (c) capacity for controlled drug delivery, and (d) biocompatibility. The volume-phase transition temperature (VPTT) of the PNIPAAm- co-PEG-b-PLLA hydrogels was adjusted using hydrophilic and hydrophobic moieties so that it is ca. 33°C. These hydrogels did not initially show evidence of degradation at 37°C due to physical cross-links of collapsed PNIPAAm. Only after addition of glutathione chain transfer agents (CTA)s to the precursor did the collapsed hydrogels become fully soluble at 37°C. CTAs significantly affected the release kinetics of biomolecules; addition of 1.0 mg/mL glutathione to 3 mM cross-linker accelerated hydrogel degradation, resulting in 100% release in less than 2 days. This work also explored the effect of PEGylation in order to tether biomolecules to the polymer matrix. It was demonstrated that non-site-specific PEGylation can postpone the burst release of solutes (up to 10 days in hydrogels with 0.5 mg/mL glutathione). Cell viability assays showed that at least two 20-minute buffer extraction steps were needed to remove cytotoxic elements from the hydrogels. Clinically-used therapeutic biomolecules LucentisRTM and AvastinRTM were demonstrated to be both stable and bioactive after release form PNIPAAm-co-PEG-b-PLLA hydrogels. The thermo-responsive hydrogels presented here offer a promising platform for the localized delivery of proteins such as recombinant antibodies.

Novel Injectable Pentablock Copolymer Based Thermoresponsive Hydrogels for Sustained Release Vaccines.

Science.gov (United States)

Bobbala, Sharan; Tamboli, Viral; McDowell, Arlene; Mitra, Ashim K; Hook, Sarah

2016-01-01

The need for multiple vaccinations to enhance the immunogenicity of subunit vaccines may be reduced by delivering the vaccine over an extended period of time. Here, we report two novel injectable pentablock copolymer based thermoresponsive hydrogels made of polyethyleneglycol-polycaprolactone-polylactide-polycaprolactone-polyethyleneglycol (PEG-PCL-PLA-PCL-PEG) with varying ratios of polycaprolactone (PCL) and polylactide (PLA), as single shot sustained release vaccines. Pentablock copolymer hydrogels were loaded with vaccine-encapsulated poly lactic-co-glycolic acid nanoparticles (PLGA-NP) or with the soluble vaccine components. Incorporation of PLGA-NP into the thermoresponsive hydrogels increased the complex viscosity of the gels, lowered the gelation temperature, and minimized the burst release of antigen and adjuvants. The two pentablock hydrogels stimulated both cellular and humoral responses. The addition of PLGA-NP to the hydrogels sustained immune responses for up to 49 days. The polymer with a higher ratio of PCL to PLA formed a more rigid gel, induced stronger immune responses, and stimulated effective anti-tumor responses in a prophylactic melanoma tumor model.

Biodegradable shape-memory block co-polymers for fast self-expandable stents.

Science.gov (United States)

Xue, Liang; Dai, Shiyao; Li, Zhi

2010-11-01

Block co-polymers PCTBVs (M(n) of 36,300-65,300 g/mol, T(m) of 39-40 and 142 degrees C) containing hyperbranched three-arm poly(epsilon-caprolactone) (PCL) as switching segment and microbial polyester PHBV as crystallizable hard segment were designed as biodegradable shape-memory polymer (SMP) for fast self-expandable stent and synthesized in 96% yield by the reaction of three-arm PCL-triol (M(n) of 4200 g/mol, T(m) of 47 degrees C) with methylene diphenyl 4,4'-diisocyanate isocynate (MDI) to form the hyperbrached MDI-linked PCL (PTCM; M(n) of 25,400 g/mol and a T(m) of 38 degrees C), followed by further polymerization with PHBV-diol (M(n) of 2200 g/mol, T(m) of 137 and 148 degrees C). The polymers were characterized by (1)H NMR, GPC, DSC, tensile test, and cyclic thermomechanical tensile test. PCTBVs showed desired thermal properties, mechanical properties, and ductile nature. PCTBV containing 25 wt% PHBV (PCTBV-25) demonstrated excellent shape-memory property at 40 degrees C, with R(f) of 94%, R(r) of 98%, and shape recovery within 25s. PCTBV-25 was also shown as a safe material with good biocompatibility by cytotoxicity tests and cell growth experiments. The stent made from PCTBV-25 film showed nearly complete self-expansion at 37 degrees C within only 25 s, which is much better and faster than the best known self-expandable stents. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Preparation of thermo-responsive graft copolymer by using a novel macro-RAFT agent and its application for drug delivery.

Science.gov (United States)

Song, Cunfeng; Yu, Shirong; Liu, Cheng; Deng, Yuanming; Xu, Yiting; Chen, Xiaoling; Dai, Lizong

2016-05-01

A methodology to prepare thermo-responsive graft copolymer by using a novel macro-RAFT agent was proposed. The macro-RAFT agent with pendant dithioester (ZC(S)SR) was facilely prepared via the combination of RAFT polymerization and esterification reaction. By means of ZC(S)SR-initiated RAFT polymerization, the thermo-responsive graft copolymer consisting of poly(methyl methacrylate-co-hydroxylethyl methacrylate) (P(MMA-co-HEMA)) backbone and hydrophilic poly(N-isopropylacrylamide) (PNIPAAm) side chains was constructed through the "grafting from" approach. The chemical compositions and molecular weight distributions of the synthesized polymers were respectively characterized by (1)H nuclear magnetic resonance ((1)H NMR) and gel permeation chromatography (GPC). Self-assembly behavior of the amphiphilic graft copolymers (P(MMA-co-HEMA)-g-PNIPAAm) was studied by transmission electron microscopy (TEM), dynamic light scattering (DLS) and spectrofluorimeter. The critical micelle concentration (CMC) value was 0.052 mg mL(-1). These micelles have thermo-responsibility and a low critical solution temperature (LCST) of 33.5°C. Further investigation indicated that the guest molecule release property of these micelles, which can be well described by a first-order kinetic model, was significantly affected by temperature. Besides, the micelles exhibited excellent biocompatibility and cellular uptake property. Hence, these micelles are considered to have potential application in controlled drug delivery. Copyright © 2016 Elsevier B.V. All rights reserved.

Tracking of double-labeled thermoresponsive polymer biological behavior

Czech Academy of Sciences Publication Activity Database

Loukotová, Lenka; Kolářová, V.; Veselá, M.; Kučka, Jan; Hrubý, Martin; Rabyk, Mariia; Francová, P.; Páral, P.; Heizer, T.; Šefc, L.

2017-01-01

Roč. 13, č. 1 (2017), s. 190 ISSN 1336-7242. [Zjazd chemikov /69./. 11.09.2017-15.09.2017, Horný Smokovec] R&D Projects: GA MŠk(CZ) LM2015064; GA MZd(CZ) NV15-25781A; GA ČR(CZ) GA16-02870S Institutional support: RVO:61389013 Keywords : glucan * radiotherapy * thermoresponsive Subject RIV: FR - Pharmacology ; Medidal Chemistry

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

Directory of Open Access Journals (Sweden)

S. A. Jadhav

2017-02-01

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

Synthesis of a cationic thermoresponsive dendrimer and its self-assembly with apoferritin protein cage

OpenAIRE

Välimäki, Salla

2015-01-01

The aim of this work was to synthesize cationic dendrimer with a thermoresponsive polymer tail and complex the dendrimer with negatively charged apoferritin protein nanocage. These kind of systems are developed, for example, for biomedical applications. Spermine dendron with atom transfer radical polymerization initiator in focal point was synthesized successfully. Thermoresponsive poly(di(ethylene glycol) methyl ether methacrylate) was in situ polymerized to the dendron to form the therm...

21 CFR 177.1810 - Styrene block polymers.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Styrene block polymers. 177.1810 Section 177.1810... FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances for Use as Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1810 Styrene block polymers. The styrene...

Synthesis of ABA Tri-Block Co-Polymer Magnetopolymersomes via Electroporation for Potential Medical Application

Directory of Open Access Journals (Sweden)

Jennifer Bain

2015-12-01

Full Text Available The ABA tri-block copolymer poly(2-methyloxazoline–poly(dimethylsiloxane–poly(2-methyloxazoline (PMOXA–PDMS–PMOXA is known for its capacity to mimic a bilayer membrane in that it is able to form vesicular polymersome structures. For this reason, it is the subject of extensive research and enables the development of more robust, adaptable and biocompatible alternatives to natural liposomes for biomedical applications. However, the poor solubility of this polymer renders published methods for forming vesicles unreproducible, hindering research and development of these polymersomes. Here we present an adapted, simpler method for the production of PMOXA–PDMS–PMOXA polymersomes of a narrow polydispersity (45 ± 5.8 nm, via slow addition of aqueous solution to a new solvent/polymer mixture. We then magnetically functionalise these polymersomes to form magnetopolymersomes via in situ precipitation of iron-oxide magnetic nanoparticles (MNPs within the PMOXA–PDMS–PMOXA polymersome core and membrane. This is achieved using electroporation to open pores within the membrane and to activate the formation of MNPs. The thick PMOXA–PDMS–PMOXA membrane is well known to be relatively non-permeable when compared to more commonly used di-block polymer membranes due a distinct difference in both size and chemistry and therefore very difficult to penetrate using standard biological methods. This paper presents for the first time the application of electroporation to an ABA tri-block polymersome membrane (PMOXA–PDMS–PMOXA for intravesicular in situ precipitation of uniform MNPs (2.6 ± 0.5 nm. The electroporation process facilitates the transport of MNP reactants across the membrane yielding in situ precipitation of MNPs. Further to differences in length and chemistry, a tri-block polymersome membrane structure differs from a natural lipid or di-block polymer membrane and as such the application and effects of electroporation on this type of

Functional Nanoporous Polymers from Block Copolymer Precursors

DEFF Research Database (Denmark)

Guo, Fengxiao

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

Thermoresponsive polymeric radionuclide delivery system - an injectable brachytherapy

Czech Academy of Sciences Publication Activity Database

Hrubý, Martin; Poučková, P.; Zadinová, M.; Kučka, Jan; Lebeda, Ondřej

2011-01-01

Roč. 42, č. 5 (2011), s. 484-488 ISSN 0928-0987 R&D Projects: GA ČR GPP207/10/P054; GA AV ČR IAAX00500803; GA MŠk 1M0505; GA MŠk 2B06165 Institutional research plan: CEZ:AV0Z40500505; CEZ:AV0Z10480505 Keywords : thermoresponsive polymer * brachytherapa * drug delivery Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.212, year: 2011

Influence of additives on thermoresponsive polymers in aqueous media: a case study of poly(N-isopropylacrylamide).

Science.gov (United States)

Umapathi, Reddicherla; Reddy, P Madhusudhana; Rani, Anjeeta; Venkatesu, Pannuru

2018-04-18

Thermoresponsive polymers (TRPs) in different solvent media have been studied over a long period and are important from both scientific and technical points of view. Despite numerous studies on the behavior of TRPs with various additives, the interactions of additives with TRPs are still poorly understood. Moreover, despite the vast available literature regarding the biomolecular interactions between various TRPs and naturally occurring additives, it is not possible to provide a unifying declaration about the behavior of different additives, in particular at the phase transition temperature of the polymer. However, potential reviews that describe the behavior of additives as stimuli upon the phase transition of TRPs are also absent. A lack of sufficient knowledge regarding the responses of TRPs to additives as stimuli has hindered the expansion of the wide spectrum of applications of these polymers. Therefore, it was proposed to review the responses of TRPs in the presence of various additives in aqueous media. In-depth knowledge acquired via a literature survey has drawn our attention towards filling this gap by analyzing the interactions of TRPs with different additives. In this perspective, we have systematically examined the stability, aggregation, and phase transition behaviours of various polymers in the presence of different additives. The perspective on the influence of additives as stimuli on the behavior of TRPs in an aqueous medium will provide new reliable information about intramolecular interactions between interior polymer segments as well as intermolecular interactions between TRPs and additive molecules, which will be helpful for industrialists in the preparation of new polymeric materials for drug-delivery systems.

Water-dispersed thermo-responsive boron nitride nanotubes: synthesis and properties

Czech Academy of Sciences Publication Activity Database

Kalay, S.; Stetsyshyn, Y.; Lobaz, Volodymyr; Harhay, K.; Ohar, H.; Ҫulha, M.

2016-01-01

Roč. 27, č. 3 (2016), 035703_1-035703_8 ISSN 0957-4484 R&D Projects: GA ČR(CZ) GA13-08336S; GA MPO(CZ) FR-TI4/625 Institutional support: RVO:61389013 Keywords : boron nitride nanotubes * thermo-responsive polymer brushes * poly(N-isopropylacrylamide) Subject RIV: CA - Inorganic Chemistry Impact factor: 3.440, year: 2016

Functionalization of Strongly Interacting Magnetic Nanocubes with (Thermo)responsive Coating and their Application in Hyperthermia and Heat-Triggered Drug Delivery

KAUST Repository

Kakwere, Hamilton; Pernia Leal, Manuel; Materia, Maria-Elena; Curcio, Alberto; Guardia, Pablo; Niculaes, Dina; Marotta, Roberto; Falqui, Andrea; Pellegrino, Teresa

2015-01-01

Herein we prepare nanohybrids by incorporating iron oxide nanocubes (cubic-IONPs) within a thermo-responsive polymer shell that can act as drug carriers for doxorubicin(doxo). The cubic-shaped nanoparticles employed are at the interface between superparamagnetic and ferromagnetic behavior and have an exceptionally high specific absorption rate (SAR) but their functionalization is extremely challenging compared to bare superparamagnetic iron oxide nanoparticles as they strongly interact with each other. By conducting the polymer grafting reaction using reversible addition-fragmentation chain transfer (RAFT) polymerization in a viscous solvent medium, we have here developed a facile approach to decorate the nanocubes with stimuli-responsive polymers. When the thermo-responsive shell is composed of poly(N-isopropyl acrylamide-co-polyethylene glycolmethylether acrylate), nanohybrids have a phase transition temperature, the lower critical solution temperature (LCST), above 37 °C in physiological conditions. Doxo loaded nanohybrids exhibited a negligible drug release below 37 °C but showed a consistent release of their cargo on demand by exploiting the capability of the nanocubes to generate heat under an alternating magnetic field (AMF). Moreover, the drug free nanocarrier does not exhibit cytotoxicity even when administered at high concentration of nanocubes (1g/L of iron) and internalized at high extent (260 pg of iron per cell). We have also implemented the synthesis protocol to decorate the surface of nanocubes with poly(vinylpyridine) polymer and thus prepare pH-responsive shell coated nanocubes.

Functionalization of Strongly Interacting Magnetic Nanocubes with (Thermo)responsive Coating and their Application in Hyperthermia and Heat-Triggered Drug Delivery

KAUST Repository

Kakwere, Hamilton

2015-04-03

Herein we prepare nanohybrids by incorporating iron oxide nanocubes (cubic-IONPs) within a thermo-responsive polymer shell that can act as drug carriers for doxorubicin(doxo). The cubic-shaped nanoparticles employed are at the interface between superparamagnetic and ferromagnetic behavior and have an exceptionally high specific absorption rate (SAR) but their functionalization is extremely challenging compared to bare superparamagnetic iron oxide nanoparticles as they strongly interact with each other. By conducting the polymer grafting reaction using reversible addition-fragmentation chain transfer (RAFT) polymerization in a viscous solvent medium, we have here developed a facile approach to decorate the nanocubes with stimuli-responsive polymers. When the thermo-responsive shell is composed of poly(N-isopropyl acrylamide-co-polyethylene glycolmethylether acrylate), nanohybrids have a phase transition temperature, the lower critical solution temperature (LCST), above 37 °C in physiological conditions. Doxo loaded nanohybrids exhibited a negligible drug release below 37 °C but showed a consistent release of their cargo on demand by exploiting the capability of the nanocubes to generate heat under an alternating magnetic field (AMF). Moreover, the drug free nanocarrier does not exhibit cytotoxicity even when administered at high concentration of nanocubes (1g/L of iron) and internalized at high extent (260 pg of iron per cell). We have also implemented the synthesis protocol to decorate the surface of nanocubes with poly(vinylpyridine) polymer and thus prepare pH-responsive shell coated nanocubes.

Data of continuous harvest of stem cells via partial detachment from thermoresponsive nanobrush surfaces

Directory of Open Access Journals (Sweden)

Chin-Chen Yeh

2016-03-01

Full Text Available This data article contains two figures and one table supporting the research article entitled: “Continuous harvest of stem cells via partial detachment from thermoresponsive nanobrush surface” [1]. The table shows coating conditions of three copolymers, poly(styrene-co-acrylic acid grafted with oligovitronectin, poly(styrene-co-N-isopropylacrylamide and poly(styrene-co-polyethylene glycol methacrylate to prepare thermoresponsive surface. XPS spectra show the nitrogen peak of the polystyrene surface coated with poly(styrene-co-acrylic acid grafted with oligovitronectin. The surface coating density analyzed from sorption of poly(styrene-co-acrylic acid grafted with oligovitronectin by UV–vis spectroscopy is also presented.

Data of continuous harvest of stem cells via partial detachment from thermoresponsive nanobrush surfaces

Science.gov (United States)

Yeh, Chin-Chen; Muduli, Saradaprasan; Peng, I-Chia; Lu, Yi-Tung; Ling, Qing-Dong; Alarfaj, Abdullah A.; Munusamy, Murugan A.; Kumar, S. Suresh; Murugan, Kadarkarai; Chen, Da-Chung; Lee, Hsin-chung; Chang, Yung; Higuchi, Akon

2016-01-01

This data article contains two figures and one table supporting the research article entitled: “Continuous harvest of stem cells via partial detachment from thermoresponsive nanobrush surface” [1]. The table shows coating conditions of three copolymers, poly(styrene-co-acrylic acid) grafted with oligovitronectin, poly(styrene-co-N-isopropylacrylamide) and poly(styrene-co-polyethylene glycol methacrylate) to prepare thermoresponsive surface. XPS spectra show the nitrogen peak of the polystyrene surface coated with poly(styrene-co-acrylic acid) grafted with oligovitronectin. The surface coating density analyzed from sorption of poly(styrene-co-acrylic acid) grafted with oligovitronectin by UV–vis spectroscopy is also presented. PMID:26909373

Thermoresponsive self-assembly of nanostructures from a collagen-like peptide-containing diblock copolymer.

Science.gov (United States)

Luo, Tianzhi; He, Lirong; Theato, Patrick; Kiick, Kristi L

2015-01-01

Temperature-triggered formation of nanostructures with distinct biological activity offers opportunities in selective modification of matrices and in drug delivery. Toward these ends, diblock polymers comprising poly(diethylene glycol methyl ether methacrylate) (PDEGMEMA) conjugated to a triple helix-forming collagen-like peptide were produced. Triggered by the collapse of the thermoresponsive domain above its LCST, the conjugate undergoes a reversible transition in aqueous solution to form well-defined nanovesicles with diameters of approximately 100 nm, with a transition temperature of 37 °C. The incorporation of CLP domains in these nanostructures may offer opportunities for the selective targeting of collagen-containing matrices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Application of thermoresponsive HPLC to forensic toxicology: determination of barbiturates in human urine

OpenAIRE

Kanno, Sanae; Watanabe, Kanako; Hirano, Seishiro; Yamagishi, Itaru; Gonmori, Kunio; Minakata, Kayoko; Suzuki, Osamu

2009-01-01

A high-performance liquid chromatography (HPLC) method has been developed for the assays of five barbiturates in human urine using a new thermoresponsive polymer separation column, which is composed of N-isopropylacrylamide polymer. According to elevating the column temperature from 10 ℃ to 50 ℃, five barbiturates, such as metharbital, primidone, phenobarbital, mephobarbital and pentobarbital, became well separated by this method. Five barbiturates showed good linearity in the range of 0.2-10...

Hydrophilic magnetic nanoclusters with thermo-responsive properties and their drug controlled release

International Nuclear Information System (INIS)

Meerod, Siraprapa; Rutnakornpituk, Boonjira; Wichai, Uthai; Rutnakornpituk, Metha

2015-01-01

Synthesis and drug controlled release properties of thermo-responsive magnetic nanoclusters grafted with poly(N-isopropylacrylamide) (poly(NIPAAm)) and poly(NIPAAm-co-poly(ethylene glycol) methyl ether methacrylate) (PEGMA) copolymers were described. These magnetic nanoclusters were synthesized via an in situ radical polymerization in the presence of acrylamide-grafted magnetic nanoparticles (MNPs). Poly(NIPAAm) provided thermo-responsive properties, while PEGMA played a role in good water dispersibility to the nanoclusters. The ratios of PEGMA to NIPAAm in the (co)polymerization in the presence of the MNPs were fine-tuned such that the nanoclusters with good water dispersibility, good magnetic sensitivity and thermo responsiveness were obtained. The size of the nanoclusters was in the range of 50–100 nm in diameter with about 100–200 particles/cluster. The nanoclusters were well dispersible in water at room temperature and can be suddenly agglomerated when temperature was increased beyond the lower critical solution temperature (LCST) (32 °C). The release behavior of an indomethacin model drug from the nanoclusters was also investigated. These novel magnetic nanoclusters with good dispersibility in water and reversible thermo-responsive properties might be good candidates for the targeting drug controlled release applications. - Highlights: • Nanoclusters with good water dispersibility and magnetic response were prepared. • They were grafted with thermo-responsive poly(NIPAAm) and/or poly(PEGMA). • Poly(NIPAAm) provided thermo-responsive properties to the nanoclusters. • Poly(PEGMA) provided good water dispersibilityto the nanoclusters. • Accelerated and controllable releases of a drug from the nanoclusters were shown

Relationships between the morphology and thermoresponsive behavior in micro/nanostructured thermosetting matrixes containing a 4'-(hexyloxy)-4-biphenylcarbonitrile liquid crystal.

Science.gov (United States)

Tercjak, Agnieszka; Mondragon, Iñaki

2008-10-07

Meso/nanostructured thermoresponsive thermosetting materials based on an epoxy resin modified with two different molecular weight amphiphilic poly(styrene- block-ethylene oxide) block copolymers (PSEO) and a low molecular weight liquid crystal, 4'-(hexyloxy)-4-biphenylcarbonitrile (HOBC), were investigated. A strong influence of the addition of PSEO on the morphology generated in HOBC--(diglicydyl ether of bisphenol A epoxy resin/ m-xylylenediamine) was detected, especially in the case of the addition of PSEO block copolymers with a higher PEO-block content and a lower molecular weight. The morphologies generated in the ternary systems also influenced the thermoresponsive behavior of the HOBC separated phase provoked by applying an external field, such as a temperature gradient and an electrical field. Thermal analysis of the investigated materials allowed for a better understanding of the relationships between generated morphology/thermo-optical properties/PSEO:HOBC ratio, and HOBC content. Controlling the relationship between the morphology and thermoresponsive behavior in micro/nanostructured thermosetting materials based on a 4'-(hexyloxy)-4-biphenylcarbonitrile liquid crystal allows the development of materials which can find application in thermo- and in some cases electroresponsive devices, with a high contrast ratio between transparent and opaque states.

Thermo- and pH-responsive polymer brushes-grafted gigaporous polystyrene microspheres as a high-speed protein chromatography matrix.

Science.gov (United States)

Qu, Jian-Bo; Xu, Yu-Liang; Liu, Jun-Yi; Zeng, Jing-Bin; Chen, Yan-Li; Zhou, Wei-Qing; Liu, Jian-Guo

2016-04-08

Dual thermo- and pH-responsive chromatography has been proposed using poly(N-isopropylacrylamide-co-butyl methacrylate-co-N,N-dimethylaminopropyl acrylamide) (P(NIPAM-co-BMA-co-DMAPAAM)) brushes grafted gigaporous polystyrene microspheres (GPM) as matrix. Atom transfer radical polymerization (ATRP) initiator was first coupled onto GPM through Friedel-Crafts acylation with 2-bromoisobutyryl bromide. The dual-responsive polymer brushes were then grafted onto GPM via surface-initiated ATRP. The surface composition, gigaporous structure, protein adsorption and dual-responsive chromatographic properties of the matrix (GPM-P(NIPAM-co-BMA-co-DMAPAAM) were characterized in detail. Results showed that GPM were successfully grafted with thermoresponsive cationic polymer brushes and that the gigaporous structure was well maintained. A column packed with GPM-P(NIPAM-co-BMA-co-DMAPAAM presented low backpressure, good permeability and appreciable thermo-responsibility. By changing pH of the mobile phase and temperature of the column in turn, the column can separate three model proteins at the mobile phase velocity up to 2528cmh(-1). A separation mechanism of this matrix was also proposed. All results indicate that the dual thermo- and pH-responsive chromatography matrix has great potentials in 'green' high-speed protein chromatography. Copyright © 2016 Elsevier B.V. All rights reserved.

VRPI Thermoresponsive Reversibly Attachable Patch for Temporary Intervention in Ocular Trauma

Science.gov (United States)

2015-11-01

closure for the eye. The enabling technology is a thermo-reversible adhesive ( poly n-isopropyl acrylamide), PNIPAM, which is adhesive to tissues at body...trauma; sclera; hydrogel; PNIPAM; thermo-responsive polymer; open globe; critical care; combat casualty care; poly -n-isopropyl acrylamide. 3...visible or observable signs of discomfort, pain or distress were observed in the treatment group animals after the placement procedure. The afternoon

CO2 Conversion: The Potential of Porous–Organic Polymers (POPs) for the cycloaddition of CO2 and epoxides

KAUST Repository

Alkordi, Mohamed Helmi

2016-03-30

Novel porous organic polymers (POPs) have been synthesized using functionalized Cr and Co-salen complexes as molecular building blocks. The integration of metalosalen catalysts into the porous polymers backbone permits the successful utilization of the materials as solid-state catalysts for CO2-epoxide cycloadditions reactions with excellent catalytic performance under mild conditions of temperature and pressure. The catalyst proved to be fully recyclable and robust thus showing the potential of POPs as smart functional materials for the heterogenization of key catalytic elements.

Thermoresponsive poly(2-oxazoline) homopolymers and copolymers in aqueous solutions studied by NMR spectroscopy and dynamic light scattering

Czech Academy of Sciences Publication Activity Database

Konefal, Rafal; Spěváček, Jiří; Černoch, Peter

2018-01-01

Roč. 100, March (2018), s. 241-252 ISSN 0014-3057 R&D Projects: GA ČR(CZ) GA15-13853S Institutional support: RVO:61389013 Keywords : thermoresponsive polymer * poly(2-ethyl-2-oxazoline) * poly(2-ethyl-oxazoline-grad-2-methyl-2-oxazoline) copolymer Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 3.531, year: 2016

New polymer material for CO_2 capture by membrane separation process

International Nuclear Information System (INIS)

Solimando, Xavier

2016-01-01

In this PhD thesis, two types of membrane materials were developed for CO_2 separation. The first ones associate a reference polymer material (Pebax) with new pseudo-peptidic bio-conjugates additives. These pseudo-peptide-polymer bio-conjugates were obtained by a 'grafting-to' synthetical pathway from alkyne-functionalized 1:1[a/a-Na-Bn-hydrazino] dimer and tetramer pseudopeptides. Poly(diethylene glycol acrylate) (PEDEGA) oligomeric part was synthesized under controlled conditions using Single Electron Transfer Living Radical Polymerization (SET-LRP) from an azido-functionalized initiator allowing direct coupling via CuAAC 'click' chemistry. The influence of these additives on CO_2 sorption and separation properties was analyzed in terms of properties-morphology-structure relationships. These original additives allowed to enhance CO_2 separation performances of the reference membrane, increasing CO_2 permeability by 46%, and maintaining good selectivities aCO_2/N_2 = 44 et aCO_2/CH_4 = 13. In another work, two families of poly(urethane-imide)s (PUIs) with controlled architecture were developed for obtaining membrane materials with high content in ethylene-oxide units while avoiding their crystallization. Linear multi-blocks PUIs were first synthesized by polycondensation with different sizes of Jeff amine polyether soft block, corresponding to soft block contents varying from 40 to 70%wt. To further increase the soft phase content until a very high level (85%wt), grafted multi-blocks PUIs were obtained by a 'grafting-to' strategy from an alkyne-functionalized precursor PUI and azido-PEDEGA oligomers with different molar weights. The evolution of their CO_2 separation performances were correlated to their soft phase content, morphology and CO_2 sorption ability. For the maximum soft phase content (85%wt), high performances were obtained for CO_2 separation (PCO_2 = 196 Barrer; aCO_2/N_2 = 39 et aCO_2/CH_4 = 12). Compared to the precursor PUI, the grafting strategy

Coupling of microphase separation and dewetting in weakly segregated diblock co-polymer ultrathin films.

Science.gov (United States)

Yan, Derong; Huang, Haiying; He, Tianbai; Zhang, Fajun

2011-10-04

We have studied the coupling behavior of microphase separation and autophobic dewetting in weakly segregated poly(ε-caprolactone)-block-poly(L-lactide) (PCL-b-PLLA) diblock co-polymer ultrathin films on carbon-coated mica substrates. At temperatures higher than the melting point of the PLLA block, the co-polymer forms a lamellar structure in bulk with a long period of L ∼ 20 nm, as determined using small-angle X-ray scattering. The relaxation procedure of ultrathin films with an initial film thickness of h = 10 nm during annealing has been followed by atomic force microscopy (AFM). In the experimental temperature range (100-140 °C), the co-polymer dewets to an ultrathin film of itself at about 5 nm because of the strong attraction of both blocks with the substrate. Moreover, the dewetting velocity increases with decreasing annealing temperatures. This novel dewetting kinetics can be explained by a competition effect of the composition fluctuation driven by the microphase separation with the dominated dewetting process during the early stage of the annealing process. While dewetting dominates the relaxation procedure and leads to the rupture of the ultrathin films, the composition fluctuation induced by the microphase separation attempts to stabilize them because of the matching of h to the long period (h ∼ 1/2L). The temperature dependence of these two processes leads to this novel relaxation kinetics of co-polymer thin films. © 2011 American Chemical Society

State of mixing of deuterated and non-deuterated block polymer chains

International Nuclear Information System (INIS)

Hasegawa, Hirokazu; Hashimoto, Takeji

1984-01-01

Prior to the small-angle neutron scattering study on the conformation of block polymer chains in the domain space, the state of mixing of two block polymers, an ordinary polystyrene-polyisoprene diblock polymer and a poly(deuterated styrene)-polyisoprene diblock polymer with a different molecular weight and composition, was investigated by a small-angle X-ray scattering (SAXS) technique. Only one kind of domain structure was observed for each blend, and the domain spacings obtained by SAXS were proportional to the two-thirds power of the number-average molecular weight of the blends (reduced to non-deuterated block polymer). The volume fractions of polystyrene domain in the blends evaluated by computer simulation of SAXS profiles well agreed with the values estimated from blend composition. All these facts suggest the molecular mixing of the two block polymers in the domain space. (author)

PNIPAAm-grafted thermoresponsive microcarriers: Surface-initiated ATRP synthesis and characterization

Energy Technology Data Exchange (ETDEWEB)

Çakmak, Soner [Nanotechnology and Nanomedicine Department, Hacettepe University, 06800, Beytepe, Ankara (Turkey); Çakmak, Anıl S. [Bioengineering Department, Hacettepe University, 06800, Beytepe, Ankara (Turkey); Gümüşderelioğlu, Menemşe, E-mail: menemse@hacettepe.edu.tr [Nanotechnology and Nanomedicine Department, Hacettepe University, 06800, Beytepe, Ankara (Turkey); Bioengineering Department, Hacettepe University, 06800, Beytepe, Ankara (Turkey); Chemical Engineering Department, Hacettepe University, 06800, Beytepe, Ankara (Turkey)

2013-07-01

In this study, we developed novel thermoresponsive microcarriers as a powerful tool for cell culture and tissue engineering applications. For this purpose, two types of commercially available spherical microparticles (approximately 100 μm in diameter), dextran-based Sephadex® and vinyl acetate-based VA-OH (Biosynth®), were used and themoresponsive poly(N-isopropylacrylamide) (PNIPAAm) was grafted to the beads' surfaces by surface-initiated atom transfer radical polymerization (SI-ATRP). Initially, hydroxyl groups of microbeads were reacted with 2-bromopropionyl bromide to form ATRP macroinitiator. Then, NIPAAm was successfully polymerized from the initiator attached microbeads by ATRP with CuBr/2,2′-dipyridyl, catalyst complex. Furthermore, grafted and ungrafted microbeads were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscope (SEM), atomic force microscopy (AFM) and electron spectroscopy for chemical analysis (ESCA). The results of characterization studies confirmed that PNIPAAm was successfully grafted onto both dextran and vinyl acetate-based beads by means of ATRP reaction and thus, grafted microbeads gained thermoresponsive characteristics which will be evaluated for cell harvesting in further studies. Highlights: • PNIPAAm was grafted to the hydroxyl group carrying polymer beads by SI-ATRP. • Dex-g-PNIPAAm and VA-OH-g-PNIPAAm beads exhibited thermoresponsive characteristics. • They are appropriate candidates for microcarrier-facilitated cell cultures.

PNIPAAm-grafted thermoresponsive microcarriers: Surface-initiated ATRP synthesis and characterization

International Nuclear Information System (INIS)

Çakmak, Soner; Çakmak, Anıl S.; Gümüşderelioğlu, Menemşe

2013-01-01

In this study, we developed novel thermoresponsive microcarriers as a powerful tool for cell culture and tissue engineering applications. For this purpose, two types of commercially available spherical microparticles (approximately 100 μm in diameter), dextran-based Sephadex® and vinyl acetate-based VA-OH (Biosynth®), were used and themoresponsive poly(N-isopropylacrylamide) (PNIPAAm) was grafted to the beads' surfaces by surface-initiated atom transfer radical polymerization (SI-ATRP). Initially, hydroxyl groups of microbeads were reacted with 2-bromopropionyl bromide to form ATRP macroinitiator. Then, NIPAAm was successfully polymerized from the initiator attached microbeads by ATRP with CuBr/2,2′-dipyridyl, catalyst complex. Furthermore, grafted and ungrafted microbeads were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscope (SEM), atomic force microscopy (AFM) and electron spectroscopy for chemical analysis (ESCA). The results of characterization studies confirmed that PNIPAAm was successfully grafted onto both dextran and vinyl acetate-based beads by means of ATRP reaction and thus, grafted microbeads gained thermoresponsive characteristics which will be evaluated for cell harvesting in further studies. Highlights: • PNIPAAm was grafted to the hydroxyl group carrying polymer beads by SI-ATRP. • Dex-g-PNIPAAm and VA-OH-g-PNIPAAm beads exhibited thermoresponsive characteristics. • They are appropriate candidates for microcarrier-facilitated cell cultures

Thermosensitive Triterpenoid-Appended Polymers with Broad Temperature Tunability Regulated by Host-Guest Chemistry.

Science.gov (United States)

Hao, Jie; Gao, Yuxia; Li, Ying; Yan, Qiang; Hu, Jun; Ju, Yong

2017-09-05

Thermoresponsive water-soluble polymers are of great importance since they typically show a lower critical solution temperature (LCST) in aqueous media. In this research, the LCST change in broad temperature ranges of copolymers composed of natural glycyrrhetinic acid (GA)-based methacrylate and N,N'-dimethylacrylamides (DMAs) was investigated as a function of the concentration and the content of GA pendants. By complexation of GA pendants with β-cyclodextrin (β-CD), a side-chain polypseudorotaxane was obtained, which exhibited a significant increase in the LCST of copolymers. Moreover, the precisely reversible control of the LCST behavior was realized through adding a competing guest molecule, sodium 1-admantylcarboxylate. This work illustrates a simple and effective approach to endow water-soluble polymers with broad temperature tunability and helps us further understand the effect of a biocompatible host-guest complementary β-CD/GA pair on the thermoresponsive process. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A chemical platform approach on cardanol oil: from the synthesis of building blocks to polymer synthesis

Directory of Open Access Journals (Sweden)

Jaillet Fanny

2016-09-01

Full Text Available This review proposes a platform approach for the synthesis of various building blocks from cardanol oil in one or two-steps synthesis. Cardanol is a natural phenol issued from Cashew nutshell liquid (CNSL. CNSL is a non-edible renewable resource, co-produced from cashew industry in large commercial volumes. Cardanol is non-toxic and particularly suitable as an aromatic renewable resource for polymers and materials. Various routes were used for the synthesis of di- and poly-functional building blocks used thereafter in polymer syntheses. Phenolation was used to dimerize/oligomerize cardanol to propose increase functionality of cardanol. Thio-ene was used to synthesize new reactive amines. Epoxidation and (methacrylation were also used to insert oxirane or (methacrylate groups in order to synthesize polymers and materials.

Tracking of double-labeled thermoresponsive polymer biological behavior

International Nuclear Information System (INIS)

Loukotova, L.; Kucka, J.; Hruby, M.; Rabyk, M.; Sefc, L.; Kolarova, V.; Vesela, M.; Francova, P.; Paral, P.; Heizer, T.

2017-01-01

To study biological behavior of this hybrid copolymer, we used mice (strain C57BL/6) bearing EL4 tumors. We separated mice into four groups. The first group (IMUNO) was treated with β-glucan-graft-poly(2-isopropyl-2- oxazoline-co-2-butyl-2-oxazoline) bearing at the graft ends fluorescence dye Dyomics-615 and 1,4,7,10-tetraazacyclododecane-1,4,7,10- tetraacetic acid (DOTA). The second group (RADIO-IMUNO) was treated with the same polymer, here having at the graft ends complex DOTA-yttrium-90(III). The third group (RADIO) was treated only with corresponding polyoxazoline grafts bearing complex DOTA-yttrium- 90(III) and the fourth group we used without treatment as a control group. We measured for two weeks polymer depot stability in vivo with Optical Imaging System. We are also able to collect signal from radioactive isotopes by converting high energy beta particles into visible light. (authors)

Pinenes: Abundant and Renewable Building Blocks for a Variety of Sustainable Polymers.

Science.gov (United States)

Winnacker, Malte

2018-05-14

Pinenes - a group of monoterpenes containing a double bond - are very suitable renewable building blocks for a variety of sustainable polymers and materials. Their abundance from mainly non-edible parts of plants as well as the feasibility to isolate them render these compounds unique amongst the variety of biomass that is utilizable for novel materials. Accordingly, their use for the synthesis of biobased polymers has been investigated intensively, and strong progress has been made with this especially within the past 2-3 years. Direct cationic or radical polymerization via the double bonds as well as polymerization upon their further functionalization can afford a variety of sustainable polymers suitable for many applications, which is summarized in this article. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermo-responsive block copolymers

NARCIS (Netherlands)

Mocan Cetintas, Merve

2017-01-01

Block copolymers (BCPs) are remarkable materials because of their self-assembly behavior into nano-sized regular structures and high tunable properties. BCPs are in used various applications such as surfactants, nanolithography, biomedicine and nanoporous membranes. In these thesis, we aimed to

Microtome Sliced Block Copolymers and Nanoporous Polymers as Masks for Nanolithography

DEFF Research Database (Denmark)

Shvets, Violetta; Schulte, Lars; Ndoni, Sokol

2014-01-01

Introduction. Block copolymers self-assembling properties are commonly used for creation of very fine nanostructures [1]. Goal of our project is to test new methods of the block-copolymer lithography mask preparation: macroscopic pieces of block-copolymers or nanoporous polymers with cross...... PDMS can be chemically etched from the PB matrix by tetrabutylammonium fluoride in tetrahydrofuran and macroscopic nanoporous PB piece is obtained. Both block-copolymer piece and nanoporous polymer piece were sliced with cryomicrotome perpendicular to the axis of cylinder alignment and flakes...... of etching patterns appear only under the certain parts of thick flakes and are not continuous. Although flakes from block copolymer are thinner and more uniform in thickness than flakes from nanoporous polymer, quality of patterns under nanoporous flakes appeared to be better than under block copolymer...

Preparation of Thermo-Responsive and Cross-Linked Fluorinated Nanoparticles via RAFT-Mediated Aqueous Polymerization in Nanoreactors.

Science.gov (United States)

Ma, Jiachen; Zhang, Luqing; Geng, Bing; Azhar, Umair; Xu, Anhou; Zhang, Shuxiang

2017-01-25

In this work, a thermo-responsive and cross-linked fluoropolymer poly(2,2,2-Trifluoroethyl) methacrylate (PTFEMA) was successfully prepared by reversible addition-fragmentation chain transfer (RAFT) mediated aqueous polymerization with a thermo-responsive diblock poly(dimethylacrylamide- b - N -isopropylacrylamide) (PDMA- b -PNIPAM) that performed a dual function as both a nanoreactor and macro-RAFT agent. The cross-linked polymer particles proved to be in a spherical-like structure of about 50 nm in diameter and with a relatively narrow particle size distribution. ¹H-NMR and 19 F-NMR spectra showed that thermo-responsive diblock P(DMA- b -NIPAM) and cross-linked PTFEMA particles were successfully synthesized. Influence of the amount of ammonium persulfate (APS), the molar ratio of monomers to RAFT agent, influence of the amount of cross-linker on aqueous polymerization and thermo-responsive characterization of the particles are investigated. Monomer conversion increased from 44% to 94% with increasing the molar ratio of APS and P(DMA- b -NIPAM) from 1:9 to1:3. As the reaction proceeded, the particle size increased from 29 to 49 nm due to the consumption of TFEMA monomer. The size of cross-linked nanoparticles sharply decreased from 50.3 to 40.5 nm over the temperature range 14-44 °C, suggesting good temperature sensitivity for these nanoparticles.

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.

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.

Thermo-responsive methylcellulose hydrogels as temporary substrate for cell sheet biofabrication.

Science.gov (United States)

Altomare, Lina; Cochis, Andrea; Carletta, Andrea; Rimondini, Lia; Farè, Silvia

2016-05-01

Methylcellulose (MC), a water-soluble polymer derived from cellulose, was investigated as a possible temporary substrate having thermo-responsive properties favorable for cell culturing. MC-based hydrogels were prepared by a dispersion technique, mixing MC powder (2, 4, 6, 8, 10, 12 % w/v) with selected salts (sodium sulphate, Na2SO4), sodium phosphate, calcium chloride, or phosphate buffered saline, to evaluate the influence of different compositions on the thermo-responsive behavior. The inversion test was used to determine the gelation temperatures of the different hydrogel compositions; thermo-mechanical properties and thermo-reversibility of the MC hydrogels were investigated by rheological analysis. Gelation temperatures and rheological behavior depended on the MC concentration and type and concentration of salt used in hydrogel preparation. In vitro cytotoxicity tests, performed using L929 mouse fibroblasts, showed no toxic release from all the tested hydrogels. Among the investigated compositions, the hydrogel composed of 8 % w/v MC with 0.05 M Na2SO4 had a thermo-reversibility temperature at 37 °C. For that reason, this formulation was thus considered to verify the possibility of inducing in vitro spontaneous detachment of cells previously seeded on the hydrogel surface. A continuous cell layer (cell sheet) was allowed to grow and then detached from the hydrogel surface without the use of enzymes, thanks to the thermo-responsive behavior of the MC hydrogel. Immunofluorescence observation confirmed that the detached cell sheet was composed of closely interacting cells.

Tremendous reinforcing, pore-stabilizing and response-accelerating effect of in situ generated nanosilica in thermoresponsive poly(N-isopropylacrylamide) cryogels

Czech Academy of Sciences Publication Activity Database

Strachota, Beata; Šlouf, Miroslav; Matějka, Libor

2017-01-01

Roč. 66, č. 11 (2017), s. 1510-1521 ISSN 0959-8103 R&D Projects: GA ČR(CZ) GA17-13103S Institutional support: RVO:61389013 Keywords : thermoresponsive hydrogel * porous hydrogel * nanocomposite Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 2.070, year: 2016

Synthesis, Characterization and Application of Thermoresponsive Polyhydroxyalkanoate-graft-Poly(N-isopropylacrylamide)

DEFF Research Database (Denmark)

Ma, Yi-Ming; Wei, Dai-Xu; Yao, Hui

2016-01-01

(3HDD-co-3H10U), a random copolymer of 3-hydroxydodecanoate (3HDD) and 3-hydroxy-10-undecylenate (3H10U), via a thiol–ene click reaction. Enhanced hydrophilicity and thermoresponsive property of the resulted PHA-g-PNIPAm were confirmed by water contact angle studies. The biocompatibility of PHA...

Thermo-responsive in-situ forming hydrogels as barriers to prevent post-operative peritendinous adhesion.

Science.gov (United States)

Chou, Pang-Yun; Chen, Shih-Heng; Chen, Chih-Hao; Chen, Shih-Hsien; Fong, Yi Teng; Chen, Jyh-Ping

2017-11-01

In this study, we aimed to assess whether thermo-responsive in-situ forming hydrogels based on poly(N-isopropylacrylamide) (PNIPAM) could prevent post-operative peritendinous adhesion. The clinical advantages of the thermo-responsive hydrogels are acting as barrier material to block penetration of fibroblasts, providing mobility and flexibility during application and enabling injection through a small opening to fill spaces of any shape after surgery. The thermo-responsiveness of hydrogels was determined to ensure their clinic uses. By grafting hydrophilic biopolymers chitosan (CS) and hyaluronic acid (HA) to PNIPAM, the copolymer hydrogels show enhanced water retention and lubrication, while reduced volume shrinkage during phase transition. In cell culture experiments, the thermo-responsive hydrogel has good biocompatibility and reduces fibroblast penetration. In animal experiments, the effectiveness of preventing post-operative peritendinous adhesion was studied in a rabbit deep flexor tendon model. From gross examination, histology, bending angles of joints, tendon gliding excursion and pull-out force, HA-CS-PNIPAM (HACPN) was confirmed to be the best barrier material to prevent post-operative peritendinous adhesion compared to PNIPAM and CS-PNIPAM (CPN) hydrogels and a commercial barrier film Seprafilm®. There was no significant difference in the breaking strength of HACPN-treated tendons and spontaneously healed ones, indicating HACPN hydrogel application did not interfere with normal tendon healing. We conclude that HACPN hydrogel can provide the best functional outcomes to significantly prevent post-operative tendon adhesion in vivo. We prepared thermo-responsive in-situ forming hydrogels based on poly(N-isopropylacrylamide) (PNIPAM) to prevent post-operative peritendinous adhesion. The injectable barrier hydrogel could have better anti-adhesive properties than current commercial products by acting as barrier material to block penetration of fibroblasts

Non-ionic, thermo-responsive DEA/DMA nanogels: synthesis, characterization, and use for DNA separations by microchip electrophoresis.

Science.gov (United States)

Lu, Xihua; Sun, Mingyun; Barron, Annelise E

2011-05-15

Thermo-responsive polymer "nanogels" (crosslinked hydrogel particles with sub-100 nm diameters) are intriguing for many potential applications in biotechnology and medicine. There have been relatively few reports of electrostatically neutral, thermosensitive nanogels comprising a high fraction of hydrophilic co-monomer. Here we demonstrate the syntheses and characterization of novel, non-ionic nanogels based on random N,N-diethylacrylamide (DEA)/N,N-dimethylacrylamide (DMA) copolymers, made by free-radical, surfactant-free dispersion polymerization. The volume-phase transition temperatures of these DEA/DMA nanogels are strongly affected by co-monomer composition, providing a way to "tune" the phase transition temperature of these non-ionic nanogels. While DEA nanogels (comprising no DMA) can be obtained at 70 °C by standard emulsion precipitation, DEA/DMA random co-polymer nanogels can be obtained only in a particular range of temperatures, above the initial phase transition temperature and below the critical precipitation temperature of the DEA/DMA copolymer, controlled by co-monomer composition. Increasing percentages of DMA in the nanogels raises the phase transition temperature, and attenuates and broadens it as well. We find that concentrated DEA/DMA nanogel dispersions are optically clear at room temperature. This good optical clarity was exploited for their use in a novel DNA sieving matrix for microfluidic chip electrophoresis. An ultrafast, high-efficiency dsDNA separation was achieved in less than 120 s for dsDNA ranging from 75 bp to 15,000 bp. Copyright © 2011 Elsevier Inc. All rights reserved.

Polyisocyanopeptide hydrogels: A novel thermo-responsive hydrogel supporting pre-vascularization and the development of organotypic structures.

Science.gov (United States)

Zimoch, Jakub; Padial, Joan Simó; Klar, Agnes S; Vallmajo-Martin, Queralt; Meuli, Martin; Biedermann, Thomas; Wilson, Christopher J; Rowan, Alan; Reichmann, Ernst

2018-04-01

Molecular and mechanical interactions with the 3D extracellular matrix are essential for cell functions such as survival, proliferation, migration, and differentiation. Thermo-responsive biomimetic polyisocyanopeptide (PIC) hydrogels are promising new candidates for 3D cell, tissue, and organ cultures. This is a synthetic, thermo-responsive and stress-stiffening material synthesized via polymerization of the corresponding monomers using a nickel perchlorate as a catalyst. It can be tailored to meet various demands of cells by modulating its stiffness and through the decoration of the polymer with short GRGDS peptides using copper free click chemistry. These peptides make the hydrogels biocompatible by mimicking the binding sites of certain integrins. This study focuses on the optimization of the PIC polymer properties for efficient cell, tissue and organ development. Screening for the optimal stiffness of the hydrogel and the ideal concentration of the GRGDS ligand conjugated with the polymer, enabled cell proliferation, migration and differentiation of various primary cell types of human origin. We demonstrate that fibroblasts, endothelial cells, adipose-derived stem cells and melanoma cells, do survive, thrive and differentiate in optimized PIC hydrogels. Importantly, these hydrogels support the spontaneous formation of complex structures like blood capillaries in vitro. Additionally, we utilized the thermo-responsive properties of the hydrogels for a rapid and gentle recovery of viable cells. Finally, we show that organotypic structures of human origin grown in PIC hydrogels can be successfully transplanted subcutaneously onto immune-compromised rats, on which they survive and integrate into the surrounding tissue. Molecular and mechanical interactions with the surrounding environment are essential for cell functions. Although 2D culture systems greatly contributed to our understanding of complex biological phenomena, they cannot substitute for crucial

Effects of Grafting Density on Block Polymer Self-Assembly: From Linear to Bottlebrush.

Science.gov (United States)

Lin, Tzu-Pin; Chang, Alice B; Luo, Shao-Xiong; Chen, Hsiang-Yun; Lee, Byeongdu; Grubbs, Robert H

2017-11-28

Grafting density is an important structural parameter that exerts significant influences over the physical properties of architecturally complex polymers. In this report, the physical consequences of varying the grafting density (z) were studied in the context of block polymer self-assembly. Well-defined block polymers spanning the linear, comb, and bottlebrush regimes (0 ≤ z ≤ 1) were prepared via grafting-through ring-opening-metathesis polymerization. ω-Norbornenyl poly(d,l-lactide) and polystyrene macromonomers were copolymerized with discrete comonomers in different feed ratios, enabling precise control over both the grafting density and molecular weight. Small-angle X-ray scattering experiments demonstrate that these graft block polymers self-assemble into long-range-ordered lamellar structures. For 17 series of block polymers with variable z, the scaling of the lamellar period with the total backbone degree of polymerization (d* ∼ N bb α ) was studied. The scaling exponent α monotonically decreases with decreasing z and exhibits an apparent transition at z ≈ 0.2, suggesting significant changes in the chain conformations. Comparison of two block polymer systems, one that is strongly segregated for all z (System I) and one that experiences weak segregation at low z (System II), indicates that the observed trends are primarily caused by the polymer architectures, not segregation effects. A model is proposed in which the characteristic ratio (C ∞ ), a proxy for the backbone stiffness, scales with N bb as a function of the grafting density: C ∞ ∼ N bb f(z) . The scaling behavior disclosed herein provides valuable insights into conformational changes with grafting density, thus introducing opportunities for block polymer and material design.

Thermoresponsive Interplay of Water Insoluble Poly(2-alkyl-2-oxazolines Composition and Supramolecular Host–Guest Interactions

Directory of Open Access Journals (Sweden)

Victor R. de la Rosa

2015-04-01

Full Text Available A series of water insoluble poly[(2-ethyl-2-oxazoline-ran-(2-nonyl-2-oxazoline] amphiphilic copolymers was synthesized and their solubility properties in the presence of different supramolecular host molecules were investigated. The resulting polymer-cavitand assemblies exhibited a thermoresponsive behavior that could be modulated by variation of the copolymer composition and length. Interestingly, the large number of hydrophobic nonyl units across the polymer chain induced the formation of kinetically-trapped nanoparticles in solution. These nanoparticles further agglomerate into larger aggregates at a temperature that is dependent on the polymer composition and the cavitand type and concentration. The present research expands the understanding on the supramolecular interactions between water insoluble copolymers and supramolecular host molecules.

A ligand exchange strategy for one-pot sequential synthesis of (hyperbranched polyethylene)-b-(linear polyketone) block polymers.

Science.gov (United States)

Zhang, Zhichao; Ye, Zhibin

2012-08-18

Upon the addition of an equimolar amount of 2,2'-bipyridine, a cationic Pd-diimine complex capable of facilitating "living" ethylene polymerization is switched to catalyze "living" alternating copolymerization of 4-tertbutylstyrene and CO. This unique chemistry is thus employed to synthesize a range of well-defined treelike (hyperbranched polyethylene)-b-(linear polyketone) block polymers.

Free-standing thermo-responsive nanoporous membranes from high molecular weight PS-PNIPAM block copolymers synthesized via RAFT polymerization

NARCIS (Netherlands)

Cetintas, Merve; de Grooth, Joris; Hofman, Anton H.; van der Kooij, Hanne M.; Loos, Katja; de Vos, Wiebe Matthijs; Kamperman, Marleen

2017-01-01

The incorporation of stimuli-responsive pores in nanoporous membranes is a promising approach to facilitate the cleaning process of the membranes. Here we present fully reversible thermo-responsive nanoporous membranes fabricated by self-assembly and non-solvent induced phase separation (SNIPS) of

Di-block co-polymer derived nanoporous polymer liquid core waveguides

DEFF Research Database (Denmark)

Christiansen, Mads Brøkner; Gopalakrishnan, Nimi; Sagar, Kaushal Shashikant

2010-01-01

pores. When the PDMS is etched, the hydrophobic PB is left with a porosity of 44%. The polymer is subsequently UV exposed through a shadow mask. This renders the exposed part hydrophilic, making it possible for water to infiltrate these areas. Water infiltration raises the refractive index, thus forming...

Synthesis and Characterization of Smart Block Copolymers for Biomineralization and Biomedical Applications

Energy Technology Data Exchange (ETDEWEB)

Kanapathipillai, Mathumai [Iowa State Univ., Ames, IA (United States)

2008-01-01

moieties depends on the pH of the solution. Polymers with polyzwitterions, anions and cations have been shown to exhibit pH responsive self assembly. Other stimuli responsive polymers include glucose sensitive polymers, calcium ion-sensitive polymers and so on. Progress in living radical polymerization (LRP) methods [10] has made it possible for the facile synthesis of these block copolymer systems with controlled molecular weights and well defined architectures. The overall theme of this work is to develop novel smart block copolymers for biomineralization and biomedical applications. Synthesis and characterization of self-assembling thermoreversible ionic block copolymers as templates in biomimetic nanocomposite synthesis using a bottom-up approach is a novel contribution in this respect. Further, we have extended these families of copolymers to include block copolymer-peptide conjugates to enhance biological specificity. Future directions on this work will focus on enhancing the polymer templating properties for biomineralization by expanding the family of block copolymers with organic polypeptides and biological polypeptide scaffolds as well as a detailed understanding of the polymer-inorganic nanocomposites at the molecular level using small angle scattering analysis. Glucose responsive polymer hydrogels for drug delivery, polymer-ligand conjugates for non-viral therapy and thermoresponsive injectable photocrosslinkable hydrogels for posttraumatic arthritis cartilage healing are other applications of these novel copolymers synthesized in our work.

Multifunctional triblock co-polymer mP3/4HB-b-PEG-b-lPEI for efficient intracellular siRNA delivery and gene silencing.

Science.gov (United States)

Zhou, Li; Chen, Zhifei; Wang, Feifei; Yang, Xiuqun; Zhang, Biliang

2013-04-01

A non-viral siRNA carrier composed of mono-methoxy-poly (3-hydroxybutyrate-co-4-hydroxybutyrate)-block-polyethylene glycol-block-linear polyethyleneimine (mP3/4HB-b-PEG-b-lPEI) was synthesized using 1800 Da linear polyethyleneimine and evaluated for siRNA delivery. Our study demonstrated that siRNA could be efficiently combined with mP3/4HB-b-PEG-b-lPEI (mAG) co-polymer and was protected from nuclease degradation. The combined siRNA were released from the complexes easily under heparin competition. The particle size of the mAG/siRNA complexes was 158 nm, with a ζ-potential of around 28 mV. Atomic force microscopy images displayed spherical and homogeneously distributed complexes. The mAG block co-polymer displayed low cytotoxicity and efficient cellular uptake of Cy3-siRNA in A549 cells by flow cytometry and confocal microscopy. In vitro transfection efficiency of the block co-polymer was assessed using siRNA against luciferase in cultured A549-Luc, HeLa-Luc, HLF-Luc, A375-Luc and MCF-7-Luc cells. A higher transfection efficiency and lower cytotoxicity was obtained by mAG block co-polymer in five cell lines. Furthermore, a remarkable improvement in luciferase gene silencing efficiency of the mAG complex (up to 90-95%) over that of Lipofectamine™ 2000 (70-82%) was observed in HLF-Luc and A375-Luc cells. Additionally, a mAG/p65-siRNA complex also showed a better capability than Lipofectamine™ 2000/p65-siRNA complex to drastically reduce the p65 mRNA level down to 10-16% in HeLa, U251 and HUVEC cells at an N/P ratio of 70. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Small molecule-guided thermoresponsive supramolecular assemblies

KAUST Repository

Rancatore, Benjamin J.

2012-10-23

Small organic molecules with strong intermolecular interactions have a wide range of desirable optical and electronic properties and rich phase behaviors. Incorporating them into block copolymer (BCP)-based supramolecules opens new routes to generate functional responsive materials. Using oligothiophene- containing supramolecules, we present systematic studies of critical thermodynamic parameters and kinetic pathway that govern the coassemblies of BCP and strongly interacting small molecules. A number of potentially useful morphologies for optoelectronic materials, including a nanoscopic network of oligothiophene and nanoscopic crystalline lamellae, were obtained by varying the assembly pathway. Hierarchical coassemblies of oligothiophene and BCP, rather than macrophase separation, can be obtained. Crystallization of the oligothiophene not only induces chain stretching of the BCP block the oligothiophene is hydrogen bonded to but also changes the conformation of the other BCP coil block. This leads to an over 70% change in the BCP periodicity (e.g., from 31 to 53 nm) as the oligothiophene changes from a melt to a crystalline state, which provides access to a large BCP periodicity using fairly low molecular weight BCP. The present studies have demonstrated the experimental feasibility of generating thermoresponsive materials that convert heat into mechanical energy. Incorporating strongly interacting small molecules into BCP supramolecules effectively increases the BCP periodicity and may also open new opportunities to tailor their optical properties without the need for high molecular weight BCP. © 2012 American Chemical Society.

Small molecule-guided thermoresponsive supramolecular assemblies

KAUST Repository

Rancatore, Benjamin J.; Mauldin, Clayton E.; Frechet, Jean; Xu, Ting

2012-01-01

Small organic molecules with strong intermolecular interactions have a wide range of desirable optical and electronic properties and rich phase behaviors. Incorporating them into block copolymer (BCP)-based supramolecules opens new routes to generate functional responsive materials. Using oligothiophene- containing supramolecules, we present systematic studies of critical thermodynamic parameters and kinetic pathway that govern the coassemblies of BCP and strongly interacting small molecules. A number of potentially useful morphologies for optoelectronic materials, including a nanoscopic network of oligothiophene and nanoscopic crystalline lamellae, were obtained by varying the assembly pathway. Hierarchical coassemblies of oligothiophene and BCP, rather than macrophase separation, can be obtained. Crystallization of the oligothiophene not only induces chain stretching of the BCP block the oligothiophene is hydrogen bonded to but also changes the conformation of the other BCP coil block. This leads to an over 70% change in the BCP periodicity (e.g., from 31 to 53 nm) as the oligothiophene changes from a melt to a crystalline state, which provides access to a large BCP periodicity using fairly low molecular weight BCP. The present studies have demonstrated the experimental feasibility of generating thermoresponsive materials that convert heat into mechanical energy. Incorporating strongly interacting small molecules into BCP supramolecules effectively increases the BCP periodicity and may also open new opportunities to tailor their optical properties without the need for high molecular weight BCP. © 2012 American Chemical Society.

Batteries: Polymers switch for safety

Energy Technology Data Exchange (ETDEWEB)

Amine, Khalil

2016-01-11

Ensuring safety during operation is a major issue in the development of lithium-ion batteries. Coating the electrode current collector with thermoresponsive polymer composites is now shown to rapidly shut the battery down when it overheats, and to quickly resume its function when normal operating conditions return

Dialkoxybithiazole: a new building block for head-to-head polymer semiconductors.

Science.gov (United States)

Guo, Xugang; Quinn, Jordan; Chen, Zhihua; Usta, Hakan; Zheng, Yan; Xia, Yu; Hennek, Jonathan W; Ortiz, Rocío Ponce; Marks, Tobin J; Facchetti, Antonio

2013-02-06

Polymer semiconductors have received great attention for organic electronics due to the low fabrication cost offered by solution-based printing techniques. To enable the desired solubility/processability and carrier mobility, polymers are functionalized with hydrocarbon chains by strategically manipulating the alkylation patterns. Note that head-to-head (HH) linkages have traditionally been avoided because the induced backbone torsion leads to poor π-π overlap and amorphous film microstructures, and hence to low carrier mobilities. We report here the synthesis of a new building block for HH linkages, 4,4'-dialkoxy-5,5'-bithiazole (BTzOR), and its incorporation into polymers for high performance organic thin-film transistors. The small oxygen van der Waals radius and intramolecular S(thiazolyl)···O(alkoxy) attraction promote HH macromolecular architectures with extensive π-conjugation, low bandgaps (1.40-1.63 eV), and high crystallinity. In comparison to previously reported 3,3'-dialkoxy-2,2'-bithiophene (BTOR), BTzOR is a promising building block in view of thiazole geometric and electronic properties: (a) replacing (thiophene)C-H with (thiazole)N reduces steric encumbrance in -BTzOR-Ar- dyads by eliminating repulsive C-H···H-C interactions with neighboring arene units, thereby enhancing π-π overlap and film crystallinity; and (b) thiazole electron-deficiency compensates alkoxy electron-donating characteristics, thereby lowering the BTzOR polymer HOMO versus that of the BTOR analogues. Thus, the new BTzOR polymers show substantial hole mobilities (0.06-0.25 cm(2)/(V s)) in organic thin-film transistors, as well as enhanced I(on):I(off) ratios and greater ambient stability than the BTOR analogues. These geometric and electronic properties make BTzOR a promising building block for new classes of polymer semiconductors, and the synthetic route to BTzOR reported here should be adaptable to many other bithiazole-based building blocks.

Simulation Studies of LCST-like Phase Transitions in Elastin-like Polypeptides (ELPs) and Conjugates of ELP with Rigid Macromolecules

Science.gov (United States)

Condon, Joshua; Martin, Tyler; Jayaraman, Arthi

We use atomistic (AA) and coarse-grained (CG) molecular dynamics simulations to elucidate the thermodynamic driving forces governing lower critical solution temperature (LCST)-like phase transition exhibited by elastin-like peptides (ELPs) and conjugates of ELP with other macromolecules. In the AA simulations, we study ELP oligomers in explicit water, and mark the transition as the temperature at which they undergo a change in ``hydration'' state. While AA simulations are restricted to small systems of short ELPs and do not capture the chain aggregation observed in experiments of ELPs, they guide the phenomenological CG model development by highlighting the solvent induced polymer-polymer effective interactions with changing temperature. In the CG simulations, we capture the LCST polymer aggregation by increasing polymer-polymer effective attractive interactions in an implicit solvent. We examine the impact of conjugating a block of LCST polymer to another rigid unresponsive macromolecular block on the LCST-like transition. We find that when multiple LCST polymers are conjugated to a rigid polymer block, increased crowding of the LCST polymers shifts the onset of chain aggregation to smaller effective polymer-polymer attraction compared to the free LCST polymers. These simulation results provide guidance on the design of conjugated bio-mimetic thermoresponsive materials, and shape the fundamental understanding of the impact of polymer crowding on phase behavior in thermoresponsive LCST polymer systems.

Microbial production of building block chemicals and polymers.

Science.gov (United States)

Lee, Jeong Wook; Kim, Hyun Uk; Choi, Sol; Yi, Jongho; Lee, Sang Yup

2011-12-01

Owing to our increasing concerns on the environment, climate change, and limited natural resources, there has recently been considerable effort exerted to produce chemicals and materials from renewable biomass. Polymers we use everyday can also be produced either by direct fermentation or by polymerization of monomers that are produced by fermentation. Recent advances in metabolic engineering combined with systems biology and synthetic biology are allowing us to more systematically develop superior strains and bioprocesses for the efficient production of polymers and monomers. Here, we review recent trends in microbial production of building block chemicals that can be subsequently used for the synthesis of polymers. Also, recent successful cases of direct one-step production of polymers are reviewed. General strategies for the production of natural and unnatural platform chemicals are described together with representative examples. Copyright © 2011 Elsevier Ltd. All rights reserved.

Nanoporous capsules of block co-polymers of [(MeO-PEG-NH)-b-(L-GluA)]-PCL for the controlled release of anticancer drugs for therapeutic applications

Science.gov (United States)

Amgoth, Chander; Dharmapuri, Gangappa; Kalle, Arunasree M.; Paik, Pradip

2016-03-01

Herein, new nanoporous capsules of the block co-polymers of MeO-PEG-NH-(L-GluA)10 and polycaprolactone (PCL) have been synthesized through a surfactant-free cost-effective self-assembled soft-templating approach for the controlled release of drugs and for therapeutic applications. The nanoporous polymer capsules are designed to be biocompatible and are capable of encapsulating anticancer drugs (e.g., doxorubicin hydrochloride (DOX) and imatinib mesylate (ITM)) with a high extent (˜279 and ˜480 ng μg-1, respectively). We have developed a nanoformulation of porous MeO-PEG-NH-(L-GluA)10-PCL capsules with DOX and ITM. The porous polymer nanoformulations have been programmed in terms of the release of anticancer drugs with a desired dose to treat the leukemia (K562) and human carcinoma cells (HepG2) in vitro and show promising IC50 values with a very high mortality of cancer cells (up to ˜96.6%). Our nanoformulation arrests the cell divisions due to ‘cellular scenescence’ and kills the cancer cells specifically. The present findings could enrich the effectiveness of idiosyncratic nanoporous polymer capsules for use in various other nanomedicinal and biomedical applications, such as for killing cancer cells, immune therapy, and gene delivery.

Nanoporous capsules of block co-polymers of [(MeO-PEG-NH)-b-(L-GluA)]-PCL for the controlled release of anticancer drugs for therapeutic applications

International Nuclear Information System (INIS)

Amgoth, Chander; Paik, Pradip; Dharmapuri, Gangappa; Kalle, Arunasree M

2016-01-01

Herein, new nanoporous capsules of the block co-polymers of MeO-PEG-NH-(L-GluA) 10 and polycaprolactone (PCL) have been synthesized through a surfactant-free cost-effective self-assembled soft-templating approach for the controlled release of drugs and for therapeutic applications. The nanoporous polymer capsules are designed to be biocompatible and are capable of encapsulating anticancer drugs (e.g., doxorubicin hydrochloride (DOX) and imatinib mesylate (ITM)) with a high extent (∼279 and ∼480 ng μg −1 , respectively). We have developed a nanoformulation of porous MeO-PEG-NH-(L-GluA) 10 -PCL capsules with DOX and ITM. The porous polymer nanoformulations have been programmed in terms of the release of anticancer drugs with a desired dose to treat the leukemia (K562) and human carcinoma cells (HepG2) in vitro and show promising IC 50 values with a very high mortality of cancer cells (up to ∼96.6%). Our nanoformulation arrests the cell divisions due to ‘cellular scenescence’ and kills the cancer cells specifically. The present findings could enrich the effectiveness of idiosyncratic nanoporous polymer capsules for use in various other nanomedicinal and biomedical applications, such as for killing cancer cells, immune therapy, and gene delivery. (paper)

Porous Organic Polymers for CO2 Capture

KAUST Repository

Teng, Baiyang

2013-05-01

Carbon dioxide (CO2) has long been regarded as the major greenhouse gas, which leads to numerous negative effects on global environment. The capture and separation of CO2 by selective adsorption using porous materials proves to be an effective way to reduce the emission of CO2 to atmosphere. Porous organic polymers (POPs) are promising candidates for this application due to their readily tunable textual properties and surface functionalities. The objective of this thesis work is to develop new POPs with high CO2 adsorption capacities and CO2/N2 selectivities for post-combustion effluent (e.g. flue gas) treatment. We will also exploit the correlation between the CO2 capture performance of POPs and their textual properties/functionalities. Chapters Two focuses on the study of a group of porous phenolic-aldehyde polymers (PPAPs) synthesized by a catalyst-free method, the CO2 capture capacities of these PPAPs exceed 2.0 mmol/g at 298 K and 1 bar, while keeping CO2/N2 selectivity of more than 30 at the same time. Chapter Three reports the gas adsorption results of different hyper-cross-linked polymers (HCPs), which indicate that heterocyclo aromatic monomers can greatly enhance polymers’ CO2/N2 selectivities, and the N-H bond is proved to the active CO2 adsorption center in the N-contained (e.g. pyrrole) HCPs, which possess the highest selectivities of more than 40 at 273 K when compared with other HCPs. Chapter Four emphasizes on the chemical modification of a new designed polymer of intrinsic microporosity (PIM) with high CO2/N2 selectivity (50 at 273 K), whose experimental repeatability and chemical stability prove excellent. In Chapter Five, we demonstrate an improvement of both CO2 capture capacity and CO2/N2 selectivity by doping alkali metal ions into azo-polymers, which leads a promising method to the design of new porous organic polymers.

Self-cleaned electrochemical protein imprinting biosensor basing on a thermo-responsive memory hydrogel.

Science.gov (United States)

Wei, Yubo; Zeng, Qiang; Hu, Qiong; Wang, Min; Tao, Jia; Wang, Lishi

2018-01-15

Herein, the self-cleaned electrochemical protein imprinting biosensor basing on a thermo-responsive memory hydrogel was constructed on a glassy carbon electrode (GCE) with a free radical polymerization method. Combining the advantages of thermo-responsive molecular imprinted polymers and electrochemistry, the resulted biosensor presents a novel self-cleaned ability for bovine serum albumin (BSA) in aqueous media. As a temperature controlled gate, the hydrogel film undergoes the adsorption and desorption of BSA basing on a reversible structure change with the external temperature stimuli. In particular, these processes have been revealed by the response of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) of electroactive [Fe(CN) 6 ] 3-/4- . The results have been supported by the evidences of scanning electron microscopy (SEM) and contact angles measurements. Under the optimal conditions, a wide detection range from 0.02μmolL -1 to 10μmolL -1 with a detection limit of 0.012 μmolL -1 (S/N = 3) was obtained for BSA. This proposed BSA sensor also possesses high selectivity, excellent stability, acceptable recovery and good reproducibility in its practical applications. Copyright © 2017. Published by Elsevier B.V.

Polymers and block copolymers of fluorostyrenes by ATRP

DEFF Research Database (Denmark)

Hvilsted, Søren; Borkar, Sachin; Abildgaard, Lillian

2002-01-01

Fully or partly fluorinated polymers have many desirable and intriguing properties. In the framework of a larger program on design and control of new functional block copolymers we recently employed the Atom Transfer Radical Polymerization (ATRP) protocol on 2,3,4,5,6-pentafluorostyrene (FS). We...... materials based on 2,3,5,6-tetrafiuoro-4-methoxy-styrene (TFMS). TFMS homopolymers as well as diblock copolymers with FS are produced by ATRP. Both types of novel polymers were subsequently demethylated and different side chains introduced on the resulting hydroxy sites....

Self-Assembly of Block Copolymer Chains To Promote the Dispersion of Nanoparticles in Polymer Nanocomposites

Science.gov (United States)

2017-01-01

In this paper we adopt molecular dynamics simulations to study the amphiphilic AB block copolymer (BCP) mediated nanoparticle (NP) dispersion in polymer nanocomposites (PNCs), with the A-block being compatible with the NPs and the B-block being miscible with the polymer matrix. The effects of the number and components of BCP, as well as the interaction strength between A-block and NPs on the spatial organization of NPs, are explored. We find that the increase of the fraction of the A-block brings different dispersion effect to NPs than that of B-block. We also find that the best dispersion state of the NPs occurs in the case of a moderate interaction strength between the A-block and the NPs. Meanwhile, the stress–strain behavior is probed. Our simulation results verify that adopting BCP is an effective way to adjust the dispersion of NPs in the polymer matrix, further to manipulate the mechanical properties. PMID:28892620

Engineering cell factories for producing building block chemicals for bio-polymer synthesis.

Science.gov (United States)

Tsuge, Yota; Kawaguchi, Hideo; Sasaki, Kengo; Kondo, Akihiko

2016-01-21

Synthetic polymers are widely used in daily life. Due to increasing environmental concerns related to global warming and the depletion of oil reserves, the development of microbial-based fermentation processes for the production of polymer building block chemicals from renewable resources is desirable to replace current petroleum-based methods. To this end, strains that efficiently produce the target chemicals at high yields and productivity are needed. Recent advances in metabolic engineering have enabled the biosynthesis of polymer compounds at high yield and productivities by governing the carbon flux towards the target chemicals. Using these methods, microbial strains have been engineered to produce monomer chemicals for replacing traditional petroleum-derived aliphatic polymers. These developments also raise the possibility of microbial production of aromatic chemicals for synthesizing high-performance polymers with desirable properties, such as ultraviolet absorbance, high thermal resistance, and mechanical strength. In the present review, we summarize recent progress in metabolic engineering approaches to optimize microbial strains for producing building blocks to synthesize aliphatic and high-performance aromatic polymers.

Thermo-responsive magnetic liposomes for hyperthermia-triggered local drug delivery.

Science.gov (United States)

Dai, Min; Wu, Cong; Fang, Hong-Ming; Li, Li; Yan, Jia-Bao; Zeng, Dan-Lin; Zou, Tao

2017-06-01

We prepared and characterised thermo-responsive magnetic liposomes, which were designed to combine features of magnetic targeting and thermo-responsive control release for hyperthermia-triggered local drug delivery. The particle size and zeta-potential of the thermo-responsive magnetic ammonium bicarbonate (MagABC) liposomes were about 210 nm and -14 mV, respectively. The MagABC liposomes showed encapsulation efficiencies of about 15% and 82% for magnetic nanoparticles (mean crystallite size 12 nm) and doxorubicin (DOX), respectively. The morphology of the MagABC liposomes was visualised using transmission electron microscope (TEM). The MagABC liposomes showed desired thermo-responsive release. The MagABC liposomes, when physically targeted to tumour cells in culture by a permanent magnetic field yielded a substantial increase in intracellular accumulation of DOX as compared to non-magnetic ammonium bicarbonate (ABC) liposomes. This resulted in a parallel increase in cytotoxicity for DOX loaded MagABC liposomes over DOX loaded ABC liposomes in tumour cells.

Block copolymer self-assembly and co-assembly : shape function and application

NARCIS (Netherlands)

Li, F.

2009-01-01

Amphiphilic block copolymers can, in selective solvents such as water, assemble into various shapes and architectures. Among those, polymer vesicles, polymer micelles and polymer fibers are very popular structures in current nanotechnology. These objects each have their own particular properties and

Co-crystallization phase transformations in all π-conjugated block copolymers with different main-chain moieties.

Science.gov (United States)

Lee, Yi-Huan; Chen, Wei-Chih; Yang, Yi-Lung; Chiang, Chi-Ju; Yokozawa, Tsutomu; Dai, Chi-An

2014-05-21

Driven by molecular affinity and balance in the crystallization kinetics, the ability to co-crystallize dissimilar yet self-crystallizable blocks of a block copolymer (BCP) into a uniform domain may strongly affect its phase diagram. In this study, we synthesize a new series of crystalline and monodisperse all-π-conjugated poly(2,5-dihexyloxy-p-phenylene)-b-poly(3-(2-ethylhexyl)thiophene) (PPP-P3EHT) BCPs and investigate this multi-crystallization effect. Despite vastly different side-chain and main-chain structures, PPP and P3EHT blocks are able to co-crystallize into a single uniform domain comprising PPP and P3EHT main-chains with mutually interdigitated side-chains spaced in-between. With increasing P3EHT fraction, PPP-P3EHTs undergo sequential phase transitions and form hierarchical superstructures including predominately PPP nanofibrils, co-crystalline nanofibrils, a bilayer co-crystalline/pure P3EHT lamellar structure, a microphase-separated bilayer PPP-P3EHT lamellar structure, and finally P3EHT nanofibrils. In particular, the presence of the new co-crystalline lamellar structure is the manifestation of the interaction balance between self-crystallization and co-crystallization of the dissimilar polymers on the resulting nanostructure of the BCP. The current study demonstrates the co-crystallization nature of all-conjugated BCPs with different main-chain moieties and may provide new guidelines for the organization of π-conjugated BCPs for future optoelectronic applications.

Exploring Poly(ethylene glycol-Polyzwitterion Diblock Copolymers as Biocompatible Smart Macrosurfactants Featuring UCST-Phase Behavior in Normal Saline Solution

Directory of Open Access Journals (Sweden)

Noverra M. Nizardo

2018-03-01

Full Text Available Nonionic-zwitterionic diblock copolymers are designed to feature a coil-to-globule collapse transition with an upper critical solution temperature (UCST in aqueous media, including physiological saline solution. The block copolymers that combine presumably highly biocompatible blocks are synthesized by chain extension of a poly(ethylene glycol (PEG macroinitiator via atom transfer radical polymerization (ATRP of sulfobetaine and sulfabetaine methacrylates. Their thermoresponsive behavior is studied by variable temperature turbidimetry and 1H NMR spectroscopy. While the polymers with polysulfobetaine blocks exhibit phase transitions in the physiologically interesting window of 30–50 °C only in pure aqueous solution, the polymers bearing polysulfabetaine blocks enabled phase transitions only in physiological saline solution. By copolymerizing a pair of structurally closely related sulfo- and sulfabetaine monomers, thermoresponsive behavior can be implemented in aqueous solutions of both low and high salinity. Surprisingly, the presence of the PEG blocks can affect the UCST-transitions of the polyzwitterions notably. In specific cases, this results in “schizophrenic” thermoresponsive behavior displaying simultaneously an UCST and an LCST (lower critical solution temperature transition. Exploratory experiments on the UCST-transition triggered the encapsulation and release of various solvatochromic fluorescent dyes as model “cargos” failed, apparently due to the poor affinity even of charged organic compounds to the collapsed state of the polyzwitterions.

Artificial muscles based on liquid crystal elastomers.

Science.gov (United States)

Li, Min-Hui; Keller, Patrick

2006-10-15

This paper presents our results on liquid crystal (LC) elastomers as artificial muscle, based on the ideas proposed by de Gennes. In the theoretical model, the material consists of a repeated series of main-chain nematic LC polymer blocks, N, and conventional rubber blocks, R, based on the lamellar phase of a triblock copolymer RNR. The motor for the contraction is the reversible macromolecular shape change of the chain, from stretched to spherical, that occurs at the nematic-to-isotropic phase transition in the main-chain nematic LC polymers. We first developed a new kind of muscle-like material based on a network of side-on nematic LC homopolymers. Side-on LC polymers were used instead of main-chain LC polymers for synthetic reasons. The first example of these materials was thermo-responsive, with a typical contraction of around 35-45% and a generated force of around 210 kPa. Subsequently, a photo-responsive material was developed, with a fast photochemically induced contraction of around 20%, triggered by UV light. We then succeeded in preparing a thermo-responsive artificial muscle, RNR, with lamellar structure, using a side-on nematic LC polymer as N block.Micrometre-sized artificial muscles were also prepared. This paper illustrates the bottom-up design of stimuli-responsive materials, in which the overall material response reflects the individual macromolecular response, using LC polymer as building block.

Thinking Outside the 'Block': Alternative Polymer Compositions for Micellar Drug Delivery.

Science.gov (United States)

Jones, Marie-Christine

2015-01-01

With a number of formulations currently in clinical trials, the interest in polymer micelles as drug carriers in unlikely to subside. Historically, linear diblock copolymers have been used as the building blocks for micelle preparation. Yet, recent advances in polymer chemistry have meant that a wider variety of polymer architectures and compositions have become available and been trialed for pharmaceutical applications. This mini-review aims to provide an overview of recent, exciting developments in triblock, graft and hyperbranched polymer chemistries that may change the way polymeric micelles drug formulations are prepared.

Thermoresponsive latexes for fragrance encapsulation and release.

Science.gov (United States)

Popadyuk, N; Popadyuk, A; Kohut, A; Voronov, A

2016-04-01

To synthesize cross-linked latex particles protecting the encapsulated fragrance at ambient temperatures and facilitating the release of cargo at the temperature of the surface of the skin that varies in different regions of the body between 33.5 and 36.9°C. Poly(stearyl acrylate) (PSA), a polymer with long crystallizable alkyl side chains (undergoes order-disorder transitions at 45°C), was chosen as the main component of the polymer particles. As a result, new thermoresponsive polymer particles for fragrance encapsulation were synthesized and characterized, including assessing the performance of particles in triggered release by elevated temperature. To obtain network domains of various crystallinity, stearyl acrylate was copolymerized with dipropylene glycol acrylate caprylate (DGAC) (comonomer) in the presence of a dipropylene glycol diacrylate sebacate (cross-linker) using the miniemulsion process. Comonomers and a cross-linker were mixed directly in a fragrance during polymerization. Fragrance release was evaluated at 25, 31, 35 and 39°C to demonstrate a new material potential in personal/health care skin-related applications. Particles protect the fragrance from evaporation at 25°C. The fragrance release rate gradually increases at 31, 35 and 39°C. Two slopes were found on release plots. The first slope corresponds to a rapid fragrance release. The second slope indicates a subsequent reduction in the release rate. Crystalline-to-amorphous transition of PSA triggers the release of fragrances from cross-linked latex particles at elevated temperatures. The presence of the encapsulated fragrance, as well as the inclusion of amorphous fragments in the polymer network, reduces the particle crystallinity and enhances the release. Release profiles can be tuned by temperature and controlled by the amount of loaded fragrance and the ratio of comonomers in the feed mixture. © 2015 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Co-polymer Films for Sensors

Science.gov (United States)

Ryan, Margaret A. (Inventor); Jewell, April D. (Inventor); Taylor, Charles (Inventor); Yen, Shiao-Pin S. (Inventor); Kisor, Adam (Inventor); Manatt, Kenneth S. (Inventor); Blanco, Mario (Inventor); Goddard, William A. (Inventor); Homer, Margie L. (Inventor); Shevade, Abhijit V. (Inventor)

2012-01-01

Embodiments include a sensor comprising a co-polymer, the co-polymer comprising a first monomer and a second monomer. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is polystyrene and the second monomer is poly-2-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium benzylamine chloride. Other embodiments are described and claimed.

An invention of thermo-responsive polymer surface, yielding cell sheet based regenerative therapies in cardiology and ophthalmology

Directory of Open Access Journals (Sweden)

Sawa Y

2015-12-01

Full Text Available The Invention: In vitro cell culture methodologies provide a conducive environment for the cells taken out of their native environment to grow and proliferate in a non-physiological environment, the culture dish. Research experiments have been focusing on various criteria for assessing how far it is possible to recapitulate the native extra-cellular environment in vitro. Scaffolds, culture media, growth factors and cell surface modified culture dishes are some of the components that provide a conducive environment for in vitro cell culture. Cells that are grown in culture dishes using conventional methodologies are usually detached using enzymatic treatment with Trypsin, Collagenase etc [1], to be transplanted when it comes to a clinical or experimental application. Such enzymes used in separating the cells may have some damaging effects to the cell membranes which might impair the cell function [1]. However, cells if can be grown as a monolayer and be harvested as a contiguous cell sheet, it is considered suitable for transplantation in certain specific applications. In addition to that, if enzymatic digestion which has some detrimental effects on the detached cells could be avoided, that is an added advantage. The work by Prof. Okano and team from the Tokyo Women's Medical University, Japan, on thermo-responsive polymer surfaces has yielded a solution which has both the advantages viz., detachability of cells grown as a monolayer in the form of a cell sheet, that too without the use of enzymes. Their research into biomaterials for more than two decades has yielded a thermo-responsive polymer, the poly(N-isopropylacrylamide (PIPAAm [1] coated culture dish for cell sheet engineering. In their technology, PIPAAm is polymerized and grafted to tissue culture polystyrene (TCPS dishes. Cells have been found to grow confluent on PIPAAm-TCPS at 37 °C. Once confluent as a monolayer, by merely reducing the temperature of the PIPAAm-TCPS to 20 °C, it

Asymmetric PS-block-(PS-co-PB)-block-PS block copolymers: morphology formation and deformation behaviour

International Nuclear Information System (INIS)

Adhikari, Rameshwar; Huy, Trinh An; Buschnakowski, Matthias; Michler, Goerg H; Knoll, Konrad

2004-01-01

Morphology formation and deformation behaviour of asymmetric styrene/butadiene triblock copolymers (total polystyrene (PS) content ∼70%) consisting of PS outer blocks held apart by a styrene-co-butadiene random copolymer block (PS-co-PB) each were investigated. The techniques used were differential scanning calorimetry, transmission electron microscopy, uniaxial tensile testing and Fourier-transform infrared spectroscopy. A significant shift of the phase behaviour relative to that of a neat symmetric triblock copolymer was observed, which can be attributed to the asymmetric architecture and the presence of PS-co-PB as a soft block. The mechanical properties and the microdeformation phenomena were mainly controlled by the nature of their solid-state morphology. Independent of morphology type, the soft phase was found to deform to a significantly higher degree of orientation when compared with the hard phase

Conjugated Polymer Chains Confined in Vertical Nanocylinders of a Block-Copolymer Film: Preparation, Characterization, and Optoelectronic Function

KAUST Repository

Dong, Ban Xuan; Honmou, Yoshihiro; Komiyama, Hideaki; Furumaki, Shu; Iyoda, Tomokazu; Vacha, Martin

2013-01-01

Hybrid materials composed of phase-separated block copolymer films and conjugated polymers of the phenylenevinylene family (PPV) are prepared. The PPV chains are embedded in vertical cylinders of nanometer diameter in the block-copolymer films. The cylinders span continuously the whole film thickness of 70 nm. Incorporation of the PPV chains into the one-dimensional cylinders leads to modified photoluminescence spectra and to large absorption anisotropy. The hybrid films show electroluminescence from the PPV chains in a simple light-emitting device at minute doping concentrations, and also exhibit a factor of 19 increase in electron transport efficiency along the single PPV chains. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Conjugated Polymer Chains Confined in Vertical Nanocylinders of a Block-Copolymer Film: Preparation, Characterization, and Optoelectronic Function

KAUST Repository

Dong, Ban Xuan

2013-01-15

Hybrid materials composed of phase-separated block copolymer films and conjugated polymers of the phenylenevinylene family (PPV) are prepared. The PPV chains are embedded in vertical cylinders of nanometer diameter in the block-copolymer films. The cylinders span continuously the whole film thickness of 70 nm. Incorporation of the PPV chains into the one-dimensional cylinders leads to modified photoluminescence spectra and to large absorption anisotropy. The hybrid films show electroluminescence from the PPV chains in a simple light-emitting device at minute doping concentrations, and also exhibit a factor of 19 increase in electron transport efficiency along the single PPV chains. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Blocking effect and numerical study of polymer particles dispersion flooding in heterogeneous reservoir

Science.gov (United States)

Zhu, Weiyao; Li, Jianhui; Lou, Yu

2018-02-01

Polymer flooding has become an effective way to improve the sweep efficiency in many oil fields. Many scholars have carried out a lot of researches on the mechanism of polymer flooding. In this paper, the effect of polymer on seepage is analyzed. The blocking effect of polymer particles was studied experimentally, and the residual resistance coefficient (RRF) were used to represent the blocking effect. We also build a mathematical model for heterogeneous concentration distribution of polymer particles. Furthermore, the effects of polymer particles on reservoir permeability, fluid viscosity and relative permeability are considered, and a two-phase flow model of oil and polymer particles is established. In addition, the model was tested in the heterogeneous stratum model, and three influencing factors, such as particle concentration, injection volume and PPD (short for polymer particle dispersion) injection time, were analyzed. Simulation results show that PPD can effectively improve sweep efficiency and especially improve oil recovery of low permeability layer. Oil recovery increases with the increase of particle concentration, but oil recovery increase rate gradually decreases with that. The greater the injected amount of PPD, the greater oil recovery and the smaller oil recovery increase rate. And there is an optimal timing to inject PPD for specific reservoir.

Controlled release of bupivacaine using hybrid thermoresponsive nanoparticles activated via photothermal heating.

Science.gov (United States)

Alejo, Teresa; Andreu, Vanesa; Mendoza, Gracia; Sebastian, Victor; Arruebo, Manuel

2018-08-01

Near-infrared (NIR) responsive nanoparticles are of great interest in the biomedical field as antennas for photothermal therapy and also as triggers for on-demand drug delivery. The present work reports the preparation of hollow gold nanoparticles (HGNPs) with plasmonic absorption in the NIR region covalently bound to a thermoresponsive polymeric shell that can be used as an on-demand drug delivery system for the release of analgesic drugs. The photothermal heating induced by the nanoparticles is able to produce the collapse of the polymeric shell thus generating the release of the local anesthetic bupivacaine in a spatiotemporally controlled way. Those HGNPs contain a 10 wt.% of polymer and present excellent reversible heating under NIR light excitation. Bupivacaine released at physiological temperature (37 °C) showed a pseudo-zero order release that could be spatiotemporally modified on-demand after applying several pulses of light/temperature above and below the lower critical solution temperature (LCST) of the polymeric shell. Furthermore, the nanomaterials obtained did not displayed detrimental effects on four mammalian cell lines at doses up to 0.2 mg/mL. From the results obtained it can be concluded than this type of hybrid thermoresponsive nanoparticle can be used as an externally activated on-demand drug delivery system. Copyright © 2018 Elsevier Inc. All rights reserved.

Spectral Signatures of Polarons in Conjugated Co-polymers

NARCIS (Netherlands)

Wiebeler, Christian; Tautz, Raphael; Feldmann, Jochen; von Hauff, Elizabeth; Da Como, Enrico; Schumacher, Stefan

2013-01-01

We study electronic and optical properties of the low-bandgap co-polymer PCPDT-BT (poly-cyclopentadithiophene-co-benzothiadiazole) and compare it with the corresponding homo-polymer PCPDT (poly-cyclopentadithiophene). We investigate the linear absorptivity in these systems for neutral molecules and

Oligomers and Polymers Based on Pentacene Building Blocks

Science.gov (United States)

Lehnherr, Dan; Tykwinski, Rik R.

2010-01-01

Functionalized pentacene derivatives continue to provide unique materials for organic semiconductor applications. Although oligomers and polymers based on pentacene building blocks remain quite rare, recent synthetic achievements have provided a number of examples with varied structural motifs. This review highlights recent work in this area and, when possible, contrasts the properties of defined-length pentacene oligomers to those of mono- and polymeric systems.

Oligomers and Polymers Based on Pentacene Building Blocks

Directory of Open Access Journals (Sweden)

Dan Lehnherr

2010-04-01

Full Text Available Functionalized pentacene derivatives continue to provide unique materials for organic semiconductor applications. Although oligomers and polymers based on pentacene building blocks remain quite rare, recent synthetic achievements have provided a number of examples with varied structural motifs. This review highlights recent work in this area and, when possible, contrasts the properties of defined-length pentacene oligomers to those of mono- and polymeric systems.

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

Science.gov (United States)

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

2013-02-07

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

Precise Control over the Rheological Behavior of Associating Stimuli-Responsive Block Copolymer Gels

Directory of Open Access Journals (Sweden)

Jérémy Brassinne

2015-12-01

Full Text Available “Smart” materials have considerably evolved over the last few years for specific applications. They rely on intelligent macromolecules or (supra-molecular motifs to adapt their structure and properties in response to external triggers. Here, a supramolecular stimuli-responsive polymer gel is constructed from heterotelechelic double hydrophilic block copolymers that incorporate thermo-responsive sequences. These macromolecular building units are synthesized via a three-step controlled radical copolymerization and then hierarchically assembled to yield coordination micellar hydrogels. The dynamic mechanical properties of this particular class of materials are studied in shear flow and finely tuned via temperature changes. Notably, rheological experiments show that structurally reinforcing the micellar network nodes leads to precise tuning of the viscoelastic response and yield behavior of the material. Hence, they constitute promising candidates for specific applications, such as mechano-sensors.

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.

Study on properties and testing methods of thermo-responsive cementing system for well cementing in heavy oil thermal recovery

Science.gov (United States)

Li, Lianjiang

2017-08-01

In this paper, thermo-responsive cement slurry system were being developed, the properties of conventional cement slurry, compressive strength high temperature of cement sheath, mechanical properties of cement sheath and thermal properties of cement sheath were being tested. Results were being used and simulated by Well-Life Software, Thermo-responsive cement slurry system can meet the requirements of heavy oil thermal recovery production. Mechanical and thermal properties of thermo-responsive cement sheath were being tested. Tensile fracture energy of the thermo-responsive cement sheath is larger than conventional cement. The heat absorption capacity of conventional cement sheath is larger than that of thermo-responsive cement sheath, this means more heat is needed for the unit mass once increasing 1.0 °C, which also indicates that thermo-responsive cement own good heat insulating and preservation effects. The heat conductivity coefficient and thermal expansion coefficient of thermo-responsive cement is less than and conventional cement, this means that thermo-responsive cement have good heat preservation and insulation effects with good thermal expansion stabilities.

Nitrogen-containing polymers as a platform for CO2 electroreduction.

Science.gov (United States)

Ponnurangam, Sathish; Chernyshova, Irina V; Somasundaran, Ponisseril

2017-06-01

Heterogeneous electroreduction of CO 2 has received considerable attention in the past decade. However, none of the earlier reviews has been dedicated to nitrogen-containing polymers (N-polymers) as an emerging platform for conversion of CO 2 to industrially useful chemicals. The term 'platform' is used here to underscore that the role of N-polymers is not only to serve as direct catalysts (through loaded metals) but also as co-catalysts/promoters and stabilizing agents. This review covers the current state, advantages, challenges, and prospects of the application of N-polymer-metal composites, also referred as polymer functionalized, coated, or modified electrodes, as well as functional hybrid materials, for the electrocatalytic conversion of CO 2 . It briefly surveys the efficiencies of the N-polymer-metal electrodes already used for this application, methods of their fabrication, and proposed mechanisms of their catalytic activities. Copyright © 2016 Elsevier B.V. All rights reserved.

Thermoresponsive Poly(2-oxazine)s

NARCIS (Netherlands)

Bloksma, M.M.; Paulus, R.M.; Kuringen, van H.P.C.; Woerdt, van der F.; Lambermont - Thijs, H.M.L.; Schubert, U.S.; Hoogenboom, R.

2012-01-01

The monomers 2-methyl-2-oxazine (MeOZI), 2-ethyl-2-oxazine (EtOZI), and 2-n-propyl-2-oxazine (nPropOZI) were synthesized and polymerized via the living cationic ring-opening polymerization (CROP) under microwave-assisted conditions. pEtOZI and pnPropOZI were found to be thermoresponsive, exhibiting

21 CFR 177.1020 - Acrylonitrile/butadiene/sty-rene co-polymer.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Acrylonitrile/butadiene/sty-rene co-polymer. 177... SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances.../butadiene/sty-rene co-polymer. Acrylonitrile/butadiene/styrene copolymer identified in this section may be...

Multi-stimulus-responsive shape-memory polymer nanocomposite network cross-linked by cellulose nanocrystals.

Science.gov (United States)

Liu, Ye; Li, Ying; Yang, Guang; Zheng, Xiaotong; Zhou, Shaobing

2015-02-25

In this study, we developed a thermoresponsive and water-responsive shape-memory polymer nanocomposite network by chemically cross-linking cellulose nanocrystals (CNCs) with polycaprolactone (PCL) and polyethylene glycol (PEG). The nanocomposite network was fully characterized, including the microstructure, cross-link density, water contact angle, water uptake, crystallinity, thermal properties, and static and dynamic mechanical properties. We found that the PEG[60]-PCL[40]-CNC[10] nanocomposite exhibited excellent thermo-induced and water-induced shape-memory effects in water at 37 °C (close to body temperature), and the introduction of CNC clearly improved the mechanical properties of the mixture of both PEG and PCL polymers with low molecular weights. In addition, Alamar blue assays based on osteoblasts indicated that the nanocomposites possessed good cytocompatibility. Therefore, this thermoresponsive and water-responsive shape-memory nanocomposite could be potentially developed into a new smart biomaterial.

Reverse-mode thermoresponsive light attenuators produced by optical anisotropic composites of nematic liquid crystals and reactive mesogens

Science.gov (United States)

Kakiuchida, Hiroshi; Ogiwara, Akifumi

2018-04-01

Polymer network liquid crystals (PNLCs) whose optical transmittance state switches between transparence at low temperatures and haze at high temperatures were fabricated from mixtures of nematic liquid crystals (LCs) and reactive mesogens (RMs). This PNLC structure is simple but effective, namely, consists of micro-scale domains of orientation-ordered LCs and anisotropically polymerized RMs. The domains form through photopolymerization induced phase separation with inhomogeneous irradiation projected by laser speckling techniques. This irradiation method enables you to control the size and shape of phase-separation domains, and these PNLCs can be applied to novel thermoresponsive optical devices; optical isolators, thermometric sheets, and smart windows.

Supramolecular materials based on hydrogen-bonded polymers

NARCIS (Netherlands)

ten Brinke, Gerrit; Ruokolainen, Janne; Ikkala, Olli; Binder, W

2007-01-01

Combining supramolecular principles with block copolymer self-assembly offers unique possibilities to create materials with responsive and/or tunable properties. The present chapter focuses on supramolecular materials based on hydrogen bonding and (block co-) polymers. Several cases will be

Engineering cell factories for producing building block chemicals for bio-polymer synthesis

OpenAIRE

Tsuge, Yota; Kawaguchi, Hideo; Sasaki, Kengo; Kondo, Akihiko

2016-01-01

Synthetic polymers are widely used in daily life. Due to increasing environmental concerns related to global warming and the depletion of oil reserves, the development of microbial-based fermentation processes for the production of polymer building block chemicals from renewable resources is desirable to replace current petroleum-based methods. To this end, strains that efficiently produce the target chemicals at high yields and productivity are needed. Recent advances in metabolic engineerin...

Thermoresponsive Membrane Based on Thermotropic Liquid Crystalline Cholesteryl - (L-lacticacidn System: Study of Its Drug Permeability

Directory of Open Access Journals (Sweden)

Massoumeh Bagheri

2013-01-01

Full Text Available The rapidly increasing interest in functional materials with reversibly switchable physico- chemical properties has led to significant work on the development of stimuli responsive membranes. Thermotropic liquid crystals with their exceptional properties have potentials for drug-delivery applications. Thermoresponsive liquid-crystal-embedded membranes were investigated for the purpose of developing the drug delivery systems with thermal stimuli response. Drug release occurs at temperatures above the phase transition temperature of thermotropic liquid crystals. Therefore, they can control drug release in response to small temperature changes. In this work, the biocompatible and thermotropic liquid crystalline polymer cholesteryl-(L-lactic acidn ,CLAn (n=30, was synthesized with accurate control of molecular weight via ring opening polymerization method. Polymerization of L-lactide was carried out in the presence of cholesterol as an initiator and catalytic amount of tin (II octoate (Sn(Oct2 at 150°C in 5 h. The number-average degree of polymerization of CLA 30 was obtained from 1H NMR spectroscopy. The phase transition behavior of liquid crystalline CLA30 was established by differential scanning calorimetry and polarizing optical microscopy. The resulting liquid crystalline CLA30 was subsequently utilized to prepare CLA30 -embedded cellulose nitrate membrane by adsorption method. The CLA30-embedded cellulose nitrate membrane was used by an in-vitro drug penetration studies. Acetaminophen was used as a model drug. The permeation study was carried out at different temperatures around glass transition temperature of polymer CLA30 (37, 45 and 40°C, respectively. The results show that the CLA30 -embedded cellulose nitrate membranes exhibit thermo-responsive sensitivity with controlled drug permeation.

Thermo-responsive mesoporous silica/lipid bilayer hybrid nanoparticles for doxorubicin on-demand delivery and reduced premature release.

Science.gov (United States)

Zhang, Qing; Chen, Xuanxuan; Shi, Huihui; Dong, Gaoqiu; Zhou, Meiling; Wang, Tianji; Xin, Hongliang

2017-12-01

Hybrid nanocarriers based on mesoporous silica nanoparticles (MSNs) and supported lipid bilayer (SLB) have been studied as drug delivery system. It still remains challenges to develop these nanocarriers (SLB-MSNs) with on-demand drug release profile for chemotherapy. Here, we reported the biocompatible SLB-MSNs with high drug loading, which could release doxorubicin (DOX) in response to hyperthermia and reduce premature release. After synthesis of MSNs via a sol-gel procedure, the thermo-responsive SLB was deposited on the MSNs by sonication to completely seal the mesopores. The obtained SLB-MSNs consisted of 50 nm-sized MSN cores and 6.3 nm-thick SLB shells. Due to the big surface and pore volume of MSNs, the high drug loading content (7.30±0.02%) and encapsulation efficiency (91.16±0.28%) were achieved. The SLB blocking the mesopores reduced 50% of premature release and achieved on-demand release in a thermo-responsive manner. Moreover, SLB-MSNs showed good hemocompatibility at any tested concentration (25-700μg/mL), while bare MSNs caused 100% of hemolysis at concentration larger than 325μg/mL. In addition, in vitro U251 cell uptake experiment demonstrated that compared with uncapped MSNs, SLB-MSNs could prevent untargeted cellular uptake of DOX owing to reduced premature release and steric hindrance of PEG, which would be beneficial to minimize toxicity for healthy tissues. These results indicated that SLB-MSNs with thermo-responsive release capacity possessed great potential in future synergistic thermo-chemotherapy. Copyright © 2017 Elsevier B.V. All rights reserved.

CO2-switchable fluorescence of a dendritic polymer and its applications

Science.gov (United States)

Gao, Chunmei; Lü, Shaoyu; Liu, Mingzhu; Wu, Can; Xiong, Yun

2015-12-01

The synthesis and properties of CO2 responsive and fluorescent dendritic polymers, poly(amido amine)/Pluronic F127 (PAMAM/F127), are reported in this paper. The morphologies and sizes of PAMAM/F127 dendritic polymers were investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). PAMAM/F127 dendritic polymers showed unimolecular micelle morphologies at low concentrations, and changed to multimolecular micelles at higher concentrations. Additionally, fluorescence spectra and confocal laser scanning microscopy images showed that PAMAM/F127 dendritic polymers exhibited a fluorescent enhancement response to the presence of CO2. Apart from that, the release behavior of PAMAM/F127 gels under simulated body fluids was investigated by choosing curcumin as the hydrophobic drug. The results indicated that PAMAM/F127 dendritic polymers can be used to improve the solubility of curcumin, and the drug released faster in the presence of CO2. Such CO2 responsive fluorescent dendritic polymers are potentially applicable in cellular imaging or drug controlled release.The synthesis and properties of CO2 responsive and fluorescent dendritic polymers, poly(amido amine)/Pluronic F127 (PAMAM/F127), are reported in this paper. The morphologies and sizes of PAMAM/F127 dendritic polymers were investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). PAMAM/F127 dendritic polymers showed unimolecular micelle morphologies at low concentrations, and changed to multimolecular micelles at higher concentrations. Additionally, fluorescence spectra and confocal laser scanning microscopy images showed that PAMAM/F127 dendritic polymers exhibited a fluorescent enhancement response to the presence of CO2. Apart from that, the release behavior of PAMAM/F127 gels under simulated body fluids was investigated by choosing curcumin as the hydrophobic drug. The results indicated that PAMAM/F127 dendritic polymers can be used to improve the

Magnetically controlled permeability membranes

KAUST Repository

Kosel, Jurgen

2013-10-31

A bioactive material delivery system can include a thermoresponsive polymer membrane and nanowires distributed within the thermoresponsive polymer membrane. Magnetic activation of a thermoresponsive polymer membrane can take place via altering the magnetization or dimensions of nanowires dispersed or ordered within the membrane matrix.

Magnetically controlled permeability membranes

KAUST Repository

Kosel, Jü rgen; Khashab, Niveen M.; Zaher, Amir

2013-01-01

A bioactive material delivery system can include a thermoresponsive polymer membrane and nanowires distributed within the thermoresponsive polymer membrane. Magnetic activation of a thermoresponsive polymer membrane can take place via altering the magnetization or dimensions of nanowires dispersed or ordered within the membrane matrix.

Application of Bottlebrush Block Copolymers as Photonic Crystals.

Science.gov (United States)

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

2017-07-01

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

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.

PEO-related block copolymer surfactants

DEFF Research Database (Denmark)

Mortensen, K.

2001-01-01

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

Block copolymer assisted self-assembly of nanoparticles into Langmuir–Blodgett films: Effect of polymer concentration

International Nuclear Information System (INIS)

Martín-García, Beatriz; Velázquez, M. Mercedes

2013-01-01

We propose to use the self-assembly ability of a block copolymer to obtain CdSe quantum dots (QDs) structures of different morphology. The methodology proposed consist in transferring mixed Langmuir monolayers of QDs and the polymer poly (styrene-co-maleic anhydride) partial 2 buthoxy ethyl ester cumene terminated, PS-MA-BEE onto mica by the Langmuir–Blodgett (LB) methodology. The morphology of the LB films was analyzed by AFM and TEM measurements. Our results show that it is possible to modulate the self-assembly process by modifying the composition of the mixed Langmuir monolayer precursor of the LB film. The different morphologies are interpreted according to two different dewetting mechanisms, growth of holes and spinodal-like dewetting. The growth of holes dewetting process is driven by gravitatory effects and was observed for LB films obtained by transferring Langmuir monolayer of the smallest elasticity values in which the polymer is in brush conformation. The spinodal dewetting mechanism prevailed when the Langmuir monolayer presents the highest elasticity values. - Graphical abstract: Display Omitted - Highlights: • Effect of the surface composition on the LB films architecture. • QDs/polymer LB films morphology interpreted in terms of dewetting mechanism. • The dewetting mechanism depends on the Langmuir monolayer state

Block copolymer assisted self-assembly of nanoparticles into Langmuir–Blodgett films: Effect of polymer concentration

Energy Technology Data Exchange (ETDEWEB)

Martín-García, Beatriz; Velázquez, M. Mercedes, E-mail: mvsal@usal.es

2013-08-15

We propose to use the self-assembly ability of a block copolymer to obtain CdSe quantum dots (QDs) structures of different morphology. The methodology proposed consist in transferring mixed Langmuir monolayers of QDs and the polymer poly (styrene-co-maleic anhydride) partial 2 buthoxy ethyl ester cumene terminated, PS-MA-BEE onto mica by the Langmuir–Blodgett (LB) methodology. The morphology of the LB films was analyzed by AFM and TEM measurements. Our results show that it is possible to modulate the self-assembly process by modifying the composition of the mixed Langmuir monolayer precursor of the LB film. The different morphologies are interpreted according to two different dewetting mechanisms, growth of holes and spinodal-like dewetting. The growth of holes dewetting process is driven by gravitatory effects and was observed for LB films obtained by transferring Langmuir monolayer of the smallest elasticity values in which the polymer is in brush conformation. The spinodal dewetting mechanism prevailed when the Langmuir monolayer presents the highest elasticity values. - Graphical abstract: Display Omitted - Highlights: • Effect of the surface composition on the LB films architecture. • QDs/polymer LB films morphology interpreted in terms of dewetting mechanism. • The dewetting mechanism depends on the Langmuir monolayer state.

Fabrication of Thermo-Responsive Molecular Layers from Self-Assembling Elastin-Like Oligopeptides Containing Cell-Binding Domain for Tissue Engineering

Directory of Open Access Journals (Sweden)

Tomoyuki Koga

2015-01-01

Full Text Available Novel thermo-responsive elastin-like oligopeptides containing cell-binding epitope (Arg-Gly-Asp-Ser sequence; arginine-glycine-aspartic acid-serine (RGDS-elastin-like peptides (ELP and RGDS-deg-ELP; were newly prepared as building blocks of self-assembled molecular layer for artificial extra cellular matrix. A detailed analysis of the conformation of the oligo(ELPs in water and their self-assembling behavior onto hydrophobic surfaces were performed by using circular dichroism, Fourier transform infrared spectroscopy (FTIR, atomic force microscopy and water contact angle measurements. The experimental results revealed that both oligo(ELPs self-assembled onto hydrophobic surfaces and formed molecular layers based on their thermo-responsive conformational change from hydrous random coil to dehydrated β-turn structure. Effective cell adhesion and spreading behaviors were observed on these self-assembled oligo(ELP layers. In addition, attached cells were found to be recovered successfully as a cell-sheet by temperature-induced disassembly of oligo(ELP layer. This achievement provides an important insight to construct novel oligopeptide-based nano-surfaces for the design of smart artificial extra-cellular matrix.

Self-Healing and Thermo-Responsive Dual-Crosslinked Alginate Hydrogels based on Supramolecular Inclusion Complexes

Science.gov (United States)

Miao, Tianxin; Fenn, Spencer L.; Charron, Patrick N.; Oldinski, Rachael A.

2015-01-01

β-cyclodextrin (β-CD), with a lipophilic inner cavity and hydrophilic outer surface, interacts with a large variety of non-polar guest molecules to form non-covalent inclusion complexes. Conjugation of β-CD onto biomacromolecules can form physically-crosslinked hydrogel networks upon mixing with a guest molecule. Herein describes the development and characterization of self-healing, thermo-responsive hydrogels, based on host-guest inclusion complexes between alginate-graft-β-CD and Pluronic® F108 (poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol)). The mechanics, flow characteristics, and thermal response were contingent on the polymer concentrations, and the host-guest molar ratio. Transient and reversible physical crosslinking between host and guest polymers governed self-assembly, allowing flow under shear stress, and facilitating complete recovery of the material properties within a few seconds of unloading. The mechanical properties of the dual-crosslinked, multi-stimuli responsive hydrogels were tuned as high as 30 kPa at body temperature, and are advantageous for biomedical applications such as drug delivery and cell transplantation. PMID:26509214

Specific Ion Effects in Thermo-Responsive Polymer Solutions

DEFF Research Database (Denmark)

Moghaddam, Saeed Zajforoushan

Stimuli-responsive polymers are macromolecules that undergo a significant change in conformation and interactions in response to an external stimulus such as temperature and addition of salts. The applications of these materials are numerous ranging from biomedical applications to fabrication of ...

Semiconducting Polymer Photodetectors with Electron and Hole Blocking Layers: High Detectivity in the Near-Infrared

Directory of Open Access Journals (Sweden)

Xiong Gong

2010-07-01

Full Text Available Sensing from the ultraviolet-visible to the infrared is critical for a variety of industrial and scientific applications. Photodetectors with broad spectral response, from 300 nm to 1,100 nm, were fabricated using a narrow-band gap semiconducting polymer blended with a fullerene derivative. By using both an electron-blocking layer and a hole-blocking layer, the polymer photodetectors, operating at room temperature, exhibited calculated detectivities greater than 1013 cm Hz1/2/W over entire spectral range with linear dynamic range approximately 130 dB. The performance is comparable to or even better than Si photodetectors.

Porous organic polymers with anchored aldehydes: A new platform for post-synthetic amine functionalization en route for enhanced CO2 adsorption properties

KAUST Repository

Guillerm, Vincent; Weselinski, Lukasz Jan; Al Kordi, Mohamed; Haja Mohideen, Mohamed Infas; Belmabkhout, Youssef; Cairns, Amy; Eddaoudi, Mohamed

2014-01-01

A novel porous organic polymer has been synthesized using the molecular building block approach to deliberately encompass aldehyde functionalities amenable to post functionalization. The resultant porous framework allows a facile, one-step quantitative and post-synthetic functionalization by amines, permitting enhanced CO2 sorption properties. © 2014 The Royal Society of Chemistry.

Efficiency of solution-processed multilayer polymer light-emitting diodes using charge blocking layers

Science.gov (United States)

Kasparek, Christian; Rörich, Irina; Blom, Paul W. M.; Wetzelaer, Gert-Jan A. H.

2018-01-01

By blending semiconducting polymers with the cross-linkable matrix ethoxylated-(4)-bisphenol-a-dimethacrylate (SR540), an insoluble layer is acquired after UV-illumination. Following this approach, a trilayer polymer light-emitting diode (PLED) consisting of a blend of poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (poly-TPD) and SR540 as an electron-blocking layer, Super Yellow-Poly(p-phenylene vinylene) (SY-PPV) blended with SR540 as an emissive layer, and poly(9,9-di-n-octylfluorenyl-2,7-diyl) as a hole-blocking layer is fabricated from solution. The trilayer PLED shows a 23% increase in efficiency at low voltage as compared to a single layer SY-PPV PLED. However, at higher voltage, the advantage in current efficiency gradually decreases. A combined experimental and modelling study shows that the increased efficiency is not only due to the elimination of exciton quenching at the electrodes but also due to suppressed nonradiative trap-assisted recombination due to carrier confinement. At high voltages, holes can overcome the hole-blocking barrier, which explains the efficiency roll-off.

Polymer-Block-Polypeptides and Polymer-Conjugated Hybrid Materials as Stimuli-Responsive Nanocarriers for Biomedical Applications.

Science.gov (United States)

John, Johnson V; Johnson, Renjith P; Heo, Min Seon; Moon, Byeong Kyu; Byeon, Seong Jin; Kim, Il

2015-01-01

Stimuli-responsive nanocarriers are a class of soft materials that includes natural polymers, synthetic polymers, and polypeptides. Recently, modern synthesis tools such as atom transfer radical polymerization, reversible addition-fragmentation chain transfer polymerization, nitroxide-mediated radical polymerization, ring-opening polymerization of α-amino acid N-carboxyanhydrides, and various "click" chemistry strategies were simultaneously employed for the design and synthesis of nanosized drug delivery vehicles. Importantly, the research focused on the improvement of the nanocarrier targetability and the site-specific, triggered release of therapeutics with high drug loading efficiency and minimal drug leakage during the delivery to specific targets. In this context, nanocarriers responsive to common stimuli such as pH, temperature, redox potential, light, etc. have been widely used for the controlled delivery of therapeutics to pathological sites. Currently, different synthesis and self-assembly strategies improved the drug loading efficacy and targeted delivery of therapeutic agents to the desired site. In particular, polypeptide-containing hybrid materials have been developed for the controlled delivery of therapeutic agents. Therefore, stimuli-sensitive synthetic polypeptide-based materials have been extensively investigated in recent years. This review focuses on recent advances in the development of polymer-block-polypeptides and polymer-conjugated hybrid materials that have been designed and evaluated for various stimuli-responsive drug and gene delivery applications.

Effect of Nanoparticle Core Size on Polymer-Coated Gold Nanoparticle Location in Block Copolymers

Science.gov (United States)

Petrie, J. D.; Fredrickson, G. H.; Kramer, E. J.

2009-03-01

Gold nanoparticles modified by short chain polymer thiols [Au-PS] can be designed to strongly localize either in the PS domains of a polystyrene-b-poly(2-vinylpyridine) [PS-PVP] block copolymer or at the interface. The P2VP block has a stronger attractive interaction with bare gold than the PS block. Thus, when the areal chain density σ of end-attached PS chains falls below a critical areal chain density σc the Au-PS nanoparticles adsorb to the PS-b-P2VP interface. The effect of the polymer ligand molecular weight on the σc has been shown to scale as σc˜ ((R + Rg)/(R*Rg))̂2, where R is the curvature of the Au nanoparticle core radius. To test this scaling relation for σc further we are synthesizing gold nanoparticles with different core radii and will present preliminary results on σc as a function of R.

Preparation of thermo-responsive membranes. II.

Science.gov (United States)

Nozawa, I; Suzuki, Y; Sato, S; Sugibayashi, K; Morimoto, Y

1991-05-01

Two types of liquid crystal (LC)-immobilized membranes were prepared by a soaking method and sandwich method to control the permeation of indomethacin, as a model drug, in response to local and systemic fever. Monooxyethylene trimethylolpropane tristearate (MTTS) was used as a model LC because it has a gel-liquid crystal phase transition temperature near the body temperature, 39-40 degrees C in phosphate buffered saline (pH 7.4). Two porous polypropylene (PP) membranes were soaked into 20% MTTS chloroform solution in the soaking method, and two PP membranes were poured with the melted MTTS and pressed in the sandwich method. Thermo-response efficacy of the soaked membrane was dependent upon the content of MTTS in MTTS membrane, and the MTTS content above the void volume of PP membrane (38%) was needed for high efficacy. On the other hand, the sandwich membrane exhibited higher thermo-response efficacy than the soaked membrane, because more LC was embedded in the pores of sandwich membrane than that of the soaked membrane. The sandwich membrane permeation of indomethacin was sharply controlled by temperature changes between 32 and 38 degrees C.

PCL-PLLA Semi-IPN Shape Memory Polymers (SMPs): Degradation and Mechanical Properties.

Science.gov (United States)

Woodard, Lindsay N; Page, Vanessa M; Kmetz, Kevin T; Grunlan, Melissa A

2016-12-01

Thermoresponsive shape memory polymers (SMPs) based on poly(ε-caprolactone) (PCL) whose shape may be actuated by a transition temperature (T trans ) have shown utility for a variety of biomedical applications. Important to their utility is the ability to modulate mechanical and degradation properties. Thus, in this work, SMPs are formed as semi-interpenetrating networks (semi-IPNs) comprised of a cross-linked PCL diacrylate (PCL-DA) network and thermoplastic poly(l-lactic acid) (PLLA). The semi-IPN uniquely allows for requisite crystallization of both PCL and PLLA. The influence of PLLA (PCL:PLLA wt% ratio) and PCL-DA molecular weight (n) on film properties are investigated. PCL-PLLA semi-IPNs are able to achieve enhanced mechanical properties and accelerated rates of degradation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of thermo-responsive bovine hemoglobin imprinted nanoparticles by combining ionic liquid immobilization with aqueous precipitation polymerization.

Science.gov (United States)

Wang, Yongmei; Yang, Chongchong; Sun, Yan; Qiu, Fengtao; Xiang, Yang; Fu, Guoqi

2018-02-01

Surface molecular imprinting over functionalized nanoparticles has proved to be an effective approach for construction of artificial nanomaterials for protein recognition. Herein, we report a strategy for synthesis of core-shell protein-imprinted nanoparticles by the functionalization of nano-cores with ionic liquids followed by aqueous precipitation polymerization to build thermo-responsive imprinted polymer nano-shells. The immobilized ionic liquids can form multiple interactions with the protein template. The polymerization process can produce thermo-reversible physical crosslinks, which are advantageous to enhancing imprinting and facilitating template removal. With bovine hemoglobin as a model template, the imprinted nanoparticles showed temperature-sensitivity in both dispersion behaviors and rebinding capacities. Compared with the ionic-liquid-modified core nanoparticles, the imprinted particles exhibited greatly increased selectivity and two orders of magnitude higher binding affinity for the template protein. The imprinted nanoparticles achieved relatively high imprinting factor up to 5.0 and specific rebinding capacity of 67.7 mg/g, respectively. These nanoparticles also demonstrated rapid rebinding kinetics and good reproducibility after five cycles of adsorption-regeneration. Therefore, the presented approach may be viable for the fabrication of high-performance protein-imprinted nanoparticles with temperature sensitivity. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Prolonged local anesthetic action through slow release from poly (lactic acid co castor oil).

Science.gov (United States)

Sokolsky-Papkov, Marina; Golovanevski, Ludmila; Domb, Abraham J; Weiniger, Carolyn F

2009-01-01

To evaluate a new formulation of bupivacaine loaded in an injectable fatty acid based biodegradable polymer poly(lactic acid co castor oil) in prolonging motor and sensory block when injected locally. The polyesters were synthesized from DL: -lactic acid and castor oil with feed ratio of 4:6 and 3:7 w/w. Bupivacaine was dispersed in poly(fatty ester) liquid and tested for drug release in vitro. The polymer p(DLLA:CO) 3:7 loaded with 10% bupivacaine was injected through a 22G needle close to the sciatic nerve of ICR mice and the duration of sensory and motor nerve blockade was measured. The DL: -lactic acid co castor oil p(DLLA:CO) 3:7 released 65% of the incorporated bupivacaine during 1 week in vitro. Single injection of 10% bupivacaine loaded into this polymer caused motor block that lasted 24 h and sensory block that lasted 48 h. Previously we developed a ricinoleic acid based polymer with incorporated bupivacaine which prolonged anesthesia to 30 h. The new polymer poly(lactic acid co castor oil) 3:7 provides slow release of effective doses of the incorporated local anesthetic agent and prolongs anesthesia to 48 h.

A novel approach in preparing polymer/nano-CaCO3 composites

Institute of Scientific and Technical Information of China (English)

Zhengying LIU; Runze YU; Mingbo YANG; Jianmin FENG; Wei YANG; Bo YIN

2008-01-01

An novel compounding process using nano-CaCO3 aqueous suspension for preparing polymer/ nano-CaCO3 composites with nanoparticles dispersed at the nanoscale is reported. The process is called the mild mixing method. In this method, the pre-dispersed nano-particle suspensions are blended with melting polymers in a weak shearing field using an extruder, followed by removing the water from the vent. The four typical poly-meric nanocomposites were prepared by mild mixing method. The dispersion of nano-CaCO3 in the matrix of the polymer at the nanoscale was confirmed by scanning electron microscopy (SEM). The molecular weights of polycarbonate (PC) and its nanocomposite showed that the degradation had not occurred during the mild mixing processing. The mechanical properties of the composite with 1.5 wt-% nano-CaCO3 improve slightly. It proved that this approach is suitable for the preparation of nano-composites based on both polar and non-polar polymers.

Synthesis of Fluorinated Amphiphilic Block Copolymers Based on PEGMA, HEMA, and MMA via ATRP and CuAAC Click Chemistry

Directory of Open Access Journals (Sweden)

Fatime Eren Erol

2014-01-01

Full Text Available Synthesis of fluorinated amphiphilic block copolymers via atom transfer radical polymerization (ATRP and Cu(I catalyzed Huisgen 1,3-dipolar cycloaddition (CuAAC was demonstrated. First, a PEGMA and MMA based block copolymer carrying multiple side-chain acetylene moieties on the hydrophobic segment for postfunctionalization was carried out. This involves the synthesis of a series of P(HEMA-co-MMA random copolymers to be employed as macroinitiators in the controlled synthesis of P(HEMA-co-MMA-block-PPEGMA block copolymers by using ATRP, followed by a modification step on the hydroxyl side groups of HEMA via Steglich esterification to afford propargyl side-functional polymer, alkyne-P(HEMA-co-MMA-block-PPEGMA. Finally, click coupling between side-chain acetylene functionalities and 2,3,4,5,6-pentafluorobenzyl azide yielded fluorinated amphiphilic block copolymers. The obtained polymers were structurally characterized by 1H-NMR, 19F-NMR, FT-IR, and GPC. Their thermal characterizations were performed using DSC and TGA.

Molecularly Imprinted Polymers with Stimuli-Responsive Affinity: Progress and Perspectives

OpenAIRE

Wei Chen; Yue Ma; Jianmin Pan; Zihui Meng; Guoqing Pan; Börje Sellergren

2015-01-01

Intelligent stimuli-responsive molecularly imprinted polymers (SR-MIPs) have attracted considerable research interest in recent years due to the potential applications in drug delivery, biotechnology and separation sciences. This review comprehensively summarizes various SR-MIPs, including the design and applications of thermo-responsive MIPs, pH-responsive MIPs, photo-responsive MIPs, biomolecule-responsive MIPs and ion-responsive MIPs. Besides the development of current SR-MIPs, the advanta...

Assessment of Polyacrylamide Based Co-Polymers Enhanced by Functional Group Modifications with Regards to Salinity and Hardness

Directory of Open Access Journals (Sweden)

Saeed Akbari

2017-11-01

Full Text Available This research aims to test four new polymers for their stability under high salinity/high hardness conditions for their possible use in polymer flooding to improve oil recovery from hydrocarbon reservoirs. The four sulfonated based polyacrylamide co-polymers were FLOCOMB C7035; SUPERPUSHER SAV55; THERMOASSOCIATIF; and AN132 VHM which are basically sulfonated polyacrylamide copolymers of AM (acrylamide with AMPS (2-Acrylamido-2-Methylpropane Sulfonate. AN132 VHM has a molecular weight of 9–11 million Daltons with 32 mol % degree of sulfonation. SUPERPUSHER SAV55 mainly has about 35 mol % sulfonation degree and a molecular weight of 9–11 million Daltons. FLOCOMB C7035, in addition, has undergone post-hydrolysis step to increase polydispersity and molecular weight above 18 million Daltons but it has a sulfonation degree much lower than 32 mol %. THERMOASSOCIATIF has a molecular weight lower than 12 million Daltons and a medium sulfonation degree of around 32 mol %, and also contains LCST (lower critical solution temperature type block, which is responsible for its thermoassociative characteristics. This paper discusses the rheological behavior of these polymers in aqueous solutions (100–4500 ppm with NaCl (0.1–10 wt % measured at 25 °C. The effect of hardness was investigated by preparing a CaCl2-NaCl solution of same ionic strength as the 5 wt % of NaCl. In summary, it can be concluded that the rheological behavior of the newly modified co-polymers was in general agreement to the existing polymers, except that THERMOASSOCIATIF polymers showed unique behavior, which could possibly make them a better candidate for enhanced oil recovery (EOR application in high salinity conditions. The other three polymers, on the other hand, are better candidates for EOR applications in reservoirs containing high divalent ions. These results are expected to be helpful in selecting and screening the polymers for an EOR application.

Unlocking Chain Exchange in Highly Amphiphilic Block Polymer Micellar Systems: Influence of Agitation.

Science.gov (United States)

Murphy, Ryan P; Kelley, Elizabeth G; Rogers, Simon A; Sullivan, Millicent O; Epps, Thomas H

2014-11-18

Chain exchange between block polymer micelles in highly selective solvents, such as water, is well-known to be arrested under quiescent conditions, yet this work demonstrates that simple agitation methods can induce rapid chain exchange in these solvents. Aqueous solutions containing either pure poly(butadiene- b -ethylene oxide) or pure poly(butadiene- b -ethylene oxide- d 4 ) micelles were combined and then subjected to agitation by vortex mixing, concentric cylinder Couette flow, or nitrogen gas sparging. Subsequently, the extent of chain exchange between micelles was quantified using small angle neutron scattering. Rapid vortex mixing induced chain exchange within minutes, as evidenced by a monotonic decrease in scattered intensity, whereas Couette flow and sparging did not lead to measurable chain exchange over the examined time scale of hours. The linear kinetics with respect to agitation time suggested a surface-limited exchange process at the air-water interface. These findings demonstrate the strong influence of processing conditions on block polymer solution assemblies.

Life Cycle CO2 Assessment by Block Type Changes of Apartment Housing

Directory of Open Access Journals (Sweden)

Cheonghoon Baek

2016-08-01

Full Text Available The block type and structural systems in buildings affect the amount of building materials required as well as the CO2 emissions that occur throughout the building life cycle (LCCO2. The purpose of this study was to assess the life cycle CO2 emissions when an apartment housing with ‘flat-type’ blocks (the reference case was replaced with more sustainable ‘T-type’ blocks with fewer CO2 emissions (the alternative case maintaining the same total floor area. The quantity of building materials used and building energy simulations were analyzed for each block type using building information modeling techniques, and improvements in LCCO2 emission were calculated by considering high-strength concrete alternatives. By changing the bearing wall system of the ‘flat-type’ block to the ‘column and beam’ system of the ‘T-type’ block, LCCO2 emissions of the alternative case were 4299 kg-CO2/m2, of which 26% was at the construction stage, 73% was as the operational stage and 1% was at the dismantling and disposal stage. These total LCCO2 emissions were 30% less than the reference case.

Co-non-solvency: Mean-field polymer theory does not describe polymer collapse transition in a mixture of two competing good solvents

Energy Technology Data Exchange (ETDEWEB)

Mukherji, Debashish; Stuehn, Torsten; Kremer, Kurt [Max-Planck Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz (Germany); Marques, Carlos M. [Max-Planck Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz (Germany); Institut Charles Sadron, Université de Strasbourg, CNRS, Strasbourg (France)

2015-03-21

Smart polymers are a modern class of polymeric materials that often exhibit unpredictable behavior in mixtures of solvents. One such phenomenon is co-non-solvency. Co-non-solvency occurs when two (perfectly) miscible and competing good solvents, for a given polymer, are mixed together. As a result, the same polymer collapses into a compact globule within intermediate mixing ratios. More interestingly, polymer collapses when the solvent quality remains good and even gets increasingly better by the addition of the better cosolvent. This is a puzzling phenomenon that is driven by strong local concentration fluctuations. Because of the discrete particle based nature of the interactions, Flory-Huggins type mean field arguments become unsuitable. In this work, we extend the analysis of the co-non-solvency effect presented earlier [D. Mukherji et al., Nat. Commun. 5, 4882 (2014)]. We explain why co-non-solvency is a generic phenomenon, which can only be understood by the thermodynamic treatment of the competitive displacement of (co)solvent components. This competition can result in a polymer collapse upon improvement of the solvent quality. Specific chemical details are not required to understand these complex conformational transitions. Therefore, a broad range of polymers are expected to exhibit similar reentrant coil-globule-coil transitions in competing good solvents.

Co-non-solvency: Mean-field polymer theory does not describe polymer collapse transition in a mixture of two competing good solvents

International Nuclear Information System (INIS)

Mukherji, Debashish; Stuehn, Torsten; Kremer, Kurt; Marques, Carlos M.

2015-01-01

Smart polymers are a modern class of polymeric materials that often exhibit unpredictable behavior in mixtures of solvents. One such phenomenon is co-non-solvency. Co-non-solvency occurs when two (perfectly) miscible and competing good solvents, for a given polymer, are mixed together. As a result, the same polymer collapses into a compact globule within intermediate mixing ratios. More interestingly, polymer collapses when the solvent quality remains good and even gets increasingly better by the addition of the better cosolvent. This is a puzzling phenomenon that is driven by strong local concentration fluctuations. Because of the discrete particle based nature of the interactions, Flory-Huggins type mean field arguments become unsuitable. In this work, we extend the analysis of the co-non-solvency effect presented earlier [D. Mukherji et al., Nat. Commun. 5, 4882 (2014)]. We explain why co-non-solvency is a generic phenomenon, which can only be understood by the thermodynamic treatment of the competitive displacement of (co)solvent components. This competition can result in a polymer collapse upon improvement of the solvent quality. Specific chemical details are not required to understand these complex conformational transitions. Therefore, a broad range of polymers are expected to exhibit similar reentrant coil-globule-coil transitions in competing good solvents

Powder wastes confinement block and manufacturing process of this block

International Nuclear Information System (INIS)

Dagot, L.; Brunel, G.

1996-01-01

This invention concerns a powder wastes containment block and a manufacturing process of this block. In this block, the waste powder is encapsulated in a thermo hardening polymer as for example an epoxy resin, the encapsulated resin being spread into cement. This block can contain between 45 and 55% in mass of wastes, between 18 and 36% in mass of polymer and between 14 and 32% in mass of cement. Such a containment block can be used for the radioactive wastes storage. (O.M.). 4 refs

Gold Nanoparticles on Polymer-Wrapped Carbon Nanotubes: An Efficient and Selective Catalyst for the Electroreduction of CO2.

Science.gov (United States)

Jhong, Huei-Ru Molly; Tornow, Claire E; Kim, Chaerin; Verma, Sumit; Oberst, Justin L; Anderson, Paul S; Gewirth, Andrew A; Fujigaya, Tsuyohiko; Nakashima, Naotoshi; Kenis, Paul J A

2017-11-17

Multiple approaches will be needed to reduce the atmospheric CO 2 levels, which have been linked to the undesirable effects of global climate change. The electroreduction of CO 2 driven by renewable energy is one approach to reduce CO 2 emissions while producing chemical building blocks, but current electrocatalysts exhibit low activity and selectivity. Here, we report the structural and electrochemical characterization of a promising catalyst for the electroreduction of CO 2 to CO: Au nanoparticles supported on polymer-wrapped multiwall carbon nanotubes. This catalyst exhibits high selectivity for CO over H 2 : 80-92 % CO, as well as high activity: partial current density for CO as high as 160 mA cm -2 . The observed high activity, originating from a high electrochemically active surface area (23 m 2  g -1 Au), in combination with the low loading (0.17 mg cm -2 ) of the highly dispersed Au nanoparticles underscores the promise of this catalyst for efficient electroreduction of CO 2 . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dynamic and biocompatible thermo-responsive magnetic hydrogels that respond to an alternating magnetic field

Energy Technology Data Exchange (ETDEWEB)

Crippa, Federica; Moore, Thomas L.; Mortato, Mariangela; Geers, Christoph; Haeni, Laetitia [Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, CH-1700 Fribourg (Switzerland); Hirt, Ann M. [Institute for Geophysics, ETH Zurich, Sonneggstrasse 5, CH-8092 Zurich (Switzerland); Rothen-Rutishauser, Barbara [Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, CH-1700 Fribourg (Switzerland); Petri-Fink, Alke, E-mail: alke.fink@unifr.ch [Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, CH-1700 Fribourg (Switzerland); Chemistry Department, University of Fribourg, Chemin du Musée 9, CH-1700 Fribourg Switzerland (Switzerland)

2017-04-01

Magnetic thermo-responsive hydrogels are a new class of materials that have recently attracted interest in biomedicine due to their ability to change phase upon magnetic stimulation. They have been used for drug release, magnetic hyperthermia treatment, and can potentially be engineered as stimuli-responsive substrates for cell mechanobiology. In this regard, we propose a series of magnetic thermo-responsive nanocomposite substrates that undergo cyclical swelling and de-swelling phases when actuated by an alternating magnetic field in aqueous environment. The synthetized substrates are obtained with a facile and reproducible method from poly-N-isopropylacrylamide and superparamagnetic iron oxide nanoparticles. Their conformation and the temperature-related, magnetic, and biological behaviors were characterized via scanning electron microscopy, swelling ratio analysis, vibrating sample magnetometry, alternating magnetic field stimulation and indirect viability assays. The nanocomposites showed no cytotoxicity with fibroblast cells, and exhibited swelling/de-swelling behavior near physiological temperatures (around 34 °C). Therefore these magnetic thermo-responsive hydrogels are promising materials as stimuli-responsive substrates allowing the study of cell-behavior by changing the hydrogel properties in situ. - Highlights: • A magnetic thermo-responsive hydrogel for mechanobiology is proposed. • Hydrogels change phase upon magnetic stimulation near physiological temperature. • Phase changes are reversible and triggered in an aqueous environment. • The hydrogels are biocompatible for murine fibroblast cells.

Preparation of pH-sensitive amphiphilic block star polymers, their self-assembling characteristics and release behavior on encapsulated molecules

KAUST Repository

Song, Xiaowan; Cao, Ming; Chen, Peng; Xia, Ru; Zheng, Zhengzhi; Miao, Jibin; Yang, Bin; Su, Lifen; Qian, Jiasheng; Feng, Xiaoshuang

2016-01-01

Poly(ethylene glycol) (PEG), a polymer with excellent biocompatibility, was widely used to form nanoparticles for drug delivery applications. In this paper, based on PEG, a series of pH-sensitive amphiphilic block star polymers of poly

Development of technology for the large-scale preparation of 60Co polymer film source

International Nuclear Information System (INIS)

Udhayakumar, J.; Pardeshi, G.S.; Gandhi, Shymala S.; Chakravarty, Rubel; Kumar, Manoj; Dash, Ashutosh; Venkatesh, Meera

2008-01-01

60 Co sources (∼37 kBq) in the form of a thin film are widely used in position identification of perforation in offshore oil-well explorations. This paper describes the large-scale preparation of such sources using a radioactive polymer containing 60 Co. 60 Co was extracted into chloroform containing 8-hydroxyquinoline. The chloroform layer was mixed with polymethyl methacrylate (PMMA) polymer. A large film was prepared using the polymer solution containing the complex. The polymer film was then cut into circular sources, mounted on a source holder and supplied to various users

Fabrication of CO2 Facilitated Transport Channels in Block Copolymer through Supramolecular Assembly

Directory of Open Access Journals (Sweden)

Yao Wang

2014-05-01

Full Text Available In this paper, the molecule 12-amidine dodecanoic acid (M with ending groups of carboxyl and amidine groups respectively was designed and synthesized as CO2-responsive guest molecules. The block copolymer polystyrene-b-polyethylene oxide (PS-b-PEO was chosen as the host polymer to fabricate a composite membrane through H-bonding assembly with guest molecule M. We attempted to tune the phase separation structure of the annealed film by varying the amount of M added, and investigated the nanostructures via transmission electron microscope (TEM, fourier transform infrared (FT-IR etc. As a result, a reverse worm-like morphology in TEM image of bright PS phase in dark PEO/M matrix was observed for PS-b-PEO/M1 membrane in which the molar ratio of EO unit to M was 1:1. The following gas permeation measurement indicated that the gas flux of the annealed membranes dramatically increased due to the forming of ordered phase separation structure. As we expected, the obtained composite membrane PS-b-PEO/M1 with EO:M mole ratio of 1:1 presented an evident selectivity for moist CO2 permeance, which is identical with our initial proposal that the guest molecule M in the membranes will play the key role for CO2 facilitated transportation since the amidine groups of M could react reversibly with CO2 molecules in membranes. This work provides a supramolecular approach to fabricating CO2 facilitated transport membranes.

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…

Porous Organic Polymers for CO2 Capture

KAUST Repository

Teng, Baiyang

2013-01-01

to reduce the emission of CO2 to atmosphere. Porous organic polymers (POPs) are promising candidates for this application due to their readily tunable textual properties and surface functionalities. The objective of this thesis work is to develop new POPs

CO tolerance of polymer electrolyte fuel cells

Energy Technology Data Exchange (ETDEWEB)

Gubler, L; Scherer, G G; Wokaun, A [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1999-08-01

Reformed methanol can be used as a fuel for polymer electrolyte fuel cells instead of pure hydrogen. The reformate gas contains mainly H{sub 2}, CO{sub 2} in the order of 20% and low levels of CO in the order of 100 ppm. CO causes severe voltage losses due to poisoning of the anode catalyst. The effect of CO on cell performance was investigated at different CO levels up to 100 ppm. Various options to improve the CO tolerance of the fuel cell were assessed thereafter, of which the injection of a few percents of oxygen into the fuel feed stream proved to be most effective. By mixing 1% of oxygen with hydrogen containing 100 ppm CO, complete recovery of the cell performance could be attained. (author) 2 figs., 2 tabs., 3 refs.

Investigating potential physicochemical errors in polymer gel dosimeters

International Nuclear Information System (INIS)

Sedaghat, Mahbod; Lepage, Martin; Bujold, Rachel

2011-01-01

Measurement errors in polymer gel dosimetry can originate either during irradiation or scanning. One concern related to the exothermic nature of polymerization reaction was that the heat released in polymer gel dosimeters during irradiation modifies their dose response. In this paper, the effect of heat released from the exothermal polymerization reaction on the dose response of a number of dosimeters was studied. In addition, we investigated whether heat-generated geometric distortion existed in newly proposed gel dosimeters that contain highly thermoresponsive polymers. Our results suggest that despite a significant internal temperature increase in some gel compositions, their dose responses are not affected when oxygen is well expelled mechanically from the gel mixture. We also report on significant pre-irradiation instability in some recently developed polymer gel dosimeters but that geometric distortions were not observed. Data obtained by a set of small calibration vials are compared to those obtained from larger phantoms, and potential physicochemical causes of deviations between them are identified.

Investigating potential physicochemical errors in polymer gel dosimeters

Energy Technology Data Exchange (ETDEWEB)

Sedaghat, Mahbod; Lepage, Martin [Centre d' imagerie moleculaire de Sherbrooke, Departement de medecine nucleaire et radiobiologie, Universite de Sherbrooke, Sherbrooke, QC (Canada); Bujold, Rachel, E-mail: martin.lepage@usherbrooke.ca [Service de radio-oncologie, Centre hospitalier universitaire de Sherbrooke, Sherbrooke, QC (Canada)

2011-09-21

Measurement errors in polymer gel dosimetry can originate either during irradiation or scanning. One concern related to the exothermic nature of polymerization reaction was that the heat released in polymer gel dosimeters during irradiation modifies their dose response. In this paper, the effect of heat released from the exothermal polymerization reaction on the dose response of a number of dosimeters was studied. In addition, we investigated whether heat-generated geometric distortion existed in newly proposed gel dosimeters that contain highly thermoresponsive polymers. Our results suggest that despite a significant internal temperature increase in some gel compositions, their dose responses are not affected when oxygen is well expelled mechanically from the gel mixture. We also report on significant pre-irradiation instability in some recently developed polymer gel dosimeters but that geometric distortions were not observed. Data obtained by a set of small calibration vials are compared to those obtained from larger phantoms, and potential physicochemical causes of deviations between them are identified.

Cell Penetrating Polymers Containing Guanidinium Trigger Apoptosis in Human Hepatocellular Carcinoma Cells unless Conjugated to a Targeting N-Acetyl-Galactosamine Block.

Science.gov (United States)

Tan, Zhe; Dhande, Yogesh K; Reineke, Theresa M

2017-12-20

A series of 3-guanidinopropyl methacrylamide (GPMA)-based polymeric gene delivery vehicles were developed via aqueous reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymers have been evaluated for their cellular internalization ability, transfection efficiency, and cytotoxicity. Two homopolymers: P(GPMA 20 ), P(GPMA 34 ), were synthesized to study the effect of guanidium polymer length on delivery efficiency and toxicity. In addition, an N-acetyl-d-galactosamine (GalNAc)-based hydrophilic block was incorporated to produce diblock polymers, which provides a neutral hydrophilic block that sterically protects plasmid-polymer complexes (polyplexes) from colloidal aggregation and aids polyplex targeting to hepatocytes via binding to asialoglycoprotein receptors (ASGPRs). Polyplexes formed with P(GPMA x ) (x = 20, 34) homopolymers were shown to be internalized via both energy-dependent and independent pathways, whereas polyplexes formed with block polymers were internalized through endocytosis. Notably, P(GPMA x ) polyplexes enter cells very efficiently but are also very toxic to human hepatocellular carcinoma (HepG2) cells and triggered cell apoptosis. In comparison, the presence of a carbohydrate block in the polymer structures reduced the cytotoxicity of the polyplex formulations and increased gene delivery efficiency with HepG2 cells. Transfection efficiency and toxicity studies were also carried out with HEK 293T (human embryonic kidney) cells for comparison. Results showed that polyplexes formed with the P(GPMA x ) homopolymers exhibit much higher transfection efficiency and lower toxicity with HEK 293T cells. The presence of the carbohydrate block did not further increase transfection efficiency in comparison to the homopolymers with HEK 293T cells, likely due to the lack of ASGPRs on the HEK 293T cell line. This study revealed that although guanidinium-based polymers have high membrane permeability, their application as plasmid

Swelling and Shrinking Properties of Thermo-Responsive Polymeric Ionic Liquid Hydrogels with Embedded Linear pNIPAAM

Directory of Open Access Journals (Sweden)

Simon Gallagher

2014-03-01

Full Text Available In this study, varying concentrations of linear pNIPAAM have been incorporated for the first time into a thermo-responsive polymeric ionic liquid (PIL hydrogel, namely tributyl-hexyl phosphonium 3-sulfopropylacrylate (P-SPA, to produce semi-interpenetrating polymer networks. The thermal properties of the resulting hydrogels have been investigated along with their thermo-induced shrinking and reswelling capabilities. The semi-interpenetrating networks (IPN hydrogels were found to have improved shrinking and reswelling properties compared with their PIL counterpart. At elevated temperatures (50–80 °C, it was found that the semi-IPN with the highest concentration of hydrophobic pNIPAAM exhibited the highest shrinking percentage of ~40% compared to the conventional P-SPA, (27%. This trend was also found to occur for the reswelling measurements, with semi-IPN hydrogels producing the highest reswelling percentage of ~67%, with respect to its contracted state. This was attributed to an increase in water affinity due to the presence of hydrophilic pNIPAAM. Moreover, the presence of linear pNIPAAM in the polymer matrix leads to improved shrinking and reswelling response compared to the equivalent PIL.

Triazine containing N-rich microporous organic polymers for CO2 capture and unprecedented CO2/N2 selectivity

International Nuclear Information System (INIS)

Bhunia, Subhajit; Bhanja, Piyali; Das, Sabuj Kanti; Sen, Tapas; Bhaumik, Asim

2017-01-01

Targeted synthesis of microporous adsorbents for CO 2 capture and storage is very challenging in the context of remediation from green house gases. Herein we report two novel N-rich microporous networks SB-TRZ-CRZ and SB-TRZ-TPA by extensive incorporation of triazine containing tripodal moiety in the porous polymer framework. These materials showed excellent CO 2 storage capacities: SB-TRZ-CRZ displayed the CO 2 uptake capacity of 25.5 wt% upto 1 bar at 273 K and SB-TRZ-TPA gave that of 16 wt% under identical conditions. The substantial dipole quadruple interaction between network (polar triazine) and CO 2 boosts the selectivity for CO 2 /N 2 . SB-TRZ-CRZ has this CO 2 /N 2 selectivity ratio of 377, whereas for SB-TRZ-TPA it was 97. Compared to other porous polymers, these materials are very cost effective, scalable and very promising material for clean energy application and environmental issues. - Graphical abstract: We report two novel N-rich microporous polymeric materials by doping of triazine containing tripodal dopant in the organic framework. These materials showed excellent CO 2 storage capacities as high as 25.5 wt% under 1 bar pressure with exceptional CO 2 /N 2 selectivity of 377. - Highlights: • Triazine containing trimodal moiety incorporated in polycarbazolic and poly triphenylamine networks. • N-rich crosslinked polymers with high BET surface area and 1.5–1.7 nm size large micropores. • CO 2 uptake capacity of 25.5 wt% upto 1 bar at 273 K. • These crosslinked porous polymers showed exceptional CO 2 /N 2 selectivity.

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

DEFF Research Database (Denmark)

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

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

A rechargeable Li-CO{sub 2} battery with a gel polymer electrolyte

Energy Technology Data Exchange (ETDEWEB)

Li, Chao; Guo, Ziyang; Yang, Bingchang; Liu, Yao; Wang, Yonggang; Xia, Yongyao [Dept. of Chemistry and Shanghai Key Lab. of Molecular Catalysis and Innovative Materials, Inst. of New Energy, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Fudan Univ. (China)

2017-07-24

The utilization of CO{sub 2} in Li-CO{sub 2} batteries is attracting extensive attention. However, the poor rechargeability and low applied current density have remained the Achilles' heel of this energy device. The gel polymer electrolyte (GPE), which is composed of a polymer matrix filled with tetraglyme-based liquid electrolyte, was used to fabricate a rechargeable Li-CO{sub 2} battery with a carbon nanotube-based gas electrode. The discharge product of Li{sub 2}CO{sub 3} formed in the GPE-based Li-CO{sub 2} battery exhibits a particle-shaped morphology with poor crystallinity, which is different from the contiguous polymer-like and crystalline discharge product in conventional Li-CO{sub 2} battery using a liquid electrolyte. Accordingly, the GPE-based battery shows much improved electrochemical performance. The achieved cycle life (60 cycles) and rate capability (maximum applied current density of 500 mA g{sup -1}) are much higher than most of previous reports, which points a new way to develop high-performance Li-CO{sub 2} batteries. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Reconfigurable photonic crystals enabled by pressure-responsive shape-memory polymers

Science.gov (United States)

Fang, Yin; Ni, Yongliang; Leo, Sin-Yen; Taylor, Curtis; Basile, Vito; Jiang, Peng

2015-01-01

Smart shape-memory polymers can memorize and recover their permanent shape in response to an external stimulus (for example, heat). They have been extensively exploited for a wide spectrum of applications ranging from biomedical devices to aerospace morphing structures. However, most of the existing shape-memory polymers are thermoresponsive and their performance is hindered by heat-demanding programming and recovery steps. Although pressure is an easily adjustable process variable such as temperature, pressure-responsive shape-memory polymers are largely unexplored. Here we report a series of shape-memory polymers that enable unusual ‘cold' programming and instantaneous shape recovery triggered by applying a contact pressure at ambient conditions. Moreover, the interdisciplinary integration of scientific principles drawn from two disparate fields—the fast-growing photonic crystal and shape-memory polymer technologies—enables fabrication of reconfigurable photonic crystals and simultaneously provides a simple and sensitive optical technique for investigating the intriguing shape-memory effects at nanoscale. PMID:26074349

Plasticisation and complexation of certain polymers in supercritical CO2

CSIR Research Space (South Africa)

Labuschagne, Philip W

2004-09-01

Full Text Available A polymer system (polyvinylpyrrolidone + polyvinyl acetate-co-crotonic acid) was successfully identified for use as encapsulation material for sensitive actives using supercritical CO2 as plasticisation medium, having the following properties: 1...

Experimental studies of contact angle hysteresis phenomena on polymer surfaces – Toward the understanding and control of wettability for different applications.

Science.gov (United States)

Grundke, K; Pöschel, K; Synytska, A; Frenzel, R; Drechsler, A; Nitschke, M; Cordeiro, A L; Uhlmann, P; Welzel, P B

2015-08-01

Contact angle hysteresis phenomena on polymer surfaces have been studied by contact angle measurements using sessile liquid droplets and captive air bubbles in conjunction with a drop shape method known as Axisymmetric Drop Shape Analysis - Profile (ADSA-P). In addition, commercially available sessile drop goniometer techniques were used. The polymer surfaces were characterized with respect to their surface structure (morphology, roughness, swelling) and surface chemistry (elemental surface composition, acid-base characteristics) by scanning electron microscopy (SEM), scanning force microscopy (SFM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and streaming potential measurements. Heterogeneous polymer surfaces with controlled roughness and chemical composition were prepared by different routes using plasma etching and subsequent dip coating or grafting of polymer brushes, anodic oxidation of aluminium substrates coated with thin polymer films, deposition techniques to create regular patterned and rough fractal surfaces from core-shell particles, and block copolymers. To reveal the effects of swelling and reorientation at the solid/liquid interface contact angle hysteresis phenomena on polyimide surfaces, cellulose membranes, and thermo-responsive hydrogels have been studied. The effect of different solutes in the liquid (electrolytes, surfactants) and their impact on contact angle hysteresis were characterized for solid polymers without and with ionizable functional surface groups in aqueous electrolyte solutions of different ion concentrations and pH and for photoresist surfaces in cationic aqueous surfactant solutions. The work is an attempt toward the understanding of contact angle hysteresis phenomena on polymer surfaces aimed at the control of wettability for different applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Smart PEGylation of trypsin.

Science.gov (United States)

Zarafshani, Zoya; Obata, Toshihiro; Lutz, Jean-François

2010-08-09

Thermoresponsive oligo(ethylene glycol)-based copolymers were investigated for trypsin conjugation. These copolymers have been synthesized by atom transfer radical polymerization of 2-(2-methoxyethoxy)ethyl methacrylate (MEO(2)MA) with oligo(ethylene glycol) methyl ether methacrylate (OEGMA(475), M(n) = 475 g.mol(-1)) at 60 degrees C in the presence of copper(I) chloride and 2,2'-bipyridyl. Two different ATRP initiators, containing succinimidyl ester moieties, were tested, namely, N-succinimidyl-2-bromopropionate and N-succinimidyl-2-bromoisobutyrate. In both cases, ATRP afforded well-defined polymers with a narrow molecular weight distribution and controlled chain-ends. However, the efficiency of initiation of the two initiators was lower than 1 and therefore the formed polymers exhibited a higher than expected mean degree of polymerization. Nevertheless, all types of polymers could be conjugated to trypsin. The conjugation reaction was performed in borax-HCl buffer. Sodium dodecyl sulfate poly(acrylamide) gel electrophoresis (SDS-PAGE) indicated that polymer/enzyme conjugates were obtained in all cases. However, (co)polymers initiated by N-succinimidyl-2-bromopropionate led to the best conjugation results. The formed P(MEO(2)MA-co-OEGMA(475))-trypsin conjugates were found to be thermoresponsive and moreover exhibited a higher enzymatic activity than unmodified trypsin.

Magnetic silica hybrids modified with guanidine containing co-polymers for drug delivery applications

Energy Technology Data Exchange (ETDEWEB)

Timin, Alexander S., E-mail: a_timin@mail.ru [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000 Ivanovo (Russian Federation); RASA Center in Tomsk, Tomsk Polytechnic University, 30, Lenin Avenue, 634500 Tomsk (Russian Federation); Khashirova, Svetlana Yu. [Kabardino-Balkar State University, ul. Chernyshevskogo 173, Nal' chik, 360004 Kabardino-Balkaria (Russian Federation); Rumyantsev, Evgeniy V.; Goncharenko, Alexander A. [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000 Ivanovo (Russian Federation)

2016-07-01

Guanidine containing co-polymers grafted onto silica nanoparticles to form core-shell structure were prepared by sol-gel method in the presence of γ-Fe{sub 2}O{sub 3} nanoparticles. The morphological features for uncoated and coated silica particles have been characterized with scanning electron microscopy. The results show that the polymer coated silicas exhibit spherical morphology with rough polymeric surface covered by γ-Fe{sub 2}O{sub 3} nanoparticles. The grafting amount of guanidine containing co-polymers evaluated by thermogravimetric analysis was in the range from 17 to 30%. Then, the drug loading properties and cumulative release of silica hybrids modified with guanidine containing co-polymers were evaluated using molsidomine as a model drug. It was shown that after polymer grafting the loading content of molsidomine could reach up to 3.42 ± 0.21 and 2.34 ± 0.14 mg/g respectively. The maximum drug release of molsidomine is achieved at pH 1.6 (approximately 71–75% release at 37 °C), whereas at pH 7.4 drug release is lower (50.4–59.6% release at 37 °C). These results have an important implication that our magneto-controlled silica hybrids modified with guanidine containing co-polymers are promising as drug carriers with controlled behaviour under influence of magnetic field. - Highlights: • Polymer coated silica hybrids containing γ-Fe{sub 2}O{sub 3} were prepared via sol–gel method. • Polymer grafting influences pH-response and surface properties of final products. • Molsidomine as a model drug was effectively loaded into polymer coated silicas. • The drug loading depends on the nature of grafted polymer and its content.

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

Science.gov (United States)

Nakamura, Issei

2014-05-29

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

Preparation of pH-sensitive amphiphilic block star polymers, their self-assembling characteristics and release behavior on encapsulated molecules

KAUST Repository

Song, Xiaowan

2016-05-28

Poly(ethylene glycol) (PEG), a polymer with excellent biocompatibility, was widely used to form nanoparticles for drug delivery applications. In this paper, based on PEG, a series of pH-sensitive amphiphilic block star polymers of poly(ethylene glycol)-block-poly(ethoxy ethyl glycidyl ether) (PEG-b-PEEGE) with different hydrophobic length were synthesized by living anionic ring-opening polymerization method. The products were characterized using 1H NMR and gel permeation chromatography. These copolymers could self-assemble in aqueous solution to form micellar structure with controlled morphologies. Transmission electron microscopy showed that the nanoparticles are spherical or rodlike with different hydrophilic mass fractions. The pH response of polymeric aggregates from PEG-b-PEEGE was detected by fluorescence probe technique at different pH. A pH-dependent release behavior was observed and pH-responsiveness of PEG-b-PEEGE was affected by the hydrophobic block length. These results demonstrated that star-shaped polymers (PEG-b-PEEGE) are attractive candidates as anticancer drug delivery carriers. © 2016 Springer-Verlag Berlin Heidelberg

Dynamic and biocompatible thermo-responsive magnetic hydrogels that respond to an alternating magnetic field

Science.gov (United States)

Crippa, Federica; Moore, Thomas L.; Mortato, Mariangela; Geers, Christoph; Haeni, Laetitia; Hirt, Ann M.; Rothen-Rutishauser, Barbara; Petri-Fink, Alke

2017-04-01

Magnetic thermo-responsive hydrogels are a new class of materials that have recently attracted interest in biomedicine due to their ability to change phase upon magnetic stimulation. They have been used for drug release, magnetic hyperthermia treatment, and can potentially be engineered as stimuli-responsive substrates for cell mechanobiology. In this regard, we propose a series of magnetic thermo-responsive nanocomposite substrates that undergo cyclical swelling and de-swelling phases when actuated by an alternating magnetic field in aqueous environment. The synthetized substrates are obtained with a facile and reproducible method from poly-N-isopropylacrylamide and superparamagnetic iron oxide nanoparticles. Their conformation and the temperature-related, magnetic, and biological behaviors were characterized via scanning electron microscopy, swelling ratio analysis, vibrating sample magnetometry, alternating magnetic field stimulation and indirect viability assays. The nanocomposites showed no cytotoxicity with fibroblast cells, and exhibited swelling/de-swelling behavior near physiological temperatures (around 34 °C). Therefore these magnetic thermo-responsive hydrogels are promising materials as stimuli-responsive substrates allowing the study of cell-behavior by changing the hydrogel properties in situ.

CO2 Selective, Zeolitic Imidazolate Framework-7 Based Polymer Composite Mixed-Matrix Membranes

KAUST Repository

Chakrabarty, Tina; Neelakanda, Pradeep; Peinemann, Klaus-Viktor

2018-01-01

CO2 removal is necessary to mitigate the effects of global warming but it is a challenging process to separate CO2 from natural gas, biogas, and other gas streams. Development of hybrid membranes by use of polymers and metal-organic framework (MOF) particles is a viable option to overcome this challenge. A ZIF-7 nano-filler that was synthesized in our lab was embedded into a designed polymer matrix at various loadings and the performance of the mixed matrix membranes was evaluated in terms of gas permeance and selectivity. Hybrid membranes with various loadings (20, 30 and 40 wt%) were developed and tested at room temperature by a custom made time lag equipment and a jump in selectivity was observed when compared with the pristine polymer. A commercially attractive region for the selectivity CO2 over CH4 was achieved with a selectivity of 39 for 40 wt% particle loading. An increase in selectivity was observed with the increase of ZIF-7 loadings. Best performance was seen at 40% ZIF-7 loaded membrane with an ideal selectivity of 39 for CO2 over CH4. The obtained selectivity was 105% higher for CO2 over CH4 than the selectivity of the pristine polymer with a slight decrease in permeance. Morphological characterization of such developed membranes showed an excellent compatibility between the polymer and particle adhesion.

CO2 Selective, Zeolitic Imidazolate Framework-7 Based Polymer Composite Mixed-Matrix Membranes

KAUST Repository

Chakrabarty, Tina

2018-05-17

CO2 removal is necessary to mitigate the effects of global warming but it is a challenging process to separate CO2 from natural gas, biogas, and other gas streams. Development of hybrid membranes by use of polymers and metal-organic framework (MOF) particles is a viable option to overcome this challenge. A ZIF-7 nano-filler that was synthesized in our lab was embedded into a designed polymer matrix at various loadings and the performance of the mixed matrix membranes was evaluated in terms of gas permeance and selectivity. Hybrid membranes with various loadings (20, 30 and 40 wt%) were developed and tested at room temperature by a custom made time lag equipment and a jump in selectivity was observed when compared with the pristine polymer. A commercially attractive region for the selectivity CO2 over CH4 was achieved with a selectivity of 39 for 40 wt% particle loading. An increase in selectivity was observed with the increase of ZIF-7 loadings. Best performance was seen at 40% ZIF-7 loaded membrane with an ideal selectivity of 39 for CO2 over CH4. The obtained selectivity was 105% higher for CO2 over CH4 than the selectivity of the pristine polymer with a slight decrease in permeance. Morphological characterization of such developed membranes showed an excellent compatibility between the polymer and particle adhesion.

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

Science.gov (United States)

Ryu, Ji Ho; Lee, Won Bo

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

Ibuprofen-loaded microspheres based on a co-polymer of Eudragit ...

African Journals Online (AJOL)

The objective of this study was to encapsulate ibuprofen in microspheres based on a co-polymer of Eudragit® RS100 and RL100 with a view to achieving a controlled release of the incorporated drug. The microparticles were prepared by an o/o emulsion-solvent evaporation method using varying polymer ratios and ...

π-Extended Isoindigo-Based Derivative: A Promising Electron-Deficient Building Block for Polymer Semiconductors.

Science.gov (United States)

Xu, Long; Zhao, Zhiyuan; Xiao, Mingchao; Yang, Jie; Xiao, Jian; Yi, Zhengran; Wang, Shuai; Liu, Yunqi

2017-11-22

The exploration of novel electron-deficient building blocks is a key task for developing high-performance polymer semiconductors in organic thin-film transistors. In view of the situation of the lack of strong electron-deficient building blocks, we designed two novel π-extended isoindigo-based electron-deficient building blocks, IVI and F 4 IVI. Owing to the strong electron-deficient nature and the extended π-conjugated system of the two acceptor units, their copolymers, PIVI2T and PF 4 IVI2T, containing 2,2'-bithiophene donor units, are endowed with deep-lying highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) energy levels and strong intermolecular interactions. In comparison to PIVI2T, the fluorinated PF 4 IVI2T exhibits stronger intra- and intermolecular interactions, lower HOMO/LUMO energy levels up to -5.74/-4.17 eV, and more ordered molecular packing with a smaller π-π stacking distance of up to 3.53 Å, resulting in an excellent ambipolar transporting behavior and a promising application in logic circuits for PF 4 IVI2T in ambient with hole and electron mobilities of up to 1.03 and 1.82 cm 2 V -1 s -1 , respectively. The results reveal that F 4 IVI is a promising and strong electron-deficient building unit to construct high-performance semiconducting polymers, which provides an insight into the structure-property relationships for the exploration and molecular engineering of excellent electron-deficient building blocks in the field of organic electronics.

The effect of different component ratios in block polymers and processing conditions on electrodeposition efficiency onto titanium

Energy Technology Data Exchange (ETDEWEB)

Fukuhara, Yusuke; Kyuzo, Megumi [Department of Materials Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Tsutsumi, Yusuke [Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-surugadai, Chiyoda-ku, Tokyo 101-0062 (Japan); Nagai, Akiko [Department of Materials Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-surugadai, Chiyoda-ku, Tokyo 101-0062 (Japan); Chen, Peng [Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-surugadai, Chiyoda-ku, Tokyo 101-0062 (Japan); Hanawa, Takao, E-mail: hanawa.met@tmd.ac.jp [Department of Materials Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-surugadai, Chiyoda-ku, Tokyo 101-0062 (Japan)

2015-11-15

Graphical abstract: - Highlights: • MPC polymers with an ability of electrodeposition were synthesized. • MPC polymers were immobilized on titanium substrates by electrodeposition. • Immobilization by electrodeposition of MPC polymer decreased water contact angle and protein adsorption. • Length of MPC unit and electrodeposition time did not influence water contact angle and protein adsorption. - Abstract: 2-Methacryloyloxyethyl phosphorylcholine (MPC) polymers for electrodeposition to titanium surfaces were synthesized. The polymers were block-type copolymers composed of a poly(MPC) segment and a poly(2-aminoethylmethacrylate (AEMA)) segment, which could electronically adsorb to a titanium oxide film on the titanium surface. The polymer was synthesized as expected by nuclear magnetic resonance and gel permeation chromatography. In a 0.26 mmol L{sup −1} PMbA solution adjusted to pH 11, −3.0 V (vs. an Ag/AgCl electrode) was applied to a titanium substrate for 300 s. We evaluated the effects of the molecular structure of poly(MPC-block-AEMA) (PMbA) with a different polymerization degree of MPC unit, whereas the polymerization degree of the AEMA units was fixed. The 15-min electrodeposition of PMbA100 was the most efficient condition in this study. On the other hand, the results of the water contact angle and the amount of adsorbed protein did not change, even when altering the MPC unit number and electrodeposition time. This indicates that the immobilization by electrodeposition of PMbA is important for the inhibition of protein adsorption, while the polymerization degree of the MPC unit and the electrodeposition time do not influence them. This study will enhance the understanding of effective polymer structures for electrodeposition and electrodeposition conditions.

Co-pyrolysis of wood biomass and synthetic polymers mixtures

Energy Technology Data Exchange (ETDEWEB)

Sharypov, V.I.; Beregovtsova, N.G.; Kuznetsov, B.N.; Baryshnikov, S.V. [Institute of Chemistry and Chemical Technology SB RAS, K. Marx Str., Krasnoyarsk 660049 (Russian Federation); Cebolla, V.L. [Instituto de Carboquimica, CSIC, Zaragoza (Spain); Weber, J.V.; Collura, S.; Finqueneisel, G.; Zimny, T. [Laboratoire de Chimie et Applications, Universite de Metz, IUT, rue V. Demange, 57500 Saint Avold (France)

2006-06-01

The pyrolysis in a hydrogen atmosphere of pine wood and synthetic polymers (polyethylene and polypropylene) mixtures was studied in a rotating autoclave. The effects of reaction temperature, wood/polymers mixture composition and catalysts, on the mixtures conversion into liquids and gases were established and discussed. The used catalysts were pyrrhotite and haematite materials activated by mechanochemical treatment. In the co-liquefaction processes the interaction between fragments of wood and polymers thermal decomposition took place. This results in non-additive increase of the wood/polymers conversion degree by 10-15wt.% and of the yield of distillate fractions by 14-19wt.%. Iron ore materials were found catalytically active in the process of hydropyrolysis of wood/polymers mixtures. By using these catalysts a significant increase of the distillable liquids amounts (by 14-21wt.%) and a sharp decrease of olefins and cycloparaffins content (by approximately two to three times) were observed. (author)

Study on the Matching Relationship between Polymer Hydrodynamic Characteristic Size and Pore Throat Radius of Target Block S Based on the Microporous Membrane Filtration Method

Directory of Open Access Journals (Sweden)

Li Yiqiang

2014-01-01

Full Text Available The concept of the hydrodynamic characteristic size of polymer was proposed in this study, to characterize the size of aggregates of many polymer molecules in the polymer percolation process. The hydrodynamic characteristic sizes of polymers used in the target block S were examined by employing microporous membrane filtration method, and the factors were studied. Natural core flow experiments were conducted in order to set up the flow matching relationship plate. According to the flow matching plate, the relationship between the hydrodynamic characteristic size of polymer and pore throat radius obtained from core mercury injection data was found. And several suitable polymers for different reservoirs permeability were given. The experimental results of microporous membrane filtration indicated that the hydrodynamic characteristic size of polymer maintained a good nonlinear relationship with polymer viscosity; the value increased as the molecular weight and concentration of the polymer increased and increased as the salinity of dilution water decreased. Additionally, the hydrodynamic characteristic size decreased as the pressure increased, so the hydrodynamic characteristic size ought to be determined based on the pressure of the target block. In the core flow studies, good matching of polymer and formation was identified as polymer flow pressure gradient lower than the fracture pressure gradient of formation. In this case, good matching that was the pore throat radius should be larger than 10 times the hydrodynamic characteristic size of polymer in this study. Using relationship, more matching relationship between the hydrodynamic characteristic sizes of polymer solutions and the pore throat radius of target block was determined.

Influence of Ethylene Glycol Methacrylate to the Hydration and Transition Behaviors of Thermo-Responsive Interpenetrating Polymeric Network Hydrogels

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Bing Li

2018-01-01

Full Text Available The influence of ethylene glycol methacrylate (EGMA to the hydration and transition behaviors of thermo-responsive interpenetrating polymeric network (IPN hydrogels containing sodium alginate, N-isopropylacrylamide (NIPAAm, and EGMA were investigated. The molar ratios of NIPAAm and EGMA were varied from 20:0 to 19.5:0.5 and 18.5:1.5 in the thermo-responsive alginate-Ca2+/P(NIPAAm-co-EGMA IPN hydrogels. Due to the more hydrophilicity and high flexibility of EGMA, the IPN hydrogels exhibited higher lower critical solution temperature (LCST and lower glass transition temperature (Tg when the ratio of EGMA increases. The swelling/deswelling kinetics of the IPN hydrogels could be controlled by adjusting the NIPAAm/EGMA molar ratio. A faster water uptake rate and a slower water loss rate could be realized by increase the amount of EGMA in the IPN hydrogel (the shrinking rate constant was decreased from 0.01207 to 0.01195 and 0.01055 with the changing of NIPAAm/EGMA ratio from 20:0, 19.5:0.5 to 18.5:1.5. By using 2-Isopropylthioxanthone (ITX as a photo initiator, the obtained alginate-Ca2+/P(NIPAAm-co-EGMA360 IPN hydrogels were successfully immobilized on cotton fabrics. The surface and cross section of the hydrogel were probed by scanning electron microscopy (SEM. They all exhibited a porous structure, and the pore size was increased with the amount of EGMA. Moreover, the LCST values of the fabric-grafted hydrogels were close to those of the pure IPN hydrogels. Their thermal sensitivity remained unchanged. The cotton fabrics grafted with hydrogel turned out to be much softer with the continuous increase of EGMA amount. Therefore, compared with alginate-Ca2+/PNIPAAm hydrogel, alginate-Ca2+/P(NIPAAm-co-EGMA360 hydrogel is a more promising candidate for wound dressing in the field of biomedical textile.

Mechanism of co-nanoprecipitation of organic actives and block copolymers in a microfluidic environment

International Nuclear Information System (INIS)

Capretto, Lorenzo; Cheng Wei; Carugo, Dario; Katsamenis, Orestis L; Zhang Xunli; Hill, Martyn

2012-01-01

Microreactors have been shown to be a powerful tool for the production of nanoparticles (NPs); however, there is still a lack of understanding of the role that the microfluidic environment plays in directing the nanoprecipitation process. Here we investigate the mechanism of nanoprecipitation of block copolymer stabilized organic NPs using a microfluidic-based reactor in combination with computational fluid dynamics (CFD) modelling of the microfluidic implementation. The latter also accounts for the complex interplay between molecular and hydrodynamic phenomena during the nanoprecipitation process, in order to understand the hydrodynamics and its influence on the NP formation process. It is demonstrated that the competitive reactions result in the formation of two types of NPs, i.e., either with or without loading organic actives. The obtained results are interpreted by taking into consideration a new parameter representing the mismatching between the aggregations of the polymers and actives, which plays a decisive role in determining the size and polydispersity of the prepared hybrid NPs. These results expand the current understanding of the co-nanoprecipitation mechanism of active and block copolymer stabilizer, and on the role exerted by the microfluidic environment, giving information that could be translated to the emerging fields of microfluidic formation of NPs and nanomedicine. (paper)

Phase separation and mechanical properties of an elastomeric biomaterial from spider wrapping silk and elastin block copolymers.

Science.gov (United States)

Muiznieks, Lisa D; Keeley, Fred W

2016-10-01

Elastin and silk spidroins are fibrous, structural proteins with elastomeric properties of extension and recoil. While elastin is highly extensible and has excellent recovery of elastic energy, silks are particularly strong and tough. This study describes the biophysical characterization of recombinant polypeptides designed by combining spider wrapping silk and elastin-like sequences as a strategy to rationally increase the strength of elastin-based materials while maintaining extensibility. We demonstrate a thermo-responsive phase separation and spontaneous colloid-like droplet formation from silk-elastin block copolymers, and from a 34 residue disordered region of Argiope trifasciata wrapping silk alone, and measure a comprehensive suite of tensile mechanical properties from cross-linked materials. Silk-elastin materials exhibited significantly increased strength, toughness, and stiffness compared to an elastin-only material, while retaining high failure strains and low energy loss upon recoil. These data demonstrate the mechanical tunability of protein polymer biomaterials through modular, chimeric recombination, and provide structural insights into mechanical design. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 693-703, 2016. © 2016 Wiley Periodicals, Inc.

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.

Polyurethane-Based Ionogels Exhibiting Durable Thermoresponsive Optical Behavior Under High-Temperature Conditions.

Science.gov (United States)

Sato, Tomoya; England, Matt W; Wang, Liming; Urata, Chihiro; Kakiuchida, Hiroshi; Hozumi, Atsushi

2018-01-01

Polyurethane (PU)-based transparent and flexible ionogels, showing unusual thermo-responsive optical properties, were successfully prepared by mixing PU-precursor and a hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI). Although the initial ionogels were transparent at room temperature, significant increases in opacity were observed with increasing temperature up to 120°C, because of macroscopic phase separation of the PU-matrix and hydrophobic EMIM-TFSI. In addition, the optical transition temperature could be arbitrarily controlled simply by varying the mixing ratio of EMIM-TFSI within the PU-matrix. As confirmed by UV-Vis spectra acquired at different temperatures, this thermo-responsive optical behavior was found to be reversible, repeatable and durable even after 30 cycles of a thermal-stress testing between 30 and 100°C.

Effect of Ligand Molecular Weight and Nanoparticle Core Size on Polymer-Coated Gold Nanoparticle Location in Block Copolymers

Science.gov (United States)

Petrie, Joshua; Kim, Bumjoon; Fredrickson, Glenn; Kramer, Ed

2008-03-01

Gold nanoparticles modified by short chain polymer thiols [Au-PS] can be designed to strongly localize in either domain of a polystyrene-b-poly(2-vinylpyridine) [PS-PVP] block copolymer or at the interface. The P2VP block has a stronger attractive interaction with bare gold than the PS block. Thus, when the areal chain density σ of end-attached PS chains falls below a critical areal chain density σc the Au-PS nanoparticles adsorb to the PS-b-P2VP interface. The effect of the polymer ligand molecular weight on the σchas been shown to scale as σc˜ ((R+Rg)/(R*Rg))̂2, where R is the curvature of the Au nanoparticle core radius. To test this scaling relation for σc further we are synthesizing gold nanoparticles with different core radii and will present preliminary results on σcas a function of R.

Electron Transfer of Myoglobin Immobilized in Au Electrodes Modified with a RAFT PMMA-Block-PDMAEMA Polymer

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Carla N. Toledo

2014-01-01

Full Text Available Myoglobin was immobilized with poly(methyl methacrylate-block-poly[(2-dimethylaminoethyl methacrylate]PMMA-block-PDMAEMA polymer synthesized by reversible addition-fragmentation chain transfer technique (RAFT. Cyclic voltammograms gave direct and slow quasireversible heterogeneous electron transfer kinetics between Mb-PMMA-block-PDMAEMA modified electrode and the redox center of the protein. The values for electron rate constant (Ks and transfer coefficient (α were 0.055±0.01·s−1 and 0.81±0.08, respectively. The reduction potential determined as a function of temperature (293–328 K revealed a value of reaction center entropy of ΔS0 of 351.3±0.0002 J·mol−1·K−1 and enthalpy change of -76.8±0.1 kJ·mol−1, suggesting solvent effects and charge ionization atmosphere involved in the reaction parallel to hydrophobic interactions with the copolymer. The immobilized protein also exhibits an electrocatalytical response to reduction of hydrogen peroxide, with an apparent Km of 114.7±58.7 μM. The overall results substantiate the design and use of RAFT polymers towards the development of third-generation biosensors.

Fundamental molecular design for precise control of thermoresponsiveness of organic polymers by using ternary systems.

Science.gov (United States)

Amemori, Shogo; Kokado, Kenta; Sada, Kazuki

2012-05-23

The de novo design of thermosensitive polymers in solution has been achieved by using the addition of small organic molecules (or "effectors"). Hydrogen bonding as an attractive polymer-polymer or polymer-effector interaction substantially dominates the responsivity, causing facile switching between LCST-type and UCST-type phase transitions, control of the transition temperature, and further coincidence of the two transitions. Small molecules having a high affinity for the polymer induce UCST-type phase behavior, whereas those having a low affinity for the polymer showed LCST-type phase behavior.

Solubilization of Phenol Derivatives in Polymer Micelles Formed by Cationic Block Copolymer

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Irma Fuentes

2017-01-01

Full Text Available The aggregation of cationic block copolymers formed by polystyrene (PS and poly(ethyl-4-vinylpyridine (PS-b-PE4VP was studied in aqueous solution. Diblock copolymers of PS and poly(4-vinylpyridine were synthesized by sequential anionic polymerization using BuLi as initiator. Subsequently, the 4-vinylpyridine units were quaternized with ethyl bromide to obtain cationic PS-b-PE4VP block copolymers with different quaternization degree. The self-aggregation of cationic block copolymers was studied by fluorescence probing, whereas the morphology and size of polymer micelles were determined by transmission electronic microscopy. Results indicate that spherical micelles with sizes lower than 100 nm were formed, whereas their micropolarity decreases with increasing quaternization degree. The partition of phenols between the micellar and aqueous phase was studied by using the pseudo-phase model, and the results show that the partition coefficients increase with increasing length of the side alkyl chain and are larger for star micelles. These results are discussed in terms of three-region model.

Poly(ferrocenylsilane)-block-Polylactide Block Copolymers

NARCIS (Netherlands)

Roerdink, M.; van Zanten, Thomas S.; Hempenius, Mark A.; Zhong, Zhiyuan; Feijen, Jan; Vancso, Gyula J.

2007-01-01

A PFS/PLA block copolymer was studied to probe the effect of strong surface interactions on pattern formation in PFS block copolymer thin films. Successful synthesis of PFS-b-PLA was demonstrated. Thin films of these polymers show phase separation to form PFS microdomains in a PLA matrix, and

Modeling CO2 Laser Ablative Impulse with Polymers

International Nuclear Information System (INIS)

Sinko, John E.; Phipps, Claude R.; Sasoh, Akihiro

2010-01-01

Laser ablation vaporization models have usually ignored the spatial dependence of the laser beam. Here, we consider effects from modeling using a Gaussian beam for both photochemical and photothermal conditions. The modeling results are compared to experimental and literature data for CO 2 laser ablation of the polymer polyoxymethylene under vacuum, and discussed in terms of the ablated mass areal density and momentum coupling coefficient. Extending the scope of discussion, laser ablative impulse generation research has lacked a cohesive strategy for linking the vaporization and plasma regimes. Existing models, mostly formulated for ultraviolet laser systems or metal targets, appear to be inappropriate or impractical for applications requiring CO 2 laser ablation of polymers. A recently proposed method for linking the vaporization and plasma regimes for analytical modeling is addressed here along with the implications of its use. Key control parameters are considered, along with the major propulsion parameters needed for laser ablation propulsion modeling.

Excimer laser micropatterning of freestanding thermo-responsive hydrogel layers for cells-on-chip applications

International Nuclear Information System (INIS)

Santaniello, Tommaso; Milani, Paolo; Lenardi, Cristina; Martello, Federico; Tocchio, Alessandro; Gassa, Federico; Webb, Patrick

2012-01-01

We report a novel reliable and repeatable technologic manufacturing protocol for the realization of micro-patterned freestanding hydrogel layers based on thermo-responsive poly-(N-isopropyl)acrylamide (PNIPAAm), which have potential to be employed as temperature-triggered smart surfaces for cells-on-chip applications. PNIPAAm-based films with controlled mechanical properties and different thicknesses (100–300 µm thickness) were prepared by injection compression moulding at room temperature. A 9 × 9 array of 20 µm diameter through-holes is machined by means of the KrF excimer laser on dry PNIPAAm films which are physically attached to flat polyvinyl chloride (PVC) substrates. Machining parameters, such as fluence and number of shots, are optimized in order to achieve highly resolved features. Micro-structured freestanding films are then easily obtained after hydrogels are detached from PVC by gradually promoting the film swelling in ethanol. In the PNIPAAm water-swollen state, the machined holes’ diameter approaches a slight larger value (30 µm) according to the measured hydrogel swelling ratio. Thermo-responsive behaviour and through-hole tapering characterization are carried out by metrology measurements using an optical inverted and confocal microscope setup, respectively. After the temperature of freestanding films is raised above 32 °C, we observe that the shrinkage of the whole through-hole array occurs, thus reducing the holes’ diameter to less than a half its original size (about 15 µm) as a consequence of the film dehydration. Different holes’ diameters (10 and 30 µm) are also obtained on dry hydrogel employing suitable projection masks, showing similar shrinking behaviour when hydrated and undergone thermo-response tests. Thermo-responsive PNIPAAm-based freestanding layers could then be integrated with other suitable micro-fabricated thermoplastic components in order to preliminary test their feasibility in operating as temperature

An implantable thermoresponsive drug delivery system based on Peltier device.

Science.gov (United States)

Yang, Rongbing; Gorelov, Alexander V; Aldabbagh, Fawaz; Carroll, William M; Rochev, Yury

2013-04-15

Locally dropping the temperature in vivo is the main obstacle to the clinical use of a thermoresponsive drug delivery system. In this paper, a Peltier electronic element is incorporated with a thermoresponsive thin film based drug delivery system to form a new drug delivery device which can regulate the release of rhodamine B in a water environment at 37 °C. Various current signals are used to control the temperature of the cold side of the Peltier device and the volume of water on top of the Peltier device affects the change in temperature. The pulsatile on-demand release profile of the model drug is obtained by turning the current signal on and off. The work has shown that the 2600 mAh power source is enough to power this device for 1.3 h. Furthermore, the excessive heat will not cause thermal damage in the body as it will be dissipated by the thermoregulation of the human body. Therefore, this simple novel device can be implanted and should work well in vivo. Copyright © 2013 Elsevier B.V. All rights reserved.

XPS and surface resistivity measurements of plasma - treated FEP co-polymer

International Nuclear Information System (INIS)

Pitrus, R.K.; Brack, N.; Liesegang, J.; Pigram, P.J.

2002-01-01

Full text: Fluorinated polymers such as fluorinated ethylene propylene (FEP) and poly(tetrafluoroethylene) (PTFE) play an important role in many applications due to their many desirable properties such as chemical resistivity, inertness, electrical stability and low dielectric constant; however, one disadvantage of fluorinated polymers is their extreme surface hydrophobicity. Previous studies show that plasma treatment will modify the surface by increasing the surface free energy and also offer a rapid and convenient method for pre-treating the polymers for many purposes. This paper, through resistivity and XPS (x-ray photoelectron spectroscopy) measurements, attempts to discover basic effects of such plasma treatment. Fluorinated ethylene propylene (FEP) co-polymer film of (0.05) mm thickness (obtained commercially) and with the following structure (CF 2 -CF 2 )-(CF(CF 3 )CF 2 )- was used. A suitable cleaning procedure was used to remove adventitious carbon from the surface. XPS has been used to study FEP film properties. The spectra of XPS were analyzed with the main focus on carbon and fluorine as they compose the elemental component of FEP film. A value of 2.05 was obtained for the F/C ratio, which is slightly higher than the theoretical F/C value estimated from the chemical structure of FEP (F/C 2). The clean film was then air plasma treated (pressure 10 -1 torr and power 30W) for various treatment times to produce a higher energy fluoropolymer surface. XPS studies investigated changes to the polymer surface and determined that oxidation occurs on the FEP surface. The oxidation reactions on the FEP surface form oxygen functional groups such as C-O and C=O groups. The results also show that the percentage of CF 2 and CF 3 in the co-polymer surface decreased with exposure time and the percentage of CF, C-C, C-O and C=O increased. There is a sharp decrease in F/C ratio and increase in O/C ratio. In addition to XPS, the resistivity of FEP-film was measured by a

Preparation and application of PVDF-HFP composite polymer electrolytes in LiNi0.5Co0.2Mn0.3O2 lithium-polymer batteries

International Nuclear Information System (INIS)

Yang, Chun-Chen; Lian, Zuo-Yu; Lin, S.J.; Shih, Jeng-Ywan; Chen, Wei-Houng

2014-01-01

Graphical abstract: - Highlights: • PVDF-HFP/SBA15 membrane and NCM cathode material were prepared for Li ion battery. • SBA15 fillers can trap more liquid electrolytes to enhance the ionic conductivity. • Modified fillers with functional groups play a key role in reducing impedance. • LiNi 0.5 Co 0.2 Mn 0.3 O 2 polymer battery showed excellent electrochemical performance. - Abstract: This study reports the preparation of a composite polymer electrolyte for application in LiNi 0.5 Co 0.2 Mn 0.3 O 2 lithium-polymer batteries. Poly(vinylidiene fluoride-hexafluoropropylene) (denoted as PVDF-HFP) was used as the polymer host and mesoporous modified-silica fillers (denoted as m-SBA15) used as the solid plasticizer were added into the polymer matrix. The characteristic properties of the composite polymer membranes were examined using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and an AC impedance method. The discharge capacities of LiNi 0.5 Co 0.2 Mn 0.3 O 2 polymer batteries with a PE separator, pure PVDF-HFP polymer membrane, or a PVDF-HFP/10 wt.%m-SBA15 composite at 0.1 C were determined to be 155.5, 159.5, and 198.6 mAh g −1 , respectively. The LiNi 0.5 Co 0.2 Mn 0.3 O 2 polymer battery containing the PVDF-HFP/10 wt.%m-SBA15 composite achieved discharge capacities of 194, 170, 161, 150, 129, 115, and 87 mAh g −1 at 0.1, 0.2, 0.5, 1, 3, 5, and 10 C, respectively. The lithium-polymer battery demonstrated a high coulomb efficiency of ca. 99%. The PVDF-HFP/m-SBA15 composite membrane is a strong candidate for application in LiNi 0.5 Co 0.2 Mn 0.3 O 2 lithium-polymer batteries

Triazine containing N-rich microporous organic polymers for CO{sub 2} capture and unprecedented CO{sub 2}/N{sub 2} selectivity

Energy Technology Data Exchange (ETDEWEB)

Bhunia, Subhajit; Bhanja, Piyali; Das, Sabuj Kanti [Department of Material Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Sen, Tapas [Nanobiomaterials Research Group, Centre for Materials Science, School of Physical Sciences and Computing, University of Central Lancashire, Preston PR1 2HE (United Kingdom); Bhaumik, Asim, E-mail: msab@iacs.res.in [Department of Material Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

2017-03-15

Targeted synthesis of microporous adsorbents for CO{sub 2} capture and storage is very challenging in the context of remediation from green house gases. Herein we report two novel N-rich microporous networks SB-TRZ-CRZ and SB-TRZ-TPA by extensive incorporation of triazine containing tripodal moiety in the porous polymer framework. These materials showed excellent CO{sub 2} storage capacities: SB-TRZ-CRZ displayed the CO{sub 2} uptake capacity of 25.5 wt% upto 1 bar at 273 K and SB-TRZ-TPA gave that of 16 wt% under identical conditions. The substantial dipole quadruple interaction between network (polar triazine) and CO{sub 2} boosts the selectivity for CO{sub 2}/N{sub 2}. SB-TRZ-CRZ has this CO{sub 2}/N{sub 2} selectivity ratio of 377, whereas for SB-TRZ-TPA it was 97. Compared to other porous polymers, these materials are very cost effective, scalable and very promising material for clean energy application and environmental issues. - Graphical abstract: We report two novel N-rich microporous polymeric materials by doping of triazine containing tripodal dopant in the organic framework. These materials showed excellent CO{sub 2} storage capacities as high as 25.5 wt% under 1 bar pressure with exceptional CO{sub 2}/N{sub 2} selectivity of 377. - Highlights: • Triazine containing trimodal moiety incorporated in polycarbazolic and poly triphenylamine networks. • N-rich crosslinked polymers with high BET surface area and 1.5–1.7 nm size large micropores. • CO{sub 2} uptake capacity of 25.5 wt% upto 1 bar at 273 K. • These crosslinked porous polymers showed exceptional CO{sub 2}/N{sub 2} selectivity.

Responsive Boronic Acid-Decorated (Co)polymers: From Glucose Sensors to Autonomous Drug Delivery.

Science.gov (United States)

Vancoillie, Gertjan; Hoogenboom, Richard

2016-10-19

Boronic acid-containing (co)polymers have fascinated researchers for decades, garnering attention for their unique responsiveness toward 1,2- and 1,3-diols, including saccharides and nucleotides. The applications of materials that exert this property are manifold including sensing, but also self-regulated drug delivery systems through responsive membranes or micelles. In this review, some of the main applications of boronic acid containing (co)polymers are discussed focusing on the role of the boronic acid group in the response mechanism. We hope that this summary, which highlights the importance and potential of boronic acid-decorated polymeric materials, will inspire further research within this interesting field of responsive polymers and polymeric materials.

Laser Co-Photolytic Approach to Copper(I) Bromide/Polymer Nanosol and Nanocomposite.

Czech Academy of Sciences Publication Activity Database

Pola, Josef; Ouichi, A.; Bezdička, Petr; Boháček, Jaroslav; Šubrt, Jan

2007-01-01

Roč. 190, 1 (2007) , s. 29-33 ISSN 1010-6030 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z40320502 Keywords : co-photolysis * CuBr/polymer nanosol * CuBr/polymer nanocomposite Subject RIV: CH - Nuclear ; Quantum Chemistry Impact factor: 1.911, year: 2007

Thermoresponsive pegylated bubble liposome nanovectors for efficient siRNA delivery via endosomal escape

KAUST Repository

Alamoudi, Kholod

2017-05-19

Improving the delivery of siRNA into cancer cells via bubble liposomes. Designing a thermoresponsive pegylated liposome through the introduction of ammonium bicarbonate salt into liposomes so as to control their endosomal escape for gene therapy.A sub-200 nm nanovector was fully characterized and examined for cellular uptake, cytotoxicity, endosomal escape and gene silencing.The siRNA-liposomes were internalized into cancer cells within 5 min and then released siRNAs in the cytosol prior to lysosomal degradation upon external temperature elevation. This was confirmed by confocal bioimaging and gene silencing reaching up to 90% and further demonstrated by the protein inhibition of both target genes.The thermoresponsiveness of ammonium bicarbonate containing liposomes enabled the rapid endosomal escape of the particles and resulted in an efficient gene silencing.

Thermoresponsive pegylated bubble liposome nanovectors for efficient siRNA delivery via endosomal escape

KAUST Repository

Alamoudi, Kholod; Martins, Patricia; Croissant, Jonas G.; Patil, Sachin; Omar, Haneen; Khashab, Niveen M.

2017-01-01

Improving the delivery of siRNA into cancer cells via bubble liposomes. Designing a thermoresponsive pegylated liposome through the introduction of ammonium bicarbonate salt into liposomes so as to control their endosomal escape for gene therapy.A sub-200 nm nanovector was fully characterized and examined for cellular uptake, cytotoxicity, endosomal escape and gene silencing.The siRNA-liposomes were internalized into cancer cells within 5 min and then released siRNAs in the cytosol prior to lysosomal degradation upon external temperature elevation. This was confirmed by confocal bioimaging and gene silencing reaching up to 90% and further demonstrated by the protein inhibition of both target genes.The thermoresponsiveness of ammonium bicarbonate containing liposomes enabled the rapid endosomal escape of the particles and resulted in an efficient gene silencing.

Binary Polymer Brushes of Strongly Immiscible Polymers.

Science.gov (United States)

Chu, Elza; Babar, Tashnia; Bruist, Michael F; Sidorenko, Alexander

2015-06-17

The phenomenon of microphase separation is an example of self-assembly in soft matter and has been observed in block copolymers (BCPs) and similar materials (i.e., supramolecular assemblies (SMAs) and homo/block copolymer blends (HBCs)). In this study, we use microphase separation to construct responsive polymer brushes that collapse to generate periodic surfaces. This is achieved by a chemical reaction between the minor block (10%, poly(4-vinylpyridine)) of the block copolymer and a substrate. The major block of polystyrene (PS) forms mosaic-like arrays of grafted patches that are 10-20 nm in size. Depending on the nature of the assembly (SMA, HBC, or neat BCP) and annealing method (exposure to vapors of different solvents or heating above the glass transition temperature), a range of "mosaic" brushes with different parameters can be obtained. Successive grafting of a secondary polymer (polyacrylamide, PAAm) results in the fabrication of binary polymer brushes (BPBs). Upon being exposed to specific selective solvents, BPBs may adopt different conformations. The surface tension and adhesion of the binary brush are governed by the polymer occupying the top stratum. The "mosaic" brush approach allows for a combination of strongly immiscible polymers in one brush. This facilitates substantial contrast in the surface properties upon switching, previously only possible for substrates composed of predetermined nanostructures. We also demonstrate a possible application of such PS/PAAm brushes in a tunable bioadhesion-bioadhesive (PS on top) or nonbioadhesive (PAAm on top) surface as revealed by Escherichia coli bacterial seeding.

Polymer brushes on nanoparticles: their positioning in and influence on block copolymer morphology.

Science.gov (United States)

Kim, Bumjoon

2007-03-01

Polymers brushes grafted to the nanoparticle surface enable the precise positioning of particles within a block copolymer matrix by determining the compatibility of nanoparticles within a polymeric matrix and modifying the interfacial properties between polymers and inorganic nanoparticle. Short thiol terminated polystyrene (PS-SH), poly(2-vinylpyridine) (P2VP-SH) and PS-r-P2VP with the molecular weight (Mn) of 3 kg/mol were used to control the location of Au nanoparticles over PS-b-P2VP diblock copolymer template. We will discuss further the approach of varying the areal chain density (σ) of PS-SH brushes on the PS coated particles, which utilizes the preferential wetting of one block of a copolymer (P2VP) on the Au substrate. Such favorable interaction provides the strong binding of Au particles to the PS/P2VP interface as σ of PS chains on the Au particle decreases. We find that at σ above a certain value, the nanoparticles are segregated to the center of the PS domains while below this value they are segregated to the interface. The transition σ for PS-SH chains (Mn = 3.4 kg/mol) is 1.3 chains/nm^2 but unexpectedly scales as Mn-0.55 as Mn is varied from 1.5 to 13 kg/mol. In addition, we will discuss changes in block copolymer morphology that occur as the nanoparticle volume fraction (φ) is increased for nanoparticles that segregate to the domain center as well as those that segregate to the interface, the latter behaving as nanoparticle surfactants. Small φ of such surfactants added to lamellar diblock copolymers lead initially to a decrease in lamellar thickness, a consequence of decreasing interfacial tension, up to a critical value of φ beyond which the block copolymer adopts a bicontinuous morphology. I thank my collaborators G. H. Fredrickson, J. Bang, C. J. Hawker, and E. J. Kramer as well as funding by the MRL as UCSB from the NSF-MRSEC-Program Award DMR05-20418.

New insights into the mechanism of interaction between CO2 and polymers from thermodynamic parameters obtained by in situ ATR-FTIR spectroscopy.

Science.gov (United States)

Gabrienko, Anton A; Ewing, Andrew V; Chibiryaev, Andrey M; Agafontsev, Alexander M; Dubkov, Konstantin A; Kazarian, Sergei G

2016-03-07

This work reports new physical insights of the thermodynamic parameters and mechanisms of possible interactions occurring in polymers subjected to high-pressure CO2. ATR-FTIR spectroscopy has been used in situ to determine the thermodynamic parameters of the intermolecular interactions between CO2 and different functional groups of the polymers capable of specific interactions with sorbed CO2 molecules. Based on the measured ATR-FTIR spectra of the polymer samples subjected to high-pressure CO2 (30 bar) at different temperatures (300-340 K), it was possible to characterize polymer-polymer and CO2-polymer interactions. Particularly, the enthalpy and entropy of the formation of the specific non-covalent complexes between CO2 and the hydroxy (-OH), carbonyl (C[double bond, length as m-dash]O) and hydroxyimino ([double bond, length as m-dash]N-OH) functional groups of the polymer samples have been measured. Furthermore, the obtained spectroscopic results have provided an opportunity for the structure of these complexes to be proposed. An interesting phenomenon regarding the behavior of CO2/polymer systems has also been observed. It has been found that only for the polyketone, the value of enthalpy was negative indicating an exothermic process during the formation of the CO2-polymer non-covalent complexes. Conversely, for the polyoxime and polyalcohol samples there is a positive enthalpy determined. This is a result of the initial polymer-polymer interactions requiring more energy to break than is released during the formation of the CO2-polymer complex. The effect of increasing temperature to facilitate the breaking of the polymer-polymer interactions has also been observed. Hence, a mechanism for the formation of CO2-polymer complexes was suggested based on these results, which occurs via a two-step process: (1) the breaking of the existing polymer-polymer interactions followed by (2) the formation of new CO2-polymer non-covalent interactions.

Water molecule-enhanced CO2 insertion in lanthanide coordination polymers

International Nuclear Information System (INIS)

Luo Liushan; Huang Xiaoyuan; Wang Ning; Wu Hongyan; Chen Wenbin; Feng Zihao; Zhu Huiping; Peng Xiaoling; Li Yongxian; Huang Ling; Yue Shantang; Liu Yingliang

2009-01-01

Two new lanthanide coordination polymers H 2 N(CH 3 ) 2 .[Eu III 2 (L 1 ) 3 (L 2 )] (1, L 1 =isophthalic acid dianion, L 2 =formic acid anion) and [La III (2,5-PDC)(L 2 )](2, 2,5-PDC=2,5-pyridinedicarboxylate dianion) were synthesized under solvothermal conditions. It is of interest that the formic ligand (L 2 ) is not contained in the stating materials, but arises from the water molecule-enhanced CO 2 insertion during the solvothermal process. Both of the two compounds exhibit complicated three dimensional sandwich-like frameworks. - Graphical abstract: Two new lanthanide coordination polymers involving water molecule-enhanced CO 2 insertion resulting in the formation of formic anion and dimethylammonium cation were synthesized under solvothermal conditions.

Gloss and Stain Resistance of Ceramic-Polymer CAD/CAM Restorative Blocks.

Science.gov (United States)

Lawson, Nathaniel C; Burgess, John O

2016-03-01

To evaluate the gloss and stain resistance of several new ceramic-polymer CAD/CAM blocks Specimens (4 mm) were sectioned from: Enamic (polymer-infused ceramic), LAVA Ultimate (nano-ceramic reinforced polymer), e.max (lithium disilicate), Paradigm C (porcelain), and Paradigm MZ100 (composite). Specimens were wet polished on a polishing wheel to either 320 grit silicon paper (un-polished, N = 8) or 2000 grit silicon carbide papers followed by a 0.05 μm alumina slurry (polished, N = 8). Initial gloss and color (L*a*b*) values were measured. Specimens were stored in a staining solution at 37°C in darkness for 12 days (simulating 1 year). After storage, L*a*b* values re-measured. Change in color was reported as ΔE00 based on the CIEDE2000 formula. Gloss and ΔE00 were analyzed by two-way analysis of variance (ANOVA) (alpha = .05). Separate one-way ANOVA and Tukey post-hoc analyses were performed for both polish conditions and all materials. Two-way ANOVA showed that factors material, polish and their interaction were significant for both gloss and ΔE00 (p gloss and less color change than all other materials. The composition and polish of CAD/CAM materials affects gloss and stain resistance. Ceramic-polymer hybrid materials can achieve the high gloss required for esthetic restorations. These materials should be polished in order to minimize staining. If polished, all of the tested materials exhibited clinically acceptable color changes at 1 year of simulated staining. (J Esthet Restor Dent 28:S40-S45, 2016). © 2015 Wiley Periodicals, Inc.

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

Science.gov (United States)

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

2012-04-05

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

Microcellular poly(hydroxybutyrate-co-hydroxyvalerate)-hyperbranched polymer-nanoclay nanocomposites

Science.gov (United States)

Alireza Javadi; Yottha Srithep; Srikanth Pilla; Craig C. Clemons; Shaoqin Gong; Lih-Sheng Turng

2012-01-01

The effects of incorporating hyperbranched polymers (HBPs) and different nanoclays [Cloisite® 30B and halloysite nanotubes (HNT)] on the mechanical, morphological, and thermal properties of solid and microcellular poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) were investigated. According to the X-ray diffraction (...

Biofunctionalized ferromagnetic CoPt{sub 3}/polymer nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Martins, M A [Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Neves, M C [Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Esteves, A C C [Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Girginova, P I [Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Guiomar, A J [Department of Biochemistry and CNC, University of Coimbra, 3001-401 Coimbra (Portugal); Amaral, V S [Department of Physics, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Trindade, T [Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal)

2007-05-30

Magnetic latexes were prepared by the encapsulation of organically capped CoPt{sub 3} nanoparticles via miniemulsion in situ radical polymerization of tert-butyl acrylate (tBA). This is the first example of a CoPt{sub 3} based polymer nanocomposite showing ferromagnetic behaviour at room temperature. Each nanocomposite particle contains a magnetic core composed of CoPt{sub 3} nanoparticles (d{approx}7 nm, a{sub 0} = 3.848 A) encapsulated by poly(t-butyl acrylate). The CoPt{sub 3}/PtBA latexes contain polyester groups that can be readily hydrolysed, rendering the surface with carboxylic functionalities and hence allowing bioconjugation. Complementary to such surface modification experiments, we report that bovine IgG antibodies can bind to the magnetic latexes, and the potential of the nanocomposites for in vitro specific bioapplications is discussed.

Mesomorphic structure of poly(styrene)-block-poly(4-vinylpyridine) with oligo(ethylene oxide)sulfonic acid side chains as a model for molecularly reinforced polymer electrolyte

NARCIS (Netherlands)

Kosonen, H; Valkama, S; Hartikainen, J; Eerikainen, H; Torkkeli, M; Jokela, K; Serimaa, R; Sundholm, F; ten Brinke, G; Ikkala, O; Eerikäinen, Hannele

2002-01-01

We report self-organized polymer electrolytes based on poly(styrene)-block-poly(4-vinylpyridine) (PS-block-P4VP). Liquidlike ethylene oxide (EO) oligomers with sulfonic acid end groups are bonded to the P4VP block, leading to comb-shaped supramolecules with the PS-block-P4VP backbone. Lithium

Production of co-polymers of polyhydroxyalkanoates by regulating the hydrolysis of biowastes.

Science.gov (United States)

Kumar, Prasun; Ray, Subhasree; Kalia, Vipin C

2016-01-01

Production of polyhydroxyalkanoate (PHA) co-polymers by Bacillus spp. was studied by feeding defined volatile fatty acids (VFAs) obtained through controlled hydrolysis of various wastes. Eleven mixed hydrolytic cultures (MHCs) each containing 6 strains could generate VFA from slurries of (2% total solids): pea-shells (PS), potato peels (PP), apple pomace (AP) and onion peels (OP). PS hydrolysates (obtained with MHC2 and MHC5) inoculated with Bacillus cereus EGU43 and Bacillus thuringiensis EGU45 produced co-polymers of PHA at the rate of 15-60mg/L with a 3HV content of 1%w/w. An enhancement in PHA yield of 3.66-fold, i.e. 205-550mg/L with 3HV content up to 7.5%(w/w) was observed upon addition of OP hydrolysate and 1% glucose (w/v) to PS hydrolysates. This is the first demonstration, where PHA co-polymer composition, under non-axenic conditions, could be controlled by customizing VFA profile of the hydrolysate by the addition of different biowastes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Poly(vinylpyridine-co-styrene) based in situ cross-linked gel polymer electrolyte for lithium-ion polymer batteries

International Nuclear Information System (INIS)

Oh, Sijin; Kim, Dong Wook; Lee, Changjin; Lee, Myong-Hoon; Kang, Yongku

2011-01-01

A gel polymer electrolyte (GPE) was successfully prepared by means of an in situ cross-linking reaction of poly(2-vinylpyridine-co-styrene) and oligo(ethylene oxide) with epoxide functional groups at 65 °C without using a polymerization initiator. A stable gel polymer electrolyte could be obtained by adding only 1% of a polymer gelator. The ionic conductivity of the GPE containing 99 wt% of liquid electrolyte was measured to be ca. 10 −2 S/cm at the ambient temperature. The ionic conductivity of the resulting GPE was comparable to that of a pure liquid electrolyte. The electrochemical stability window of the prepared gel polymer electrolytes was measured to be 5.2 V. The test cell carried a discharge capacity of 133.2 mAh/g at 0.1 C and showed good cycling performance with negligible capacity fading after the 200th cycle, maintaining 99.5% coulombic efficiency throughout 200 cycles. The resulting gel polymer electrolyte prepared by in situ thermal cross-linking without a polymerization initiator holds promise for application to on the high power lithium-ion polymer batteries.

Towards improved solubility of poorly water-soluble drugs: cryogenic co-grinding of piroxicam with carrier polymers.

Science.gov (United States)

Penkina, Anna; Semjonov, Kristian; Hakola, Maija; Vuorinen, Sirpa; Repo, Timo; Yliruusi, Jouko; Aruväli, Jaan; Kogermann, Karin; Veski, Peep; Heinämäki, Jyrki

2016-01-01

Amorphous solid dispersions (SDs) open up exciting opportunities in formulating poorly water-soluble active pharmaceutical ingredients (APIs). In the present study, novel catalytic pretreated softwood cellulose (CPSC) and polyvinylpyrrolidone (PVP) were investigated as carrier polymers for preparing and stabilizing cryogenic co-ground SDs of poorly water-soluble piroxicam (PRX). CPSC was isolated from pine wood (Pinus sylvestris). Raman and Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) were used for characterizing the solid-state changes and drug-polymer interactions. High-resolution scanning electron microscope (SEM) was used to analyze the particle size and surface morphology of starting materials and final cryogenic co-ground SDs. In addition, the molecular aspects of drug-polymer interactions and stabilization mechanisms are presented. The results showed that the carrier polymer influenced both the degree of amorphization of PRX and stabilization against crystallization. The cryogenic co-ground SDs prepared from PVP showed an enhanced dissolution rate of PRX, while the corresponding SDs prepared from CPSC exhibited a clear sustained release behavior. In conclusion, cryogenic co-grinding provides a versatile method for preparing amorphous SDs of poorly water-soluble APIs. The solid-state stability and dissolution behavior of such co-ground SDs are to a great extent dependent on the carrier polymer used.

Responsive linear-dendritic block copolymers.

Science.gov (United States)

Blasco, Eva; Piñol, Milagros; Oriol, Luis

2014-06-01

The combination of dendritic and linear polymeric structures in the same macromolecule opens up new possibilities for the design of block copolymers and for applications of functional polymers that have self-assembly properties. There are three main strategies for the synthesis of linear-dendritic block copolymers (LDBCs) and, in particular, the emergence of click chemistry has made the coupling of preformed blocks one of the most efficient ways of obtaining libraries of LDBCs. In these materials, the periphery of the dendron can be precisely functionalised to obtain functional LDBCs with self-assembly properties of interest in different technological areas. The incorporation of stimuli-responsive moieties gives rise to smart materials that are generally processed as self-assemblies of amphiphilic LDBCs with a morphology that can be controlled by an external stimulus. Particular emphasis is placed on light-responsive LDBCs. Furthermore, a brief review of the biomedical or materials science applications of LDBCs is presented. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of amylose-block-polystyrene rod-coil block copolymers

NARCIS (Netherlands)

Loos, Katja; Stadler, Reimund

1997-01-01

In the present communication we demonstrate the synthesis of a hybrid block copolymer based on the combination of a biopolymer (amylose) with a synthetic block (polystyrene). To obtain such materials, amino-functionalized polymers were modified with maltoheptaose moieties that serve as initiators

A Thieno[3,2-b][1]benzothiophene Isoindigo Building Block for Additive- and Annealing-Free High-Performance Polymer Solar Cells

KAUST Repository

Yue, Wan; Ashraf, Raja Shahid; Nielsen, Christian B.; Collado-Fregoso, Elisa; Niazi, Muhammad Rizwan; Yousaf, Syeda Amber; Kirkus, Mindaugas; Chen, Hung-Yang; Amassian, Aram; Durrant, James R.; McCulloch, Iain

2015-01-01

A novel photoactive polymer with two different molecular weights is reported, based on a new building block: thieno[3,2-b][1]benzothiophene isoindigo. Due to the improved crystallinity, optimal blend morphology, and higher charge mobility, solar-cell devices of the high-molecular-weight polymer exhibit a superior performance, affording efficiencies of 9.1% without the need for additives, annealing, or additional extraction layers during device fabrication.

A Thieno[3,2-b][1]benzothiophene Isoindigo Building Block for Additive- and Annealing-Free High-Performance Polymer Solar Cells

KAUST Repository

Yue, Wan

2015-08-20

A novel photoactive polymer with two different molecular weights is reported, based on a new building block: thieno[3,2-b][1]benzothiophene isoindigo. Due to the improved crystallinity, optimal blend morphology, and higher charge mobility, solar-cell devices of the high-molecular-weight polymer exhibit a superior performance, affording efficiencies of 9.1% without the need for additives, annealing, or additional extraction layers during device fabrication.

Ultrasonic, Molecular and Mechanical Testing Diagnostics in Natural Fibre Reinforced, Polymer-Stabilized Earth Blocks

Directory of Open Access Journals (Sweden)

C. Galán-Marín

2013-01-01

Full Text Available The aim of this research study was to evaluate the influence of utilising natural polymers as a form of soil stabilization, in order to assess their potential for use in building applications. Mixtures were stabilized with a natural polymer (alginate and reinforced with wool fibres in order to improve the overall compressive and flexural strength of a series of composite materials. Ultrasonic pulse velocity (UPV and mechanical strength testing techniques were then used to measure the porous properties of the manufactured natural polymer-soil composites, which were formed into earth blocks. Mechanical tests were carried out for three different clays which showed that the polymer increased the mechanical resistance of the samples to varying degrees, depending on the plasticity index of each soil. Variation in soil grain size distributions and Atterberg limits were assessed and chemical compositions were studied and compared. X-ray diffraction (XRD, X-ray fluorescence spectroscopy (XRF, and energy dispersive X-ray fluorescence (EDXRF techniques were all used in conjunction with qualitative identification of the aggregates. Ultrasonic wave propagation was found to be a useful technique for assisting in the determination of soil shrinkage characteristics and fibre-soil adherence capacity and UPV results correlated well with the measured mechanical properties.

Naphthalene Bis(4,8-diamino-1,5-dicarboxyl)amide Building Block for Semiconducting Polymers.

Science.gov (United States)

Eckstein, Brian J; Melkonyan, Ferdinand S; Manley, Eric F; Fabiano, Simone; Mouat, Aidan R; Chen, Lin X; Facchetti, Antonio; Marks, Tobin J

2017-10-18

We report a new naphthalene bis(4,8-diamino-1,5-dicarboxyl)amide (NBA) building block for polymeric semiconductors. Computational modeling suggests that regio-connectivity at the 2,6- or 3,7-NBA positions strongly modulates polymer backbone torsion and, therefore, intramolecular π-conjugation and aggregation. Optical, electrochemical, and X-ray diffraction characterization of 3,7- and 2,6-dithienyl-substituted NBA molecules and corresponding isomeric NBA-bithiophene copolymers P1 and P2, respectively, reveals the key role of regio-connectivity. Charge transport measurements demonstrate that while the twisted 3,7-NDA-based P1 is a poor semiconductor, the planar 2,6-functionalized NBA polymers (P2-P4) exhibit ambipolarity, with μ e and μ h of up to 0.39 and 0.32 cm 2 /(V·s), respectively.

Thermo- and pH-responsive poly(A-ProOMe)-graft-poly(AAc) membrane for selective separation of metal ions

International Nuclear Information System (INIS)

Hasegawa, Shin; Maekawa, Yasunari; Yoshida, Masaru; Ohashi, Hitoshi; Katakai, Ryoichi

2009-01-01

We investigated the permeation behavior of Li, Co, and Ni ions through thermo- and pH-responsive gel membranes, which were prepared by γ-ray grafting of pH-responsive poly(acrylic acid) (poly(AAc)) onto a thermo-responsive polymer gel of acryloyl-L-proline methyl ester (A-ProOMe). Using 15% AAc grafted membranes, the permeation constants of Li ions are 2.8 and 3.5 times higher than those of Co and Ni ions in a pH 6.0 buffer solution at 30degC. These ratios are two and three times higher than those of 5 and 43% grafted gel membranes, respectively. By comparison with the permeation of metal ions through the non-thermo-responsive porous polyethylene membranes grafted with AAc chains or random copolymer gel membranes (poly(A-ProOMe-co-AAc)), it is clear that the structure in which adjacent carboxyl groups of poly(AAc) are surrounded by thermo-responsive A-ProOMe matrix causes selective permeability of Li ion over Co and Ni ions. The distributions of Co and Ni ions in the microscopic structures clearly show that the structure consisting of flexible chains of the carboxyl groups grafted onto the thermo-response gel membrane plays a decisive role in the superior selective permeation of a Li ion. (author)

Transport of Water in Semicrystalline Block Copolymer Membranes

Science.gov (United States)

Hallinan, Daniel; Oparaji, Onyekachi

Poly(styrene)-block-poly(ethylene oxide) (PS- b-PEO) is a semicrystalline block copolymer (BCP) with interesting properties. It is mechanically tough, amphiphilic, and has a polar phase. The mechanical toughness is due to the crystallinity of PEO and the high glass transition temperature of PS, as well as the morphological structure of the BCP. The polymer has high CO2, water, and salt solubility that derive from the polar PEO component. Potential applications include CO2 separation, water purification, and lithium air batteries. In all of the aforementioned applications, water transport is an important parameter. The presence of water can also affect thermal and mechanical properties. Water transport and thermal and mechanical properties of a lamellar PS- b-PEO copolymer have been measured as a function of water activity. Water transport can be affected by the heterogeneous nature of a semicrystalline BCP. Therefore, Fourier transform infrared - attenuated total reflectance (FTIR-ATR) spectroscopy has been employed, because water transport and polymer swelling can be measured simultaneously. The effect of BCP structure on transport has been investigated by comparing water transport in PS- b-PEO to a PEO homopolymer. The crystalline content of the PEO and the presence of glassy PS lamellae will be used to explain the transport results.

Examining the Self-Assembly of Rod-Coil Block Copolymers via Physics Based Polymer Models and Polarized X-Ray Scattering

Science.gov (United States)

Hannon, Adam; Sunday, Daniel; Windover, Donald; Liman, Christopher; Bowen, Alec; Khaira, Gurdaman; de Pablo, Juan; Delongchamp, Dean; Kline, R. Joseph

Photovoltaics, flexible electronics, and stimuli-responsive materials all require enhanced methodology to examine their nanoscale molecular orientation. The mechanical, electronic, optical, and transport properties of devices made from these materials are all a function of this orientation. The polymer chains in these materials are best modeled as semi-flexible to rigid rods. Characterizing the rigidity and molecular orientation of these polymers non-invasively is currently being pursued by using polarized resonant soft X-ray scattering (P-RSoXS). In this presentation, we show recent work on implementing such a characterization process using a rod-coil block copolymer system in the rigid-rod limit. We first demonstrate how we have used physics based models such as self-consistent field theory (SCFT) in non-polarized RSoXS work to fit scattering profiles for thin film coil-coil PS- b-PMMA block copolymer systems. We then show by using a wormlike chain partition function in the SCFT formulism to model the rigid-rod block, the methodology can be used there as well to extract the molecular orientation of the rod block from a simulated P-RSoXS experiment. The results from the work show the potential of the technique to extract thermodynamic and morphological sample information.

Self-Assembly of Diblock Molecular Polymer Brushes in the Spherical Confinement of Nanoemulsion Droplets.

Science.gov (United States)

Steinhaus, Andrea; Pelras, Théophile; Chakroun, Ramzi; Gröschel, André H; Müllner, Markus

2018-05-02

Understanding the self-assembly behavior of polymers of various topologies is key to a reliable design of functional polymer materials. Self-assembly under confinement conditions emerges as a versatile avenue to design polymer particles with complex internal morphologies while simultaneously facilitating scale-up. However, only linear block copolymers have been studied to date, despite the increasing control over macromolecule composition and architecture available. This study extends the investigation of polymer self-assembly in confinement from regular diblock copolymers to diblock molecular polymer brushes (MPBs). Block-type MPBs with polystyrene (PS) and polylactide (PLA) compartments of different sizes are incorporated into surfactant-stabilized oil-in-water (chloroform/water) emulsions. The increasing confinement in the nanoemulsion droplets during solvent evaporation directs the MPBs to form solid nano/microparticles. Microscopy studies reveal an intricate internal particle structure, including interpenetrating networks and axially stacked lamellae of PS and PLA, depending on the PS/PLA ratio of the brushes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of glutathione as chain transfer agent in PNIPAAm-based thermo-responsive hydrogels for controlled release of proteins.

Science.gov (United States)

Drapala, Pawel W; Jiang, Bin; Chiu, Yu-Chieh; Mieler, William F; Brey, Eric M; Kang-Mieler, Jennifer J; Pérez-Luna, Victor H

2014-03-01

To control degradation and protein release using thermo-responsive hydrogels for localized delivery of anti-angiogenic proteins. Thermo-responsive hydrogels derived from N-isopropylacrylamide (NIPAAm) and crosslinked with poly(ethylene glycol)-co-(L-lactic acid) diacrylate (Acry-PLLA-b-PEG-b-PLLA-Acry) were synthesized via free radical polymerization in the presence of glutathione, a chain transfer agent (CTA) added to modulate their degradation and release properties. Immunoglobulin G (IgG) and the recombinant proteins Avastin® and Lucentis® were encapsulated in these hydrogels and their release was studied. The encapsulation efficiency of IgG was high (75-87%) and decreased with CTA concentration. The transition temperature of these hydrogels was below physiological temperature, which is important for minimally invasive therapies involving these materials. The toxicity from unreacted monomers and free radical initiators was eliminated with a minimum of three buffer extractions. Addition of CTA accelerated degradation and resulted in complete protein release. Glutathione caused the degradation products to become solubilized even at 37°C. Hydrogels prepared without glutathione did not disintegrate nor released protein completely after 3 weeks at 37°C. PEGylation of IgG postponed the burst release effect. Avastin® and Lucentis® released from degraded hydrogels retained their biological activity. These systems offer a promising platform for the localized delivery of proteins.

The guanidinium group as a key part of water-soluble polymer carriers for siRNA complexation and protection against degradation.

Science.gov (United States)

Tabujew, Ilja; Freidel, Christoph; Krieg, Bettina; Helm, Mark; Koynov, Kaloian; Müllen, Klaus; Peneva, Kalina

2014-07-01

Here, the preparation of a novel block copolymer consisting of a statistical copolymer N-(2-hydroxypropyl) methacrylamide-s-N-(3-aminopropyl) methacrylamide and a short terminal 3-guanidinopropyl methacrylamide block is reported. This polymer structure forms neutral but water-soluble nanosized complexes with siRNA. The siRNA block copolymer complexes are first analyzed using agarose gel electrophoresis and their size is determined with fluorescence correlation spectroscopy. The protective properties of the polymer against RNA degradation are investigated by treating the siRNA block copolymer complexes with RNase V1. Heparin competition assays confirm the efficient release of the cargo in vitro. In addition, the utilization of microscale thermophoresis is demonstrated for the determination of the binding strength between a fluorescently labeled polyanion and a polymer molecule. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solubilization of trace organics in block copolymer micelles for environmental separation using membrane extraction principles

Energy Technology Data Exchange (ETDEWEB)

Hatton, T.A.

1992-12-01

The solubilization of a range of polycyclic aromatic hydrocarbons in block copolymer micelles has been studied as a function of polymer composition, architecture, and temperature. Micelle formation is favored at high temperatures, leading to significant enhancements in solubilization capacity. At low temperatures, however, micelles do not form and the solubilization capacity of the block copolymer solution for the organics is low; this provides a convenient method for the regeneration of micellar solutions used as solvents'' in the treatment of contaminated feed streams using membrane extraction principles. It has also been shown (in collaboration with K.P. Johnston of University of Texas, Austin) that supercritical CO[sub 2] can be used effectively for micelle regeneration. Theoretical calculations of the structure of block copolymer micelles in the presence and absence of solutes using self-consistent mean-field lattice theories have successfully captured the trends observed with changing polymer composition and architecture, often quantitatively. The temperature and composition dependence of the micellar properties were determined by allowing the individual polymer segments to assume both polar and non-polar conformations.

Combinational Effect of Cell Adhesion Biomolecules and Their Immobilized Polymer Property to Enhance Cell-Selective Adhesion

Directory of Open Access Journals (Sweden)

Rio Kurimoto

2016-01-01

Full Text Available Although surface immobilization of medical devices with bioactive molecules is one of the most widely used strategies to improve biocompatibility, the physicochemical properties of the biomaterials significantly impact the activity of the immobilized molecules. Herein we investigate the combinational effects of cell-selective biomolecules and the hydrophobicity/hydrophilicity of the polymeric substrate on selective adhesion of endothelial cells (ECs, fibroblasts (FBs, and smooth muscle cells (SMCs. To control the polymeric substrate, biomolecules are immobilized on thermoresponsive poly(N-isopropylacrylamide-co-2-carboxyisopropylacrylamide (poly(NIPAAm-co-CIPAAm-grafted glass surfaces. By switching the molecular conformation of the biomolecule-immobilized polymers, the cell-selective adhesion performances are evaluated. In case of RGDS (Arg-Gly-Asp-Ser peptide-immobilized surfaces, all cell types adhere well regardless of the surface hydrophobicity. On the other hand, a tri-Arg-immobilized surface exhibits FB-selectivity when the surface is hydrophilic. Additionally, a tri-Ile-immobilized surface exhibits EC-selective cell adhesion when the surface is hydrophobic. We believe that the proposed concept, which is used to investigate the biomolecule-immobilized surface combination, is important to produce new biomaterials, which are highly demanded for medical implants and tissue engineering.

Synthesis and Self-Assembly of Block Copolymers Containing Temperature Sensitive and Degradable Chain Segments.

Science.gov (United States)

Gong, Hong-Liang; Lei, Lei; Shi, Shu-Xian; Xia, Yu-Zheng; Chen, Xiao-Nong

2018-05-01

In this work, polylactide-b-poly(N-isopropylacrylamide) were synthesized by the combination of controlled ring-opening polymerization and reversible addition fragmentation chain transfer polymerization. These block copolymers with molecular weight range from 7,900 to 12,000 g/mol and narrow polydispersity (≤1.19) can self-assemble into micelles (polylactide core, poly(N-isopropylacrylamide) shell) in water at certain temperature range, which have been evidenced by laser particle size analyzer proton nuclear magnetic resonance and transmission electron microscopy. Such micelles exhibit obvious thermo-responsive properties: (1) Poly(N-isopropylacrylamide) blocks collapse on the polylactide core as system temperature increase, leading to reduce of micelle size. (2) Micelles with short poly(N-isopropylacrylamide) blocks tend to aggregate together when temperature increased, which is resulted from the reduction of the system hydrophilicity and the decreased repulsive force between micelles.

Visualizing phase transition behavior of dilute stimuli responsive polymer solutions via Mueller matrix polarimetry.

Science.gov (United States)

Narayanan, Amal; Chandel, Shubham; Ghosh, Nirmalya; De, Priyadarsi

2015-09-15

Probing volume phase transition behavior of superdiluted polymer solutions both micro- and macroscopically still persists as an outstanding challenge. In this regard, we have explored 4 × 4 spectral Mueller matrix measurement and its inverse analysis for excavating the microarchitectural facts about stimuli responsiveness of "smart" polymers. Phase separation behavior of thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and pH responsive poly(N,N-(dimethylamino)ethyl methacrylate) (PDMAEMA) and their copolymers were analyzed in terms of Mueller matrix derived polarization parameters, namely, depolarization (Δ), diattenuation (d), and linear retardance (δ). The Δ, d, and δ parameters provided useful information on both macro- and microstructural alterations during the phase separation. Additionally, the two step action ((i) breakage of polymer-water hydrogen bonding and (ii) polymer-polymer aggregation) at the molecular microenvironment during the cloud point generation was successfully probed via these parameters. It is demonstrated that, in comparison to the present techniques available for assessing the hydrophobic-hydrophilic switch over of simple stimuli-responsive polymers, Mueller matrix polarimetry offers an important advantage requiring a few hundred times dilute polymer solution (0.01 mg/mL, 1.1-1.4 μM) at a low-volume format.

Approaches for Making High Performance Polymer Materials from Commodity Polymers

Institute of Scientific and Technical Information of China (English)

Xu Xi

2004-01-01

A brief surrey of ongoing research work done for improving and enhancing the properties of commodity polymers by the author and author's colleagues is given in this paper. A series of high performance polymers and polymer nanomaterials were successfully prepared through irradiation and stress-induced reactions of polymers and hydrogen bonding. The methods proposed are viable, easy in operation, clean and efficient.1. The effect of irradiation source (UV light, electron beam, γ -ray and microwave), irradiation dose, irradiation time and atmosphere etc. on molecular structure of polyolefine during irradiation was studied. The basic rules of dominating oxidation, degradation and cross-linking reactions were mastered. Under the controlled conditions, cross-linking reactions are prevented, some oxygen containing groups are introduced on the molecular chain of polyolefine to facilitate the interface compatibility of their blends. A series of high performance polymer materials: u-HDPE/PA6,u-HDPE/CaCO3, u-iPP/STC, γ-HDPE/STC, γ-LLDPE/ATH, e-HDPE, e-LLDPE and m-HDPEfilled system were prepared (u- ultraviolet light irradiated, γ- γ-ray irradiated, e- electron beam irradiated, m- microwave irradiated)2. The effect of ultrasonic irradiation, jet and pan-milling on structure and changes in properties of polymers were studied. Imposition of critical stress on polymer chain can cause the scission of bonds to form macroradicals. The macroradicals formed in this way may recombine or react with monomer or other radicals to form linear, branched or cross-linked polymers or copolymers. About 20 kinds of block/graft copolymers have been synthesized from polymer-polymer or polymer-monomer through ultrasonic irradiation.Through jet-milling, the molecular weight of PVC is decreased somewhat, the intensity of its crystalline absorption bonds becomes indistinct. The processability, the yield strength, strength at break and elongation at break of PVC get increased quite a lot after

Studies on the antifungal activities of the novel synthesized chelating co-polymer emulsion lattices and their silver complexes

Directory of Open Access Journals (Sweden)

Abd-El-Ghaffar M.A.

2008-01-01

Full Text Available The novel binary chelating co-polymers of butyl acrylate with itaconic and maleic acids were prepared by emulsion polymerization process. The chelating co-polymers of butyl acrylate-co-itaconic acid (BuA/IA and butyl acrylate-co-maleic acid (BuA/MA and their silver complexes were characterized and identified using IR spectroscopy and differential scanning calorimetry (DSC measurements. The biological activities of these compounds were studied against various types of fungal species. The dose and the rate of leached silver ions were controlled by the type of the co-polymers used and the solubility in the medium. The results provided laboratory support for the concept that the polymers containing chemically bound biocide are useful for controlling microbial growth. The silver uptake by strains of different fungal species was studied to determine their difference in behavior to the antifungal activities of these compounds. The uptake strategy was examined by transmission electron microscopy (TEM.

Amplifying (Im)perfection: The Impact of Crystallinity in Discrete and Disperse Block Co-oligomers.

Science.gov (United States)

van Genabeek, Bas; Lamers, Brigitte A G; de Waal, Bas F M; van Son, Martin H C; Palmans, Anja R A; Meijer, E W

2017-10-25

Crystallinity is seldomly utilized as part of the microphase segregation process in ultralow-molecular-weight block copolymers. Here, we show the preparation of two types of discrete, semicrystalline block co-oligomers, comprising an amorphous oligodimethylsiloxane block and a crystalline oligo-l-lactic acid or oligomethylene block. The self-assembly of these discrete materials results in lamellar structures with unforeseen uniformity in the domain spacing. A systematic introduction of dispersity reveals the extreme sensitivity of the microphase segregation process toward chain length dispersity in the crystalline block.

Embodied Energy and CO2 Analyses of Mud-brick and Cement-block Houses

Directory of Open Access Journals (Sweden)

Abanda F.Henry

2014-01-01

Full Text Available In building projects, the extraction of vast quantities of materials is too common. The extraction of materials and the erection of buildings consume embodied energy and emit carbon dioxide (CO2 that impact negatively on the environment. Therefore it is necessary to consider embodied energy and CO2 amongst other factors in selecting building materials for use in building projects. In most developing countries, building environmental performance analysis has yet to gain interest from the construction community. However, with recent increase in sustainability awareness, both developed and developing nations have engaged in efforts to tackle this challenge. Embodied energy and CO2 are among the leading parameters in assessing environmental building performance. In Cameroon, studies about the assessment of embodied energy and CO2 of building projects are scarce. Hence, professionals find it difficult to make alternative choices for building materials to use in their different building projects. This study uses a detailed process analysis approach supported by two popular housing types in Cameroon (mud-brick and cement-block houses to assess the embodied energy and CO2 impacts from building materials. The emerging Building Information Modelling (BIM tool was used to validate the computational results of the process analysis method. The findings revealed the embodied energy and CO2 for the mud-brick houses are 137934.91 MJ (2007.8 MJ/m2 and 15665.56 Kg CO2 (228.03 Kg CO2/m2; the cement-block houses are 292326.81 MJ (3065.51 MJ/m2 and 37829.19 Kg CO2 (396.7 Kg CO2/m2 respectively. Thus, the cement-block house expends at least 1.5 times more embodied energy and emits at least 1.7 times more embodied CO2 than mud-brick house. Although these findings cannot be generalized, they nonetheless indicate the importance of considering embodied energy and CO2 in making alternative choices for use in different building projects.

Tunable thermo-responsive hydrogels: synthesis, structural analysis and drug release studies.

Science.gov (United States)

Cirillo, Giuseppe; Spataro, Tania; Curcio, Manuela; Spizzirri, U Gianfranco; Nicoletta, Fiore Pasquale; Picci, Nevio; Iemma, Francesca

2015-03-01

Thermo-responsive hydrogel films, synthesized by UV-initiated radical polymerization, are proposed as delivery devices for non-steroidal anti-inflammatory drugs (Diclofenac sodium and Naproxen). N-isopropylacrylamide and N,N'-ethylenebisacrylamide were chosen as thermo-sensitive monomer and crosslinker, respectively. Infrared spectroscopy was used to assess the incorporation of monomers into the network, and the network density of hydrogel films was found to strictly depend on both feed composition and film thickness. Calorimetric analyses showed negative thermo-responsive behaviour with shrinking/swelling transition values in the range 32.8-36.1°C. Equilibrium swelling studies around the LCST allowed the correlation between the structural changes and the temperature variations. The mesh size, indeed, rapidly changed from a collapsed to a swollen state, with beneficial effects in applications such as size-selective permeation or controlled drug delivery, while the crosslinking degree, the film thickness, and the loading method deeply influenced the drug release profiles at 25 and 40°C. The analysis of both 3D-network structure, release kinetics and diffusional constraints at different temperatures was evaluated by mathematical modelling. Copyright © 2014 Elsevier B.V. All rights reserved.

Growing Embossed Nanostructures of Polymer Brushes on Wet-Etched Silicon Templated via Block Copolymers

Science.gov (United States)

Lu, Xiaobin; Yan, Qin; Ma, Yinzhou; Guo, Xin; Xiao, Shou-Jun

2016-02-01

Block copolymer nanolithography has attracted enormous interest in chip technologies, such as integrated silicon chips and biochips, due to its large-scale and mass production of uniform patterns. We further modified this technology to grow embossed nanodots, nanorods, and nanofingerprints of polymer brushes on silicon from their corresponding wet-etched nanostructures covered with pendent SiHx (X = 1-3) species. Atomic force microscopy (AFM) was used to image the topomorphologies, and multiple transmission-reflection infrared spectroscopy (MTR-IR) was used to monitor the surface molecular films in each step for the sequential stepwise reactions. In addition, two layers of polymethacrylic acid (PMAA) brush nanodots were observed, which were attributed to the circumferential convergence growth and the diffusion-limited growth of the polymer brushes. The pH response of PMAA nanodots in the same region was investigated by AFM from pH 3.0 to 9.0.

Helix-sense-selective co-precipitation for preparing optically active helical polymer nanoparticles/graphene oxide hybrid nanocomposites.

Science.gov (United States)

Huang, Huajun; Li, Weifei; Shi, Yan; Deng, Jianping

2017-05-25

Constructing optically active helical polymer based nanomaterials without using expensive and limited chirally helical polymers has become an extremely attractive research topic in both chemical and materials science. In this study, we prepared a series of optically active helical polymer nanoparticles/graphene oxide (OAHPNs/GO) hybrid nanocomposites through an unprecedented strategy-the co-precipitation of optically inactive helical polymers and chirally modified GO. This approach is named helix-sense-selective co-precipitation (HSSCP), in which the chirally modified GO acted as a chiral source for inducing and further stabilizing the predominantly one-handed helicity in the optically inactive helical polymers. SEM and TEM images show quite similar morphologies of all the obtained OAHPNs/GO nanocomposites; specifically, the chirally modified GO sheets were uniformly decorated with spherical polymer nanoparticles. Circular dichroism (CD) and UV-vis absorption spectra confirmed the preferentially induced helicity in the helical polymers and the optical activity of the nanocomposites. The established HSSCP strategy is thus proven to be widely applicable and is expected to produce numerous functional OAHPNs/GO nanocomposites and even the analogues.

Polymer coated nanogold for tracing mobility of engineered nanoparticles in subsurface water

DEFF Research Database (Denmark)

Uthuppu, Basil; Fjordbøge, Annika Sidelmann; Fischer, Søren Vang

2014-01-01

Gold nanoparticles coated with amphiphilic block co-polymer PVP-VA are found to be extremely mobile in sand columns in laboratory based experiments. The ultra-stability obtained by such surface modification is also shown by diluting down to a concentration of 62.5 ppb in groundwater having other ...

Amphiphilic block copolymers as efficiency boosters in microemulsions a SANS investigation of the role of polymers

CERN Document Server

Endo, H; Mihailescu, M; Monkenbusch, M; Gompper, G; Richter, D; Jakobs, B; Sottmann, T; Strey, R

2002-01-01

The effect of amphiphilic block copolymers on ternary microemulsions (water, oil and non-ionic surfactant) is investigated. Small amounts of PEP-PEO block copolymer lead to a dramatic expansion of the one-phase region where water and oil can be solubilized by the mediation of surfactant molecules. Small-angle neutron-scattering experiments employing a high-precision two-dimensional contrast-variation technique demonstrate that the polymer is distributed uniformly on the surfactant membrane, where it modifies the membrane curvature elasticity. Furthermore, a new approach to determine the bending rigidity of an amphiphilic membrane is proposed, which is precise enough to measure the logarithmic scale dependence of the bending rigidity and its universal prefactor in bicontinuous microemulsions. (orig.)

Thermoresponsive microgels containing trehalose as soft matrices for 3D cell culture.

Science.gov (United States)

Burek, Małgorzata; Waśkiewicz, Sylwia; Lalik, Anna; Student, Sebastian; Bieg, Tadeusz; Wandzik, Ilona

2017-01-31

A series of thermoresponsive glycomicrogels with trehalose in the cross-links or with trehalose in the cross-links and as pending moieties was synthesized. These materials were obtained by surfactant-free precipitation copolymerization of N-isopropylacrylamide and various amounts of trehalose monomers. The resultant particles showed a spherical shape and a submicrometer hydrodynamic size with a narrow size distribution. At 25 °C, glycomicrogels in solutions with physiological ionic strength formed stable colloids, which further gelled upon heating to physiological temperature forming a macroscopic hydrogel with an interconnected porous structure. These extremely soft matrices with dynamic storage modulus in the range of 9-70 Pa were examined in 3D culture systems for HeLa cell culture in comparison to traditional 2D mode. They showed relatively low syneresis over time, especially when glycomicrogels with a high content of hydrophilic trehalose were used as building blocks. An incorporated pending trehalose composed of two α,α'-1,1'-linked d-glucose moieties was used with the intention of providing multivalent interactions with glucose transporters (GLUTs) expressed on the cell surface. A better cell viability was observed when a soft hydrogel with the highest content of trehalose and the lowest syneresis was used as a matrix compared to a 2D control assay.

Polymer Nanocomposites with Cellulose Nanocrystals Featuring Adaptive Surface Groups.

Science.gov (United States)

Natterodt, Jens C; Sapkota, Janak; Foster, E Johan; Weder, Christoph

2017-02-13

Cellulose nanocrystals (CNCs) are mechanically rigid, toxicologically benign, fiber-like nanoparticles. They can easily be extracted from renewable biosources and have attracted significant interest as reinforcing fillers in polymers. We here report the modification of CNCs with the 2-ureido-4[1H]pyrimidinone (UPy) motif as an adaptive compatibilizer, which permits the dispersion of UPy-modified CNCs in nonpolar as well as polar media. In toluene, the UPy motifs appear to form intra-CNC dimers, so that the particles are somewhat hydrophobized and well-dispersible in this nonpolar solvent. By contrast, the UPy motifs dissociate in DMF and promote dispersibility through interactions with this polar solvent. We have exploited this adaptiveness and integrated UPy-modified CNCs into nonpolar and polar host polymers, which include different poly(ethylene)s, a polystyrene-block-polybutadiene-block-polystyrene elastomer and poly(ethylene oxide-co-epichlorohydrin). All nanocomposites display an increase of stiffness and strength in comparison to the neat polymer, and some compositions retain a high elongation at break, even at a filler content of 15% w/w.

Sulfonate-grafted porous polymer networks for preferential CO(2) adsorption at low pressure

NARCIS (Netherlands)

Lu, W.; Yuan, D.; Sculley, J.; Zhao, D.; Krishna, R.; Zhou, H.-C.

2011-01-01

A porous polymer network (PPN) grafted with sulfonic acid (PPN-6-SO3H) and its lithium salt (PPN-6-SO3Li) exhibit significant increases in isosteric heats of CO2 adsorption and CO2-uptake capacities. IAST calculations using single-component-isotherm data and a 15/85 CO2/N2 ratio at 295 K and 1 bar

CO2-Philic polymer membrane with extremely high separation performance

KAUST Repository

Yave, Wilfredo

2010-01-12

Polymeric membranes are attractive for CO2 separation and concentration from different gas streams because of their versatility and energy efficiency; they can compete with, and they may even replace, traditional absorption processes. Here we describe a simple and powerful method for developing nanostructured and CO2-philic polymer membranes for CO2 separation. A poly(ethylene oxide)-poly(butylene terephthalate) multiblock copolymer is used as membrane material. Smart additives such as polyethylene glycol dibutyl ether are incorporated as spacers or fillers for producing nanostructured materials. The addition of these specific additives produces CO2-philic membranes and increases the CO2 permeability (750 barrer) up to five-fold without the loss of selectivity. The membranes present outstanding performance for CO2 separation, and the measured CO2 flux is extremely high ( > 2 m3 m -2 h-1 bar-1) with selectivity over H2 and N2 of 10 and 40, respectively, making them attractive for CO 2 capture. © 2009 American Chemical Society.

CO2-Philic polymer membrane with extremely high separation performance

KAUST Repository

Yave, Wilfredo; Car, Anja; Funari, S.; Nunes, Suzana Pereira; Peinemann, Klaus-Viktor

2010-01-01

Polymeric membranes are attractive for CO2 separation and concentration from different gas streams because of their versatility and energy efficiency; they can compete with, and they may even replace, traditional absorption processes. Here we describe a simple and powerful method for developing nanostructured and CO2-philic polymer membranes for CO2 separation. A poly(ethylene oxide)-poly(butylene terephthalate) multiblock copolymer is used as membrane material. Smart additives such as polyethylene glycol dibutyl ether are incorporated as spacers or fillers for producing nanostructured materials. The addition of these specific additives produces CO2-philic membranes and increases the CO2 permeability (750 barrer) up to five-fold without the loss of selectivity. The membranes present outstanding performance for CO2 separation, and the measured CO2 flux is extremely high ( > 2 m3 m -2 h-1 bar-1) with selectivity over H2 and N2 of 10 and 40, respectively, making them attractive for CO 2 capture. © 2009 American Chemical Society.

CO2-assisted high pressure homogenization: a solvent-free process for polymeric microspheres and drug-polymer composites.

Science.gov (United States)

Kluge, Johannes; Mazzotti, Marco

2012-10-15

The study explores the enabling role of near-critical CO(2) as a reversible plasticizer in the high pressure homogenization of polymer particles, aiming at their comminution as well as at the formation of drug-polymer composites. First, the effect of near-critical CO(2) on the homogenization of aqueous suspensions of poly lactic-co-glycolic acid (PLGA) was investigated. Applying a pressure drop of 900 bar and up to 150 passes across the homogenizer, it was found that particles processed in the presence of CO(2) were generally of microspherical morphology and at all times significantly smaller than those obtained in the absence of a plasticizer. The smallest particles, exhibiting a median x(50) of 1.3 μm, were obtained by adding a small quantity of ethyl acetate, which exerts on PLGA an additional plasticizing effect during the homogenization step. Further, the study concerns the possibility of forming drug-polymer composites through simultaneous high pressure homogenization of the two relevant solids, and particularly the effect of near-critical CO(2) on this process. Therefore, PLGA was homogenized together with crystalline S-ketoprofen (S-KET), a non-steroidal anti-inflammatory drug, at a drug to polymer ratio of 1:10, a pressure drop of 900 bar and up to 150 passes across the homogenizer. When the process was carried out in the presence of CO(2), an impregnation efficiency of 91% has been reached, corresponding to 8.3 wt.% of S-KET in PLGA; moreover, composite particles were of microspherical morphology and significantly smaller than those obtained in the absence of CO(2). The formation of drug-polymer composites through simultaneous homogenization of the two materials is thus greatly enhanced by the presence of CO(2), which increases the efficiency for both homogenization and impregnation. Copyright © 2012 Elsevier B.V. All rights reserved.

Preparation and drug-loading properties of Fe3O4/Poly(styrene-co-acrylic acid) magnetic polymer nanocomposites

International Nuclear Information System (INIS)

Lu, Wensheng; Shen, Yuhua; Xie, Anjian; Zhang, Weiqiang

2013-01-01

Fe 3 O 4 /poly(styrene-co-acrylic acid) magnetic polymer nanocomposites were synthesized by the dispersion polymerization method using styrene as hard monomer, acrylic acid as functional monomer, Fe 3 O 4 nanoparticles modified with oleic acid as core, and poly(styrene-co-acrylic acid) as shell. Drug-loading properties of magnetic polymer nanocomposites with curcumin as a model drug were also studied. The results indicated that magnetic polymer nanocomposites with monodisperse were obtained, the particle size distribution was 50–120 nm, and the average size was about 100 nm. The contents of poly(styrene-co-acrylic acid) and Fe 3 O 4 nanoparticles in magnetic polymer nanocomposites were 74% and 24.7%, respectively. The drug-loading capacity and entrapment efficiency were 2.5% and 44.4%, respectively. The saturation magnetization of magnetic polymer nanocomposites at 300 K was 20.2 emu/g without coercivity and remanence. The as-prepared magnetic polymer nanocomposites have not only lots of functional carboxyl groups but also stronger magnetic response, which might have potential applications in drug carrier and targeted drug release

Surface modification of polyacrylonitrile co-polymer membranes using pulsed direct current nitrogen plasma

Energy Technology Data Exchange (ETDEWEB)

Pal, Dipankar; Neogi, Sudarsan; De, Sirshendu, E-mail: sde@che.iitkgp.ernet.in

2015-12-31

Low temperature plasma treatment using pulsed direct current discharge of nitrogen gas was employed to enhance hydrophilicity of the polyacrylonitrile co-polymer membranes. The membranes were characterized in terms of morphology, structure, hydrophilicity, and membrane performance. Properties and functional groups on the surface of polyacrylonitrile co-polymer membranes were investigated by contact angle, scanning electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopy. Effects of plasma conditions, namely, pulsed voltage, duty cycle and treatment time on increase in membrane hydrophilicity were studied. Permeability of treated membrane was increased by 47% and it was retained up to 70 days. Surface etching due to plasma treatment was confirmed by weight loss of the treated membranes. Due to surface etching, average pore size increased and rejection of 200 kDa polyethylene glycol decreased to about 70% for the treated membrane. Oxygen and nitrogen functional groups were responsible for surface hydrophilicity. - Highlights: • Surface modification of polyacrylonitrile co-polymer membranes by pulsed direct current nitrogen plasma • Hydrophilic functional groups incorporated on the membrane surface • Significant enhancement of the permeability and wettability of the membranes • Water contact angle increased with storage time and finally stabilized.

Surface modification of polyacrylonitrile co-polymer membranes using pulsed direct current nitrogen plasma

International Nuclear Information System (INIS)

Pal, Dipankar; Neogi, Sudarsan; De, Sirshendu

2015-01-01

Low temperature plasma treatment using pulsed direct current discharge of nitrogen gas was employed to enhance hydrophilicity of the polyacrylonitrile co-polymer membranes. The membranes were characterized in terms of morphology, structure, hydrophilicity, and membrane performance. Properties and functional groups on the surface of polyacrylonitrile co-polymer membranes were investigated by contact angle, scanning electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopy. Effects of plasma conditions, namely, pulsed voltage, duty cycle and treatment time on increase in membrane hydrophilicity were studied. Permeability of treated membrane was increased by 47% and it was retained up to 70 days. Surface etching due to plasma treatment was confirmed by weight loss of the treated membranes. Due to surface etching, average pore size increased and rejection of 200 kDa polyethylene glycol decreased to about 70% for the treated membrane. Oxygen and nitrogen functional groups were responsible for surface hydrophilicity. - Highlights: • Surface modification of polyacrylonitrile co-polymer membranes by pulsed direct current nitrogen plasma • Hydrophilic functional groups incorporated on the membrane surface • Significant enhancement of the permeability and wettability of the membranes • Water contact angle increased with storage time and finally stabilized.

Hot Melt Extrusion and Spray Drying of Co-amorphous Indomethacin-Arginine With Polymers.

Science.gov (United States)

Lenz, Elisabeth; Löbmann, Korbinian; Rades, Thomas; Knop, Klaus; Kleinebudde, Peter

2017-01-01

Co-amorphous drug-amino acid systems have gained growing interest as an alternative to common amorphous formulations which contain polymers as stabilizers. Several preparation methods have recently been investigated, including vibrational ball milling on a laboratory scale or spray drying in a larger scale. In this study, the feasibility of hot melt extrusion for continuous manufacturing of co-amorphous drug-amino acid formulations was examined, challenging the fact that amino acids melt with degradation at high temperatures. Furthermore, the need for an addition of a polymer in this process was evaluated. After a polymer screening via the solvent evaporation method, co-amorphous indomethacin-arginine was prepared by a melting-solvent extrusion process without and with copovidone. The obtained products were characterized with respect to their solid-state properties, non-sink dissolution behavior, and stability. Results were compared to those of spray-dried formulations with the same compositions and to spray-dried indomethacin-copovidone. Overall, stable co-amorphous systems could be prepared by extrusion without or with copovidone, which exhibited comparable molecular interaction properties to the respective spray-dried products, while phase separation was detected by differential scanning calorimetry in several cases. The formulations containing indomethacin in combination with arginine and copovidone showed enhanced dissolution behavior over the formulations with only copovidone or arginine. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Synthesis, spectroscopic and thermochemical studies of some novel carbazole-pyridine co-polymers (abstract)

International Nuclear Information System (INIS)

Saeed, A.; Irfan, M.

2011-01-01

Two series of a novel class of carbazole-4-phenylpyridine co-polymers has been synthesized by a modified Chichibabin reaction. The synthesis was carried out by a simple and cheaper method compared to the lengthy methods usually adopted for the preparation of carbazole-pyridine copolymers which involve costly catalysts. All the polymers were characterized by IR, /sup 1/H and /sup 13/C NMR, UV-vis spectroscopy, fluorimetry, TGA and DSC. The weight average molecular masses (M/sub w/) of the polymers were estimated by Laser Light Scattering (LLS) technique. (author)

Control of colloidal CaCO3 suspension by using biodegradable polymers during fabrication

Directory of Open Access Journals (Sweden)

Nemany Abdelhamid Nemany Hanafy

2015-03-01

The aim of this work was to investigate the synthesis process of CaCO3 particles in different experimental conditions: calcium carbonate was produced in presence and in absence of water and with addition of appropriate polymers. In particular, chitosan (CHI and poly acrylic acid (PAA were chosen as biodegradable polymers whereas PSS and PAH were chosen as non-biodegradable polymers. Shape and diameter of particles were investigated by using transmission and scanning electron microscopy, elemental composition was inferred by energy dispersive X-ray analyses whereas their charges were explored by using zeta potential.

Polymer-assisted co-precipitation route for the synthesis of Al 2 O 3

Indian Academy of Sciences (India)

It has been observed by field emission scanning electron microscopy analysis that the particle size reduced effectively (below 100 nm) when polymer-assisted co-precipitation route is used instead of the simple co-precipitation technique. A highly dense microstructure of sintered samples has been obtained, driven by ...

Block copolymer battery separator

Science.gov (United States)

Wong, David; Balsara, Nitash Pervez

2016-04-26

The invention herein described is the use of a block copolymer/homopolymer blend for creating nanoporous materials for transport applications. Specifically, this is demonstrated by using the block copolymer poly(styrene-block-ethylene-block-styrene) (SES) and blending it with homopolymer polystyrene (PS). After blending the polymers, a film is cast, and the film is submerged in tetrahydrofuran, which removes the PS. This creates a nanoporous polymer film, whereby the holes are lined with PS. Control of morphology of the system is achieved by manipulating the amount of PS added and the relative size of the PS added. The porous nature of these films was demonstrated by measuring the ionic conductivity in a traditional battery electrolyte, 1M LiPF.sub.6 in EC/DEC (1:1 v/v) using AC impedance spectroscopy and comparing these results to commercially available battery separators.

Rapid self-assembly of block copolymers to photonic crystals

Science.gov (United States)

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

2016-07-05

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

The use of poly(vinylpyridine-co-acrylonitrile) in polymer electrolytes for quasi-solid dye-sensitized solar cells

International Nuclear Information System (INIS)

Li, Minyu; Feng, Shujing; Fang, Shibi; Xiao, Xurui; Li, Xueping; Zhou, Xiaowen; Lin, Yuan

2007-01-01

Poly(vinylpyridine-co-acrylonitrile) (P(VP-co-AN)) was used to form polymer electrolytes for dye-sensitized solar cells (DSSCs). The effects of P(VP-co-AN) on the photovoltaic performances of DSSCs have been investigated with nonaqueous electrolytes containing alkali-iodide and iodine. It was found that the effect of P(VP-co-AN) on V oc closely related to its amount in the electrolyte. Lower amount of P(VP-co-AN) was benefit for the construction of a solar cell containing P(VP-co-AN) with higher energy conversion efficiency. Chemically crosslinking solidification with backbone polymer P(VP-co-AN) amount of 3% fabricated quasi-solid DSSCs with 10% increased conversion efficiencies with relative to that of the initial liquid DSSCs

Thermo-responsive cell culture carriers based on poly(vinyl methyl ether)—the effect of biomolecular ligands to balance cell adhesion and stimulated detachment

International Nuclear Information System (INIS)

Teichmann, Juliane; Valtink, Monika; Funk, Richard H W; Engelmann, Katrin; Nitschke, Mirko; Pette, Dagmar; Gramm, Stefan; Werner, Carsten; Härtel, Frauke V; Noll, Thomas

2015-01-01

Two established material systems for thermally stimulated detachment of adherent cells were combined in a cross-linked polymer blend to merge favorable properties. Through this approach poly(N-isopropylacrylamide) (PNiPAAm) with its superior switching characteristic was paired with a poly(vinyl methyl ether)-based composition that allows adjusting physico-chemical and biomolecular properties in a wide range. Beyond pure PNiPAAm, the proposed thermo-responsive coating provides thickness, stiffness and swelling behavior, as well as an apposite density of reactive sites for biomolecular functionalization, as effective tuning parameters to meet specific requirements of a particular cell type regarding initial adhesion and ease of detachment. To illustrate the strength of this approach, the novel cell culture carrier was applied to generate transplantable sheets of human corneal endothelial cells (HCEC). Sheets were grown, detached, and transferred onto planar targets. Cell morphology, viability and functionality were analyzed by immunocytochemistry and determination of transepithelial electrical resistance (TEER) before and after sheet detachment and transfer. HCEC layers showed regular morphology with appropriate TEER. Cells were positive for function-associated marker proteins ZO-1, Na + /K + -ATPase, and paxillin, and extracellular matrix proteins fibronectin, laminin and collagen type IV before and after transfer. Sheet detachment and transfer did not impair cell viability. Subsequently, a potential application in ophthalmology was demonstrated by transplantation onto de-endothelialized porcine corneas in vitro. The novel thermo-responsive cell culture carrier facilitates the generation and transfer of functional HCEC sheets. This paves the way to generate tissue engineered human corneal endothelium as an alternative transplant source for endothelial keratoplasty. (paper)

Thermo-responsive cell culture carriers based on poly(vinyl methyl ether)—the effect of biomolecular ligands to balance cell adhesion and stimulated detachment

Science.gov (United States)

Teichmann, Juliane; Nitschke, Mirko; Pette, Dagmar; Valtink, Monika; Gramm, Stefan; Härtel, Frauke V; Noll, Thomas; Funk, Richard H W; Engelmann, Katrin; Werner, Carsten

2015-01-01

Two established material systems for thermally stimulated detachment of adherent cells were combined in a cross-linked polymer blend to merge favorable properties. Through this approach poly(N-isopropylacrylamide) (PNiPAAm) with its superior switching characteristic was paired with a poly(vinyl methyl ether)-based composition that allows adjusting physico-chemical and biomolecular properties in a wide range. Beyond pure PNiPAAm, the proposed thermo-responsive coating provides thickness, stiffness and swelling behavior, as well as an apposite density of reactive sites for biomolecular functionalization, as effective tuning parameters to meet specific requirements of a particular cell type regarding initial adhesion and ease of detachment. To illustrate the strength of this approach, the novel cell culture carrier was applied to generate transplantable sheets of human corneal endothelial cells (HCEC). Sheets were grown, detached, and transferred onto planar targets. Cell morphology, viability and functionality were analyzed by immunocytochemistry and determination of transepithelial electrical resistance (TEER) before and after sheet detachment and transfer. HCEC layers showed regular morphology with appropriate TEER. Cells were positive for function-associated marker proteins ZO-1, Na+/K+-ATPase, and paxillin, and extracellular matrix proteins fibronectin, laminin and collagen type IV before and after transfer. Sheet detachment and transfer did not impair cell viability. Subsequently, a potential application in ophthalmology was demonstrated by transplantation onto de-endothelialized porcine corneas in vitro. The novel thermo-responsive cell culture carrier facilitates the generation and transfer of functional HCEC sheets. This paves the way to generate tissue engineered human corneal endothelium as an alternative transplant source for endothelial keratoplasty. PMID:27877823

Shape memory and actuation behavior of semicrystalline polymer networks

Energy Technology Data Exchange (ETDEWEB)

Bothe, Martin

2014-07-01

Shape memory polymers (SMPs) can change their shape on application of a suitable stimulus. To enable such behavior, a 'programming' procedure fixes a deformation, yielding a stable temporary shape. In thermoresponsive SMPs, subsequent heating triggers entropy-elastic recovery of the initial shape. An additional shape change on cooling, i.e. thermoreversible two-way actuation, can be stimulated by a crystallization phenomenon. In this thesis, cyclic thermomechanical measurements systematically determined (1) the shape memory and (2) the actuation behavior under constant load as well as under stress-free conditions. Chemically cross-linked, star-shaped polyhedral oligomeric silsesquioxane polyurethane (SPOSS-PU) hybrid polymer networks and physically cross-linked poly(ester urethane) (PEU) block copolymers were investigated around the melting and crystallization temperatures of their polyester soft segments. (1) The SPOSS-PUs showed excellent shape fixities and recoverabilities of almost 100% at high cross-linking density, while PEUs exhibited pronounced shape memory properties at increased soft segment content. Furthermore, two-fold programmed SPOSS-PU specimens were able to recover their initial shape in two thermally separated events. Even a neck, which formed during deformation of SPOSS-PUs with high soft segment content, was reversed. (2) In PEUs, globally oriented crystallization on cooling drove expansion of the sample, in particular at high soft segment content and after application of a strong deformation. Melting reversed that orientation; the PEU sample contracted and thereby completed the thermoreversible actuation cycle. Under load, multiple polymorphic phase transitions enabled two successive expansion and contraction steps, while under stress-free conditions various geometric shape changes, including the increase and decrease of PEU sample length and thickness as well as twisting and untwisting could be experimentally witnessed. Such

Shape memory and actuation behavior of semicrystalline polymer networks

International Nuclear Information System (INIS)

Bothe, Martin

2014-01-01

Shape memory polymers (SMPs) can change their shape on application of a suitable stimulus. To enable such behavior, a 'programming' procedure fixes a deformation, yielding a stable temporary shape. In thermoresponsive SMPs, subsequent heating triggers entropy-elastic recovery of the initial shape. An additional shape change on cooling, i.e. thermoreversible two-way actuation, can be stimulated by a crystallization phenomenon. In this thesis, cyclic thermomechanical measurements systematically determined (1) the shape memory and (2) the actuation behavior under constant load as well as under stress-free conditions. Chemically cross-linked, star-shaped polyhedral oligomeric silsesquioxane polyurethane (SPOSS-PU) hybrid polymer networks and physically cross-linked poly(ester urethane) (PEU) block copolymers were investigated around the melting and crystallization temperatures of their polyester soft segments. (1) The SPOSS-PUs showed excellent shape fixities and recoverabilities of almost 100% at high cross-linking density, while PEUs exhibited pronounced shape memory properties at increased soft segment content. Furthermore, two-fold programmed SPOSS-PU specimens were able to recover their initial shape in two thermally separated events. Even a neck, which formed during deformation of SPOSS-PUs with high soft segment content, was reversed. (2) In PEUs, globally oriented crystallization on cooling drove expansion of the sample, in particular at high soft segment content and after application of a strong deformation. Melting reversed that orientation; the PEU sample contracted and thereby completed the thermoreversible actuation cycle. Under load, multiple polymorphic phase transitions enabled two successive expansion and contraction steps, while under stress-free conditions various geometric shape changes, including the increase and decrease of PEU sample length and thickness as well as twisting and untwisting could be experimentally witnessed. Such actuation

Fabrications and Applications of Stimulus-Responsive Polymer Films and Patterns on Surfaces: A Review

Directory of Open Access Journals (Sweden)

Jem-Kun Chen

2014-01-01

Full Text Available In the past two decades, we have witnessed significant progress in developing high performance stimuli-responsive polymeric materials. This review focuses on recent developments in the preparation and application of patterned stimuli-responsive polymers, including thermoresponsive layers, pH/ionic-responsive hydrogels, photo-responsive film, magnetically-responsive composites, electroactive composites, and solvent-responsive composites. Many important new applications for stimuli-responsive polymers lie in the field of nano- and micro-fabrication, where stimuli-responsive polymers are being established as important manipulation tools. Some techniques have been developed to selectively position organic molecules and then to obtain well-defined patterned substrates at the micrometer or submicrometer scale. Methods for patterning of stimuli-responsive hydrogels, including photolithography, electron beam lithography, scanning probe writing, and printing techniques (microcontact printing, ink-jet printing were surveyed. We also surveyed the applications of nanostructured stimuli-responsive hydrogels, such as biotechnology (biological interfaces and purification of biomacromoles, switchable wettability, sensors (optical sensors, biosensors, chemical sensors, and actuators.

Non-immunogenic, hydrophilic/cationic block copolymers and uses thereof

Science.gov (United States)

Scales, Charles W.; Huang, Faqing; McCormick, Charles L.

2010-05-18

The present invention provides novel non-immunogenic, hydrophilic/cationic block copolymers comprising a neutral-hydrophilic polymer and a cationic polymer, wherein both polymers have well-defined chain-end functionality. A representative example of such a block copolymer comprises poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) and poly(N-[3-(dimethylamino)propyl]methacrylamide) (PDMAPMA). Also provided is a synthesis method thereof in aqueous media via reversible addition fragmentation chain transfer (RAFT) polymerization. Further provided are uses of these block copolymers as drug delivery vehicles and protection agents.

Gel polymer electrolytes for batteries

Science.gov (United States)

Balsara, Nitash Pervez; Eitouni, Hany Basam; Gur, Ilan; Singh, Mohit; Hudson, William

2014-11-18

Nanostructured gel polymer electrolytes that have both high ionic conductivity and high mechanical strength are disclosed. The electrolytes have at least two domains--one domain contains an ionically-conductive gel polymer and the other domain contains a rigid polymer that provides structure for the electrolyte. The domains are formed by block copolymers. The first block provides a polymer matrix that may or may not be conductive on by itself, but that can soak up a liquid electrolyte, thereby making a gel. An exemplary nanostructured gel polymer electrolyte has an ionic conductivity of at least 1.times.10.sup.-4 S cm.sup.-1 at 25.degree. C.

CO2 capture by polymeric membranes composed of hyper-branched polymers with dense poly(oxyethylene comb and poly(amidoamine

Directory of Open Access Journals (Sweden)

Taniguchi Ikuo

2017-11-01

Full Text Available Due to CO2-philic nature of polyoxyethylene (POE, a dense POE comb structure was tethered onto PMMA backbone to develop CO2 separation membranes over N2. The resulting hyper-branched polymers displayed preferential CO2 permeation. When the polymer thin layer was formed on a high gas permeable polydimethylsiloxane (PDMS support by a spray-coating manner, the resulting thin film composite (TFC membranes displayed very high CO2 permeability. However, the CO2 selectivity, which was the permeability ratio of CO2 over N2, was moderate and lower than 50. To enhance the selectivity, poly(amidoamine (PAMAM was introduced to the hyper-branched polymers in the CO2-selective layer of the TFC membranes. The CO2 selectivity increased from 47 to 90 with increasing PAMAM content to 40 wt%, and it was drastically enhanced to 350 with PAMAM content of 50 wt%. Differential scanning calorimetry (DSC and laser microscope revealed formation of PAMAM-rich domain at the higher amine content, where CO2 could readily migrate in comparison to the other polymeric fractions.

CO2 capture by polymeric membranes composed of hyper-branched polymers with dense poly(oxyethylene) comb and poly(amidoamine)

Science.gov (United States)

Taniguchi, Ikuo; Wada, Norihisa; Kinugasa, Kae; Higa, Mitsuru

2017-11-01

Due to CO2-philic nature of polyoxyethylene (POE), a dense POE comb structure was tethered onto PMMA backbone to develop CO2 separation membranes over N2. The resulting hyper-branched polymers displayed preferential CO2 permeation. When the polymer thin layer was formed on a high gas permeable polydimethylsiloxane (PDMS) support by a spray-coating manner, the resulting thin film composite (TFC) membranes displayed very high CO2 permeability. However, the CO2 selectivity, which was the permeability ratio of CO2 over N2, was moderate and lower than 50. To enhance the selectivity, poly(amidoamine) (PAMAM) was introduced to the hyper-branched polymers in the CO2-selective layer of the TFC membranes. The CO2 selectivity increased from 47 to 90 with increasing PAMAM content to 40 wt%, and it was drastically enhanced to 350 with PAMAM content of 50 wt%. Differential scanning calorimetry (DSC) and laser microscope revealed formation of PAMAM-rich domain at the higher amine content, where CO2 could readily migrate in comparison to the other polymeric fractions.

Identifying the nature of surface chemical modification for directed self-assembly of block copolymers

Directory of Open Access Journals (Sweden)

Laura Evangelio

2017-09-01

Full Text Available In recent years, block copolymer lithography has emerged as a viable alternative technology for advanced lithography. In chemical-epitaxy-directed self-assembly, the interfacial energy between the substrate and each block copolymer domain plays a key role on the final ordering. Here, we focus on the experimental characterization of the chemical interactions that occur at the interface built between different chemical guiding patterns and the domains of the block copolymers. We have chosen hard X-ray high kinetic energy photoelectron spectroscopy as an exploration technique because it provides information on the electronic structure of buried interfaces. The outcome of the characterization sheds light onto key aspects of directed self-assembly: grafted brush layer, chemical pattern creation and brush/block co-polymer interface.

Studies on guanidinated N-3-aminopropyl methacrylamide-N-2-hydroxypropyl methacrylamide co-polymers as gene delivery carrier.

Science.gov (United States)

Qin, Zhu; Liu, Wei; Guo, Liang; Li, Xinsong

2012-01-01

Guanidinated N-3-aminopropyl methacrylamide (APMA)-N-2-hydroxypropyl methacrylamide (HPMA) co-polymers were prepared and evaluated to develop novel non-viral gene transfection carriers. The co-polymers were synthesized via radical co-polymerization of APMA and HPMA followed by total guanidination of amino groups, which employed guanidinated APMA (GPMA) for increasing cell-penetrating and HPMA as the positive shielding content. The molecular weight of guanidinated APMA-HPMA co-polymers (GPMA-HPMA) was determined by static light scattering. Furthermore, cytotoxicity and transfection experiments of GPMA-HPMA/pDNA complexes were conducted. A significant decrease of their parent cytotoxicity and an efficient transfection at relative low charge ratios were observed. The cellular distribution of most GPMA-HPMA/pDNA complexes was partially localized in the nucleus, as indicated by confocal laser scanning microscopy. The guanidination strategy employed may lead to non-viral gene delivery carriers that combine satisfactory transfection efficiency and cytotoxicity, which contribute to their cell-penetrating ability.

New photoresponsive (meth)acrylate (co)polymers containing azobenzene pendant sidegroups with carboxylic and dimethylamino substituents .2. Synthesis and characterization of polymers and copolymers

NARCIS (Netherlands)

Haitjema, HJ; Buruma, R; VanEkenstein, GORA; Tan, YY; Challa, G

1996-01-01

The title (co)polymers, used for our investigations on their photoresponsive behaviour were obtained by free radical (co)polymerization. The monomer was either an acrylate or a methacrylate to which an azobenzene group, modified with a para-placed dimethylamino or a carboxylic pendant group, was

Newton Output Blocking Force under Low-Voltage Stimulation for Carbon Nanotube-Electroactive Polymer Composite Artificial Muscles.

Science.gov (United States)

Chen, I-Wen Peter; Yang, Ming-Chia; Yang, Chia-Hui; Zhong, Dai-Xuan; Hsu, Ming-Chun; Chen, YiWen

2017-02-15

This is a study on the development of carbon nanotube-based composite actuators using a new ionic liquid-doped electroactive ionic polymer. For scalable production purposes, a simple hot-pressing method was used. Carbon nanotube/ionic liquid-Nafion/carbon nanotube composite films were fabricated that exhibited a large output blocking force and a stable cycling life with low alternating voltage stimuli in air. Of particular interest and importance, a blocking force of 1.5 N was achieved at an applied voltage of 6 V. Operational durability was confirmed by testing in air for over 30 000 cycles (or 43 h). The superior actuation performance of the carbon nanotube/ionic liquid-Nafion/carbon nanotube composite, coupled with easy manufacturability, low driving voltage, and reliable operation, promises great potential for artificial muscle and biomimetic applications.

Artificially Engineered Protein Polymers.

Science.gov (United States)

Yang, Yun Jung; Holmberg, Angela L; Olsen, Bradley D

2017-06-07

Modern polymer science increasingly requires precise control over macromolecular structure and properties for engineering advanced materials and biomedical systems. The application of biological processes to design and synthesize artificial protein polymers offers a means for furthering macromolecular tunability, enabling polymers with dispersities of ∼1.0 and monomer-level sequence control. Taking inspiration from materials evolved in nature, scientists have created modular building blocks with simplified monomer sequences that replicate the function of natural systems. The corresponding protein engineering toolbox has enabled the systematic development of complex functional polymeric materials across areas as diverse as adhesives, responsive polymers, and medical materials. This review discusses the natural proteins that have inspired the development of key building blocks for protein polymer engineering and the function of these elements in material design. The prospects and progress for scalable commercialization of protein polymers are reviewed, discussing both technology needs and opportunities.

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)

Hofmeister effect on thermo-responsive poly(propylene oxide): Role of polymer molecular weight and concentration.

Science.gov (United States)

Moghaddam, Saeed Zajforoushan; Thormann, Esben

2016-03-01

Although a vast amount of research has been dedicated to investigate the Hofmeister effect on the stability of polymer solutions, a clear understanding of the role of polymer properties in this phenomenon is still missing. Here, the Hofmeister effect of NaCl (destabilizing) and NaSCN (stabilizing) salts on aqueous solutions of poly(propylene oxide) (PPO) is studied. Four different molecular weights of PPO were investigated, to determine how the variation in the polymer coil size affects the Hofmeister effect. The investigation was further conducted for different PPO concentrations, in order to understand the effect of inter-chain interactions on the response to addition of salt. The temperature-driven phase separation of the solutions was monitored by differential scanning calorimetry, which provides the precise value of the phase separation temperature, as well as the enthalpy change accompanied with the transition. It was observed that increasing the molecular weight weakens the effect of the both salts, which is interpreted in terms of a scaling law between the molecular weight and the accessible surface area of the polymers. Increasing the PPO concentration further diminished the NaCl effect, but amplified the NaSCN effect. This difference is attributed to an electrostatic stabilization mechanism in the case of NaSCN. Copyright © 2015 Elsevier Inc. All rights reserved.

Reduction of birefringence in a skin-layer of injection molded polymer strips using CO{sub 2} laser irradiation

Energy Technology Data Exchange (ETDEWEB)

Kurosaki, Yasuo; Satoh, Isao; Saito, Takushi [Tokyo Inst. of Tech. (Japan). Dept. of Mechanical Intelligent Systems Engineering

1995-12-31

Injection molding of polymers is currently utilized for numerous industrial applications. Because of high productivity and stable quality of molded products, the injection-molding process makes the production costs lower, and therefore, is expected to spread more widely in the future. This paper deals with a technique for improving the optical quality of injection molded polymer products using radiative heating. The birefringence frozen in a skin-layer of the molded part was reduced by CO{sub 2} laser heating, and the efficiency of this technique was investigated experimentally. Namely, a simple numerical calculation was performed to estimate the heating efficiency of CO{sub 2} laser in the polymer, effects of radiation heating on the skin-layer of the molded polymer were observed by using a mold with transparent windows, and the residual birefringence frozen in the final molded specimen was measured. The results clearly showed that the birefringence in the skin-layer of injection molded polymer strips was reduced with CO{sub 2} laser heating. The authors believe that the proposed method for reducing the birefringence frozen in injection-molded polymer products is suitable for practical molding, because process time required for the injection-molding is only slightly increased with this method.

Lanthanide co-ordination frameworks: Opportunities and diversity

International Nuclear Information System (INIS)

Hill, Robert J.; Long, De-Liang; Hubberstey, Peter; Schroeder, Martin; Champness, Neil R.

2005-01-01

Significant successes have been made over recent years in preparing co-ordination framework polymers that show macroscopic material properties, but in the vast majority of cases this has been achieved with d-block metal-based systems. Lanthanide co-ordination frameworks also offer attractive properties in terms of their potential applications as luminescent, non-linear optical and porous materials. However, lanthanide-based systems have been far less studied to date than their d-block counterparts. One possible reason for this is that the co-ordination spheres of lanthanide cations are more difficult to control and, in the absence of design strategies for lanthanide co-ordination frameworks, it is significantly more difficult to target materials with specific properties. However, this article highlights some of the exciting possibilities that have emerged from the earliest investigations in this field with new topological families of compounds being discovered from relatively simple framework components, including unusual eight, seven and five-connected framework systems. Our own research, as well as others, is leading to a much greater appreciation of the factors that control framework formation and the resultant observed topologies of these polymers. As this understanding develops targeting particular framework types will become more straightforward and the development of designed polyfunctional materials more accessible. Thus, it can be seen that lanthanide co-ordination frameworks have the potential to open up previously unexplored directions for materials chemistry. This article focuses on the underlying concepts for the construction of these enticing and potentially highly important materials

Multilayer polymer light-emitting diodes by blade coating method

Science.gov (United States)

Tseng, Shin-Rong; Meng, Hsin-Fei; Lee, Kuan-Chen; Horng, Sheng-Fu

2008-10-01

Multilayer polymer light-emitting diodes fabricated by blade coating are presented. Multilayer of polymers can be easily deposited by blade coating on a hot plate. The multilayer structure is confirmed by the total thickness and the cross section view in the scanning electron microscope. The film thickness variation is only 3.3% in 10cm scale and the film roughness is about 0.3nm in the micron scale. The efficiency of single layer poly(para-phenylene vinylene) copolymer Super Yellow and poly(9,9-dioctylfluorene) (PFO, deep blue) devices are 9 and 1.7cd/A, respectively, by blade coating. The efficiency of the PFO device is raised to 2.9cd/A with a 2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole (PBD) hole-blocking layer and to 2.3cd/A with a poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine)] elec-tron-blocking layer added by blade coating.

Application of polyhydroxybutyrate-b-polyethyleneglycol (a block co-polymer) for solid phase extraction of lead and copper in different food samples

International Nuclear Information System (INIS)

Kazi, T.G.; Afridi, H.I.; Tuzen, M.; Naeemullah, A.

2014-01-01

In present work, a new adsorbent, polyhydroxybutyrate-b-polyethyleneglycol (block copolymer) was used for the preconcentration and separation of copper (Cu) and lead (Pb) ions without consuming expensive complexing reagent. The influence of various parameters like pH, adsorbent amount, and rates of flow of eluent, sample and sample volumes has been investigated. The polymer does not interact with alkaline earth metals, transition metals, alkaline, and few anions. The enrichment factor 50 was achieved in this method. The detection limit of method was found to be 0.36 micro g L/sup 1/ and 1.93 micro g L/sup 1/ for copper and lead, respectively. The recovery values of both analytes were found >96% and relative standard deviations (RSD) for all experiments were found less than 5%. The present method was validated by the analysis of Cu and Pb contents in various related certified reference materials (CRM) like; NIST SRM 1515 Apple leaves, IAEA -336 Lichen and GBW-07605 Tea. Found results and CRM values were precise and accurate. This developed method was then successfully applied for analysis of Cu and Pb in tap and bottled mineral water and real food samples. (author)

Electrospun aniline-tetramer-co-polycaprolactone fibres for conductive, biodegradable scaffolds.

Science.gov (United States)

Guex, A G; Spicer, C D; Armgarth, A; Gelmi, A; Humphrey, E J; Terracciano, C M; Harding, S; Stevens, M M

2017-09-01

Conjugated polymers have been proposed as promising materials for scaffolds in tissue engineering applications. The restricted processability and biodegradability of conjugated polymers limit their use for biomedical applications however. Here we synthesised a block- co -polymer of aniline tetramer and PCL (AT-PCL), and processed it into fibrous non-woven scaffolds by electrospinning. We showed that fibronectin (Fn) adhesion was dependant on the AT-PCL oxidative state, with a reduced Fn unfolding length on doped membranes. Furthermore, we demonstrated the cytocompatibility and potential of these membranes to support the growth and osteogenic differentiation of MC3T3-E1 over 21 days.

Extrudable polymer-polymer composites based on ultra-high molecular weight polyethylene

Science.gov (United States)

Panin, S. V.; Kornienko, L. A.; Alexenko, V. O.; Buslovich, D. G.; Dontsov, Yu. V.

2017-12-01

Mechanical and tribotechnical characteristics of polymer-polymeric composites of UHMWPE are studied with the aim of developing extrudable, wear-resistant, self-lubricant polymer mixtures for Additive Manufacturing (AM). The motivation of the study is their further application as feedstocks for 3D printing. Blends of UHMWPE with graft- and block copolymers of low-density polyethylene (HDPE-g-VTMS, HDPE-g-SMA, HDPE-b-EVA), polypropylene (PP), block copolymers of polypropylene and polyamide with linear low density polyethylene (PP-b-LLDPE, PA-b-LLDPE), as well as cross-linked polyethylene (PEX-b), are examined. The choice of compatible polymer components for an ultra- high molecular weight matrix for increasing processability (extrudability) is motivated by the search for commercially available and efficient additives aimed at developing wear-resistant extrudable polymer composites for additive manufacturing. The extrudability, mechanical properties and wear resistance of UHMWPE-based polymer-polymeric composites under sliding friction with different velocities and loads are studied.

Post-Synthesis Functionalization of Porous Organic Polymers for CO2 Capture

KAUST Repository

Al Otaibi, Mona S.

2014-07-01

Solid porous materials are network materials that contain space void. Porous Organic Polymers (POPs) are porous materials, which are constructed from organic building blocks and exhibit large surface area with low densities. Due to these characteristics, POPs have attracted attentions because of their potential use in application such as gas storage and chemical separation. This thesis presents a study of the synthesis of novel POP being a network based on 2,5- dibromobenzaldehyde and 1,3,5-triethynylbenzene linked together via Sonogashira- Hagihara (SH) coupling. This network showed a relatively good surface area of 770 m2/g and total pore volume of 0.59 cc/g. In addition, it proved to be chemically and thermally stable, maintaining the thermal stability up to 350oC. In addition to synthesize novel aldehyde-POP network, it was also possible to post synthetically modify a network via one-step post synthetic functionalization by amine. Ethelynediamine (EDA), Diethylenetriamine (DETA), and Tris(2-aminoethyl)amine (Tris-amine) are three different amines used for aldehyde-POP functionalization. The produced networks were aminated via different amine species substitution the aldehyde group present within the network. Modification to these networks resulted in a decrease in surface area from 770 m2.g-1 to 333 m2.g-1, 162 m2.g-1, and 211 m2.g-1 in respective to EDA, DETA, and Tris-amine. Although the surface areas were decreased, the CO2 adsorption was enhanced as evidenced by the increase of Qst (i.e., from 25 to 45 kJ.mol-1 for DETA at low coverage). Our findings are expected to strengthen existing research areas of the influence of different type of amines (e.g aromatic amine) on CO2 adsorption. Although amine grafting has been studied in other systems (e.g., PAFs and MOFs), we are the first to reported amine functionalized POPs using a novel one-step amine grafting PSM procedure. Future research might extend to study the interaction between CO2 and amine species under

Porous carbon derived via KOH activation of a hypercrosslinked porous organic polymer for efficient CO_2, CH_4, H_2 adsorptions and high CO_2/N_2 selectivity

International Nuclear Information System (INIS)

Modak, Arindam; Bhaumik, Asim

2015-01-01

Microporous carbon having Brunauer-Emmett-Teller (BET) surface area of 2186 m"2 g"−"1 and micropore volume of 0.85 cm"3 g"−"1 has been synthesized via KOH induced high temperature carbonization of a non-conjugated hypercrosslinked organic polymer. Owing to the templating and activation by KOH, we have succeeded in making a microporous carbon from this porous polymer and the resultant carbon material showed high uptake for CO_2 (7.6 mmol g"−"1) and CH_4 (2.4 mmol g"−"1) at 1 atm, 273 K together with very good selectivity for the CO_2/N_2 (30.2) separation. Furthermore, low pressure (1 atm) H_2 (2.6 wt%, 77 K) and water uptake (57.4 wt%, 298 K) ability of this polymer derived porous activated carbon is noteworthy. - Graphical abstract: Microporous carbon with BET surface area of 2186 m"2 g"−"1 has been synthesized via KOH activation of a porous organic polymer and it showed high uptake for CO_2 (7.6 mmol g"−"1), CH_4 (2.4 mmol g"−"1) and H_2 (2.6 wt%) at 1 atm together with very good selectivity for CO_2. - Highlights: • Porous carbon from hypercrosslinked organic polymer. • KOH activated carbon with BET surface area 2186 m"2 g"−"1. • High CO2 uptake (7.6 mmol g"−"1) and CO_2/N_2 selectivity (30.2). • Porous carbon also showed high H_2 (2.6 wt%) and H_2O (57.4 wt%) uptakes.

Design of nanocarriers for nanoscale drug delivery to enhance cancer treatment using hybrid polymer and lipid building blocks.

Science.gov (United States)

Zhang, Rui Xue; Ahmed, Taksim; Li, Lily Yi; Li, Jason; Abbasi, Azhar Z; Wu, Xiao Yu

2017-01-26

Polymer-lipid hybrid nanoparticles (PLN) are an emerging nanocarrier platform made from building blocks of polymers and lipids. PLN integrate the advantages of biomimetic lipid-based nanoparticles (i.e. solid lipid nanoparticles and liposomes) and biocompatible polymeric nanoparticles. PLN are constructed from diverse polymers and lipids and their numerous combinations, which imparts PLN with great versatility for delivering drugs of various properties to their nanoscale targets. PLN can be classified into two types based on their hybrid nanoscopic structure and assembly methods: Type-I monolithic matrix and Type-II core-shell systems. This article reviews the history of PLN development, types of PLN, lipid and polymer candidates, fabrication methods, and unique properties of PLN. The applications of PLN in delivery of therapeutic or imaging agents alone or in combination for cancer treatment are summarized and illustrated with examples. Important considerations for the rational design of PLN for advanced nanoscale drug delivery are discussed, including selection of excipients, synthesis processes governing formulation parameters, optimization of nanoparticle properties, improvement of particle surface functionality to overcome macroscopic, microscopic and cellular biological barriers. Future directions and potential clinical translation of PLN are also suggested.

The Recent Developments in Biobased Polymers toward General and Engineering Applications: Polymers that Are Upgraded from Biodegradable Polymers, Analogous to Petroleum-Derived Polymers, and Newly Developed

OpenAIRE

Nakajima, Hajime; Dijkstra, Peter; Loos, Katja

2017-01-01

The main motivation for development of biobased polymers was their biodegradability, which is becoming important due to strong public concern about waste. Reflecting recent changes in the polymer industry, the sustainability of biobased polymers allows them to be used for general and engineering applications. This expansion is driven by the remarkable progress in the processes for refining biomass feedstocks to produce biobased building blocks that allow biobased polymers to have more versati...

N-donor co-ligands driven two new Co(II)- coordination polymers with bi- and trinuclear units: Crystal structures, and magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Zhou, Zhi-Hang [College of Materials and Chemical Engineering, Hubei Provincial Collaborative Innovation Center for New Energy Microgrid, Key Laboratory of Inorganic Non-metallic Crystalline and Energy Conversion Materials, China Three Gorges University, Yichang 443002 (China); Han, Min-Le [College of Chemistry and Chemical Engineering, Henan Key Laboratory of Function-Oriented Porous Materials, Luoyang Normal University, Luoyang 471022 (China); Wu, Ya-Pan; Dong, Wen-Wen [College of Materials and Chemical Engineering, Hubei Provincial Collaborative Innovation Center for New Energy Microgrid, Key Laboratory of Inorganic Non-metallic Crystalline and Energy Conversion Materials, China Three Gorges University, Yichang 443002 (China); Li, Dong-Sheng, E-mail: lidongsheng1@126.com [College of Materials and Chemical Engineering, Hubei Provincial Collaborative Innovation Center for New Energy Microgrid, Key Laboratory of Inorganic Non-metallic Crystalline and Energy Conversion Materials, China Three Gorges University, Yichang 443002 (China); Lu, Jack Y., E-mail: lu@uhcl.edu [Department of Chemistry, University of Houstons-Clear Lake, Houston, TX 77058 (United States)

2016-10-15

Two new Co(II) coordination polymers(CPs), namely [Co{sub 2}(bpe){sub 2}(Hbppc)]{sub n} (1) and [Co{sub 3}(μ{sub 3}-OH)(bppc)(bpm)(H{sub 2}O)]·3H{sub 2}O (2) (H{sub 5}bppc=biphenyl-2,4,6,3′,5′-pentacarboxylic acid, bpe=1,2-bis(4-pyridyl)ethene, bpm=bis(4-pyridyl)amine), have been obtained and characterized by elemental analysis, single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), IR spectra and thermogravimetric analysis (TGA). 1 shows a binodal (4,6)-connected fsc net with a (4{sup 4}·6{sup 10}·8)(4{sup 4}·6{sup 2}) topology, while 2 shows a binodal (5,7)-connected 3D network based on trinuclear [Co{sub 3}(μ{sub 3}-OH)]{sup 5+} units with unusual (3.4{sup 6}.5{sup 2}.6)(3{sup 2}.4{sup 6}.5{sup 7}.6{sup 5}.7) topology. Variable-temperature magnetic susceptibility measurements reveals that complex 1 shows ferromagnetic interactions between the adjacent Co(II) ions, whereas 2 is a antiferromagnetic system. - Graphical abstract: Two new Co(II) coordination polymers with bi- and trinuclear units have been obtained. 1 shows a binodal (4,6)-connected fsc net with a (4{sup 4}·6{sup 10}·8)(4{sup 4}·6{sup 2}) topology and antiferromagnetic interactions between the adjacent Co(II) ions, while 2 is a binodal (5,7)-connected 3D network with unusual (3.4{sup 6}.5{sup 2}.6)(3{sup 2}.4{sup 6}.5{sup 7}.6{sup 5}.7) topology and a ferromagnetic system. - Highlights: • Two Co(II) coordination polymers with different multimetallic clusters as building units. • A (4,6)-connected fsc net and a (5,7)-connected 3D network. • A antiferromagnetic coupling for 1 and A ferromagnetic coupling for 2.

Compliant gel polymer electrolyte based on poly(methyl acrylate-co-acrylonitrile)/poly(vinyl alcohol) for flexible lithium-ion batteries

International Nuclear Information System (INIS)

Ma, Xianguo; Huang, Xinglan; Gao, Jiandong; Zhang, Shu; Deng, Zhenghua; Suo, Jishuan

2014-01-01

Highlights: •Compliant gel polymer electrolyte based on P(MA-co-AN)/PVA is facilely prepared for flexible lithium-ion batteries. •The compliant gel polymer electrolyte displays high ionic conductivity, self-standing and mechanical flexible. •The compliant gel polymer electrolyte exhibits excellent chemical and electrochemical performances. -- Abstract: In this report, mechanically compliant gel polymer electrolyte (GPE) for flexible lithium-ion batteries is facilely fabricated. The GPE that based on the poly(methyl acrylate-co-acrylonitrile)/poly(vinyl alcohol) (P(MA-co-AN)/PVA) was prepared via emulsion polymerization. Herein, the P(MA-co-AN) copolymer is anticipated to exert beneficial for the bendability of the GPE, as well as swollen with the liquid electrolyte to provide a facile pathway for ion movement. The PVA serves as a stabilizer during the emulsion polymerization and a mechanical framework for the compliant polymer membrane. Performance benefits of the mechanically compliant membrane are elucidated in terms of mechanical behavior, thermostability and ionic conductivity. The GPE is still self-standing and mechanical flexible after swollen with liquid electrolyte. The GPE displays a conductivity of 0.98 mS cm −1 with the uptake electrolyte up to 150% of its own weight at 30 °C, excellent electrochemical stability window (5.2 V vs. Li/Li + ) and favorable interfacial characteristics. When used in flexible lithium-ion batteries, such a GPE demonstrates satisfactory compatibility with LiCoO 2 and graphite electrodes

High-Pressure CO2 Sorption in Polymers of Intrinsic Microporosity under Ultrathin Film Confinement.

Science.gov (United States)

Ogieglo, Wojciech; Ghanem, Bader; Ma, Xiaohua; Wessling, Matthias; Pinnau, Ingo

2018-04-04

Ultrathin microporous polymer films are pertinent to the development and further spread of nanotechnology with very promising potential applications in molecular separations, sensors, catalysis, or batteries. Here, we report high-pressure CO 2 sorption in ultrathin films of several chemically different polymers of intrinsic microporosity (PIMs), including the prototypical PIM-1. Films with thicknesses down to 7 nm were studied using interference-enhanced in situ spectroscopic ellipsometry. It was found that all PIMs swell much more than non-microporous polystyrene and other high-performance glassy polymers reported previously. Furthermore, chemical modifications of the parent PIM-1 strongly affected the swelling magnitude. By investigating the behavior of relative refractive index, n rel , it was possible to study the interplay between micropores filling and matrix expansion. Remarkably, all studied PIMs showed a maximum in n rel at swelling of 2-2.5% indicating a threshold point above which the dissolution in the dense matrix started to dominate over sorption in the micropores. At pressures above 25 bar, all PIMs significantly plasticized in compressed CO 2 and for the ones with the highest affinity to the penetrant, a liquidlike mixing typical for rubbery polymers was observed. Reduction of film thickness below 100 nm revealed pronounced nanoconfinement effects and resulted in a large swelling enhancement and a quick loss of the ultrarigid character. On the basis of the partial molar volumes of the dissolved CO 2 , the effective reduction of the T g was estimated to be ∼200 °C going from 128 to 7 nm films.

High-Pressure CO2 Sorption in Polymers of Intrinsic Microporosity under Ultrathin Film Confinement

KAUST Repository

Ogieglo, Wojciech

2018-03-12

Ultrathin microporous polymer films are pertinent to the development and further spread of nanotechnology with very promising potential applications in molecular separations, sensors, catalysis, or batteries. Here, we report high-pressure CO2 sorption in ultrathin films of several chemically different polymers of intrinsic microporosity (PIMs), including the prototypical PIM-1. Films with thicknesses down to 7 nm were studied using interference-enhanced in situ spectroscopic ellipsometry. It was found that all PIMs swell much more than non-microporous polystyrene and other high-performance glassy polymers reported previously. Furthermore, chemical modifications of the parent PIM-1 strongly affected the swelling magnitude. By investigating the behavior of relative refractive index, nrel, it was possible to study the interplay between micropores filling and matrix expansion. Remarkably, all studied PIMs showed a maximum in nrel at swelling of 2-2.5% indicating a threshold point above which the dissolution in the dense matrix started to dominate over sorption in the micropores. At pressures above 25 bar, all PIMs significantly plasticized in compressed CO2 and for the ones with the highest affinity to the penetrant, a liquidlike mixing typical for rubbery polymers was observed. Reduction of film thickness below 100 nm revealed pronounced nanoconfinement effects and resulted in a large swelling enhancement and a quick loss of the ultrarigid character. On the basis of the partial molar volumes of the dissolved CO2, the effective reduction of the Tg was estimated to be ∼200 °C going from 128 to 7 nm films.

High-Pressure CO2 Sorption in Polymers of Intrinsic Microporosity under Ultrathin Film Confinement

KAUST Repository

Ogieglo, Wojciech; Ghanem, Bader; Ma, Xiaohua; Wessling, Matthias; Pinnau, Ingo

2018-01-01

Ultrathin microporous polymer films are pertinent to the development and further spread of nanotechnology with very promising potential applications in molecular separations, sensors, catalysis, or batteries. Here, we report high-pressure CO2 sorption in ultrathin films of several chemically different polymers of intrinsic microporosity (PIMs), including the prototypical PIM-1. Films with thicknesses down to 7 nm were studied using interference-enhanced in situ spectroscopic ellipsometry. It was found that all PIMs swell much more than non-microporous polystyrene and other high-performance glassy polymers reported previously. Furthermore, chemical modifications of the parent PIM-1 strongly affected the swelling magnitude. By investigating the behavior of relative refractive index, nrel, it was possible to study the interplay between micropores filling and matrix expansion. Remarkably, all studied PIMs showed a maximum in nrel at swelling of 2-2.5% indicating a threshold point above which the dissolution in the dense matrix started to dominate over sorption in the micropores. At pressures above 25 bar, all PIMs significantly plasticized in compressed CO2 and for the ones with the highest affinity to the penetrant, a liquidlike mixing typical for rubbery polymers was observed. Reduction of film thickness below 100 nm revealed pronounced nanoconfinement effects and resulted in a large swelling enhancement and a quick loss of the ultrarigid character. On the basis of the partial molar volumes of the dissolved CO2, the effective reduction of the Tg was estimated to be ∼200 °C going from 128 to 7 nm films.

Polymers with alternating anthracene and phenylene building blocks linked by ethynylene and/or vinylene units: Studying structure-properties-relationships

Czech Academy of Sciences Publication Activity Database

Boudiba, S.; Růžička, Aleš; Ulbricht, C.; Enengl, S.; Enengl, C.; Gasiorowski, J.; Yumusak, C.; Pokorná, Veronika; Výprachtický, Drahomír; Hingerl, K.; Zahn, D. R. T.; Tinti, F.; Camaioni, N.; Bouguessa, S.; Gouasmia, A.; Cimrová, Věra; Egbe, D. A. M.

2017-01-01

Roč. 55, č. 1 (2017), s. 129-143 ISSN 0887-624X R&D Projects: GA ČR(CZ) GA13-26542S Institutional support: RVO:61389013 Keywords : anthracene building block * charge transport * conjugated polymers Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.952, year: 2016

Thiazoloisoindigo: a Building Block that Merges the Merits of Thienoisoindigo and Diazaisoindigo for Conjugated Polymers.

Science.gov (United States)

Wan, Xiaobo; Li, Chenchen; Wang, Xiao; Hio-Ieng, Un; Peng, Jiawei; Lan, Zhenggang; Cai, Mian; Pei, Jian; Wang, Jieyu

2018-04-24

Thiazoloisoindigo, a novel structural variation of isoindigo, is for the first time utilized to synthesize conjugated polymers. Polymer based on thiazoloisoindigo merges the advantages of the one based on thienoisoindigo and diazaisoindigo: It not only exhibits a greatly red shifted UV-vis absorption to the near-infrared region due to its strong tendency to form quinoidal structures, similar to that based on thienoisoindigo, but also shows excellent ambipolar mobility (hole 3.93 and electron 1.07 cm2 V-1 s-1, respectively) in organic field-effect transistors (OFETs), superior than that based on diazaisoindigo, showing the strong electron-withdrawing capability of thiazoloisoindigo. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A One-Step Route to CO2 -Based Block Copolymers by Simultaneous ROCOP of CO2 /Epoxides and RAFT Polymerization of Vinyl Monomers.

Science.gov (United States)

Wang, Yong; Zhao, Yajun; Ye, Yunsheng; Peng, Haiyan; Zhou, Xingping; Xie, Xiaolin; Wang, Xianhong; Wang, Fosong

2018-03-26

The one-step synthesis of well-defined CO 2 -based diblock copolymers was achieved by simultaneous ring-opening copolymerization (ROCOP) of CO 2 /epoxides and RAFT polymerization of vinyl monomers using a trithiocarbonate compound bearing a carboxylic group (TTC-COOH) as the bifunctional chain transfer agent (CTA). The double chain-transfer effect allows for independent and precise control over the molecular weight of the two blocks and ensures narrow polydispersities of the resultant block copolymers (1.09-1.14). Notably, an unusual axial group exchange reaction between the aluminum porphyrin catalyst and TTC-COOH impedes the formation of homopolycarbonates. By taking advantage of the RAFT technique, it is able to meet the stringent demand for functionality control to well expand the application scopes of CO 2 -based polycarbonates. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Water-soluble building blocks for terpyridine-containing supramolecular polymers : synthesis, complexation, and pH stability studies of poly(ethylene oxide) moieties

NARCIS (Netherlands)

Lohmeijer, B.G.G.; Schubert, U.S.

2003-01-01

Poly(ethylene oxide) of various molecular weights ([bar M ]n = 3 000, 5 200, 10 000, 16 500 g · mol-1) has been modified with terpyridine end groups as building blocks for water-soluble metallo-supramolecular polymers. Metallo-supramolecular A-A homopolymers have been prepared and characterized by

Hofmeister effect on thermo-responsive poly(propylene oxide): Role of polymer molecular weight and concentration

DEFF Research Database (Denmark)

Moghaddam, Saeed Zajforoushan; Thormann, Esben

2016-01-01

) salts on aqueous solutions of poly(propylene oxide) (PPO) is studied. Four different molecular weights of PPO were investigated, to determine how the variation in the polymer coil size affects the Hofmeister effect. The investigation was further conducted for different PPO concentrations, in order...... with the transition. It was observed that increasing the molecular weight weakens the effect of the both salts, which is interpreted in terms of a scaling law between the molecular weight and the accessible surface area of the polymers. Increasing the PPO concentration further diminished the NaCl effect...

(1-Adamantyl)methyl glycidyl ether: a versatile building block for living polymerization.

Science.gov (United States)

Moers, Christian; Wrazidlo, Robert; Natalello, Adrian; Netz, Isabelle; Mondeshki, Mihail; Frey, Holger

2014-06-01

(1-Adamantyl)methyl glycidyl ether (AdaGE) is introduced as a versatile monomer for oxyanionic polymerization, enabling controlled incorporation of adamantyl moieties in aliphatic polyethers. Via copolymerization with ethoxyethyl glycidyl ether (EEGE) and subsequent cleavage of the acetal protection groups of EEGE, hydrophilic linear polyglycerols with an adjustable amount of pendant adamantyl moieties are obtained. The adamantyl unit permits control over thermal properties and solubility profile of these polymers (LCST). Additionally, AdaGE is utilized as a termination agent in carbanionic polymerization, affording adamantyl-terminated polymers. Using these structures as macroinitiators for the polymerization of ethylene oxide affords amphiphilic, in-chain adamantyl-functionalized block copolymers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydrogen Bond Induces Hierarchical Self-Assembly in Liquid-Crystalline Block Copolymers.

Science.gov (United States)

Huang, Shuai; Pang, Linlin; Chen, Yuxuan; Zhou, Liming; Fang, Shaoming; Yu, Haifeng

2018-03-01

Microphase-separated structures of block copolymers (BCs) with a size of sub-10 nm are usually obtained by hydrogen-bond-induced self-assembly of BCs through doping with small molecules as functional additives. Here, fabrication of hierarchically self-assembled sub-10 nm structures upon microphase separation of amphiphilic liquid-crystalline BCs (LCBCs) at the existence of hydrogen bonds but without any dopants is reported. The newly introduced urethane groups in the side chain of the hydrophobic block of LCBCs interact with the ether groups of the hydrophilic poly(ethylene oxide) (PEO) block, leading to imperfect crystallization of the PEO blocks. Both crystalline and amorphous domains coexist in the separated PEO phase, enabling a lamellar structure to appear inside the PEO nanocylinders. This provides an elegant method to fabricate controllable sub-10 nm microstructures in well-defined polymer systems without the introduction of any dopants. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

RAFT technology for the production of advanced photoresist polymers

Science.gov (United States)

Sheehan, Michael T.; Farnham, William B.; Okazaki, Hiroshi; Sounik, James R.; Clark, George

2008-03-01

Reversible Addition Fragmentation Chain Transfer (RAFT) technology has been developed for use in producing high yield low polydispersity (PD) polymers for many applications. RAFT technology is being used to produce low PD polymers and to allow control of the polymer architecture. A variety of polymers are being synthesized for use in advanced photoresists using this technique. By varying the RAFT reagent used we can modulate the system reactivity of the RAFT reagent and optimize it for use in acrylate or methacrylate monomer systems (193 and 193i photoresist polymers) or for use in styrenic monomer systems (248 nm photoresist polymers) to achieve PD as low as 1.05. RAFT polymerization technology also allows us to produce block copolymers using a wide variety of monomers. These block copolymers have been shown to be useful in self assembly polymer applications to produce unique and very small feature sizes. The mutual compatibilities of all the components within a single layer 193 photoresist are very important in order to achieve low LWR and low defect count. The advent of immersion imaging demands an additional element of protection at the solid/liquid interface. We have used RAFT technology to produce block copolymers comprising a random "resist" block with composition and size based on conventional dry photoresist materials, and a "low surface energy" block for use in 193i lithography. The relative block lengths and compositions may be varied to tune solution behavior, surface energy, contact angles, and solubility in developer. The use of this technique will be explored to produce polymers used in hydrophobic single layer resists as well as additives compatible with the main photoresist polymer.

Micro-shear bond strength of different resin cements to ceramic/glass-polymer CAD-CAM block materials.

Science.gov (United States)

Cekic-Nagas, Isil; Ergun, Gulfem; Egilmez, Ferhan; Vallittu, Pekka Kalevi; Lassila, Lippo Veli Juhana

2016-10-01

The aim of this study was to evaluate the effects of hydrofluoric acid treatment on bond strength of resin cements to three different types of ceramic/glass containing CAD-CAM block composite materials. CAD-CAM block materials of polymer infiltrated (Vita Enamic), resin nanoceramic (Lava Ultimate) and nanoceramic (Cerasmart) with a thickness of 1.5mm were randomly divided into two groups according to the surface treatment performed. In Group 1, specimens were wet-ground with silicon carbide abrasive papers up to no. 1000. In Group 2, 9.6% hydrofluoric acid gel was applied to ceramics. Three different resin cements (RelyX, Variolink Esthetic and G-CEM LinkAce) were applied to the tubes in 1.2-mm thick increments and light-cured for 40s using LED light curing unit. Half of the specimens (n=10) were submitted to thermal cycling (5000 cycles, 5-55°C). The strength measurements were accomplished with a universal testing machine (Lloyd Instruments) at a cross-head speed of 0.5mm/min until the failure occurs. Failure modes were examined using a stereomicroscope and scanning electron microscope. The data were analyzed with multivariate analysis of variance (MANOVA) and Tukey's post hoc tests (α=0.05). There were significant differences between ceramics and resin cements (pceramics (pceramic/glass-polymer materials might promote the bonding capacity of these systems. Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Nanostructured Block Polymer Membranes as High Capacity Adsorbers for the Capture of Metal Ions from Water

Science.gov (United States)

Boudouris, Bryan; Weidman, Jacob; Mulvenna, Ryan; Phillip, William

The efficient removal of metal ions from aqueous streams is of significant import in applications ranging from industrial waste treatment to the purification of drinking water. An emerging paradigm associated with this separation is one that utilizes membrane adsorbers as a means by which to bind metal salt contaminants. Here, we demonstrate that the casting of an A-B-C triblock polymer using the self-assembly and non-solvent induced phase separation (SNIPS) methodology results in a nanoporous membrane geometry. The nature of the triblock polymer affords an extremely high density of binding sites within the membrane. As such, we demonstrate that the membranes with binding capacities equal to that of state-of-the-art packed bed columns. Moreover, because the affinity of the C moiety can be tuned, highly selective binding events can occur based solely on the chemistry of the block polymer and the metal ions in solution (i.e., in a manner that is independent of the size of the metal ions). Due to these combined facts, these membranes efficiently remove heavy metal (e.g., lead- and cadmium-based) salts from contaminated water streams with greater than 95% efficiency. Finally, we show that the membranes can be regenerated through a simple treatment in order to provide long-lasting adsorber systems as well. Thus, it is anticipated that these nanostructured triblock polymer membranes are a platform by which to obtain next-generation water purification processes.

Preparation and drug-loading properties of Fe{sub 3}O{sub 4}/Poly(styrene-co-acrylic acid) magnetic polymer nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Lu, Wensheng [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China); Coordination Chemistry Institute, School of Chemistry and Chemical Engineering and Life Science, Chaohu University, Chaohu 238000 (China); Shen, Yuhua, E-mail: s_yuhua@163.com [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China); Xie, Anjian [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China); Zhang, Weiqiang [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China); Coordination Chemistry Institute, School of Chemistry and Chemical Engineering and Life Science, Chaohu University, Chaohu 238000 (China)

2013-11-15

Fe{sub 3}O{sub 4}/poly(styrene-co-acrylic acid) magnetic polymer nanocomposites were synthesized by the dispersion polymerization method using styrene as hard monomer, acrylic acid as functional monomer, Fe{sub 3}O{sub 4} nanoparticles modified with oleic acid as core, and poly(styrene-co-acrylic acid) as shell. Drug-loading properties of magnetic polymer nanocomposites with curcumin as a model drug were also studied. The results indicated that magnetic polymer nanocomposites with monodisperse were obtained, the particle size distribution was 50–120 nm, and the average size was about 100 nm. The contents of poly(styrene-co-acrylic acid) and Fe{sub 3}O{sub 4} nanoparticles in magnetic polymer nanocomposites were 74% and 24.7%, respectively. The drug-loading capacity and entrapment efficiency were 2.5% and 44.4%, respectively. The saturation magnetization of magnetic polymer nanocomposites at 300 K was 20.2 emu/g without coercivity and remanence. The as-prepared magnetic polymer nanocomposites have not only lots of functional carboxyl groups but also stronger magnetic response, which might have potential applications in drug carrier and targeted drug release.

Chemically selective soft x-ray patterning of polymers

International Nuclear Information System (INIS)

Wang, J.; Stover, H.D.; Hitchcock, A.P.; Tyliszczak, T.

2007-01-01

The chemically selective modification of polymer mixtures by monochromated soft X-rays has been explored using the high-brightness fine-focused 50 nm beam of a scanning transmission X-ray microscope. Four different polymer systems were examined: a polymethylmethacrylate (PMMA) polyacrylonitrile (PAN) bilayer film; a PMMA-blend-PAN microphase-separated film; a poly(MMA-co-AN) copolymer film; and a poly(ethyl cyanoacrylate) homopolymer film. A high level of chemically selective modification was achieved for the PMMA/PAN bilayer; in particular, irradiation at 288.45 eV selectively removed the carbonyl group from PMMA while irradiation at 286.80 eV selectively reduced the nitrile group of PAN, even when these irradiations were carried out at the same (x,y) position of the sample. In the last two homogeneous polymer systems, similar amounts of damage to the nitrile and carbonyl groups occurred during irradiation at either 286.80 or 288.45 eV. This is attributed to damage transfer between the C=N and C=O groups mediated by primary electrons, secondary electrons or radical/ionic processes, aided by their close spatial proximity. Although the overall thickness of the bilayer sample at 70 nm is smaller than the lateral line spreading of 100 nm, the interface between the layers appears to effectively block the transport of energy, and hence damage, between the two layers. The origins of the line spreading in homogeneous phases and possible origins of the damage blocking effect of the interface are discussed. To demonstrate chemically selective patterning, high-resolution multi-wavelength patterns were created in the PMMA/PAN bilayer system

Homochiral Evolution in Self-Assembled Chiral Polymers and Block Copolymers.

Science.gov (United States)

Wen, Tao; Wang, Hsiao-Fang; Li, Ming-Chia; Ho, Rong-Ming

2017-04-18

The significance of chirality transfer is not only involved in biological systems, such as the origin of homochiral structures in life but also in man-made chemicals and materials. How the chiral bias transfers from molecular level (molecular chirality) to helical chain (conformational chirality) and then to helical superstructure or phase (hierarchical chirality) from self-assembly is vital for the chemical and biological processes in nature, such as communication, replication, and enzyme catalysis. In this Account, we summarize the methodologies for the examination of homochiral evolution at different length scales based on our recent studies with respect to the self-assembly of chiral polymers and chiral block copolymers (BCPs*). A helical (H*) phase to distinguish its P622 symmetry from that of normal hexagonally packed cylinder phase was discovered in the self-assembly of BCPs* due to the chirality effect on BCP self-assembly. Enantiomeric polylactide-containing BCPs*, polystyrene-b-poly(l-lactide) (PS-PLLA) and polystyrene-b-poly(d-lactide) (PS-PDLA), were synthesized for the examination of homochiral evolution. The optical activity (molecular chirality) of constituted chiral repeating unit in the chiral polylactide is detected by electronic circular dichroism (ECD) whereas the conformational chirality of helical polylactide chain can be explicitly determined by vibrational circular dichroism (VCD). The H* phases of the self-assembled polylactide-containing BCPs* can be directly visualized by 3D transmission electron microscopy (3D TEM) technique at which the handedness (hierarchical chirality) of the helical nanostructure is thus determined. The results from the ECD, VCD, and 3D TEM for the investigated chirality at different length scales suggest the homochiral evolution in the self-assembly of the BCPs*. For chiral polylactides, twisted lamellae in crystalline banded spherulite can be formed by dense packing scheme and effective interactions upon helical

Blocking temperature distribution in implanted Co-Ni nanoparticles obtained by magneto-optical measurements

Energy Technology Data Exchange (ETDEWEB)

D' Orazio, F.; Lucari, F. E-mail: franco.lucari@aquila.infn.it; Melchiorri, M.; Julian Fernandez, C. de; Mattei, G.; Mazzoldi, P.; Sangregorio, C.; Gatteschi, D.; Fiorani, D

2003-05-01

Three samples of Co-Ni alloy nanoparticles with different compositions were prepared by sequential ion implantation in silica slides. Transmission electron microscopy (TEM) showed the presence of spherical nanoparticles dispersed in the matrix. Magneto-optical Kerr effect analysis identified two magnetic components attributed to superparamagnetic particles in unblocked and blocked states, respectively. Magnetic field loops were measured as a function of temperature. Blocking temperature distributions were obtained; and their comparison with the size distributions derived from TEM provided the average magnetic anisotropy of the particles.

Blocking temperature distribution in implanted Co-Ni nanoparticles obtained by magneto-optical measurements

International Nuclear Information System (INIS)

D'Orazio, F.; Lucari, F.; Melchiorri, M.; Julian Fernandez, C. de; Mattei, G.; Mazzoldi, P.; Sangregorio, C.; Gatteschi, D.; Fiorani, D.

2003-01-01

Three samples of Co-Ni alloy nanoparticles with different compositions were prepared by sequential ion implantation in silica slides. Transmission electron microscopy (TEM) showed the presence of spherical nanoparticles dispersed in the matrix. Magneto-optical Kerr effect analysis identified two magnetic components attributed to superparamagnetic particles in unblocked and blocked states, respectively. Magnetic field loops were measured as a function of temperature. Blocking temperature distributions were obtained; and their comparison with the size distributions derived from TEM provided the average magnetic anisotropy of the particles

Modeling CO2 laser ablation impulse of polymers in vapor and plasma regimes

International Nuclear Information System (INIS)

Sinko, John E.; Phipps, Claude R.

2009-01-01

An improved model for CO 2 laser ablation impulse in polyoxymethylene and similar polymers is presented that describes the transition effects from the onset of vaporization to the plasma regime in a continuous fashion. Several predictions are made for ablation behavior.

A Comprehensive Systematic Study on Thermoresponsive Gels: Beyond the Common Architectures of Linear Terpolymers

Directory of Open Access Journals (Sweden)

Anna P. Constantinou

2017-01-01

Full Text Available In this study, seven thermoresponsive methacrylate terpolymers with the same molar mass (MM and composition but various architectures were successfully synthesized using group transfer polymerization (GTP. These terpolymers were based on tri(ethylene glycol methyl ether methacrylate (TEGMA, A unit, n-butyl methacrylate (BuMA, B unit, and 2-(dimethylaminoethyl methacrylate (DMAEMA, C unit. Along with the more common ABC, ACB, BAC, and statistical architectures, three diblock terpolymers were also synthesized and investigated for the first time, namely (ABC, A(BC, and B(AC; where the units in the brackets are randomly copolymerized. Two BC diblock copolymers were also synthesized for comparison. Their hydrodynamic diameters and their effective pKas were determined by dynamic light scattering (DLS and hydrogen ion titrations, respectively. The self-assembly behavior of the copolymers was also visualized by transmission electron microscopy (TEM. Both dilute and concentrated aqueous copolymer solutions were extensively studied by visual tests and their cloud points (CP and gel points were determined. It is proven that the aqueous solution properties of the copolymers, with specific interest in their thermoresponsive properties, are influenced by the architecture, with the ABC and A(BC ones to show clear sol-gel transition.

Preparation of dual-responsive hybrid fluorescent nano probe based on graphene oxide and boronic acid/BODIPY-conjugated polymer for cell imaging

Energy Technology Data Exchange (ETDEWEB)

Khoerunnisa [Department of IT Convergence, Korea National University of Transportation, Chungju 380–702 (Korea, Republic of); Kang, Eun Bi [Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju 380–702 (Korea, Republic of); Mazrad, Zihnil Adha Islamy [Department of IT Convergence, Korea National University of Transportation, Chungju 380–702 (Korea, Republic of); Lee, Gibaek [Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju 380–702 (Korea, Republic of); In, Insik [Department of IT Convergence, Korea National University of Transportation, Chungju 380–702 (Korea, Republic of); Department of Polymer Science and Engineering, Korea National University of Transportation, Chungju 380–702 (Korea, Republic of); Park, Sung Young, E-mail: parkchem@ut.ac.kr [Department of IT Convergence, Korea National University of Transportation, Chungju 380–702 (Korea, Republic of); Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju 380–702 (Korea, Republic of)

2017-02-01

Here, we report a pH- and thermo-responsive fluorescent nanomaterial of functionalized reduced graphene oxide (rGO) with cross-linked polymer produced via catechol-boronate diol binding mechanism. When conjugated with the hydrophobic dye boron dipyrromethane (BODIPY), this material can act as a dual-responsive nanoplatform for cells imaging. 2-Chloro-3′,4′-dihydroxyacetophenone (CCDP)-quaternized-poly(dimethylaminoethyl methacrylate-co-N-isopropylacrylamide) [C-PDN] was cross-linked with BODIPY and 4-chlorophenyl boronic acid (BA)-quaternized-poly(ethylene glycol)-g-poly(dimethylaminoethyl methacrylate-co-N-isopropylacrylamide) [BB-PPDN]. The GO was then reduced by the catechol group in the cross-linked polymer to synthesize rGO nanoparticles, which able to stabilize the quenching mechanism. This nanoplatform exhibits intense fluorescence at acidic pH and low fluorescence at physiological pH. Confocal laser scanning microscopy (CLSM) images shows bright fluorescence at lysosomal pH and total quench at physiological pH. Therefore, we have successfully developed a promising sensitive bio-imaging probe for identifying cancer cells. - Graphical abstract: [BB-PPDN]-[C-PDN]/rGO nanoparticles with boronic acid-catechol cis-diol binding mechanism toward change in pH demonstrated good biocompatibility and effective quenching for cancer cell detection. - Highlights: • Dual responsive (pH- and thermo) fluorescent nano probe was proposed for cells imaging. • The mechanism was based on cis-diol binding mechanism of boronic acid and catechol. • Reduced graphene oxide was used as quencher on nano-platform. • Detection was controlled dependent on pH based on diol compound of boron chemistry.

Associate host in single-layer co-host polymer electrophosphorescent devices

International Nuclear Information System (INIS)

Wang Yuanmin; Teng Feng; Feng Bin; Wang Yongsheng; Xu Xurong

2006-01-01

The definition and role of 'host' in polymer LED materials are studied in the present work. 'Primary host' and 'associate host' have been proposed and the rules of how to select an associate host are reported. Based on our experiments and the analysis of the energy scheme of the devices, we suggest that the values of the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) are critical determinant in selecting a suitable associate host. On one hand, the associate host should be a hole-blocking material. This can confine the excitons in the active layer. On the other hand, the associate host should have a suitable LUMO that is convenient for electrons to transport

Improved power conversion efficiency of dye-sensitized solar cells using side chain liquid crystal polymer embedded in polymer electrolytes

Energy Technology Data Exchange (ETDEWEB)

Cho, Woosum [Department of Chemistry Education, and Department of Frontier Materials Chemistry, and Institute for Plastic Information and Energy Materials, Pusan National University, Busan 609-735 (Korea, Republic of); Lee, Jae Wook, E-mail: jlee@donga.ac.kr [Department of Chemistry, Dong-A University, Busan 604-714 (Korea, Republic of); Gal, Yeong-Soon [Polymer Chemistry Lab, College of General Education, Kyungil University, Hayang 712-701 (Korea, Republic of); Kim, Mi-Ra, E-mail: mrkim2@pusan.ac.kr [Department of Polymer Science and Engineering, Pusan National University, Busan 609-735 (Korea, Republic of); Jin, Sung Ho, E-mail: shjin@pusan.ac.kr [Department of Chemistry Education, and Department of Frontier Materials Chemistry, and Institute for Plastic Information and Energy Materials, Pusan National University, Busan 609-735 (Korea, Republic of)

2014-02-14

Side chain liquid crystal polymer (SCLCP) embedded in poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP)-based polymer electrolytes (PVdF-co-HFP:side chain liquid crystal polymer (SCLCP)) was prepared for dye-sensitized solar cell (DSSC) application. The polymer electrolytes contained tetrabutylammonium iodide (TBAI), iodine (I{sub 2}), and 8 wt% PVdF-co-HFP in acetonitrile. DSSCs comprised of PVdF-co-HFP:SCLCP-based polymer electrolytes displayed enhanced redox couple reduction and reduced charge recombination in comparison to those of the conventional PVdF-co-HFP-based polymer electrolyte. The significantly increased short-circuit current density (J{sub sc}, 10.75 mA cm{sup −2}) of the DSSCs with PVdF-co-HFP:SCLCP-based polymer electrolytes afforded a high power conversion efficiency (PCE) of 5.32% and a fill factor (FF) of 0.64 under standard light intensity of 100 mW cm{sup −2} irradiation of AM 1.5 sunlight. - Highlights: • We developed the liquid crystal polymer embedded on polymer electrolyte for DSSCs. • We fabricated the highly efficient DSSCs using polymer electrolyte. • The best PCE achieved for P1 is 5.32% using polymer electrolyte.

Improved power conversion efficiency of dye-sensitized solar cells using side chain liquid crystal polymer embedded in polymer electrolytes

International Nuclear Information System (INIS)

Cho, Woosum; Lee, Jae Wook; Gal, Yeong-Soon; Kim, Mi-Ra; Jin, Sung Ho

2014-01-01

Side chain liquid crystal polymer (SCLCP) embedded in poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP)-based polymer electrolytes (PVdF-co-HFP:side chain liquid crystal polymer (SCLCP)) was prepared for dye-sensitized solar cell (DSSC) application. The polymer electrolytes contained tetrabutylammonium iodide (TBAI), iodine (I 2 ), and 8 wt% PVdF-co-HFP in acetonitrile. DSSCs comprised of PVdF-co-HFP:SCLCP-based polymer electrolytes displayed enhanced redox couple reduction and reduced charge recombination in comparison to those of the conventional PVdF-co-HFP-based polymer electrolyte. The significantly increased short-circuit current density (J sc , 10.75 mA cm −2 ) of the DSSCs with PVdF-co-HFP:SCLCP-based polymer electrolytes afforded a high power conversion efficiency (PCE) of 5.32% and a fill factor (FF) of 0.64 under standard light intensity of 100 mW cm −2 irradiation of AM 1.5 sunlight. - Highlights: • We developed the liquid crystal polymer embedded on polymer electrolyte for DSSCs. • We fabricated the highly efficient DSSCs using polymer electrolyte. • The best PCE achieved for P1 is 5.32% using polymer electrolyte

Solubilization of trace organics in block copolymer micelles for environmental separation using membrane extraction principles. Progress report, May 1, 1992--December 31, 1992

Energy Technology Data Exchange (ETDEWEB)

Hatton, T.A.

1992-12-01

The solubilization of a range of polycyclic aromatic hydrocarbons in block copolymer micelles has been studied as a function of polymer composition, architecture, and temperature. Micelle formation is favored at high temperatures, leading to significant enhancements in solubilization capacity. At low temperatures, however, micelles do not form and the solubilization capacity of the block copolymer solution for the organics is low; this provides a convenient method for the regeneration of micellar solutions used as ``solvents`` in the treatment of contaminated feed streams using membrane extraction principles. It has also been shown (in collaboration with K.P. Johnston of University of Texas, Austin) that supercritical CO{sub 2} can be used effectively for micelle regeneration. Theoretical calculations of the structure of block copolymer micelles in the presence and absence of solutes using self-consistent mean-field lattice theories have successfully captured the trends observed with changing polymer composition and architecture, often quantitatively. The temperature and composition dependence of the micellar properties were determined by allowing the individual polymer segments to assume both polar and non-polar conformations.

Microbial production of polyhydroxyalkanoate block copolymer by recombinant Pseudomonas putida.

Science.gov (United States)

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

2011-04-01

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

Donor-Acceptor Block Copolymers: Synthesis and Solar Cell Applications

Directory of Open Access Journals (Sweden)

Kazuhiro Nakabayashi

2014-04-01

Full Text Available Fullerene derivatives have been widely used for conventional acceptor materials in organic photovoltaics (OPVs because of their high electron mobility. However, there are also considerable drawbacks for use in OPVs, such as negligible light absorption in the visible-near-IR regions, less compatibility with donor polymeric materials and high cost for synthesis and purification. Therefore, the investigation of non-fullerene acceptor materials that can potentially replace fullerene derivatives in OPVs is increasingly necessary, which gives rise to the possibility of fabricating all-polymer (polymer/polymer solar cells that can deliver higher performance and that are potentially cheaper than fullerene-based OPVs. Recently, considerable attention has been paid to donor-acceptor (D-A block copolymers, because of their promising applications as fullerene alternative materials in all-polymer solar cells. However, the synthesis of D-A block copolymers is still a challenge, and therefore, the establishment of an efficient synthetic method is now essential. This review highlights the recent advances in D-A block copolymers synthesis and their applications in all-polymer solar cells.

77 FR 65831 - Polymers; exemptions from the requirement of a tolerance.

Science.gov (United States)

2012-10-31

...]-Nonylphenyl)poly(oxypropylene) Block Polymer With Poly(oxyethylene); Tolerance Exemption AGENCY: Environmental... requirement of a tolerance for residues of [alpha]-([rho]-Nonylphenyl)poly(oxypropylene) block polymer with... polymer with poly(oxyethylene) on food or feed commodities. DATES: This regulation is effective October 31...

Biofunctionalized conductive polymers enable efficient CO2 electroreduction

Science.gov (United States)

Coskun, Halime; Aljabour, Abdalaziz; De Luna, Phil; Farka, Dominik; Greunz, Theresia; Stifter, David; Kus, Mahmut; Zheng, Xueli; Liu, Min; Hassel, Achim W.; Schöfberger, Wolfgang; Sargent, Edward H.; Sariciftci, Niyazi Serdar; Stadler, Philipp

2017-01-01

Selective electrocatalysts are urgently needed for carbon dioxide (CO2) reduction to replace fossil fuels with renewable fuels, thereby closing the carbon cycle. To date, noble metals have achieved the best performance in energy yield and faradaic efficiency and have recently reached impressive electrical-to-chemical power conversion efficiencies. However, the scarcity of precious metals makes the search for scalable, metal-free, CO2 reduction reaction (CO2RR) catalysts all the more important. We report an all-organic, that is, metal-free, electrocatalyst that achieves impressive performance comparable to that of best-in-class Ag electrocatalysts. We hypothesized that polydopamine—a conjugated polymer whose structure incorporates hydrogen-bonded motifs found in enzymes—could offer the combination of efficient electrical conduction, together with rendered active catalytic sites, and potentially thereby enable CO2RR. Only by developing a vapor-phase polymerization of polydopamine were we able to combine the needed excellent conductivity with thin film–based processing. We achieve catalytic performance with geometric current densities of 18 mA cm−2 at 0.21 V overpotential (−0.86 V versus normal hydrogen electrode) for the electrosynthesis of C1 species (carbon monoxide and formate) with continuous 16-hour operation at >80% faradaic efficiency. Our catalyst exhibits lower overpotentials than state-of-the-art formate-selective metal electrocatalysts (for example, 0.5 V for Ag at 18 mA cm−1). The results confirm the value of exploiting hydrogen-bonded sequences as effective catalytic centers for renewable and cost-efficient industrial CO2RR applications. PMID:28798958

Green polymer chemistry: biocatalysis and biomaterials

Science.gov (United States)

This overview briefly surveys the practice of green chemistry in polymer science. Eight related themes can be discerned from the current research activities: 1) biocatalysis, 2) bio-based building blocks and agricultural products, 3) degradable polymers, 4) recycling of polymer products and catalys...

Thermoresponsive PNIPAAm-modified cotton fabric surfaces that switch between superhydrophilicity and superhydrophobicity

International Nuclear Information System (INIS)

Jiang Cheng; Wang Qihua; Wang Tingmei

2012-01-01

Thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) was grafted onto the cotton fabric by atom transfer radical polymerization (ATRP). Introducing 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTS) onto the surface, the density of PNIPAAm chains can be adjusted because of the competitive reactions of (3-aminopropyl) triethoxysilane (APS) and PFDTS. With the appropriate ratio of APS and PFDTS, the cotton fabric can be switched from superhydrophilic to superhydrophobic by controlling temperature. The prepared cotton fabric may find application in functional textiles, soft and folding superhydrophobic materials.

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.

Room temperature synthesis of heptazine-based microporous polymer networks as photocatalysts for hydrogen evolution.

Science.gov (United States)

Kailasam, Kamalakannan; Schmidt, Johannes; Bildirir, Hakan; Zhang, Guigang; Blechert, Siegfried; Wang, Xinchen; Thomas, Arne

2013-06-25

Two emerging material classes are combined in this work, namely polymeric carbon nitrides and microporous polymer networks. The former, polymeric carbon nitrides, are composed of amine-bridged heptazine moieties and showed interesting performance as a metal-free photocatalyst. These materials have, however, to be prepared at high temperatures, making control of their chemical structure difficult. The latter, microporous polymer networks have received increasing interest due to their high surface area, giving rise to interesting applications in gas storage or catalysis. Here, the central building block of carbon nitrides, a functionalized heptazine as monomer, and tecton are used to create microporous polymer networks. The resulting heptazine-based microporous polymers show high porosity, while their chemical structure resembles the ones of carbon nitrides. The polymers show activity for the photocatalytic production of hydrogen from water, even under visible light illumination. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

CONJUGATED BLOCK-COPOLYMERS FOR ELECTROLUMINESCENT DIODES

NARCIS (Netherlands)

Hilberer, A; Gill, R.E; Herrema, J.K; Malliaras, G.G; Wildeman, J.; Hadziioannou, G

In this article we review results obtained in our laboratory on the design and study of new light-emitting polymers. We are interested in the synthesis and characterisation of block copolymers with regularly alternating conjugated and non conjugated sequences. The blocks giving rise to luminescence

Synthesis and conformational characterization of functional di-block copolymer brushes for microarray technology

Energy Technology Data Exchange (ETDEWEB)

Di Carlo, Gabriele; Damin, Francesco [Institute of Chemistry of Molecular Recognition, National Research Council of Italy, Via M. Bianco 9, 20131 Milano (Italy); Armelao, Lidia [ISTM-CNR and INSTM, Department of Chemistry, University of Padova, Via F. Marzolo 1, 35131 Padova (Italy); Maccato, Chiara [Department of Chemistry and INSTM, University of Padova, Via F. Marzolo 1, 35131 Padova (Italy); Unlu, Selim [Department of Electrical and Computer Engineering, Boston University, St. Mary Street 8, Boston, MA 02215 (United States); Department of Biomedical Engineering, Boston University, St. Mary Street 8, Boston, MA 02215 (United States); Spuhler, Philipp S. [Department of Biomedical Engineering, Boston University, St. Mary Street 8, Boston, MA 02215 (United States); Chiari, Marcella, E-mail: marcella.chiari@icrm.cnr.it [Institute of Chemistry of Molecular Recognition, National Research Council of Italy, Via M. Bianco 9, 20131 Milano (Italy)

2012-02-01

Surface initiated polymerization (SIP) coupled with reversible addition-fragmentation chain transfer polymerization (RAFT) was used to functionalize microarray glass slides with block polymer brushes. N,N-dimethylacrylamide (DMA) and N-acryloyloxysuccinimide (NAS) (graft-poly[DMA-b-(DMA-co-NAS)]) brushes, with di-block architecture, were prepared from a novel RAFT chain transfer agent bearing a silanating moiety (RAFT silane) directly anchored onto the glass surfaces. Conformational characterization of the coatings was performed by Self Spectral Interference Fluorescence Microscopy (SSFM), an innovative technique that describes the location of a fluorescent DNA molecule relative to a surface with sub-nanometer accuracy. X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM) were used to characterize the coatings composition and morphology.

Synthesis and conformational characterization of functional di-block copolymer brushes for microarray technology

International Nuclear Information System (INIS)

Di Carlo, Gabriele; Damin, Francesco; Armelao, Lidia; Maccato, Chiara; Unlu, Selim; Spuhler, Philipp S.; Chiari, Marcella

2012-01-01

Surface initiated polymerization (SIP) coupled with reversible addition-fragmentation chain transfer polymerization (RAFT) was used to functionalize microarray glass slides with block polymer brushes. N,N-dimethylacrylamide (DMA) and N-acryloyloxysuccinimide (NAS) (graft-poly[DMA-b-(DMA-co-NAS)]) brushes, with di-block architecture, were prepared from a novel RAFT chain transfer agent bearing a silanating moiety (RAFT silane) directly anchored onto the glass surfaces. Conformational characterization of the coatings was performed by Self Spectral Interference Fluorescence Microscopy (SSFM), an innovative technique that describes the location of a fluorescent DNA molecule relative to a surface with sub-nanometer accuracy. X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM) were used to characterize the coatings composition and morphology.

UV-crosslinkable and thermo-responsive chitosan hybrid hydrogel for NIR-triggered localized on-demand drug delivery.

Science.gov (United States)

Wang, Lei; Li, Baoqiang; Xu, Feng; Xu, Zheheng; Wei, Daqing; Feng, Yujie; Wang, Yaming; Jia, Dechang; Zhou, Yu

2017-10-15

Innovative drug delivery technologies based on smart hydrogels for localized on-demand drug delivery had aroused great interest. To acquire smart UV-crosslinkable chitosan hydrogel for NIR-triggered localized on-demanded drug release, a novel UV-crosslinkable and thermo-responsive chitosan was first designed and synthesized by grafting with poly N-isopropylacrylamide, acetylation of methacryloyl groups and embedding with photothermal carbon. The UV-crosslinkable unit (methacryloyl groups) endowed chitosan with gelation via UV irradiation. The thermo-responsive unit (poly N-isopropylacrylamide) endowed chitosan hydrogel with temperature-triggered volume shrinkage and reversible swelling/de-swelling behavior. The chitosan hybrid hydrogel embedded with photothermal carbon exhibited distinct NIR-triggered volume shrinkage (∼42% shrinkage) in response to temperature elevation as induced by NIR laser irradiation. As a demonstration, doxorubicin release rate was accelerated and approximately 40 times higher than that from non-irradiated hydrogels. The UV-crosslinkable and thermal-responsive hybrid hydrogel served as in situ forming hydrogel-based drug depot is developed for NIR-triggered localized on-demand release. Copyright © 2017 Elsevier Ltd. All rights reserved.

Three Arm Star Homo- And Co-Polymers Via Atom Transfer Radical Polymerization

International Nuclear Information System (INIS)

Amin, A.; Sobh, R.A.; Ayoub, M.M.H.

2005-01-01

Star homo and co-polymers of some vinyl monomers such as methylmethacrylate, butylmethacrylate and styrene (MMA, BMA, St.) were prepared using N, N, N', N' tetramethylethylenediamine ligand/ CuBr catalytic system via atom transfer radical polymerization (ATRP). Three armed benzene based core was successfully used as initiator. Low polydispersities and regular molecular weight values were obtained in most cases especially at low conversions. MMA and BuMA showed comparable behavior where controlled and true ATRP was observed even at the high conversions. However, styrene monomer recorded irregular high polydispersities at high conversions in spite of the relatively low molecular weight values. 1HNMR confirmed the structures of the resulting polymers. Transmission Electron microscope (TEM) proved the nano-structure of the star polymers. The thermal behavior of the MMA star homo and copolymers was studied. The effect of the star shape on the thermal behavior was very clear with respect to the linear ones

Thermoresponsive chitosan-agarose hydrogel for skin regeneration.

Science.gov (United States)

Miguel, Sónia P; Ribeiro, Maximiano P; Brancal, Hugo; Coutinho, Paula; Correia, Ilídio J

2014-10-13

Healing enhancement and pain control are critical issues on wound management. So far, different wound dressings have been developed. Among them, hydrogels are the most applied. Herein, a thermoresponsive hydrogel was produced using chitosan (deacetylation degree 95%) and agarose. Hydrogel bactericidal activity, biocompatibility, morphology, porosity and wettability were characterized by confocal microscopy, MTS assay and SEM. The performance of the hydrogel in the wound healing process was evaluated through in vivo assays, during 21 days. The attained results revealed that hydrogel has a pore size (90-400 μm) compatible with cellular internalization and proliferation. A bactericidal activity was observed for hydrogels containing more than 188 μg/mL of chitosan. The improved healing and the lack of a reactive or a granulomatous inflammatory reaction in skin lesions treated with hydrogel demonstrate its suitability to be used in a near future as a wound dressing. Copyright © 2014 Elsevier Ltd. All rights reserved.

Mapping the location of grafted PNIPAAM in mesoporous SBA-15 silica using gas adsorption analysis

DEFF Research Database (Denmark)

Reichhardt, Nina Viola; Guillet-Nicolas, Rémy; Thommes, Matthias

2012-01-01

The thermoresponsive polymer poly-N-isopropylacrylamide (PNIPAAM) was grafted in mesoporous SBA-15 silica. The grafting process consists of three steps: (i) increasing the amount of surface silanol groups of SBA-15 by hydroxylation, (ii) attachment of an anchor (1-(trichlorosilyl)-2-(m/p- (chloro......The thermoresponsive polymer poly-N-isopropylacrylamide (PNIPAAM) was grafted in mesoporous SBA-15 silica. The grafting process consists of three steps: (i) increasing the amount of surface silanol groups of SBA-15 by hydroxylation, (ii) attachment of an anchor (1-(trichlorosilyl)-2-(m...

Micellar Self-Assembly of Recombinant Resilin-/Elastin-Like Block Copolypeptides.

Science.gov (United States)

Weitzhandler, Isaac; Dzuricky, Michael; Hoffmann, Ingo; Garcia Quiroz, Felipe; Gradzielski, Michael; Chilkoti, Ashutosh

2017-08-14

Reported here is the synthesis of perfectly sequence defined, monodisperse diblock copolypeptides of hydrophilic elastin-like and hydrophobic resilin-like polypeptide blocks and characterization of their self-assembly as a function of structural parameters by light scattering, cryo-TEM, and small-angle neutron scattering. A subset of these diblock copolypeptides exhibit lower critical solution temperature and upper critical solution temperature phase behavior and self-assemble into spherical or cylindrical micelles. Their morphologies are dictated by their chain length, degree of hydrophilicity, and hydrophilic weight fraction of the ELP block. We find that (1) independent of the length of the corona-forming ELP block there is a minimum threshold in the length of the RLP block below which self-assembly does not occur, but that once that threshold is crossed, (2) the RLP block length is a unique molecular parameter to independently tune self-assembly and (3) increasing the hydrophobicity of the corona-forming ELP drives a transition from spherical to cylindrical morphology. Unlike the self-assembly of purely ELP-based block copolymers, the self-assembly of RLP-ELPs can be understood by simple principles of polymer physics relating hydrophilic weight fraction and polymer-polymer and polymer-solvent interactions to micellar morphology, which is important as it provides a route for the de novo design of desired nanoscale morphologies from first principles.

Toughening of Thermoresponsive Arrested Networks of Elastin-Like Polypeptides To Engineer Cytocompatible Tissue Scaffolds.

Science.gov (United States)

Glassman, Matthew J; Avery, Reginald K; Khademhosseini, Ali; Olsen, Bradley D

2016-02-08

Formulation of tissue engineering or regenerative scaffolds from simple bioactive polymers with tunable structure and mechanics is crucial for the regeneration of complex tissues, and hydrogels from recombinant proteins, such as elastin-like polypeptides (ELPs), are promising platforms to support these applications. The arrested phase separation of ELPs has been shown to yield remarkably stiff, biocontinuous, nanostructured networks, but these gels are limited in applications by their relatively brittle nature. Here, a gel-forming ELP is chain-extended by telechelic oxidative coupling, forming extensible, tough hydrogels. Small angle scattering indicates that the chain-extended polypeptides form a fractal network of nanoscale aggregates over a broad concentration range, accessing moduli ranging from 5 kPa to over 1 MPa over a concentration range of 5-30 wt %. These networks exhibited excellent erosion resistance and allowed for the diffusion and release of encapsulated particles consistent with a bicontinuous, porous structure with a broad distribution of pore sizes. Biofunctionalized, toughened networks were found to maintain the viability of human mesenchymal stem cells (hMSCs) in 2D, demonstrating signs of osteogenesis even in cell media without osteogenic molecules. Furthermore, chondrocytes could be readily mixed into these gels via thermoresponsive assembly and remained viable in extended culture. These studies demonstrate the ability to engineer ELP-based arrested physical networks on the molecular level to form reinforced, cytocompatible hydrogel matrices, supporting the promise of these new materials as candidates for the engineering and regeneration of stiff tissues.

CORRELATION BETWEEN POLYMER PACKING AND GAS TRANSPORT PROPERTIES FOR CO2/N2 SEPARATION IN GLASSY FLUORINATED POLYIMIDE MEMBRANE

Directory of Open Access Journals (Sweden)

P. C. TAN

2016-07-01

Full Text Available Gas separation performance of a membrane highly hinges on its physical properties. In this study, the interplay between polymer packing of a membrane and its gas transport behaviours (permeability and selectivity was investigated through a series of 6FDA-DAM:DABA (3:2 polyimide membranes with different polymer compactness. The chemical structure and the polymer packing of the resulting membrane were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR and packing density measurement, respectively. CO2/N2 separation efficiency of the membrane was evaluated at 25oC with feed pressure up to 6 bar. N2 permeability was found to rely on the membrane’s packing density, which signified its greater dependence on molecular sieving. In contrast, sorption showed a more vital role in determining the CO2 permeability. In this work, the membrane with a final thickness of 97±2 µm had successfully surpassed the Robeson’s 2008 upper bound plot with a CO2 permeability of 83 Barrer and CO2/N2 selectivity of 97 at 3 bar permeation.

Fluctuation effects in bulk polymer phase behavior

International Nuclear Information System (INIS)

Bates, F.S.; Rosedale, J.H.; Stepanek, P.; Lodge, T.P.; Wiltzius, P.; Hjelm R, Jr.; Fredrickson, G.H.

1990-01-01

Bulk polymer-polymer, and block copolymer, phase behaviors have traditionally been interpreted using mean-field theories. Recent small-angle neutron scattering (SANS) studies of critical phenomena in model binary polymer mixtures confirm that non-mean-field behavior is restricted to a narrow range of temperatures near the critical point, in close agreement with the Ginzburg criterion. In contrast, strong derivations from mean-field behavior are evident in SANS and rheological measurements on model block copolymers more than 50C above the order-disorder transition (ODT), which can be attributed to sizeable composition fluctuations. Such fluctuation effects undermine the mean-field assumption, conventionally applied to bulk polymers, and result in qualitative changes in phase behavior, such as the elimination of a thermodynamic stability limit in these materials. The influence of fluctuation effects on block copolymer and binary mixture phase behavior is compared and contrasted in this presentation

Modular Assembly of Hierarchically Structured Polymers

Science.gov (United States)

Leophairatana, Porakrit

The synthesis of macromolecules with complex yet highly controlled molecular architectures has attracted significant attention in the past few decades due to the growing demand for specialty polymers that possess novel properties. Despite recent efforts, current synthetic routes lack the ability to control several important architectural variables while maintaining low polydispersity index. This dissertation explores a new synthetic scheme for the modular assembly of hierarchically structured polymers (MAHP) that allows virtually any complex polymer to be assembled from a few basic molecular building blocks using a single common coupling chemistry. Complex polymer structures can be assembled from a molecular toolkit consisting of (1) copper-catalyzed azide-alkyne cycloaddition (CuAAC), (2) linear heterobifunctional macromonomers, (3) a branching heterotrifunctional molecule, (4) a protection/deprotection strategy, (5) "click" functional solid substrates, and (6) functional and responsive polymers. This work addresses the different challenges that emerged during the development of this synthetic scheme, and presents strategies to overcome those challenges. Chapter 3 investigates the alkyne-alkyne (i.e. Glaser) coupling side reactions associated with the atom transfer radical polymerization (ATRP) synthesis of alkyne-functional macromonomers, as well as with the CuAAC reaction of alkyne functional building blocks. In typical ATRP synthesis of unprotected alkyne functional polymers, Glaser coupling reactions can significantly compromise the polymer functionality and undermine the success of subsequent click reactions in which the polymers are used. Two strategies are reported that effectively eliminate these coupling reactions: (1) maintaining low temperature post-ATRP upon exposure to air, followed by immediate removal of copper catalyst; and (2) adding excess reducing agents post-ATRP, which prevents the oxidation of Cu(I) catalyst required by the Glaser coupling

Synthesis of Functional Block Copolymers Carrying One Poly( p -phenylenevinylene) and One Nonconjugated Block in a Facile One-Pot Procedure

KAUST Repository

Menk, Florian

2016-02-29

Block copolymers composed of a MEH-PPV block and a nonconjugated functional block (molecular weights between 5 and 90 kg/mol) were synthesized in a facile one-pot procedure via ROMP. This one-pot procedure permits the synthesis of numerous block copolymers with little effort. Amphiphilic block copolymers were obtained via incorporation of oxanorbornene carrying a PEG side chain as well as via postpolymerization modification of a reactive ester carrying norbornene derivative with methoxypoly(ethylene glycol)amine. These amphiphilic block copolymers can be self-assembled into micelles exhibiting different sizes (60-95 nm), morphologies (micelles or fused, caterpillar-like micelles), and optical properties depending on the polymer composition and the micellization procedure. Furthermore, the reactive ester carrying block copolymers enabled the introduction of anchor groups which facilitated the preparation of nanocomposites with CdSe/CdZnS core-shell QDs. The obtained composites were studied using time-resolved photoluminescence measurements. The results revealed an increased interaction based on an accelerated decay of the QD emission for composites as compared to the mixture of the QDs with unfunctionalized polymers. © 2016 American Chemical Society.

Synthesis of Functional Block Copolymers Carrying One Poly( p -phenylenevinylene) and One Nonconjugated Block in a Facile One-Pot Procedure

KAUST Repository

Menk, Florian; Shin, Suyong; Kim, Kyung-Oh; Scherer, Martin; Gehrig, Dominik; Laquai, Fré dé ric; Choi, Tae-Lim; Zentel, Rudolf

2016-01-01

Block copolymers composed of a MEH-PPV block and a nonconjugated functional block (molecular weights between 5 and 90 kg/mol) were synthesized in a facile one-pot procedure via ROMP. This one-pot procedure permits the synthesis of numerous block copolymers with little effort. Amphiphilic block copolymers were obtained via incorporation of oxanorbornene carrying a PEG side chain as well as via postpolymerization modification of a reactive ester carrying norbornene derivative with methoxypoly(ethylene glycol)amine. These amphiphilic block copolymers can be self-assembled into micelles exhibiting different sizes (60-95 nm), morphologies (micelles or fused, caterpillar-like micelles), and optical properties depending on the polymer composition and the micellization procedure. Furthermore, the reactive ester carrying block copolymers enabled the introduction of anchor groups which facilitated the preparation of nanocomposites with CdSe/CdZnS core-shell QDs. The obtained composites were studied using time-resolved photoluminescence measurements. The results revealed an increased interaction based on an accelerated decay of the QD emission for composites as compared to the mixture of the QDs with unfunctionalized polymers. © 2016 American Chemical Society.

Experimental data and thermodynamic modeling of ternary aqueous biphasic systems of EO/PO polymers–Na2SO4–H2O

NARCIS (Netherlands)

Milosevic, M.; Staal, K.J.J.; Schuur, Boelo; de Haan, A.B.

2014-01-01

Liquid–liquid extraction using thermoresponsive polymers as solvents in aqueous two phase systems followed by induced phase separation to recover the polymers is a potential technology for water–salt separations. Here we report for seven polymers on their ternary systems containing water, sodium

Influence of Filler Pore Structure and Polymer on the Performance of MOF-based Mixed Matrix Membranes for CO2 Capture.

Science.gov (United States)

Sabetghadam, Anahid; Liu, Xinlei; Benzaqui, Marvin; Gkaniatsou, Effrosyni; Orsi, Angelica; Lozinska, Magdalena M; Sicard, Clemence; Johnson, Timothy; Steunou, Nathalie; Wright, Paul A; Serre, Christian; Gascon, Jorge; Kapteijn, Freek

2018-03-24

In order to gain insight into the influence of metal-organic framework (MOF) filler and polymer on membrane performance, eight different composites are studied by combining four MOFs and two polymers. MOF materials (NH2-MIL-53(Al), MIL-69(Al), MIL-96(Al) and ZIF-94) with various chemical functionalities, topologies, and dimensionalities of porosity were employed as fillers, while two typical polymers with different permeability-selectivity properties (6FDA-DAM and Pebax) were deliberately selected as matrices. The best performing MOF-polymer composites were prepared by loading 25 wt.% of MIL-96(Al) as filler which improved the permeability and selectivity of 6FDA-DAM up to 32% and 10%, while for Pebax this enhancement was 25% and 18%, respectively. The observed differences in membrane performance in the separation of CO2 from N2 are explained on the basis of gas solubility, diffusivity properties and compatibility between the filler and polymer phases. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ionic Liquid Confined in Mesoporous Polymer Membrane with Improved Stability for CO2/N2 Separation

Directory of Open Access Journals (Sweden)

Ming Tan

2017-09-01

Full Text Available Supported ionic liquid membranes (SILMs have a promising prospect of application in flue gas separation, owing to its high permeability and selectivity of CO2. However, existing SILMs have the disadvantage of poor stability due to the loss of ionic liquid from the large pores of the macroporous support. In this study, a novel SILM with high stability was developed by confining ionic liquid in a mesoporous polymer membrane. First, a mesoporous polymer membrane derived from a soluble, low-molecular-weight phenolic resin precursor was deposited on a porous Al2O3 support, and then 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4] was immobilized inside mesopores of phenolic resin, forming the SILM under vacuum. Effects of trans-membrane pressure difference on the SILM separation performance were investigated by measuring the permeances of CO2 and N2. The SILM exhibits a high ideal CO2/N2 selectivity of 40, and an actual selectivity of approximately 25 in a mixed gas (50% CO2 and 50% N2 at a trans-membrane pressure difference of 2.5 bar. Compared to [emim][BF4] supported by polyethersulfone membrane with a pore size of around 0.45 μm, the [emim][BF4] confined in a mesoporous polymer membrane exhibits an improved stability, and its separation performance remained stable for 40 h under a trans-membrane pressure difference of 1.5 bar in a mixed gas before the measurement was intentionally stopped.

Nanosecond optical limiting response of sandwich-type neodymium dyphthalocyanine in a co-polymer host

NARCIS (Netherlands)

Aneeshkumar, B.N.; Gopinath, P.; Thomas, J.; Vallabhan, C.P.G.; Nampoori, V.P.N.; Radhakrishnan, P.

2004-01-01

The nanosecond optical limiting characteristics of sandwich-type neodymium diphthalocyanine in a co-polymer matrix of polymethyl methacrylate (PMMA) and methyl-2-cyanoacrylate have been studied for the first time. The measurements were performed using 9 ns laser pulses generated from a

Facile synthesis of triazine-triphenylamine-based microporous covalent polymer adsorbent for flue gas CO2 capture

KAUST Repository

Das, Swapan Kumar

2017-07-17

The sustainable capture and sequestration of CO2 from flue gas emission is an important and unavoidable challenge to control greenhouse gas release and climate change. In this report, we describe a triazine-triphenylamine-based microporous covalent organic polymer under mild synthetic conditions. 13C and 15N solid-state NMR and FTIR analyses confirm the linkage of the triazine and triphenylamine components in the porous polymer skeleton. The material is composed of spherical particles 1.0 to 2.0 μm in size and possesses a high surface area (1104 m2/g). The material exhibits superb chemical robustness under acidic and basic conditions and high thermal stability. Single-component gas adsorption exhibits an enhanced CO2 uptake of 3.12 mmol/g coupled with high sorption selectivity for CO2/N2 of 64 at 273 K and 1 bar, whereas the binary gas mixture breakthrough study using a model flue gas composition at 298 K shows a high CO2/N2 selectivity of 58. The enhanced performance is attributed to the high Lewis basicity of the framework, as it favors the interaction with CO2.

Novel Inorganic/Polymer Composite Membranes for CO₂ Capture

Energy Technology Data Exchange (ETDEWEB)

Ho, W.S. Winston [The Ohio State Univ., Columbus, OH (United States). Depts. of Chemical and Biomolecular Engineering, Chemistry, and Materials Science and Engineering; Dutta, Prabir K. [The Ohio State Univ., Columbus, OH (United States). Depts. of Chemical and Biomolecular Engineering, Chemistry, and Materials Science and Engineering; Schmit, Steve J. [Gradient Technology, Elk River, MN (United States)

2016-10-01

The objective of this project is to develop a cost-effective design and manufacturing process for new membrane modules that capture CO₂ from flue gas in coal-fired power plants. The membrane consisted of a thin selective layer including inorganic (zeolite) embedded in a polymer structure so that it can be made in a continuous manufacturing process. The membrane was incorporated in spiral-wound modules for the field test with actual flue gas at the National Carbon Capture Center (NCCC) in Wilsonville, AL and bench scale tests with simulated flue gas at the Ohio State University (OSU). Using the modules for post-combustion CO₂ capture is expected to achieve the DOE target of $40/tonne CO₂ captured (in 2007 dollar) for 2025. Membranes with the amine-containing polymer cover layer on zeolite-Y (ZY) nanoparticles deposited on the polyethersulfone (PES) substrate were successfully synthesized. The membranes showed a high CO₂ permeance of about 1100 GPU (gas permeation unit, 1 GPU = 10^-6 cm³ (STP)/(cm² • s • cm Hg), 3000 GPU = 10-6 mol/(m² • s • Pa)) with a high CO₂/N₂ selectivity of > 200 at the typical flue gas conditions at 57°C (about 17% water vapor in feed gas) and > 1400 GPU CO₂ permeance with > 500 CO₂/N₂ selectivity at 102°C (~ 80% water vapor). The synthesis of ZY nanoparticles was successfully scaled up, and the pilot-scale membranes were also successfully fabricated using the continuous membrane machine at OSU. The transport performance of the pilot-scale membranes agreed reasonably well with the lab-scale membranes. The results from both the lab-scale and scale-up membranes were used for the techno-economic analysis. The scale-up membranes were fabricated into prototype spiral-wound membrane modules for continuous testing with simulated or real flue gas. For real flue gas testing, we worked with NCCC, in

Thermo-responsive polymer-functionalized mesoporous carbon for controlled drug release

Energy Technology Data Exchange (ETDEWEB)

Zhu Shenmin, E-mail: smzhu@sjtu.edu.cn [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); Chen Chenxin [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); Chen Zhixin [Faculty of Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Liu Xinye; Li Yao; Shi Yang; Zhang Di [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China)

2011-03-15

Research highlights: {yields} A responsive drug delivery system based on poly(N-isopropyl acrylamide) (PNIPAM) functionalized ordered mesoporous carbon (CMK-3) is developed. {yields} A combination of surface modification of CMK-3 and in situ internal polymerization of PNIPAM was used. {yields} The system exhibited a pronounced transition at around 20-25 deg. C. - Abstract: A novel responsive drug delivery system based on poly(N-isopropyl acrylamide) (PNIPAM) functionalized ordered mesoporous carbon (CMK-3) is developed. The polymer-functionalized CMK-3 was obtained by a combination of simple surface modification of CMK-3 and in situ internal polymerization of PNIPAM. The formation of the PNIPAM inside the CMK-3 was confirmed by thermal gravimetric analysis, Fourier transform-infrared spectroscopy, scanning and transmission electron microscopy and N{sub 2} adsorption/desorption measurements. Controlled drug release tests through the porous network of the PNIPAM functionalized CMK-3 were carried out by measuring the uptake and release of ibuprofen in vitro. The release profiles exhibited a pronounced transition at around 20-25 deg. C. This thermo-sensitive release property of this delivery system was further confirmed by temperature-variable hydrogen nuclear magnetic resonance analysis. The internal PNIPAM layers acted as a storage gate as well as a release switch in response to the stimuli of environment.

Modified Thermoresponsive Hyperbranched Polymers for Improved Viscosity and Enhanced Lubricity of Engine Oils

Energy Technology Data Exchange (ETDEWEB)

Cosimbescu, Lelia [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Robinson, Joshua W. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bays, John Timothy [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qu, Jun [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); West, Brian [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2016-09-30

The manuscript captures the chronological succession of the molecular design progression through multiple architectures and topologies of the polymeric viscosity index improvers and their rheology bench test performance. Tribology testing was also performed on selected analogs and their friction and wear was evaluated. Finally, a top performing polymer was selected for engine testing, scaled-up, and its rheological performance in a complete formulation was assessed. The engine performance of the viscosity index improver was examined against an industry-established baseline.

Green-Yellow Electroluminescence from a host-dopant blended system as the active layer in a bilayer polymer light emitting diode: Poly(n-vinyl carbazole) as the host and a new soluble thiophene based copolymer [poly(2,2‧-BT)-co-(3-DDT)] as the dopant

Science.gov (United States)

Shahalizad, Afshin; Ahmadi-Kandjani, Sohrab; Movla, Hossein; Omidi, Hafez; Massoumi, Bakhshali; Zakerhamidi, Mohammad Sadegh; Entezami, Ali Akbar

2014-11-01

A new type of bilayer Polymer Light Emitting Diode (PLED) which emits green-yellow light is reported. In this PLED, a novel thiophene-based copolymer [poly(2,2‧-BT)-co-(3-DDT)] with an excellent electron transporting property has been doped in hole transporting and electron blocking poly(n-vinylcarbazole) (PVK). Formation of type-II heterojunctions among nm-size features in PVK:poly(2,2‧-BT)-co-(3-DDT) blended system makes exciplex and electroplex emissions would be dominant in the Electroluminescence (EL) spectrum of the device. These cross recombinations between electrons in the LUMO of poly(2,2‧-BT)-co-(3-DDT) and holes in the HOMO of PVK is a reason for the low driving voltage of the PLED because there is no need for the charge carriers to hop or tunnel to the adjacent polymer. Morphological investigations demonstrate that the mixing degree between the components is high, favoring formation of exciplexes and electroplexes at the interface of the components.

Free volume dependence on electrical properties of Poly (styrene co-acrylonitrile)/Nickel oxide polymer nanocomposites

Science.gov (United States)

Ningaraju, S.; Hegde, Vinayakaprasanna N.; Prakash, A. P. Gnana; Ravikumar, H. B.

2018-04-01

Polymer nanocomposites of Poly (styrene co-acrylonitrile)/Nickel Oxide (PSAN/NiO) have been prepared. The increased free volume sizes up to 0.4 wt% of NiO loading indicates overall reduction in packing density of polymer network. The decreased o-Ps lifetime (τ3) at higher concentration of NiO indicates improved interfacial interaction between the surface of NiO nanoparticles and side chain of PSAN polymer matrix. The increased AC/DC conductivity at lower wt% of NiO loading demonstrates increased number of electric charge carriers/mobile ions and their mobility. The increased dielectric constant and dielectric loss up to 0.4 wt% of NiO loading suggests the increased dipoles polarization.

Pattern Formation During Phase Separation of Polymer-Ionic Liquid Co-Solutions

Science.gov (United States)

Meng, Zhiyong; Osuji, Chinedum

2010-03-01

Co-solutions of polystyrene (PS) with a 1-butyl-3-methylimidazolium based ionic liquid (IL) in DMF phase separated into IL-rich and PS-rich domains on solvent evaporation. Over a limited range of polymer molecular weights and substrate temperatures, a variety of striped and cellular or polygonal structures were found on the resulting film surface, as visualized using bright-field and phase-contrast optical microscopy. This effect appears to be due to a Benard-Marangoni instability at the free surface of the liquid film as it undergoes evaporation, setting up convection rolls inside the fluid which become locked in place as the system vitrifies on solvent removal. Differential scanning calorimetry shows that the IL does not significantly plasticize the polymer, suggesting that the viscosity of the polystyrene solution itself controls the formation of this instability.

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

NARCIS (Netherlands)

Diepens, M.; Gijsman, P.

2009-01-01

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

The application of radiothermoluminescence method to the analysis of polymers and polymer composites

International Nuclear Information System (INIS)

Nikol'skii, V.G.

1982-01-01

The basic results concerning the examination of copolymers, cross-linked polymers and polyblends structure, obtained by means of radiothermoluminescence method, are reviewed. The main emphasis is on the glow curve shape analysis that allows: a) to determine quantitatively the random copolymer composition; b) to reveal the existence of blocks in macromolecules; c) to examine the grafted copolymer distribution in polymer matrix; d) to estimate the degree of cross-linking both for individual polymers and heterogeneous polyblends; e) to study the mutual solubility of polymers. (author)

Water Soluble Polymers for Pharmaceutical Applications

OpenAIRE

Veeran Gowda Kadajji; Guru V. Betageri

2011-01-01

Advances in polymer science have led to the development of novel drug delivery systems. Some polymers are obtained from natural resources and then chemically modified for various applications, while others are chemically synthesized and used. A large number of natural and synthetic polymers are available. In the present paper, only water soluble polymers are described. They have been explained in two categories (1) synthetic and (2) natural. Drug polymer conjugates, block copolymers, hydrogel...

Motion of the Bird's Head Block and co-seismic deformation from GPS data

Science.gov (United States)

Tikku, A. A.; Subarya, C.; N/A, M.; McCaffrey, R.; Genrich, J.

2006-05-01

The Bird's Head region of Eastern Indonesia, comprising the western end of New Guinea, behaves as an independent block at a juncture of subduction zones. It is bound on the north by the Manokwari and New Guinea Trenches, on the west by the Sorong fault, on the southwest by the Seram Trough, and on the east and southeast by the Lowland fault. Previous analysis of regional campaign global positioning system [GPS] data collected between 1991 and 1997 revealed rotation of the Bird's Head Block and high shear rates between the Pacific and Australian plates accommodated within the block. We have collected and analyzed additional regional campaign GPS data collected between 1998 and 2005, which includes data from newly established stations in the vicinity of the Cenderwasih Bay and Lowlands fault. During this span of time there were four large (Mw greater than 7.0) earthquakes in the region: a magnitude Mw=7.5 on a historically inactive NW-SE trending strike-slip fault bounding the western end of the Cenderwasih Bay on October 10th, 2002, two events, with magnitudes Mw=7.0 and 7.3, separated by a time span of two days (February 5th and 7th 2004) and a distance of ~100 km on the NE-SW trending Lowlands fault, and a third event (Mw=7.1) on November 26th 2004, coincident with the location of the February 5th 2004 event on the Lowlands fault. Destruction and fatalities were associated with all these large earthquakes. The Lowlands fault is a known seismically active fault. The historically inactive fault active that ruptured in 2002 is in the middle of the Bird's Head Block and disrupted the collection of a long seismically quiescent time-series of deformation within the block, but we have been able to constrain the co-seismic slip on this fault with the GPS data and modeling, and here present these results. We have also estimated the corruption of the co-seismic deformation from the 2002 and 2004 earthquakes and removed these from the campaign data to here present estimates

Precursor polymers for the carbon coating of Au@ZnO multipods for application as active material in lithium-ion batteries.

Science.gov (United States)

Oschmann, Bernd; Tahir, Muhammad Nawaz; Mueller, Franziska; Bresser, Dominic; Lieberwirth, Ingo; Tremel, Wolfgang; Passerini, Stefano; Zentel, Rudolf

2015-06-01

The synthesis of statistical and block copolymers based on polyacrylonitrile, as a source for carbonaceous materials, and thiol-containing repeating units as inorganic nanoparticle anchoring groups is reported. These polymers are used to coat Au@ZnO multipod heteroparticles with polymer brushes. IR spectroscopy and transmission electron microscopy prove the successful binding of the polymer onto the inorganic nanostructures. Thermogravimetric analysis is applied to compare the binding ability of the block and statistical copolymers. Subsequently, the polymer coating is transformed into a carbonaceous (partially graphitic) coating by pyrolysis. The obtained carbon coating is characterized by Raman spectroscopy and energy-dispersive X-ray (EDX) spectroscopy. The benefit of the conformal carbon coating of the Au@ZnO multipods regarding its application as lithium-ion anode material is revealed by performing galvanostatic cycling, showing a highly enhanced and stabilized electrochemical performance of the carbon-coated particles (still 831 mAh g(-1) after 150 cycles) with respect to the uncoated ones (only 353 mAh g(-1) after 10 cycles). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A field study of the geomorphic effects of sublimating CO2 blocks on dune slopes at Coral Pink Dunes, Utah.

Science.gov (United States)

Bourke, Mary; Nield, Jo; Diniega, Serina; Hansen, Candy; McElwaine, Jim

2016-04-01

The seasonal sublimation of CO2 ice is an active driver of present-day surface change on Mars. Diniega et al (2013) proposed that a discrete type of Martian gully, found on southern hemisphere dunes, were formed by the movement of CO2 seasonal ice blocks. These 'Linear Gullies' consist primarily of long (100 m - 2.5 km) grooves with near-uniform width (few-10 m wide), and typical depth of nudge it moved downslope. The dynamics of the block movement were recorded using a pair of high resolution video cameras. Geomorphological observations were noted and topographic change was quantified using a Leica P20 terrestrial laser scanner with a resolution of 0.8 mm at 10 m, and change detection limits less than 3 mm. The block run was repeated a total of 10 times and launched from the same location at the dune brink. The experiment ran for 45 minutes. The block size was reduced to (45 x 190 x 195 mm) by the end of the run series. The resultant geomorphology shows that the separate block runs occupied different tracks leading to a triangular plan form shape with a maximum width of 3.5 m. This is different from the findings in Arizona where a narrower track span was recorded (1.7m) (Bourke et al, 2016). Similar block dynamics were observed at both sites (as blocks moved straight, swiveled and bounced downslope). Distinctive pits with arcuate rims on their downslope edge were formed where blocks bounced on the surface. These pits are at an almost equidistant spacing. Despite a longer slope (16 m as opposed to 8m at Grand Falls), no depositional apron was formed. Levee development was less consistent compared to the Arizona site, but a pronounced unpaired-levee formed towards the base of the lee slope. These data show that sublimating blocks of CO2 ice leave signatures of transport paths and are capable of eroding and transporting sediment. Diniega,S. et al (2013) A new dry hypothesis for the formation of Martian linear gullies. Icarus. Vol. 225, 1, p. 526-537. Bourke, M.C. et

Innovative CO{sub 2} separation of biogas by polymer resins: operation of a continuous lab-scale plant

Energy Technology Data Exchange (ETDEWEB)

Raab, Katharina; Lamprecht, Martina; Brechtel, Kevin; Scheffknecht, Guenter

2012-06-15

Upgrading biogas allows for the injection of biomethane into the natural gas grid and thus a decentralized use. Since the currently available techniques have a high energy demand, there is a high potential to improve biogas upgrading. Innovative CO{sub 2} separation of biogas by the use of polymer resins can reduce the energy demand, the capital expenditure, and the operational costs. In this study, we show the ability of polymer resin to selectively adsorb CO{sub 2}. Desorption tests showed the potential for continuous use of the resin. In a continuous lab-scale plant, numerous variations of process parameters were carried out and optimization possibilities were demonstrated. Methane purity up to 98% was achieved. The favorable estimated energy demand indicates the great potential of the demonstrated improved process. (copyright 2012 WILEY-VCH Verlag GmbH 8 Co. KGaA, Weinheim)

Synthesis and aqueous phase behavior of thermoresponsive biodegradable poly(D,L-3-methylglycolide)-block-poly(ethyelene glycol)-block-poly(D,L-3-methylglycolide) triblock copolymers

NARCIS (Netherlands)

Zhong, Zhiyuan; Dijkstra, Pieter J.; Feijen, Jan; Kwon, Young-Min; Bae, You Han; Kim, Sung Wan

2002-01-01

Novel biodegradable thermosensitive triblock copolymers of poly(D,L-3-methylglycolide)-block-poly(ethylene glycol)-block-poly(D,L-3-methylglycolide) (PMG-PEG-PMG) have been synthesized. Ring-opening polymerization of D,L-3-methyl-glycolide (MG) initiated with poly(ethylene glycol) (PEG) and

Amendment of saturation magnetization, blocking temperature and particle size homogeneity in Mn-ferrite nanoparticles using Co-Zn substitution

Energy Technology Data Exchange (ETDEWEB)

Eltabey, M.M. [Basic Engineering Science Department, Faculty of Engineering, Menoufiya University (Egypt); Physics Department, Faculty of Science, Jazan University, Jazan (Saudi Arabia); Massoud, A.M., E-mail: Amassouda1@yahoo.com [Physics Department, Faculty of Science, Ain Shams University, Abbassia 11566, Cairo (Egypt); Radu, Cosmin [Lake Shore Cryotronics, Inc., Westerville, OH (United States)

2017-01-15

Nanocrystalline particles of compositions (CoZn){sub x}Mn{sub 1−x}Fe{sub 2}O{sub 4} were prepared by the coprecipitation method from stoichiometric aqueous solutions, where x varies from 0 to 0.3 in steps of 0.05. The synthesized powders were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and Fourier transform infrared spectroscopy (FT-IR). A vibrating sample magnetometer (VSM) was used to measure the hysteresis parameters at 300 and 6 K. Zero field cooling (ZFC) and field cooling (FC) curves were obtained at the temperature range 6–400 K and the blocking temperature values were determined. XRD analysis confirmed the formation of the obtained powder in a single cubic spinel phase and it showed also that the lattice parameter is decreasing with the increase of (Co-Zn) content. FT-IR measurements between 160 and 650 cm{sup −1} also confirmed the intrinsic cation vibrations of the spinel structure. The magnetic measurements showed that the saturation magnetization, coercivity and the values of blocking temperatures were increased with the (Co-Zn) content. TEM micrographs declared the improvement of particle size homogeneity with the increase of (Co-Zn) content without remarkable change in the average particle size. The obtained results were discussed in view of A-B sublattices interaction and superparamagnetic phenomenon. - Highlights: • Nanocrystalline particles of compositions (CoZn){sub x}Mn{sub 1-x}Fe{sub 2}O{sub 4} were prepared by the coprecipitation method. • XRD analysis showed that the lattice parameter is decreased with the increase of (Co,Zn) content. • The saturation magnetization is improved with the (Co,Zn) content. • Particle size homogeneity is enhanced with (Co,Zn) content. • The values of blocking temperatures are enhanced with increasing (Co,Zn) content.

Highχ block copolymers for directed self-assembly patterning without the need for topcoat or solvent annealing

Science.gov (United States)

Xu, Kui; Hockey, Mary Ann; Calderas, Eric; Guerrero, Douglas; Sweat, Daniel; Fiehler, Jeffrey

2017-03-01

High-χ block copolymers for directed self-assembly (DSA) patterning that do not need topcoat or solvent annealing have been developed. A variety of functionalities have been successfully added into the block copolymers, such as balanced surface energy between the polymer blocks, outstandingly high χ, tunable glass transition temperature (Tg), and selective crosslinking. Perpendicular orientation control, as desired for patterning, of the block copolymers can be simply achieved by thermal annealing due to the equal surface energy of the polymer blocks at the annealing temperatures, which allows avoiding solvent annealing or top-coat. The χ value can be tuned up to achieve L0 as low as 8-10 nm for lamellar-structured block copolymers and hole/pillar size as small as 5-6 nm for cylinder-structured block copolymers. The Tg of the block copolymers can be tuned to improve the kinetics of thermal annealing by enhancing the polymer chain mobility. Block-selective crosslinking facilitates the pattern transfer by mitigating pattern collapse during wet etching and improving oxygen plasma etching selectivity between the polymer blocks. This paper provides an introductory review of our high-χ block copolymer materials with various functionalities for achieving improved DSA performance.

Novel Polymer Architectures for Optical Storage

DEFF Research Database (Denmark)

Hvilsted, Søren; Forcén, Patrica; Oriol, Luis

2007-01-01

Azobenzene containing polymers have been shown to have a large potential for high capacity olographic information storage. However, it has been difficult to fabricate thick films of the polymers with good op~ical quality so far. Liquid crystalline block copolymers prepared by Atom Transfer Radical...... Polymerization and based on azobenzene methacrylate and methyl methacrylate show some promise due to the observed block segregation. Thus, lamellar nanostructure was observed'when the azobenzene content was > 20% by weight, and both birefringence and dichroism can be induced by linearly polarized 488 nm light....... The formation of azo-aggregation inside the azo blocks is strongly,reduced when going from the homopolymer to the copolymers....

Rapid prototyping of biodegradable microneedle arrays by integrating CO2 laser processing and polymer molding

International Nuclear Information System (INIS)

Tu, K T; Chung, C K

2016-01-01

An integrated technology of CO 2 laser processing and polymer molding has been demonstrated for the rapid prototyping of biodegradable poly-lactic-co-glycolic acid (PLGA) microneedle arrays. Rapid and low-cost CO 2 laser processing was used for the fabrication of a high-aspect-ratio microneedle master mold instead of conventional time-consuming and expensive photolithography and etching processes. It is crucial to use flexible polydimethylsiloxane (PDMS) to detach PLGA. However, the direct CO 2 laser-ablated PDMS could generate poor surfaces with bulges, scorches, re-solidification and shrinkage. Here, we have combined the polymethyl methacrylate (PMMA) ablation and two-step PDMS casting process to form a PDMS female microneedle mold to eliminate the problem of direct ablation. A self-assembled monolayer polyethylene glycol was coated to prevent stiction between the two PDMS layers during the peeling-off step in the PDMS-to-PDMS replication. Then the PLGA microneedle array was successfully released by bending the second-cast PDMS mold with flexibility and hydrophobic property. The depth of the polymer microneedles can range from hundreds of micrometers to millimeters. It is linked to the PMMA pattern profile and can be adjusted by CO 2 laser power and scanning speed. The proposed integration process is maskless, simple and low-cost for rapid prototyping with a reusable mold. (paper)

Rapid prototyping of biodegradable microneedle arrays by integrating CO2 laser processing and polymer molding

Science.gov (United States)

Tu, K. T.; Chung, C. K.

2016-06-01

An integrated technology of CO2 laser processing and polymer molding has been demonstrated for the rapid prototyping of biodegradable poly-lactic-co-glycolic acid (PLGA) microneedle arrays. Rapid and low-cost CO2 laser processing was used for the fabrication of a high-aspect-ratio microneedle master mold instead of conventional time-consuming and expensive photolithography and etching processes. It is crucial to use flexible polydimethylsiloxane (PDMS) to detach PLGA. However, the direct CO2 laser-ablated PDMS could generate poor surfaces with bulges, scorches, re-solidification and shrinkage. Here, we have combined the polymethyl methacrylate (PMMA) ablation and two-step PDMS casting process to form a PDMS female microneedle mold to eliminate the problem of direct ablation. A self-assembled monolayer polyethylene glycol was coated to prevent stiction between the two PDMS layers during the peeling-off step in the PDMS-to-PDMS replication. Then the PLGA microneedle array was successfully released by bending the second-cast PDMS mold with flexibility and hydrophobic property. The depth of the polymer microneedles can range from hundreds of micrometers to millimeters. It is linked to the PMMA pattern profile and can be adjusted by CO2 laser power and scanning speed. The proposed integration process is maskless, simple and low-cost for rapid prototyping with a reusable mold.

Degradation and protein release properties of microspheres prepared from biodegradable poly(lactide-co-glycolide) and ABA triblock copolymers: influence of buffer media on polymer erosion and bovine serum albumin release.

Science.gov (United States)

Bittner, B; Witt, C; Mäder, K; Kissel, T

1999-08-05

The aim of the present study was to investigate the influence of the chemical insertion of poly(ethylene oxide), PEO, into a poly(lactide-co-glycolide), PLG, backbone on the mechanisms of in vitro degradation and erosion of the polymer. For this purpose microspheres prepared by a modified W/O/W double emulsion technique using ABA triblock copolymers, consisting of PLG A-blocks attached to central PEO B-blocks were compared with microspheres prepared from PLG. Due to their molecular architecture the ABA triblock copolymers differed in their erosion and degradation behavior from PLG. Degradation occurred faster in the ABA polymers by cleavage of ester bonds inside the polymer backbone. Even erosion was shown to start immediately after incubation in different buffer media. By varying pH and ionic strength of the buffer it was found that both mass loss and molecular weight decay were accelerated in alkaline and acidic pH in the case of the ABA triblock copolymers. Although the pH of the medium had a moderate influence on the degradation of PLG, the molecular weight decay was not accompanied by a mass loss during the observation time. In a second set of experiments we prepared bovine serum albumin, BSA, loaded microspheres from both polymers. The release of BSA from ABA microspheres under in vitro conditions parallels the faster swelling and erosion rates. This could be confirmed by electron paramagnetic resonance, EPR, measurements with spin labeled albumin where an influx of buffer medium into the ABA microspheres was already observed within a few minutes. In contrast, PLG microspheres revealed a burst release without any erosion. The current study shows that the environmental conditions affected the degradation and erosion of the pure polymer microspheres in the same way as the release of the model protein. This leads to the conclusion that the more favorable degradation profile of the ABA triblock copolymers was responsible for the improvement of the release profile.

Polymer blends made of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and epoxidized natural rubber: Thermal and mechanical response

Science.gov (United States)

Salim, Yoga Sugama; Han, Chan Chin; Kammer, Hans-Werner; Kumar, Sudesh; Neon, Gan Seng

2015-08-01

The ever-increasing demand of biodegradable over conventional polymers places microbial polyhydroxyalkanoates (PHA) as an ideal choice of research material for specific applications. In this study, polymer blends made of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HHx) and epoxidized natural rubber (ENR) were prepared using solution casting technique. The influence of ENR on thermal, morphological and mechanical properties of P(3HB-co-3HHx) was investigated. There are two glass transition (Tg) temperatures observed using differential scanning calorimeter. This indicates that P(3HB-co-3HHx) and ENR are immiscible at macroscopic level. Although the Tg of P(3HB-co-3HHx) is seen to shift toward ENR in the least manner, infrared analysis suggests that the crystal structure of P(3HB-co-3HHx) retains its conformational structure. In terms of morphology, ENR exists as droplets in P(3HB-co-3HHx)-rich phase, e.g. at ENR weight fraction (wENR) of 0.3. In dynamic mechanical analysis, all blend compositions exhibit solid-like behavior, with storage moduli larger than loss moduli, across the frequency sweep at room temperature.

Fabrication of Orientation-Controlled 3D Tissues Using a Layer-by-Layer Technique and 3D Printed a Thermoresponsive Gel Frame.

Science.gov (United States)

Tsukamoto, Yoshinari; Akagi, Takami; Shima, Fumiaki; Akashi, Mitsuru

2017-06-01

Herein, we report the fabrication of orientation-controlled tissues similar to heart and nerve tissues using a cell accumulation and three-dimensional (3D) printing technique. We first evaluated the 3D shaping ability of hydroxybutyl chitosan (HBC), a thermoresponsive polymer, by using a robotic dispensing 3D printer. HBC polymer could be laminated to a height of 1124 ± 14 μm. Based on this result, we fabricated 3D gel frames of various shapes, such as square, triangular, rectangular, and circular, for shape control of 3D tissue and then normal human cardiac fibroblasts (NHCFs) coated with extracellular matrix nanofilms were seeded in the frames. Observation of shape-controlled tissues after 1 day of cultivation showed that the orientation of fibroblasts was in one direction when a short-sided, thin, rectangular-shaped frame was used. Next, we tried to fabricate orientation-controlled tissue with a vascular network by coculturing NHCF and normal human cardiac microvascular endothelial cells. As a consequence of cultivation for 4 days, observation of cocultured tissue confirmed aligned cells and blood capillaries in orientation-controlled tissue. Our results clearly demonstrated that it would be possible to control the cell orientation by controlling the shape of the tissues by combining a cell accumulation technique and a 3D printing system. The results of this study suggest promising strategies for the fabrication of oriented 3D tissues in vitro. These tissues, mimicking native organ structures, such as muscle and nerve tissue with a cell alignment structure, would be useful for tissue engineering, regenerative medicine, and pharmaceutical applications.

Bis-polymer lipid-peptide conjugates and nanoparticles thereof

Energy Technology Data Exchange (ETDEWEB)

Xu, Ting; Dong, He; Shu, Jessica; Dube, Nikhil

2018-04-24

The present invention provides bis-polymer lipid-peptide conjugates containing a hydrophobic block and headgroup containing a helical peptide and two polymer blocks. The conjugates can self-assemble to form helix bundle subunits, which in turn assemble to provide micellar nanocarriers for drug cargos and other agents. Particles containing the conjugates and methods for forming the particles are also disclosed.

Effect of shell thickness on the exchange bias blocking temperature and coercivity in Co-CoO core-shell nanoparticles

Science.gov (United States)

Thomas, S.; Reethu, K.; Thanveer, T.; Myint, M. T. Z.; Al-Harthi, S. H.

2017-08-01

The exchange bias blocking temperature distribution of naturally oxidized Co-CoO core-shell nanoparticles exhibits two distinct signatures. These are associated with the existence of two magnetic entities which are responsible for the temperature dependence of an exchange bias field. One is from the CoO grains which undergo thermally activated magnetization reversal. The other is from the disordered spins at the Co-CoO interface which exhibits spin-glass-like behavior. We investigated the oxide shell thickness dependence of the exchange bias effect. For particles with a 3 nm thick CoO shell, the predominant contribution to the temperature dependence of exchange bias is the interfacial spin-glass layer. On increasing the shell thickness to 4 nm, the contribution from the spin-glass layer decreases, while upholding the antiferromagnetic grain contribution. For samples with a 4 nm CoO shell, the exchange bias training was minimal. On the other hand, 3 nm samples exhibited both the training effect and a peak in coercivity at an intermediate set temperature Ta. This is explained using a magnetic core-shell model including disordered spins at the interface.

Self-assembly of poly(vinylidene fluoride–polystyrene block copolymers in solution: Effects of the length of polystyrene block and solvent compositions

Directory of Open Access Journals (Sweden)

Yao Wu

2017-09-01

Full Text Available We report the first preliminary and extensive study on the solution self-assembly behaviors of poly(vinylidene fluoride–b-polystyrene (PVDF–PS block copolymers. The two PVDF–PS polymers we examined have the same length of PVDF block with number averaged repeating unit of 180, but distinctly different lengths of PS block with number averaged repeating unit of 125 and 1202. The self-assembly experiments were carried out in a series of mixture solutions containing a good solvent N,N-dimethylformamide and a selective solvent with different ratios. Our results showed that the self-assembly process was greatly affected by the two factors we examined, i.e. the length of the PS block and the solvent composition. We hope that our study could stimulate more research on the self-assembly of PVDF-containing polymers in solution.

Star-shaped poly(oligoethylene glycol) copolymer-based gels: Thermo-responsive behaviour and bioapplicability for risedronate intranasal delivery.

Science.gov (United States)

Soliman, Mahmoud E; Elmowafy, Enas; Casettari, Luca; Alexander, Cameron

2018-05-30

The aim of this work was to obtain an intranasal delivery system with improved mechanical and mucoadhesive properties that could provide prolonged retention time for the delivery of risedronate (RS). For this, novel in situ forming gels comprising thermo-responsive star-shaped polymers, utilizing either polyethylene glycol methyl ether (PEGMA-ME 188, Mn 188) or polyethylene glycol ethyl ether (PEGMA-EE 246, Mn 246), with polyethylene glycol methyl ether (PEGMA-ME 475, Mn 475), were synthesized and characterized. RS was trapped in the selected gel-forming solutions at a concentration of 0.2% w/v. The pH, rheological properties, in vitro drug release, ex vivo permeation as well as mucoadhesion were also examined. MTT assays were conducted to verify nasal tolerability of the developed formulations. Initial in vivo studies were carried out to evaluate anti-osteoporotic activity in a glucocorticoid induced osteoporosis model in rats. The results showed successful development of thermo-sensitive formulations with favorable mechanical properties at 37 °C, which formed non-irritant, mucoadhesive porous networks, facilitating nasal RS delivery. Moreover, sustained release of RS, augmented permeability and marked anti-osteoporotic efficacy as compared to intranasal (IN) and intravenous (IV) RS solutions were realized. The combined results show that the in situ gels should have promising application as nasal drug delivery systems. Copyright © 2018 Elsevier B.V. All rights reserved.

Shape Recovery with Concomitant Mechanical Strengthening of Amphiphilic Shape Memory Polymers in Warm Water

International Nuclear Information System (INIS)

Zhang, Ben; DeBartolo, Janae E.; Song, Jie

2017-01-01

Maintaining adequate or enhancing mechanical properties of shape memory polymers (SMPs) after shape recovery in an aqueous environment are greatly desired for biomedical applications of SMPs as self-fitting tissue scaffolds or minimally invasive surgical implants. Here we report stable temporary shape fixing and facile shape recovery of biodegradable triblock amphiphilic SMPs containing a poly(ethylene glycol) (PEG) center block and flanking poly(lactic acid) or poly(lactic-co-glycolic acid) blocks in warm water, accompanied with concomitant enhanced mechanical strengths. Differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WXRD) and small-angle X-ray scattering (SAXS) analyses revealed that the unique stiffening of the amphiphilic SMPs upon hydration was due to hydration-driven microphase separation and PEG crystallization. We further demonstrated that the chemical composition of degradable blocks in these SMPs could be tailored to affect the persistence of hydration-induced stiffening upon subsequent dehydration. These properties combined open new horizons for these amphiphilic SMPs for smart weight-bearing in vivo applications (e.g. as self-fitting intervertebral discs). In conclusion, this study also provides a new material design strategy to strengthen polymers in aqueous environment in general.

Association and Structure of Thermo Sensitive Comblike Block Copolymers in Aqueous Solutions

International Nuclear Information System (INIS)

Cheng, Gang

2008-01-01

The structures and association properties of thermo sensitive poly(methoxyoligo(ethylene glycol) norbornenyl esters) block copolymers in D2O were investigated by Small Angle Neutron Scattering (SANS). Each block is a comb-like polymer with a polynorbornene (PNB) backbone and oligo ethylene glycol (OEG) side chains (one side chain per NB monomer). The chemical formula of the block copolymer is (OEG3NB)79-(OEG6.6NB)67, where subscripts represent the degree of polymerization (DP) of OEG and NB in each block The polymer concentration was fixed at 2.0 wt % and the structural changes were investigated over a temperature range between 25 C and 68 C. It was found that at room temperature polymers associate to form micelles with a spherical core formed by the block (OEG3NB)79 and corona formed by the block (OEG6.6NB)67 and that the shape of the polymer in the corona could be described by the form factor of rigid cylinders. At elevated temperatures, the aggregation number increases and the micelles become more compact. At temperatures round the cloud point temperature (CPT) T = 60 C a correlation peak started to appear and became pronounced at 68 C due to the formation of a partially ordered structure with a correlation length ∼ 349

Responsive Block Copolymer and Gold Nanoparticle Hybrid Nanotubes.

Science.gov (United States)

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

2009-03-01

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

Charge photogeneration and transport in side-chain carbazole polymers and co-polymers

KAUST Repository

Li, Huawei; Termine, Roberto; Godbert, Nicolas; Angiolini, Luigi; Giorgini, Loris; Golemme, Attilio

2011-01-01

The photoconductivity, hole mobility and charge photogeneration efficiency of a series of side-chain carbazole homopolymers and copolymers (with azo side-chains) have been investigated. Cyclic voltammetry measurement of frontier orbitals energies show that the HOMO energy is determined by the nature and the position of attachment of the linker between the main chain and the carbazole, the azo-moiety being not relevant in this respect. Hole mobility is not influenced by the HOMO energy but seems to depend on the degree of conformational mobility of the side-chains, reaching values of the order of 10-3cm2V-1s-1 in the best cases. The HOMO energy is instead extremely important when considering photogeneration efficiency, that can change by 10 orders of magnitude depending on the density of the carbazole side-chains in co-polymers and on the linker nature and attachment position. © 2011 Elsevier B.V. All rights reserved.

Charge photogeneration and transport in side-chain carbazole polymers and co-polymers

KAUST Repository

Li, Huawei

2011-07-01

The photoconductivity, hole mobility and charge photogeneration efficiency of a series of side-chain carbazole homopolymers and copolymers (with azo side-chains) have been investigated. Cyclic voltammetry measurement of frontier orbitals energies show that the HOMO energy is determined by the nature and the position of attachment of the linker between the main chain and the carbazole, the azo-moiety being not relevant in this respect. Hole mobility is not influenced by the HOMO energy but seems to depend on the degree of conformational mobility of the side-chains, reaching values of the order of 10-3cm2V-1s-1 in the best cases. The HOMO energy is instead extremely important when considering photogeneration efficiency, that can change by 10 orders of magnitude depending on the density of the carbazole side-chains in co-polymers and on the linker nature and attachment position. © 2011 Elsevier B.V. All rights reserved.

Shape-tailored polymer colloids on the road to become structural motifs for hierarchically organized materials.

Science.gov (United States)

Plüisch, Claudia Simone; Wittemann, Alexander

2013-12-01

Anisometric polymer colloids are likely to behave differently when compared with centrosymmetric particles. Their study may not only shine new light on the organization of matter; they may also serve as building units with specific symmetries and complexity to build new materials from them. Polymer colloids of well-defined complex geometries can be obtained by packing a limited number of spherical polymer particles into clusters with defined configurations. Such supracolloidal architectures can be fabricated at larger scales using narrowly dispersed emulsion droplets as templates. Assemblies built from at least two different types of particles as elementary building units open perspectives in selective targeting of colloids with specific properties, aiming for mesoscale building blocks with tailor-made morphologies and multifunctionality. Polymer colloids with defined geometries are also ideal to study shape-dependent properties such as the diffusion of complex particles. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanopatterning of Co/Pt-multilayers via self-assembled block-copolymer micelles; Magnetische Nanostrukturen basierend auf Co/Pt-Multilagen, hergestellt mittels selbstorganisierter Masken aus Blockcopolymer-Micellen

Energy Technology Data Exchange (ETDEWEB)

Stillrich, H.

2007-07-01

The production and characterization of magnetic nanostructures based on Co/Ptmultilayers are described in this thesis. Nanostructure arrays of Co/Pt multilayer films are generated utilizing the self-assembly of block copolymer micelles with a few 10nm diameter. For an understanding of the magnetic properties of nanostructures the properties of Co/Pt-multilayer films are examined first. The films are grown via different sputter techniques. The structural and magnetic properties are investigated depending on the deposition technique. The sources of magnetic anisotropy are discussed based on these investigations. One major topic concerning Co/Pt-multilayers is the reorientation of the easy axis of magnetization from perpendicular to in-plane as a function of the cobalt and platinum layer thicknesses. Combining averaging magnetization measurements and high resolution magnetic imaging, the canting of magnetization within the reorientation transition and a canted domain structure were found. The basis for magnetic nanostructures are Co/Pt-multilayers that were optimized for strong magnetic anisotropy. Magnetic antidot and dot arrays are generated from Co/Pt-multilayers via novel methods utilizing block copolymer micelle masks and ion milling. The generation of nanostructure arrays is proven by the morphologic and topographic properties, combined with the evolution of magneto-optic signals. Two different approaches for the generation of antidot arrays are shown. The magnetic properties of antidot arrays with perpendicular and in-plane easy magnetization are investigated. Magnetic dot arrays are produced utilizing the cores of SiO{sub 2} filled block copolymer micelles. The dot arrays consist of single domain particles. The switching field distribution of the dot arrays is analysed and described using the size distribution of the magnetic particles. Magnetic nanostructures in the region of the superparamagnetic limit are investigated. (orig.)

Adsorption and flocculation by polymers and polymer mixtures.

Science.gov (United States)

Gregory, John; Barany, Sandor

2011-11-14

Polymers of various types are in widespread use as flocculants in several industries. In most cases, polymer adsorption is an essential prerequisite for flocculation and kinetic aspects are very important. The rates of polymer adsorption and of re-conformation (relaxation) of adsorbed chains are key factors that influence the performance of flocculants and their mode of action. Polyelectrolytes often tend to adopt a rather flat adsorbed configuration and in this state their action is mainly through charge effects, including 'electrostatic patch' attraction. When the relaxation rate is quite low, particle collisions may occur while the adsorbed chains are still in an extended state and flocculation by polymer bridging may occur. These effects are now well understood and supported by much experimental evidence. In recent years there has been considerable interest in the use of multi-component flocculants, especially dual-polymer systems. In the latter case, there can be significant advantages over the use of single polymers. Despite some complications, there is a broad understanding of the action of dual polymer systems. In many cases the sequence of addition of the polymers is important and the pre-adsorbed polymer can have two important effects: providing adsorption sites for the second polymer or causing a more extended adsorbed conformation as a result of 'site blocking'. Copyright © 2011 Elsevier B.V. All rights reserved.

Porous carbon derived via KOH activation of a hypercrosslinked porous organic polymer for efficient CO{sub 2}, CH{sub 4}, H{sub 2} adsorptions and high CO{sub 2}/N{sub 2} selectivity

Energy Technology Data Exchange (ETDEWEB)

Modak, Arindam; Bhaumik, Asim, E-mail: msab@iacs.res.in

2015-12-15

Microporous carbon having Brunauer-Emmett-Teller (BET) surface area of 2186 m{sup 2} g{sup −1} and micropore volume of 0.85 cm{sup 3} g{sup −1} has been synthesized via KOH induced high temperature carbonization of a non-conjugated hypercrosslinked organic polymer. Owing to the templating and activation by KOH, we have succeeded in making a microporous carbon from this porous polymer and the resultant carbon material showed high uptake for CO{sub 2} (7.6 mmol g{sup −1}) and CH{sub 4} (2.4 mmol g{sup −1}) at 1 atm, 273 K together with very good selectivity for the CO{sub 2}/N{sub 2} (30.2) separation. Furthermore, low pressure (1 atm) H{sub 2} (2.6 wt%, 77 K) and water uptake (57.4 wt%, 298 K) ability of this polymer derived porous activated carbon is noteworthy. - Graphical abstract: Microporous carbon with BET surface area of 2186 m{sup 2} g{sup −1} has been synthesized via KOH activation of a porous organic polymer and it showed high uptake for CO{sub 2} (7.6 mmol g{sup −1}), CH{sub 4} (2.4 mmol g{sup −1}) and H{sub 2} (2.6 wt%) at 1 atm together with very good selectivity for CO{sub 2}. - Highlights: • Porous carbon from hypercrosslinked organic polymer. • KOH activated carbon with BET surface area 2186 m{sup 2} g{sup −1}. • High CO2 uptake (7.6 mmol g{sup −1}) and CO{sub 2}/N{sub 2} selectivity (30.2). • Porous carbon also showed high H{sub 2} (2.6 wt%) and H{sub 2}O (57.4 wt%) uptakes.

High-Tg Polynorbornene-Based Block and Random Copolymers for Butanol Pervaporation Membranes

Science.gov (United States)

Register, Richard A.; Kim, Dong-Gyun; Takigawa, Tamami; Kashino, Tomomasa; Burtovyy, Oleksandr; Bell, Andrew

Vinyl addition polymers of substituted norbornene (NB) monomers possess desirably high glass transition temperatures (Tg); however, until very recently, the lack of an applicable living polymerization chemistry has precluded the synthesis of such polymers with controlled architecture, or copolymers with controlled sequence distribution. We have recently synthesized block and random copolymers of NB monomers bearing hydroxyhexafluoroisopropyl and n-butyl substituents (HFANB and BuNB) via living vinyl addition polymerization with Pd-based catalysts. Both series of polymers were cast into the selective skin layers of thin film composite (TFC) membranes, and these organophilic membranes investigated for the isolation of n-butanol from dilute aqueous solution (model fermentation broth) via pervaporation. The block copolymers show well-defined microphase-separated morphologies, both in bulk and as the selective skin layers on TFC membranes, while the random copolymers are homogeneous. Both block and random vinyl addition copolymers are effective as n-butanol pervaporation membranes, with the block copolymers showing a better flux-selectivity balance. While polyHFANB has much higher permeability and n-butanol selectivity than polyBuNB, incorporating BuNB units into the polymer (in either a block or random sequence) limits the swelling of the polyHFANB and thereby improves the n-butanol pervaporation selectivity.

Structural Characterization of Polymer-Clay Nanocomposites Prepared by Co-Precipitation Using EPR Techniques

Directory of Open Access Journals (Sweden)

Udo Kielmann

2014-02-01

Full Text Available Polymer-clay nanocomposites (PCNCs containing either a rubber or an acrylate polymer were prepared by drying or co-precipitating polymer latex and nanolayered clay (synthetic and natural suspensions. The interface between the polymer and the clay nanoparticles was studied by electron paramagnetic resonance (EPR techniques by selectively addressing spin probes either to the surfactant layer (labeled stearic acid or the clay surface (labeled catamine. Continuous-wave (CW EPR studies of the surfactant dynamics allow to define a transition temperature T* which was tentatively assigned to the order-disorder transition of the surfactant layer. CW EPR studies of PCNC showed that completely exfoliated nanoparticles coexist with agglomerates. HYSCORE spectroscopy in PCNCs showed couplings within the probe −assigned with DFT computations− and couplings with nuclei of the environment, 1H and 23Na for the surfactant layer probe, and 29Si, 7Li, 19F and 23Na for the clay surface probe. Analysis of these couplings indicates that the integrity of the surfactant layer is conserved and that there are sizeable ionic regions containing sodium ions directly beyond the surfactant layer. Simulations of the very weak couplings demonstrated that the HYSCORE spectra are sensitive to the composition of the clay and whether or not clay platelets stack.

Secondary ligand-directed assembly of Co(II) coordination polymers based on a pyridine carboxylate ligand

International Nuclear Information System (INIS)

Cao, Ke-Li; Zhang, Yi-Ping; Cai, Yi-Ni; Xu, Xiao-Wei; Feng, Yun-Long

2014-01-01

To investigate the influence of hydrogen bonds and secondary ligands on the structures and properties of the resulting frameworks, five new Co(II) compounds have been synthesized by the reactions of Co(II) salts and 3,5-bis(pyridin-4-ylmethoxy)benzoic acid (HL) with four rationally selected dicarboxylic acid ligands. Without secondary ligand, we got one compound [CoL 2 (H 2 O) 2 ] n ·2nH 2 O (1), which possesses a 1D chain structure. In the presence of ancillary ligands, namely, 1,3-adamantanedicarboxylic acid (H 2 adbc), terephthalic acid (H 2 tpa), thiophene-2,5-dicarboxylic acid (H 2 tdc) and 1,4-benzenedithioacetic acid (H 2 bdtc), four 3D structures [Co 2 L 2 (adbc)] n ·nH 2 O (2), [Co 2 L 2 (tpa)] n (3), [Co 2 L 2 (tdc)] n (4), [Co 2 L 2 (bdtc)(H 2 O)] n (5) were obtained, respectively. It can be observed from the architectures of 1–5 that hydrogen bonds and secondary ligands both have great effects on the spatial connective fashions, resulting in the formation of various dimensional compounds. The XRPD, TGA data of title polymers and the magnetic properties for 2 and 5 have also been investigated. - Graphical abstract: The structural differences show that the ancillary ligands have great effects on the spatial connective fashions, resulting in the formation of various dimensional compounds. - Highlights: • Five new Co(II) coordination polymers have been synthesized by solvothermal reactions based on 3,5-bis(pyridin-4-ylmethoxy)benzoic acid (HL). • The long-flexible ligand (HL) is a good candidate to produce interpenetrating architectures. • The secondary dicarboxylic acid ligands play important roles in the spatial connective fashions and the formation of various dimensional compounds. • The magnetism studies show that both 2 and 5 exhibit antiferromagnetic interactions

Substrate tolerant direct block copolymer nanolithography

DEFF Research Database (Denmark)

Li, Tao; Wang, Zhongli; Schulte, Lars

2016-01-01

Block copolymer (BC) self-assembly constitutes a powerful platform for nanolithography. However, there is a need for a general approach to BC lithography that critically considers all the steps from substrate preparation to the final pattern transfer. We present a procedure that significantly sim...... plasma treatment enables formation of the oxidized PDMS hard mask, PS block removal and polymer or graphene substrate patterning....

Nanocomposites from polymers and layered minerals

NARCIS (Netherlands)

Fischer, H.R.; Gielgens, L.H.; Koster, T.P.M.

1999-01-01

Composites consisting of polymer matrix materials and natural or synthetic layered minerals e.g. clays were prepared by using special compatibilizing agents betsveen these two intrinsically non-miscible components. Block or graft copolymers combining one part of the polymer that is identically

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

NARCIS (Netherlands)

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

2003-01-01

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

Polymer-silica hybrids for separation of CO2 and catalysis of organic reactions

Science.gov (United States)

Silva Mojica, Ernesto

spectroscopic investigation of the interactions of CO 2 with amine molecules under simulated CO2 capture conditions. Industrial CO2 capture processes involve fluidization and require degradation-resistant sorbents in the form of pellets. Agglomeration of silica-based CO2 capture sorbents involved the formulation of a polymer binder solution and the design of a scalable pelletization process. The characterization of these pellets revealed the formation of a CO 2-permeable polymer-silica network, which is resistant to attrition, and exhibits similar CO2 capture and degradation performance as the non-pelletized sorbents. The performance of these sorbents and pellets was tested in lab-scale and bench-scale adsorption units, using in-house fabricated fixed-bed and fluidized-bed reactors. A compartmental modeling technique was used to simulate the CO2 adsorption process and to elucidate the kinetic and thermodynamic parameters that impact the commercial viability of emerging CO2 capture technologies. The fundamental concepts and experimental techniques developed for the preparation of CO2 capture sorbents served as a basis for fabricating amine-functionalized polymer-silica hybrids for applications in catalysis of organic reactions. (i) Basic catalysts for carbon-carbon addition reactions were prepared by immobilization of amine molecules on silica supports. The activity of these catalysts and the mechanisms of base-catalyzed organic condensation reactions were investigated by an in-situ FTIR micro-scale reactor. (ii) Particle-loaded PVA composite membranes were selected for immobilization of glucose oxidase (GOx). GOx was immobilized by adsorption at pH values between 3.5 and 7.1. The results showed that adsorption was primarily achieved via hydrophobic interactions, and that PVA membranes loaded with amine-functionalized particles could help retain the activity of immobilized GOx by providing a proper hydrophilic/hydrophobic balance to the immobilized enzymes micro-environment.

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.

Rheological Properties of Associative Star Polymers in Aqueous Solutions: Effect of Hydrophobe Length and Polymer Topology

DEFF Research Database (Denmark)

Hietala, Sami; Strandman, Satu; Jarvi, Paula

2009-01-01

triblock copolymer. These polymers, synthesized by atom transfer radical polymerization (ATRP), were found to form hydrogels due to intermolecular association originating from the PS blocks. The increasing length of the PS block was observed to lead to more elastic networks due to increased hydrophobic...

Effect of Perfluoroalkyl Endgroups on the Interactions of Tri-Block Copolymers with Monofluorinated F-DPPC Monolayers

Directory of Open Access Journals (Sweden)

Syed W. H. Shah

2017-10-01

Full Text Available We studied the interaction of amphiphilic and triphilic polymers with monolayers prepared from F-DPPC (1-palmitoyl-2-(16-fluoropalmitoyl-sn-glycero-3-phosphocholine, a phospholipid with a single fluorine atom at the terminus of the sn-2 chain, an analogue of dipalmitoyl-phosphatidylcholine (DPPC. The amphiphilic block copolymers contained a hydrophobic poly(propylene oxide block flanked by hydrophilic poly(glycerol monomethacrylate blocks (GP. F-GP was derived from GP by capping both termini with perfluoro-n-nonyl segments. We first studied the adsorption of GP and F-GP to lipid monolayers of F-DPPC. F-GP was inserted into the monolayer up to a surface pressure Π of 42.4 mN m−1, much higher than GP (32.5 mN m−1. We then studied isotherms of lipid-polymer mixtures co-spread at the air-water interface. With increasing polymer content in the mixture a continuous shift of the onset of the liquid-expanded (LE to liquid-condensed (LC transition towards higher molecular and higher area per lipid molecule was observed. F-GP had a larger effect than GP indicating that it needed more space. At a Π-value of 32 mN m−1, GP was excluded from the mixed monolayer, whereas F-GP stayed in F-DPPC monolayers up to 42 mN m−1. F-GP is thus more stably anchored in the monolayer up to higher surface pressures. Images of mixed monolayers were acquired using different fluorescent probes and showed the presence of perfluorinated segments of F-GP at LE-LC domain boundaries.

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

Science.gov (United States)

Ferebee, Rachel L.

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

Radiation crosslinked block copolymer blends with improved impact resistance

International Nuclear Information System (INIS)

Saunders, F.L.; Pelletier, R.R.

1976-01-01

Polymer blends having high impact resistance after mechanical working are produced by blending together a non-elastomeric monovinylidene aromatic polymer such as polystyrene with an elastomeric copolymer, such as a block copolymer of styrene and butadiene, in the form of crosslinked, colloidal size particles

Poly(2-vinyl pyridine)-block-poly(ethylene oxide) featuring a furan group at the block junction-synthesis and functionalization.

Science.gov (United States)

Rudolph, Tobias; Barthel, Markus J; Kretschmer, Florian; Mansfeld, Ulrich; Hoeppener, Stephanie; Hager, Martin D; Schubert, Ulrich S; Schacher, Felix H

2014-05-01

Furfuryl glycidyl ether (FGE) represents a highly versatile monomer for the preparation of reversibly cross-linkable nanostructured materials via Diels-Alder reactions. Here, the use of FGE for the mid-chain functionalization of a P2VP-b-PEO diblock copolymer is reported. The material features one furan moiety at the block junction, P2VP68 -FGE-b-PEO390 , which can be subsequently addressed in Diels-Alder reactions using maleimide-functionalized counterparts. The presence of the FGE moiety enables the introduction of dyes as model labels or the formation of hetero-grafted brushes as shell on hybrid Au@Polymer nanoparticles. This renders P2VP68 -FGE-b-PEO390 , a powerful tool for selective functionalization reactions, including the modification of surfaces. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The selective flow of volatile organic compounds in conductive polymer-coated microchannels

Science.gov (United States)

Hossein-Babaei, Faramarz; Hooshyar Zare, Ali

2017-02-01

Many gaseous markers of critical biological, physicochemical, or industrial occurrences are masked by the cross-sensitivity of the sensors to the other active components present at higher concentrations. Here, we report the strongly selective diffusion and drift of contaminant molecules in air-filled conductive polymer-coated microfluidic channels for the first time. Monitoring the passage of different target molecules through microchannels coated with Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) revealed that contaminants such as hexane, benzene, and CO pass through the channel unaffected by the coating while methanol, ethanol, and partly acetone are blocked. The observations are explained with reference to the selective interactions between the conductive polymer surface and target gas molecules amplified by the large wall/volume ratio in microchannels. The accumulated quantitative data point at the hydrogen bonding as the mechanism of wall adsorption; dipole-dipole interactions are relatively insignificant. The presented model facilitates a better understanding of how the conductive polymer-based chemical sensors operate.

Mechanistic analysis of Zein nanoparticles/PLGA triblock in situ forming implants for glimepiride

Directory of Open Access Journals (Sweden)

Ahmed OAA

2016-02-01

Full Text Available Osama Abdelhakim Aly Ahmed,1,2 Ahmed Samir Zidan,1,3 Maan Khayat4 1Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, King Abdulaziz University, Jeddah, Saudi Arabia; 2Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Minia University, Minia, Egypt; 3Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt; 4Department of Pharmaceutical Chemistry, Faculty of Pharmacy, King Abdulaziz University, Jeddah, Saudi Arabia Objectives: The study aims at applying pharmaceutical nanotechnology and D-optimal fractional factorial design to screen and optimize the high-risk variables affecting the performance of a complex drug delivery system consisting of glimepiride–Zein nanoparticles and inclusion of the optimized formula with thermoresponsive triblock copolymers in in situ gel. Methods: Sixteen nanoparticle formulations were prepared by liquid–liquid phase separation method according to the D-optimal fractional factorial design encompassing five variables at two levels. The responses investigated were glimepiride entrapment capacity (EC, particle size and size distribution, zeta potential, and in vitro drug release from the prepared nanoparticles. Furthermore, the feasibility of embedding the optimized Zein-based glimepiride nanoparticles within thermoresponsive triblock copolymers poly(lactide-co-glycolide-block-poly(ethylene glycol-block-poly(lactide-co-glycolide in in situ gel was evaluated for controlling glimepiride release rate. Results: Through the systematic optimization phase, improvement of glimepiride EC of 33.6%, nanoparticle size of 120.9 nm with a skewness value of 0.2, zeta potential of 11.1 mV, and sustained release features of 3.3% and 17.3% drug released after 2 and 24 hours, respectively, were obtained. These desirability functions were obtained at Zein and glimepiride loadings of 50 and 75 mg, respectively, utilizing

Properties of polymer-silver nanocomposites fabricated by co-sputtering; Eigenschaften von Polymer-Silber-Nanokompositen hergestellt durch Co-Sputtern

Energy Technology Data Exchange (ETDEWEB)

Schuermann, Ulrich

2006-07-01

In this thesis polymer-metal nanocomposites were fabricated by simultaneous sputtering of silver and polymers from two independent magnetron sputtering sources. By the netted structure and the dielectric properties PTFE is suited for the use as matrix material. The metal content of the composite films was determined via the measurement of EDX intensities. The size of the nanoparticles was determined by means of TEM and XRD and lies in the range of 10 nm. The composite materials show at the percolation limit a sudden transition of the properties from polymer- to metal-like behaviour. The specific resistance decreases in a range between 35 and 40 % silver content by at least nine orders of magnitude. The optical properties change with the metal content. The absorption caused by plasmon resonance, which has at small filling degrees its maximum at about 000 nm and has an intense yellow colour of the composite material as consequence shifts with increasing silver content to longer wavelengths. The difference in the optical.behaviour of the nanocomposites and the pure polymers can be used for the fabrication of Bragg reflectors. Small changes in the metal content can in the polymer-silver nanocomposites in the range of the percolation threshold effect a drastic change in ther properties, by which applications as sensors are thinkable. [German] In dieser Arbeit wurden Polymer-Metall-Nanokomposite durch gleichzeitiges Sputtern von Silber und Polymeren aus zwei unabhaengigen Magnetron-Sputterquellen hergestellt. Durch die vernetzte Struktur und die dielektrischen Eigenschaften eignet sich PTFE zur Verwendung als Matrixmaterial. Der Metallgehalt der Kompositfilme wurde ueber die Messung von EDX-Intensitaeten ermittelt. Die Groesse der Nanopartikel wurde mit Hilfe von TEM und XRD bestimmt und liegt im Bereich von 10 nm. Die Kompositmaterialien zeigen an der Perkolationsgrenze einen schlagartigen Uebergang der Eigenschaften vom polymer- zum metallaehnlichen Verhalten. Der

One-Pot Synthesis of Co-Based Coordination Polymer Nanowire for Li-Ion Batteries with Great Capacity and Stable Cycling Stability

Science.gov (United States)

Wang, Peng; Lou, Xiaobing; Li, Chao; Hu, Xiaoshi; Yang, Qi; Hu, Bingwen

2018-06-01

Nanowire coordination polymer cobalt-terephthalonitrile (Co-BDCN) was successfully synthesized using a simple solvothermal method and applied as anode material for lithium-ion batteries (LIBs). A reversible capacity of 1132 mAh g-1 was retained after 100 cycles at a rate of 100 mA g-1, which should be one of the best LIBs performances among metal organic frameworks and coordination polymers-based anode materials at such a rate. On the basis of the comprehensive structural and morphology characterizations including fourier transform infrared spectroscopy, 1H NMR, 13C NMR, and scanning electron microscopy, we demonstrated that the great electrochemical performance of the as-synthesized Co-BDCN coordination polymer can be attributed to the synergistic effect of metal centers and organic ligands, as well as the stability of the nanowire morphology during cycling.[Figure not available: see fulltext.

Inexpensive CO2 Thickening Agents for Improved Mobility Control of CO2 Floods

Energy Technology Data Exchange (ETDEWEB)

Robert Enick; Eric Beckman; Andrew Hamilton

2005-08-31

The objective of this research was the design, synthesis and evaluation of inexpensive, non-fluorous carbon dioxide thickening agents. We followed the same strategy employed in the design of fluorinated CO{sub 2} polymeric thickeners. First, a highly CO{sub 2}-philic, hydrocarbon-based monomer was to be identified. Polymers or oligomers of this monomer were then synthesized. The second step was to design a CO{sub 2}-thickener based on these CO{sub 2}-philic polymers. Two types of thickeners were considered. The first was a copolymer in which the CO{sub 2}-philic monomer was combined with a small proportion of CO{sub 2}-phobic associating groups that could cause viscosity-enhancing intermolecular interactions to occur. The second was a small hydrogen-bonding compound with urea groups in the core to promote intermolecular interactions that would cause the molecules to 'stack' in solution while the arms were composed of the CO{sub 2}-philic oligomers. Although we were not able to develop a viable thickener that exhibited high enough CO{sub 2} solubility at EOR MMP conditions to induce a viscosity increase, we made significant progress in our understanding of CO{sub 2}-soluble compounds that can be used in subsequent studies to design CO{sub 2}-soluble thickeners or CO{sub 2}-soluble surfactant-based foaming agents. These findings are detailed in this final report. In summary, we assessed many polymers and verified that the most CO{sub 2}-soluble oxygenated hydrocarbon polymer is poly(vinyl acetate), PVAc. This is primarily due to the presence of both ether and carbonyl oxygens associated with acetate-rich compounds. In addition to polymers, we also made small acetate-rich molecules that were also capable of associating in solution via the inclusion of hydrogen-bonding groups in hopes of forming viscosity-enhancing macromolecules. Despite the presence of multiple acetate groups in these compounds, which can impart incredible CO{sub 2}-solubility to many

Smart ampholytic ABC block copolypeptide

Czech Academy of Sciences Publication Activity Database

Schlaad, H.; Sun, J.; Černoch, Peter; Ruokolainen, J.

2017-01-01

Roč. 254, 20 August (2017), s. 79 ISSN 0065-7727. [ACS National Meeting & Exposition /254./. 20.08.2017-24.08.2017, Washington] Institutional support: RVO:61389013 Keywords : block copolypeptide * smart ampholytic Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science

Selective molecular annealing: in situ small angle X-ray scattering study of microwave-assisted annealing of block copolymers.

Science.gov (United States)

Toolan, Daniel T W; Adlington, Kevin; Isakova, Anna; Kalamiotis, Alexis; Mokarian-Tabari, Parvaneh; Dimitrakis, Georgios; Dodds, Christopher; Arnold, Thomas; Terrill, Nick J; Bras, Wim; Hermida Merino, Daniel; Topham, Paul D; Irvine, Derek J; Howse, Jonathan R

2017-08-09

Microwave annealing has emerged as an alternative to traditional thermal annealing approaches for optimising block copolymer self-assembly. A novel sample environment enabling small angle X-ray scattering to be performed in situ during microwave annealing is demonstrated, which has enabled, for the first time, the direct study of the effects of microwave annealing upon the self-assembly behavior of a model, commercial triblock copolymer system [polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene]. Results show that the block copolymer is a poor microwave absorber, resulting in no change in the block copolymer morphology upon application of microwave energy. The block copolymer species may only indirectly interact with the microwave energy when a small molecule microwave-interactive species [diethylene glycol dibenzoate (DEGDB)] is incorporated directly into the polymer matrix. Then significant morphological development is observed at DEGDB loadings ≥6 wt%. Through spatial localisation of the microwave-interactive species, we demonstrate targeted annealing of specific regions of a multi-component system, opening routes for the development of "smart" manufacturing methodologies.

Evolution of sequence-defined highly functionalized nucleic acid polymers

Science.gov (United States)

Chen, Zhen; Lichtor, Phillip A.; Berliner, Adrian P.; Chen, Jonathan C.; Liu, David R.

2018-03-01

The evolution of sequence-defined synthetic polymers made of building blocks beyond those compatible with polymerase enzymes or the ribosome has the potential to generate new classes of receptors, catalysts and materials. Here we describe a ligase-mediated DNA-templated polymerization and in vitro selection system to evolve highly functionalized nucleic acid polymers (HFNAPs) made from 32 building blocks that contain eight chemically diverse side chains on a DNA backbone. Through iterated cycles of polymer translation, selection and reverse translation, we discovered HFNAPs that bind proprotein convertase subtilisin/kexin type 9 (PCSK9) and interleukin-6, two protein targets implicated in human diseases. Mutation and reselection of an active PCSK9-binding polymer yielded evolved polymers with high affinity (KD = 3 nM). This evolved polymer potently inhibited the binding between PCSK9 and the low-density lipoprotein receptor. Structure-activity relationship studies revealed that specific side chains at defined positions in the polymers are required for binding to their respective targets. Our findings expand the chemical space of evolvable polymers to include densely functionalized nucleic acids with diverse, researcher-defined chemical repertoires.

Water Soluble Polymers for Pharmaceutical Applications

Directory of Open Access Journals (Sweden)

Veeran Gowda Kadajji

2011-11-01

Full Text Available Advances in polymer science have led to the development of novel drug delivery systems. Some polymers are obtained from natural resources and then chemically modified for various applications, while others are chemically synthesized and used. A large number of natural and synthetic polymers are available. In the present paper, only water soluble polymers are described. They have been explained in two categories (1 synthetic and (2 natural. Drug polymer conjugates, block copolymers, hydrogels and other water soluble drug polymer complexes have also been explained. The general properties and applications of different water soluble polymers in the formulation of different dosage forms, novel delivery systems and biomedical applications will be discussed.

N-donor co-ligands driven two new Co(II)- coordination polymers with bi- and trinuclear units: Crystal structures, and magnetic properties

Science.gov (United States)

Zhou, Zhi-Hang; Han, Min-Le; Wu, Ya-Pan; Dong, Wen-Wen; Li, Dong-Sheng; Lu, Jack Y.

2016-10-01

Two new Co(II) coordination polymers(CPs), namely [Co2(bpe)2(Hbppc)]n (1) and [Co3(μ3-OH)(bppc)(bpm)(H2O)]·3H2O (2) (H5bppc=biphenyl-2,4,6,3‧,5‧-pentacarboxylic acid, bpe=1,2-bis(4-pyridyl)ethene, bpm=bis(4-pyridyl)amine), have been obtained and characterized by elemental analysis, single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), IR spectra and thermogravimetric analysis (TGA). 1 shows a binodal (4,6)-connected fsc net with a (44·610·8)(44·62) topology, while 2 shows a binodal (5,7)-connected 3D network based on trinuclear [Co3(μ3-OH)]5+ units with unusual (3.46.52.6)(32.46.57.65.7) topology. Variable-temperature magnetic susceptibility measurements reveals that complex 1 shows ferromagnetic interactions between the adjacent Co(II) ions, whereas 2 is a antiferromagnetic system.

Polymer architecture and drug delivery.

Science.gov (United States)

Qiu, Li Yan; Bae, You Han

2006-01-01

Polymers occupy a major portion of materials used for controlled release formulations and drug-targeting systems because this class of materials presents seemingly endless diversity in topology and chemistry. This is a crucial advantage over other classes of materials to meet the ever-increasing requirements of new designs of drug delivery formulations. The polymer architecture (topology) describes the shape of a single polymer molecule. Every natural, seminatural, and synthetic polymer falls into one of categorized architectures: linear, graft, branched, cross-linked, block, star-shaped, and dendron/dendrimer topology. Although this topic spans a truly broad area in polymer science, this review introduces polymer architectures along with brief synthetic approaches for pharmaceutical scientists who are not familiar with polymer science, summarizes the characteristic properties of each architecture useful for drug delivery applications, and covers recent advances in drug delivery relevant to polymer architecture.

Light-Emitting Devices Based on Pyridine-Containing Conjugated Polymers

National Research Council Canada - National Science Library

Wang, Y

1997-01-01

...) as hole transporting/electron blocking polymer, which improves the device efficiency and brightness significantly due to the charge confinement and exciplex emission at the PVK/emitting polymer interface...

Synthesis and morphology of hydroxyapatite/polyethylene oxide nanocomposites with block copolymer compatibilized interfaces

Science.gov (United States)

Lee, Ji Hoon; Shofner, Meisha

2012-02-01

In order to exploit the promise of polymer nanocomposites, special consideration should be given to component interfaces during synthesis and processing. Previous results from this group have shown that nanoparticles clustered into larger structures consistent with their native shape when the polymer matrix crystallinity was high. Therefore in this research, the nanoparticles are disguised from a highly-crystalline polymer matrix by cloaking them with a matrix-compatible block copolymer. Specifically, spherical and needle-shaped hydroxyapatite nanoparticles were synthesized using a block copolymer templating method. The block copolymer used, polyethylene oxide-b-polymethacrylic acid, remained on the nanoparticle surface following synthesis with the polyethylene oxide block exposed. These nanoparticles were subsequently added to a polyethylene oxide matrix using solution processing. Characterization of the nanocomposites indicated that the copolymer coating prevented the nanoparticles from assembling into ordered clusters and that the matrix crystallinity was decreased at a nanoparticle spacing of approximately 100 nm.

Burkholderia sacchari DSM 17165: A source of compositionally-tunable block-copolymeric short-chain poly(hydroxyalkanoates) from xylose and levulinic acid.

Science.gov (United States)

Ashby, Richard D; Solaiman, Daniel K Y; Nuñez, Alberto; Strahan, Gary D; Johnston, David B

2018-04-01

Burkholderia sacchari was used to produce poly-3-hydroxybutyrate-co-3-hydroxyvalerate block copolymers from xylose and levulinic acid. Levulinic acid was the preferred substrate resulting in 3-hydroxyvalerate (3HV) contents as high as 95 mol% at 24 h. The 3HB:3HV ratios were controlled by the initial levulinic acid media concentration and fermentation length. Higher levulinic acid concentrations and longer durations, resulted in polymers with two glass transition temperatures, each approximating those associated with poly-3HB and poly-3HV. 13 C NMR confirmed the presence of high concentrations of 3HB-3HB and 3HV-3HV homopolymeric dyads, while mass spectrometry of the partial hydrolysis products did not conform to Bernoullian statistics for randomness, confirming block sequences. MS/MS analysis of specific oligomers showed the mass-loss of 86 amu (a 3HB unit) and 100 amu (a 3HV unit) attesting to some randomness within the polymers. This study verifies the potential for producing Poly-3HB-block-3HV copolymers from inexpensive biorenewable feedstocks without sequential addition of carbon sources. Published by Elsevier Ltd.

Polymer-based platform for microfluidic systems

Science.gov (United States)

Benett, William [Livermore, CA; Krulevitch, Peter [Pleasanton, CA; Maghribi, Mariam [Livermore, CA; Hamilton, Julie [Tracy, CA; Rose, Klint [Boston, MA; Wang, Amy W [Oakland, CA

2009-10-13

A method of forming a polymer-based microfluidic system platform using network building blocks selected from a set of interconnectable network building blocks, such as wire, pins, blocks, and interconnects. The selected building blocks are interconnectably assembled and fixedly positioned in precise positions in a mold cavity of a mold frame to construct a three-dimensional model construction of a microfluidic flow path network preferably having meso-scale dimensions. A hardenable liquid, such as poly (dimethylsiloxane) is then introduced into the mold cavity and hardened to form a platform structure as well as to mold the microfluidic flow path network having channels, reservoirs and ports. Pre-fabricated elbows, T's and other joints are used to interconnect various building block elements together. After hardening the liquid the building blocks are removed from the platform structure to make available the channels, cavities and ports within the platform structure. Microdevices may be embedded within the cast polymer-based platform, or bonded to the platform structure subsequent to molding, to create an integrated microfluidic system. In this manner, the new microfluidic platform is versatile and capable of quickly generating prototype systems, and could easily be adapted to a manufacturing setting.

Surface morphological modification of crosslinked hydrophilic co-polymers by nanosecond pulsed laser irradiation

Energy Technology Data Exchange (ETDEWEB)

Primo, Gastón A.; Alvarez Igarzabal, Cecilia I. [IMBIV (CONICET), Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Edificio de Ciencias II, Ciudad Universitaria, Córdoba X5000HUA (Argentina); Pino, Gustavo A.; Ferrero, Juan C. [INFIQC (CONICET), Departamento de Fisicoquímica, Facultad de Ciencias Químicas, and Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba, Córdoba X5000IUS (Argentina); Rossa, Maximiliano, E-mail: mrossa@fcq.unc.edu.ar [INFIQC (CONICET), Departamento de Fisicoquímica, Facultad de Ciencias Químicas, and Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba, Córdoba X5000IUS (Argentina)

2016-04-30

Graphical abstract: - Highlights: • Laser-induced surface modification of crosslinked hydrophilic co-polymers by ns pulses. • Formation of ablation craters observed under most of the single-pulse experimental conditions. • UV laser foaming of dried hydrogel samples resulting from single- and multiple-pulse experiments. • Threshold values of the incident laser fluence reported for the observed surface modifications. • Lower threshold fluences for acrylate-based, compared to acrylamide-based hydrogels. - Abstract: This work reports an investigation of the surface modifications induced by irradiation with nanosecond laser pulses of ultraviolet and visible wavelengths on crosslinked hydrophilic co-polymeric materials, which have been functionalized with 1-vinylimidazole as a co-monomer. A comparison is made between hydrogels differing in the base co-monomer (N,N-dimethylaminoethyl methacrylate and N-[3-(dimethylamino)propyl] methacrylamide) and in hydration state (both swollen and dried states). Formation of craters is the dominant morphological change observed by ablation in the visible at 532 nm, whereas additional, less aggressive surface modifications, chiefly microfoams and roughness, are developed in the ultraviolet at 266 nm. At both irradiation wavelengths, threshold values of the incident laser fluence for the observation of the various surface modifications are determined under single-pulse laser irradiation conditions. It is shown that multiple-pulse irradiation at 266 nm with a limited number of laser shots can be used alternatively for generating a regular microfoam layer at the surface of dried hydrogels based on N,N-dimethylaminoethyl methacrylate. The observations are rationalized on the basis of currently accepted mechanisms for laser-induced polymer surface modification, with a significant contribution of the laser foaming mechanism. Prospective applications of the laser-foamed hydrogel matrices in biomolecule immobilization are suggested.

Surface functionalization of quantum dots with fine-structured pH-sensitive phospholipid polymer chains.

Science.gov (United States)

Liu, Yihua; Inoue, Yuuki; Ishihara, Kazuhiko

2015-11-01

To add novel functionality to quantum dots (QDs), we synthesized water-soluble and pH-responsive block-type polymers by reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymers were composed of cytocompatible 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer segments, which contain a small fraction of active ester groups and can be used to conjugate biologically active compounds to the polymer, and pH-responsive poly(2-(N,N-diethylamino) ethyl methacrylate (DEAEMA)) segments. One terminal of the polymer chain had a hydrophobic alkyl group that originated from the RAFT initiator. This hydrophobic group can bind to the hydrophobic layer on the QD surface. A fluorescent dye was conjugated to the polymer chains via the active ester group. The block-type polymers have an amphiphilic nature in aqueous medium. The polymers were thus easily bound to the QD surface upon evaporation of the solvent from a solution containing the block-type polymer and QDs, yielding QD/fluorescence dye-conjugated polymer hybrid nanoparticles. Fluorescence resonance energy transfer (FRET) between the QDs (donors) and the fluorescent dye molecules (acceptors) was used to obtain information on the conformational dynamics of the immobilized polymers. Higher FRET efficiency of the QD/fluorescent dye-conjugated polymer hybrid nanoparticles was observed at pH 7.4 as compared to pH 5.0 due to a stretching-shrinking conformational motion of the poly(DEAEMA) segments in response to changes in pH. We concluded that the block-type MPC polymer-modified nanoparticles could be used to evaluate the pH of cells via FRET fluorescence based on the cytocompatibility of the MPC polymer. Copyright © 2015 Elsevier B.V. All rights reserved.

Functional polymers as nanoscopic building blocks

International Nuclear Information System (INIS)

Hernandez-Lopez, J.L.; Bauer, R.E.; Chang, W.-S.; Glasser, G.; Grebel-Koehler, D.; Klapper, M.; Kreiter, M.; Leclaire, J.; Majoral, J.-P.; Mittler, S.; Muellen, K.; Vasilev, K.; Weil, T.; Wu, J.; Zhu, T.; Knoll, W.

2003-01-01

Polyphenylene dendrimers are introduced as polymeric building blocks--with a strictly monodisperse particle size distribution within the nanometer range--for the construction of nanostructured materials and devices. The possibility for the introduction of different functionalities in the core, the scaffold or the periphery of the dendrimers offer their use as interesting modules for photonic, electronic or bioactive structures and supramolecular functional assemblies. Thus, dendrimers complement the available set of nanoscopic building blocks made from metals, e.g., Au nanoclusters and semiconductors, e.g., luminescent quantum dots. In a first set of experiments, we describe the fabrication of multilayer architectures using dendrimers with chargeable groups at the surface. This way, the polyelectrolyte deposition technique can be applied for the construction of hybrid layered assemblies with a control of the internal supramolecular structure at the nanometer level. Surface plasmon field-enhanced fluorescence spectroscopy is used to monitor the luminescent properties of dendrimers with a phthalocyanine core integrated into such a multilayer assembly. AFM and SEM micrographs demonstrate the use of surface-functionalized dendrimers (exposing sulfur groups at the periphery) in combination with Au nanoparticles for the controlled assembly of hybrid aggregates as nanoscopic functional devices

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

Science.gov (United States)

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

2018-05-15

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

Synthesis and application of PLA and PLA/GO fibers through thermo-responsive transformation of PLA particles

OpenAIRE

Bolakhrif, Sabah

2016-01-01

PLA nanofibers were successively produced by thermo-responsive transformation of PLA particles in water. The morphological structure of the nanofibers could be optimized by the heat treatment as well as the incorporation of GO to the fiber surface. PLA/GO fiber demonstrated a more stable morphology and GO provided good compatibility between PLA and starch. Both PLA and PLA/GO fibers incorporated in starch films resulted in increased thermal stability and mechanical properties. However, the mo...

Amphiphilic block copolymers for biomedical applications

Science.gov (United States)