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Grafted Copolymers (grafted + copolymer)
Selected AbstractsMicrowave and Ionic Liquids: Inverse Temperature Dependence of Viscosity in Aqueous Medium of Grafted CopolymersMACROMOLECULAR REACTION ENGINEERING, Issue 9 2009Ella Bezdushna Abstract We elaborated a route to the thermosensitive polyelectrolyte system composed of 1-methyl-3-vinylimidazolium salt with , -cyclodextrin complexed counterions and mono-(meth)acrylic functionalized poly(N -isopropylacrylamide) as grafted side chains via a three-step synthetic procedure. The aqueous solution of the polyelectrolyte displays partially inverse thermoresponsive behavior; it exhibits enhancement of shear viscosity up to body temperature. Furthermore, based on classically prepared poly(NIPAAm) bearing terminal amino groups, corresponding (meth-) acrylamide-type of macromonomers were easily obtained under microwave conditions. [source] Preparation of novel poly(ethylene oxide- co -glycidol)-graft-poly(,-caprolactone) copolymers and inclusion complexation of the grafted chains with ,-cyclodextrinJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2006Juan Huang Abstract A well-defined comblike copolymer of poly(ethylene oxide- co -glycidol) [(poly(EO- co -Gly)] as the main chain and poly(,-caprolactone) (PCL) as the side chain was successfully prepared by the combination of anionic polymerization and ring-opening polymerization. The glycidol was protected by ethyl vinyl ether to form 2,3-epoxypropyl-1-ethoxyethyl ether (EPEE) first, and then ethylene oxide was copolymerized with EPEE by an anionic mechanism. The EPEE segments of the copolymer were deprotected by formic acid, and the glycidol segments of the copolymers were recovered after saponification. Poly(EO- co -Gly) with multihydroxyls was used further to initiate the ring-opening polymerization of ,-caprolactone in the presence of stannous octoate. When the grafted copolymer was mixed with ,-cyclodextrin, crystalline inclusion complexes (ICs) were formed, and the intermediate and final products, poly(ethylene oxide- co -glycidol)- graft -poly(,-caprolactone) and ICs, were characterized with gel permeation chromatography, NMR, differential scanning calorimetry, X-ray diffraction, and thermogravimetric analysis in detail. The obtained ICs had a channel-type crystalline structure, and the ratio of ,-caprolactone units to ,-cyclodextrin for the ICs was higher than 1:1. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3684,3691, 2006 [source] Development of a robust hydrogel system based on agar and sodium alginate blendPOLYMER INTERNATIONAL, Issue 2 2008Ramavatar Meena Abstract BACKGROUND: As part of an ongoing research and development programme of our laboratory on functional modification of seaweed polysaccharides for preparing hydrogels with improved properties, we report herein the preparation of a robust hydrogel system based on grafting of agar and sodium alginate blend (Agar/Na-Alg) with acrylamide (AAm) to obtain the copolymer Agar/Na-Alg- graft -PAAm. RESULTS: A robust hydrogel system with superior absorbency and pH resistance has been developed based on a PAAm-grafted seaweed polysaccharide blend of Agar/Na-Alg. The blend (Agar/Na-Alg) and grafted product (Agar/Na-Alg- graft -PAAm) were evaluated using Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, swelling capacity, rheology and scanning electron microscopy. The swelling capacity of the grafted copolymer exhibited an enhancement over that of the blend from 14 to 24 g g,1 in acidic medium. The blend and grafted copolymer produced hydrogels with lower gelling points of 31 and 29 °C and gel strengths were 170 and 120 g cm,2, respectively. CONCLUSION: This study constitutes an example of value addition of seaweed polysaccharides targeting new applications. The copolymer hydrogel may be useful in health, personal care and agricultural applications. Copyright © 2007 Society of Chemical Industry [source] Evaluation of the potential of polymeric carriers based on chitosan- grafted -polyacrylonitrile in the formulation of drug delivery systemsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010A. A. Sarhan Abstract Graft copolymerization of chitosan with acrylonitrile (AN) was carried out by free radical polymerization using KMnO4 and oxalic acid as a combined redox initiator system. Graft copolymerization was confirmed by Fourier transform infrared spectra (FTIR), proton nuclear magnetic resonance spectra (1H-NMR), thermal gravimetric analysis (TGA) measurements, and wide angle X-ray diffraction (WAXD). In addition, further modification of the cyano groups of the grafted copolymers was performed by partial hydrolysis into carboxylic function groups with various extents. The extent of hydrolysis was monitored using FTIR spectroscopy. The potential of the hydrolyzed and unhydrolyzed grafted copolymers as polymeric carriers for drug delivery systems was extensively studied by preparation of tablets incorporated with methyl orange (MO) as a drug model. In vitro drug release was carried out in simulated gastric and intestinal conditions. The effects of grafting percentage (GP) and the extent of hydrolysis on the release kinetics were evaluated. Release continued up to 24 h for both hydrolyzed and unhydrolysed chitosan- g -PAN copolymers. The nature of drug transport through the polymer matrices was studied by comparing with power law or Kormeyer-Peppas equation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Optimized conditions for the grafting reaction of poly(methyl methacrylate) onto oil-palm empty fruit bunch fibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Aznizam Abu Bakar Abstract This article describes the graft copolymerization of poly(methyl methacrylate) (PMMA) onto oil-palm empty fruit bunches (OPEFBs) with a fiber length of less than 75 ,m. The graft copolymerization was carried out under a nitrogen atmosphere by a free-radical initiation technique in an aqueous medium. Hydrogen peroxide and ferrous ions were used as a redox initiator/cocatalyst system. The PMMA homopolymer that formed during the reaction was removed from the grafted copolymers by Soxhlet extraction. Determining the effects of the reaction period, reaction temperature, and monomer concentration on the grafting percentage was the main objective, and they were investigated systematically. The optimum reaction period, reaction temperature, monomer concentration, and initiator concentration were 60 min, 50°C, 47.15 × 10,3 mol, and 3.92 × 10,3 mol, respectively. The maximum percentage of grafting achieved under these optimum conditions was 173%. The presence of PMMA functional groups on OPEFB and the enormous reduction of the hydroxyl-group absorption band in PMMA- g -OPEFB spectra provided evidence of the successful grafting reaction. The improvement of the thermal stability of PMMA- g -OPEFB also showed the optimal achievement of the grafting reaction of PMMA onto OPEFB. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Graft copolymerization of methyl acrylate onto cellulose initiated by potassium ditelluratoargentate(III)POLYMER INTERNATIONAL, Issue 10 2004Yinghai Liu Abstract A novel redox system, potassium ditelluratoargentate(III) (DTA),cellulose, was employed to initiate the graft copolymerization of methyl acrylate onto cellulose in alkali aqueous solution. Grafting parameters, such as total conversion, grafting efficiency and grafting yield, were evaluated comparatively. The dependence of these parameters on temperature, reaction time, initiator concentration and ratio of monomer to cellulose was also investigated. Graft copolymers with high grafting parameters were obtained, which indicated that the DTA,cellulose redox pair is an efficient initiator for cellulose grafting. The proof of grafting was obtained from gravimetric analysis and infrared spectra. A tentative mechanism involving a two-step single-electron-transfer process of DTA is proposed to explain the generation of radicals and initiation. Thermogravimetry, X-ray diffraction and scanning electron microscopy were also carried out to study the thermal stability, crystallinity and morphology of the grafted copolymers. Copyright © 2004 Society of Chemical Industry [source] | ||||||||||