Search results for "Crosslinking"
showing 10 items of 32 documents
Triblock SEBS/DVB crosslinked and sulfonated membranes: Fuel cell performance and conductivity
2021
[EN] A set of styrene-ethylene-butylene-styrene triblock copolymer (SEBS) membranes with 10 or 25 wt.% divinyl-benzene (DVB) as a crosslinking agent were prepared and validated. Physicochemical characterization revealed suitable hydrolytic and thermal stability of photo-crosslinked membranes containing 25%wt. DVB and post-sulfonated. These compositions were evaluated in H2/O2 single cells, and electrical and proton conductivities were furtherly assessed. The membranes with the milder post-sulfonation showed greater proton conductivity than those with excessive sulfonation. In terms of electrical conductivity, a universal power law was applied, and the values obtained were low enough for bei…
Photocrosslinking of dextran and polyaspartamide derivatives: a combination suitable for colon-specific drug delivery.
2007
Abstract The aim of this study was to prepare and characterize novel hydrogels with polysaccharide–polyaminoacid structure, able to undergo an enzymatic hydrolysis in the colon and potentially useful for treating inflammatory bowel diseases (IBD). Starting materials were methacrylated dextran (DEX-MA) and methacrylated α,β-poly(N-2-hydroxyethyl)- dl -aspartamide (PHM). These polymers were photocrosslinked by exposure of their aqueous solutions at 313 nm without photoinitiators. Different samples, shaped as microparticles, were obtained as a function of polymer concentration and irradiation time. FT-IR analysis confirmed the occurrence of a co-crosslinking between DEX-MA and PHM in all exper…
Photo-crosslinking in freely-suspended films of ferroelectric lc-polymers
1995
Effect of an organoclay on the photochemical transformations of a PBAT/PLA blend and morpho-chemical features of crosslinked networks
2021
Abstract In this work, we report the effect of an organoclay on the photochemical weathering of nanocomposites based on a poly(butylene adipate-co-terephthalate) (PBAT)/poly(lactic acid) (PLA) blend. The evolution of physicochemical properties was monitored by integrating spectroscopic, mechanical, and morphological analyses. A robust relationship was found between the molecular transformations of the polymer macromolecules and the morpho-mechanical properties of irradiated films. Moreover, the analysis of insoluble fractions extracted from nanocomposites pointed out that free-standing, porous structures, displaying an unprecedented thickness as great as 100 µm, were formed, thus unambiguou…
Photoaffinity cross-linking of F1ATPase from the thermophilic bacterium PS3 by 3′-arylazido-β-alanyl-2-azido ATP
1989
AbstractThe photoactivatable bifunctional 3′-arylazido-β-alanyl-2-azido ATP (2,3′-DiN3ATP) has been applied to study the localization of the nucleotide-binding sites of coupling factor 1 (F1ATPase, TF1) from the thermophilic bacterium PS3 by photoaffinity cross-linking. UV irradiation of TF1 in the presence of 2,3′-DiN3ATP results in the nucleotide-dependent formation of various higher molecular mass cross-links formed by two, three or even four α- and/or β-subunits. The differences observed upon photoaffinity cross-linking by the bifunctional 2-azido ATP or 8-azido ATP analog are discussed. They are probably due to the varied maximal distance between both azido groups, or to the different …
Evaluation of radiation stability of electron beam irradiated Nafion® and sulfonated poly(ether ether ketone) membranes
2022
Proton exchange membranes (PEM), which have been commonly used in fuel cells have raised interest for the application in harsh environments involving ionizing radiation. Therefore, radiation stability and ability to sustain their functionality under the radiation environment are of great interest. Within this study, electron beam irradiation in dose range from 50 to 500kGy was used to evaluate the effects of radiation on the physico-chemical and mechanical properties of two types of PEM: commercial Nafion®117 and sulfonated poly(ether-ether-ketone) (SPEEK) with high degree of sulfonation (DS = 0.75±0.5). SPEEK membrane presented higher mechanical and thermal stability compared to that of Na…
Effect of electron-beam irradiation on structure of ultra high molecular weight polyethylene used in medical implants
2004
Określono wpływ napromieniania strumieniem elektronów dawką równoważną stosowanej w praktyce podczas sterylizacji radiacyjnej endoprotez chirurgicznych (26 kGy) oraz dwukrotnie większą (2 . 26 kGy) na zmianę struktury PE-UHMW o nazwie handlowej „,Chirulen 1120”' (tabela 1) służącego do otrzymywania panewek endoprotez biodrowych. Metodą FT-IR zbadano zmiany strukturalne polimeru, stwierdzając głównie występowanie skutków jego utlenienia (wzrost udziału grup karbonylowych typu ketonowego, estrowego i nadestrowego, grup hydroksylowych oraz winylowych) (rys. 1). Metodą GPC stwierdzono, że napromienianie powoduje także częściową degradację makrocząsteczek (zmniejszenie ciężaru cząsteczkowego o j…
Drug release from α,β-poly(N-2-hydroxyethyl)-DL-aspartamide based microparticles
2004
Spherical pH-sensitive microparticles have been prepared by reverse phase suspension polymerization technique. Starting polymer has been alpha,beta-poly(N-2-hydroxyethyl)-dl-aspartamide (PHEA) partially derivatized with glycidylmethacrylate (GMA). PHEAGMA copolymer (PHG) has been crosslinked in the presence of acrylic acid (AA) or methacrylic acid (MA) at various concentration. The obtained microparticles have been characterized by FT-IR spectrophotometry, particle size distribution analysis and scanning electron microscopy. In order to have information about water affinity of the prepared samples, swelling measurements have been carried out in aqueous media which simulate some biological f…
Preparation of Polymeric Nanoparticles by Photo-Crosslinking of an Acryloylated Polyaspartamide in w/o Microemulsion
2004
Biodegradable polymeric nanoparticles have been prepared by UV irradiation of an acryloylated water soluble polymer by an inverse microemulsion. The starting polymer was a α,β‐poly(N‐2‐hydroxyethyl)‐D,L‐aspartamide (PHEA) partially functionalized with glycidyl methacrylate (GMA) in order to introduce reactive vinyl groups in the side chain. The PHEA‐GMA copolymer obtained (PHG) was crosslinked by UV irradiation of the inverse microemulsion prepared by mixing an aqueous solution of PHG with propylene carbonate (PC)/ethyl acetate (EtOAc) in the presence of sorbitan trioleate (SPAN 85) as surfactant. Nanoparticles obtained were characterized by FTIR spectrophotometry, transmission electron mic…
Modyfikacja polietylenu kwasem itakonowym
2003
W celu nadania właściwości hydrofilowych, które powinny ułatwić rozkład odpadów w środowisku naturalnym, przeprowadzono szczepienie PE-LD kwasem itakonowym (KI) wobec nadtlenku dikumylu (DCP). Proces realizowano dwuetapowo w wytłaczarce jednoślimakowej, stosując różne stężenia KI (3—10% mas.) i DCP (do 1,1% mas.). Metodą pirolitycznej chromatografiigazowej (Py/GC/MS) zidentyfikowano produkty termicznego rozkładu KI. Analiza FT-IR wykluczyła ich obecność w kompozycjach po szczepieniu, natomiast sugerowała szczepienie KI. Metodą ekstrakcji wodnej ustalono, że wraz ze wzrostem stężenia KI i DCP wzrasta stopień szczepienia, natomiast w całym badanym zakresie stężeń DCP w kompozycjach zawierając…