Home About us Contact
|
Home About us Contact | ||
|
|
||
Graft Copolymerization (graft + copolymerization)
Kinds of Graft Copolymerization Selected AbstractsFree Radical Graft Copolymerization of Methyl Methacrylate onto Polyolefin Backbone: Kinetics Modeling through Model Compounds ApproachMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 13-14 2009Thierry Badel Abstract The grafting of poly(methyl methacrylate) (PMMA) from poly[ethylene- co -(1-octene)] in the molten state by in situ radical polymerization of methyl methacrylate (MMA) was investigated through a kinetic modeling using a model compound approach. We resorted to pentadecane (C15H32) and 2,6,10,15,19,23-hexamethyltetracosane (Squalane, C30H62) as models for both the copolymer ethylene and octene moieties. The attention was focused on the simulation of MMA conversion and PMMA average polymerization degree according to temperature, reaction time, and initiator ratio required for the polymerization of MMA in the presence of alkoxyl radicals and alkanes. [source] A Solvent Free Graft Copolymerization of Maleic Anhydride onto Cellulose Acetate Butyrate Bioplastic by Reactive ExtrusionMACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2006Arief C. Wibowo Abstract Summary: Interfacial adhesion between fibers and matrix is a crucial factor for effective stress transfer from matrix to fiber; especially in short fiber reinforced composite systems. The use of a chemical compatibilizer is an efficient means to achieve such adhesion. Maleic anhydride-grafted-cellulose acetate butyrate (CAB-g-MA) is one such compatibilizer which can be used in biocomposite fabrication, and this has been synthesized in our laboratory by utilizing a twin-screw reactive extrusion process in the presence of a free radical initiator (2,5-dimethyl-2,5-di(tert -butylperoxy)hexane). The unique feature of this process is its solvent-free approach for grafting of maleic anhydride onto CAB, without hydroxyl group protection. CAB-g-MA was characterized using FTIR as well as by a non-aqueous titration method. The effects of initiator and monomer concentrations and various processing conditions on the graft content were also investigated. The preliminary results show that by adding approximately 10 wt.-% of CAB-g-MA into a plasticized cellulose acetate butyrate (TEB)-industrial hemp fiber biocomposites system, an improvement in tensile strength (20%) and in tensile modulus (45%) were obtained. These results are promising in that they pave the way for future studies involving the use of CAB-g-MA as a suitable compatibilizer for cellulose ester-natural fiber biocomposites. [source] Free radical graft copolymerization of poly(n -butyl methacrylate) and poly(butyl acrylate) onto chlorinated rubber: Characterization and mechanical properties,ADVANCES IN POLYMER TECHNOLOGY, Issue 2 2004Shanaz Ahmed Abstract Graft copolymerization of n -butyl methacrylate and butyl acrylate onto chlorinated rubber was carried out in solution medium (xylene) using benzoyl peroxide as initiator. The chlorinated rubber-g-(n -butyl methacrylate- co -butyl acrylate) (CR-g-nBMA- co -BA) was isolated from the copolymerization mixture by extracting with isopropyl ether. Infrared (FT-IR) spectra, proton nuclear magnetic resonance (1H NMR) and thermogravimetric analysis of the graft copolymer showed the occurrence of grafting. Percent grafting and grafting efficiency calculated under different experimental conditions are discussed. The mechanical properties of the grafted CR films were studied under different strain rates. © 2004 Wiley Periodicals, Inc. Adv Polym Techn 23: 103,110, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20003 [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] Graft copolymerization of methyl methacrylate with an N -substituted maleimide,liquid-crystalline copolymer by atom transfer radical polymerizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008T. Çak Abstract The synthesis of novel copolymers consisting of a side-group liquid-crystalline backbone and poly (methyl methacrylate) grafts were realized by the use of atom transfer radical polymerization (ATRP). In the first stage, the bromine-functional copolymers 6-(4-cyanobiphenyl-4,-oxy)hexyl acrylate and (2,5-dioxo-2,5-dihydro-1H -pyrrole-1-yl)methyl 2-bromopropanoate were synthesized by free-radical polymerization. These copolymers were used as initiators in the ATRP of methyl methacrylate to yield graft copolymers. Both the macroinitiator and graft copolymers were characterized by 1H-NMR, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. The ATRP graft copolymerization was supported by an increase in the molecular weight of the graft copolymers compared to that of the macroinitiator and also by their monomodal molecular weight distribution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Ceric(IV) ion-induced graft copolymerization of acrylamide and ethyl acrylate onto cellulosePOLYMER INTERNATIONAL, Issue 2 2006Prof. Kailash C Gupta Abstract Graft copolymerization of acrylamide (AAm) and ethyl acrylate (EA) onto cellulose has been carried out from their binary mixtures using ceric ammonium nitrate (CAN) as an initiator in the presence of nitric acid at 25 ± 1 °C. The extent of acrylamide grafting increased in the presence of the EA comonomer. The composition of the grafted chains (FAAm = 0.52) was found to be constant during the feed molarity variation from 7.5 × 10,2 to 60.0 × 10,2 mol L,1, whereas the composition of the grafted chains (FAAm) was found to be dependent on feed composition (fAAm) and reaction temperature. The effects of ceric(IV) ion concentration, reaction time and temperature on the grafting parameters have been studied. The grafting parameters showed an increasing trend up to 6.0 × 10,3 mol L,1 concentration of CAN at a feed molarity of 30.0 × 10,2 mol L,1 and showed a decreasing trend on further increasing the concentration of CAN (>6.0 × 10,3 mol L,1) at a constant concentration of nitric acid (5.0 × 10,2 mol L,1). The composition of the grafted chains (FAAm) was determined by IR spectroscopy and nitrogen content and the data obtained then used to determine the reactivity ratios of the acrylamide (r1) and ethyl acrylate (r2) comonomers by using a Mayo and Lewis plot. The reactivity ratios of acrylamide and ethyl acrylate were found to be r1 = 0.54 and r2 = 1.10, respectively, and hence the sequence lengths of acrylamide (m,M1) and ethyl acrylate (m,M2) in the grafted chains are arranged in an alternating form, as the product of the reactivity ratios of acrylamide and ethyl acrylate (r1 × r2) is less than unity. The rate of graft copolymerization of the comonomers onto cellulose was found to be dependant on the ,squares' of the concentrations of the comonomers and on the ,square root' of the concentration of ceric ammonium nitrate. The energy of activation (,Ea) of graft copolymerzation was found to be 5.57 kJ mol,1 within the temperature range from 15 to 50 °C. On the basis of the results, suitable reaction steps have been proposed for the graft copolymerzation of acrylamide and ethyl acrylate comonomers from their mixtures. Copyright © 2005 Society of Chemical Industry [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] Irradiation synthesis of biopolymer-based superabsorbent hydrogel: Optimization using the Taguchi method and investigation of its swelling behaviorADVANCES IN POLYMER TECHNOLOGY, Issue 2 2009Ghasem R. Bardajee Abstract In this report, the synthesis of a novel superabsorbent hydrogel via ,-irradiation graft copolymerization of acrylamide onto sodium alginate and kappa-carrageenan hybrid backbones in a homogeneous solution is described. The Taguchi method was used as a powerful experimental design tool for synthesis optimization. A series of superabsorbent hydrogels was synthesized by proposed conditions of Qualitek-4 software. Considering the results of nine trials according to analysis of variance, optimum conditions were proposed. The swelling behavior of optimum superabsorbent hydrogels was studied in various solutions, with pH values ranging from 1 to 13. In addition, swelling kinetics, swelling in various organic solvents, the absorbency under load, and on,off switching behavior were investigated. Also, hydrogel formation was confirmed by Fourier transform infrared spectroscopy. Surface morphology of the synthesized hydrogels was assessed by scanning electron microscopy. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:131,140, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20154 [source] Free radical graft copolymerization of poly(n -butyl methacrylate) and poly(butyl acrylate) onto chlorinated rubber: Characterization and mechanical properties,ADVANCES IN POLYMER TECHNOLOGY, Issue 2 2004Shanaz Ahmed Abstract Graft copolymerization of n -butyl methacrylate and butyl acrylate onto chlorinated rubber was carried out in solution medium (xylene) using benzoyl peroxide as initiator. The chlorinated rubber-g-(n -butyl methacrylate- co -butyl acrylate) (CR-g-nBMA- co -BA) was isolated from the copolymerization mixture by extracting with isopropyl ether. Infrared (FT-IR) spectra, proton nuclear magnetic resonance (1H NMR) and thermogravimetric analysis of the graft copolymer showed the occurrence of grafting. Percent grafting and grafting efficiency calculated under different experimental conditions are discussed. The mechanical properties of the grafted CR films were studied under different strain rates. © 2004 Wiley Periodicals, Inc. Adv Polym Techn 23: 103,110, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20003 [source] Novel polymeric flocculants based on polyacrylamide grafted dextran in kaolin suspensionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010S. Krishnamoorthi Abstract A study is done on ceric-ammonium-nitrate (CAN) initiated graft copolymerization of polyacrylamide (PAM) on to dextran (Dx) by solution polymerization technique. The average molecular weight of dextran is 7.0 × 10,6 g/mole. By changing the concentrations of the initiator in the reaction feed, a series of graft copolymer (Dx-g-PAM1 to Dx-g-PAM4) with variation in the number and length of the grafted PAM chains are obtained. The flocculation characteristics of various polymers are investigated by the use of settling tests in 2 wt % using kaolin suspensions. Among the series of graft copolymers, the one with highest molecular weight shows superior performance. The flocculation characteristics of the best-performing graft copolymer (Dx-g-PAM3) are compared with those of various commercially available flocculants and PAM in the kaolin suspension. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Polymer electrolyte membranes having sulfoalkyl grafts into ETFE film prepared by radiation-induced copolymerization of methyl acrylate and methyl methacrylateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009Truong Thi Hanh Abstract Polymer electrolyte membranes (PEMs) containing alkylsulfonic acid grafts can be prepared by radiation-induced graft copolymerization of methyl acrylate (MA) and methyl methacrylate (MMA) into a poly(ethylene- co -tetrafluoroethylene) film followed by sulfonation of the MA units in the copolymer grafts using an equimolar complex of chlorosulfonic acid and 1,4-dioxane (ClSO3H-Complex). PEMs with MA/MMA copolymer grafts that are 33%,79% MA units were prepared by preirradiation with a dose of 20 kGy and grafting in bulk comonomers at 60°C. The grafted films are treated with ClSO3H-Complex to obtain PEMs with ion exchange capacity of 0.36-0.81 mmol/g (sulfonation degrees of 20%,40%) and proton conductivity of 0.04-0.065 S/cm. These values can be controlled by changing the MA content the sulfonation occurring at an ,-carbonyl carbon. The PEMs with higher MMA content showed higher durability in water (80°C) and under oxidative conditions (3% H2O2) at 60°C. This is because the PMMA grafts in the PEMs have no proton at an ,-carbonyl carbon, which is considered to be a trigger of the degradation of grafting polymers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Swelling properties of CMC- g -poly (AAm- co -AMPS) superabsorbent hydrogelJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2009Ali Pourjavadi Abstract A series of biopolymer-based superabsorbent hydrogels based on carboxymethyl cellulose has been prepared by free-radical graft copolymerization of acrylamide and 2-acrylamido-2-methylpropan sulfonic acid (AMPS) in aqueous solution using methylenebisacrylamide as a crosslinking agent and ammonium persulfate as an initiator. The effect of variables on the swelling capacity such as: acrylamide/AMPS weight ratio, reaction temperature, and concentration of the initiator and crosslinker were systematically optimized. The results indicated that with increasing the amount of AMPS, the swelling capacity is increased. FT-IR spectroscopy and scanning electron microscope analysis were used to confirm the hydrogel structure. Swelling measurements of the synthesized hydrogels in different salt solutions indicated considerable swelling capacity. The absorbency under load of the superabsorbent hydrogels was determined by using an absorbency under load tester at various applied pressures. A preliminary swelling and deswelling behaviors of the hydrogels were also studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Induction of chemical and moisture resistance in Saccharum spontaneum L fiber through graft copolymerization with methyl methacrylate and study of morphological changesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009Balbir Singh Kaith Abstract In this article, morphological modification of Saccharum spontaneum L, a natural fiber through graft copolymerization with methylmethacrylate using ferrous ammonium sulfate,potassium per sulfate redox initiator has been reported. Different reaction parameters such as reaction temperature, time, initiator molar ratio, monomer concentration, pH and solvent were optimized to get maximum graft yield (144%). The graft copolymers thus formed were characterized by Fourier transform infrared, scanning electron microscopy, X-ray diffraction and thermogravimetric, differential thermal analysis, and differential thermogravimetric techniques. Graft copolymer has been found to be more moisture resistant and also showed higher chemical and thermal resistance. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [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] Novel jute yarns grafted with methyl methacrylateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008M. Montazer Abstract This research work involves graft copolymerization of jute fibers with methyl methacrylate (MMA), initiated by cerric ions, and optimization of the grafting parameters as a function of different polymerization conditions. It was considered to produce a hydrophobic jute fiber with enhanced properties. To achieve this, the effects of monomer concentration and grafting percentage on FTIR spectra, mechanical properties, moisture regain, oil-adsorption capacity, and surface morphology were investigated, and optimum percentage of MMA with reasonable properties was suggested. The results indicated that cerric ions initiated graft copolymerization of MMA onto jute with 30% of weight of monomers at optimum conditions of acid concentration and temperature. The FTIR studies proposed grafting of MMA onto jute at hydroxyl groups. The results showed that mechanical properties and moisture regain (%) of samples decrease with increasing of graft percentage. The most remarkable features of this investigation include reducing oil-adsorption capacity with increasing of lipophilic monomer percentages after one limitation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Pectin and acrylamide based hydrogels for environment management technologies: Synthesis, characterization, and metal ions sorptionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Ghanshyam S. Chauhan Abstract The present article describes various aspects of preparation and characterization of hydrogels based on pectin and three different amide monomers viz: acrylamide (AAm), N -isopropyl acrylamide (N -i-PAAm), and 2-acrylamido-2-methyl-1-propane sulfonic acid (AAmPSA). Hydrogels have been prepared by graft copolymerization as well as in the presence of crosslinker N,N -Methylene bisacrylamide ((N,N -MBAAm) and initiated by redox system comprising of ammonium peroxysulphate,ferrous ammonium sulfate (APS: FAS) at two temperatures. Hydrogels thus synthesized have been characterized by SEM, FTIR, and water uptake studies. The later has been carried as a function of time, temperature, pH, crosslinker concentration, and temperature at which the hydrogels were prepared. Candidate hydrogels have been used for the sorption of some common metal ions pollutants found in soil, industrial, and mining water bodies. Biodegradability studies have been carried by soil burial method to investigate the effect of chemical modification on biodegradability of pectin and to understand the possibility of eco-friendly nature and to explore the scope of reusability of the hydrogels and waste minimization. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Modification of guar gum through grafting of 4-vinyl pyridine using potassium peroxymonosulphate/ascorbic acid redox pairJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007Abhishek Srivastava Abstract In the present article, the graft copolymerization of 4-vinyl pyridine onto guar gum initiated by potassium peroxymonosulphate/ascorbic acid redox pair in an aqueous medium was studied gravimetrically under a nitrogen atmosphere. Grafting ratio, grafting efficiency, and add on increased on increasing the concentration of potassium peroxymonosulphate from 5.0 × 10,4 to 10 × 10,4 mol/L and ascorbic acid concentration from 0.4 × 10,3 to 2.0 × 10,3 mol/L. On increasing the hydrogen ion concentration from 2.5 × 10,3 to 10.0 × 10,3 mol/L, grafting ratio, efficiency, add on and conversion were increased. Maximum grafting was obtained when guar gum and monomer concentration were 1.0 g/L and 20.0 × 10,2 mol/L, respectively. An increase in temperature from 30 to 35°C increased the grafting ratio, but conversion and homopolymer decreased. The graft copolymers were characterized by IR spectroscopy and thermogravimetric analysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Grafting of poly(N -isopropylacrylamide) onto nylon and polystyrene surfaces by atmospheric plasma treatment followed with free radical graft copolymerizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Xiaoling Wang Abstract Stimuli-responsive polymer materials (SRPs) have potential uses in drug delivery, tissue engineering, bioreactors, and cell-surface adhesion control. Temperature-responsive surfaces were fabricated by grafting poly(N -isopropylacrylamide) (PNIPAM) onto nylon and polystyrene surfaces via a new procedure, i.e., He atmospheric plasma treatment followed by free radical graft copolymerization. The atmospheric plasma exhibits the activation capability to initiate graft copolymerization. The procedure is suitable for integration into a continuous manufacturing process. To reduce homopolymerization and enhance graft yield, Mohr's salt was added. The graft of PNIPAM was confirmed by Fourier transform infrared spectroscopy and atomic force microscopy. Dramatic water contact angle increase was found for PNIPAM-grafted polymers at about 32°C, indicating the temperature sensitivity of the grafted surface, i.e., the change of surface from hydrophilic to hydrophobic when temperature increases above the lower critical solution temperature (LCST). The addition of Mohr's salt enhances the grafting reaction and the magnitude of temperature sensitivity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3614,3621, 2007 [source] Surface modification of nylon-6 fibers for medical applicationsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007S. E. Shalaby Abstract Hydroxyethylmethacrylate (HEMA) is considered to be one of the important vinyl monomers. The ability of polyhydroxyethyl-methacylate (PHEMA) graft sites to consecutive chemical modification makes the use of nylon-6 fibers grafted with PHEMA a feasible bed for immobilization of a wide range of biologically active reagents, specially enzymes, drugs, cells, and immunadsorbents. Stemming from the above discussions, in this article, the graft copolymerization of HEMA onto modified nylon-6 fibers containing Polydiallyldimethylammonium chloride (PDADMAC) in the presence of Cu2+,K2S2O8 as a redox initiating system was carried out, with very high rate and almost without homopolymer formation. The factors affecting the grafting reaction (monomer, K2S2O8 and cupric ion concentrations, the amount of PDADMAC as well as the reaction temperature) were studied. Kinetic investigation revealed that the rate of grafting (Rp) of HEMA onto modified nylon-6 fibers is proportional to [HEMA]1, [CuSO4.5H2O] 0.7, [PDADMAC]0.4, and [K2S2O8]1.4. The overall activation energy was calculated (71 KJ/mol). The fine structure, surface topography, thermal and electrical properties of parent and grafted nylon-6 fibers were investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3788,3796, 2007 [source] Kinetics of graft copolymerization of poly(hexanedioic acid ethylene glycol) and methyl acrylate initiated by potassium diperiodatocuprate(III)JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Libin Bai Abstract A redox system, potassium diperiodatocuprate(III) [DPC]/poly(hexanedioic acid ethylene glycol) (PEA) system, was employed to initiate graft copolymers of methyl acrylate (MA) and PEA in alkaline medium. The results indicate that the equation of the polymerization rate (Rp) is as follows: Rp = k [MA]1.62[Cu(III)]0.69, and that the overall activation energy of graft polymerization is 42.5 kJ/mol. The total conversion at different conditions (concentration of reactants, temperature, concentration of the DPC, and reaction time) was also investigated. The infrared spectra proved that the graft copolymers were synthesized successfully. Some basic properties of the graft copolymer were studied by instrumental analyses, including thermogravimetry and scanning electron microscope. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2376,2381, 2007 [source] Thermoresponsive brush copolymers with poly(propylene oxide- ran -ethylene oxide) side chains via metal-free anionic polymerization "grafting from" techniqueJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2010Junpeng Zhao Abstract Thermoresponsive brush copolymers with poly(propylene oxide- ran -ethylene oxide) side chains were synthesized via a "grafting from" technique. Poly(p -hydroxystyrene) was used as the backbone, and the brush copolymers were prepared by random copolymerization of mixtures of oxyalkylene monomers, using metal-free anionic ring-opening polymerization, with the phosphazene base (t -BuP4) being the polymerization promoter. By controlling the monomer feed ratios in the graft copolymerization, two samples with the same side-chain length and different compositions were prepared, both of which possessed high molecular weights and low molecular weight distributions. The results from light scattering and fluorescence spectroscopy indicated that the brush copolymers in their dilute aqueous solutions were near completely solvated at low temperature and underwent slight intramolecular chain contraction/association and much more profound intermolecular aggregation at different stages of the step-by-step heating process. Above 50 °C, very turbid solutions, followed by macrophase separation, were observed for both of the samples, which implied that it was difficult for the brush copolymers to form stable nanoscopic aggregates at high temperature. All these observations were attributed, at least partly, to the distribution of the oxyalkylene monomers along the side chains and the overall brush-like molecular architecture. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2320,2328, 2010 [source] Copolymerization of poly(vinyl alcohol)- graft -poly(1,4-dioxan-2-one) with designed molecular structure by a solid-state polymerization methodJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2006Si-Chong Chen Abstract Poly(vinyl alcohol)- graft -poly(1,4-dioxan-2-one) (PVA- g -PPDO) with designed molecular structure was synthesized by a solid-state polymerization. The solid-state copolymerization was preceded by a graft copolymerization of PDO initiated with PVA as a multifunctional initiator, and Sn (Oct)2 as a coininitiator/catalyst in a homogeneous molten state. The polymerization temperature was then decreased and the copolymerization was carried out in a solid state. The products prepared by solid-state polymerization were characterized by 1H NMR and DSC, and were compared with those synthesized in the homogeneous molten state. The degree of polymerization (Dp), degree of substitution (Ds), yield and the average molecular weight of the graft copolymer with different molecular structure were calculated from the 1H NMR spectra. The results show that the crystallization process during the solid-state polymerization may suppress the undesirable inter- or intramolecular side reactions, then resulting in a controlled molecular structure of PVA- g -PPDO. The results of DSC measurement show that the molecular structures determine the thermal behavior of the PVA- g -PPDO. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3083,3091, 2006 [source] Synthesis and characterization of poly(methyl methacrylate)/casein nanoparticles with a well-defined core-shell structureJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2003Junmin Zhu Abstract Well-defined, core-shell poly(methyl methacrylate) (PMMA)/casein nanoparticles, ranging from 80 to 130 nm in diameter, were prepared via a direct graft copolymerization of methyl methacrylate (MMA) from casein. The polymerization was induced by a small amount of alkyl hydroperoxide (ROOH) in water at 80 °C. Free radicals on the amino groups of casein and alkoxy radicals were generated concurrently, which initiated the graft copolymerization and homopolymerization of MMA, respectively. The presence of casein micelles promoted the emulsion polymerization of the monomer and provided particle stability. The conversion and grafting efficiency of the monomer strongly depended on the type of radical initiator, ROOH concentration, casein to MMA ratio, and reaction temperature. The graft copolymers and homopolymer of PMMA were isolated and characterized with Fourier transform infrared spectroscopy and differential scanning calorimetry. The molecular weight determination of both the grafted and homopolymer of PMMA suggested that the graft copolymerization and homopolymerization of MMA proceeded at a similar rate. The transmission electron microscopic image of the nanoparticles clearly showed a well-defined core-shell morphology, where PMMA cores were coated with casein shells. The casein shells were further confirmed with a zeta-potential measurement. Finally, this synthetic method allowed us to prepare PMMA/casein nanoparticles with a solid content of up to 31%. Thus, our new process is commercially viable. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3346,3353, 2003 [source] Ring-opening graft copolymerization of epoxide with polyaniline: Chemical properties and lithium ionic conductivity of the copolymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2001Isao Yamaguchi The NaH-promoted deprotonation of leucoemeraldine base polyaniline (LEB) and its subsequent treatment with phenyl glycidyl ether (PGE) caused the ring-opening polymerization of PGE to give a graft copolymer (LEB- g -PGE). LEB- g -PGE was soluble in acetone and chloroform, which were poor solvents for LEB. An LEB- g -PGE/LiBF4 composite film was obtained through the evaporation of a dimethylformamide solution containing LEB- g -PGE and LiBF4; the film showed an electroconductivity of 1.0 × 10,6 S cm,1 at 295 K, as determined by complex impedance analysis. [source] Use of N -(N,-arylamino)maleimides to improve the thermal properties of poly(vinyl chloride) through chemical modification and graft copolymerizationJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 4 2008Abir S. Abdel-Naby The reaction of poly(vinyl chloride) (PVC) with N -(N,-arylamino)maleimide derivatives was studied. The thermal stability of the modified polymer was improved markedly when compared with that of the unmodified polymer. The stability improvement was attributed to the replacement of the labile chlorine atoms by more stable organic groups. The modified polymer also showed a lower extent of discoloration when compared with that of unmodified PVC. In order to introduce a polymeric stabilizer into PVC, the dienophilic monomer was chemically grafted onto the polymeric chains. The mechanism of the chemical modification as well as that of the graft copolymerization are discussed. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers. [source] Characterization of Methyl Methacrylate Grafting onto Preirradiated Biodegradable Lignocellulose Fiber by , -RadiationMACROMOLECULAR BIOSCIENCE, Issue 1 2005Ferdous Khan Abstract Summary: Gamma-radiation-induced graft copolymerization of methyl methacrylate onto natural lignocellulose (jute) fiber was carried out by the preirradiation method in an aqueous medium by using octylphenoxy-polyethoxyethanol as an emulsifier. The different factors that influenced the graft copolymer reaction process were investigated. In the case of radiation-dose-dependent grafting, samples irradiated in the presence of air produced up to 73% graft weight compared to 53% obtained in the case of irradiation in a nitrogen environment. By assuming Arrhenius reaction kinetics, the activation energy (Ea) of the grafting reaction process was evaluated for different reaction temperatures. Moreover, the graft copolymer reaction was controlled by incorporating a homopolymer-inhibiting agent and three different chain-transfer agents in the reaction medium. The mechanical and thermal properties of jute fiber ,as received' and jute- graft -poly(methyl methacrylate) were also investigated. The results showed that the percentage of grafting with jute fiber has a significant effect on the properties. The kinetic parameters were evaluated from TGA thermograms by using Broido's method in the temperature range 240,350,°C. Scanning electron micrographs show that the structural changes on the surface of jute fibers were induced by graft copolymerization of methyl methacrylate monomer. Fiber-fiber surface friction was measured in terms of the average maximum load and the kinetic friction. SEM of jute- graft -poly(methyl methacrylate). [source] Cellulose Acetate- graft -Poly(hydroxyalkanoate)s: Synthesis and Dependence of the Thermal Properties on Copolymer CompositionMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 14 2004Yoshikuni Teramoto Abstract Summary: Several different series of cellulose acetate- graft -poly(hydroxyalkanoate)s (CA- g -PHAs) were synthesized over a wide range of compositions by the graft copolymerization of lactic acid, L -lactide, (R,S)- , -butyrolactone, , -valerolactone and , -caprolactone onto the residual hydroxyl positions of CA, by virtue of a suitable catalyst, solvent and procedure for each individual case. To achieve a diversity of molecular architectures of the respective graft copolymer series, the degree of acetyl substitution (acetyl DS) of the CA starting material was also varied, resulting in different levels of the intramolecular density of grafts. The CA- g -PHAs thus obtained were subjected to differential scanning calorimetric measurements and the relationship between their molecular structure and thermal transition behavior was estimated, in comparison with some semi-empirical equations available for polymer blends or comb-like polymers. In particular, the composition dependence of the Tgs of the graft copolymers was represented well in terms of a formula proposed by Reimschuessel for comb-like polymers, when CAs of acetyl DS ,2 were employed as a trunk polymer. The deviation of the glass transition data from the model function was discussed in connection with the manner of graft modification. [source] Architecture of Polymeric Superstructures Constructed by Mesoscopically Ordered Cubic LatticesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 4 2003Koji Ishizu Abstract Highly monodisperse crosslinked core-shell polymer microspheres could be prepared easily by introducing special crosslinking reagents into the segregated core in block copolymer assembly films. The crosslinked core was stabilized sterically by highly branched shell chains in solution. These microspheres moved like pseudo-latex. The microspheres formed a lattice with a body-centered cubic (BCC) structure near the overlap threshold (C*). This structure changed to a face-centered cubic (FCC) lattice in the bulk region of the films. Photofunctionalized core-shell microspheres were prepared by introducing dithiocarbamate (DC) groups into shell parts by means of polymer reactions, where DC groups could be propagated using vinyl monomers such as methyl methacrylate (MMA) with living radical mechanism. Polymeric superstructure (three microphase-separated structure) films were constructed by graft copolymerization of MMA initiated with photofunctionalized microspheres such as macroinitiators under UV irradiation, exhibiting self-coloring due to Bragg diffraction. These materials can be used for the construction of optical devices such as for the fabrication of light modulators. Photograph of a solution of the microsphere in MMA. [source] Study on superabsorbent composite XXV.POLYMER COMPOSITES, Issue 4 2010Synthesis, characterization, swelling behaviors of poly(acrylic acid- co - N -acryloylmorpholine)/attapulgite superabsorbent composites In this work, a novel poly(acrylic acid- co - N -acryloylmorpholine)/attapulgite superabsorbent composite was prepared by graft copolymerization among acrylic acid, N -acryloylmorpholine and attapulgite in aqueous solution, using N,N, -methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The result from FTIR spectra showed that OH of attapulgite participated in graft copolymerization with acrylic acid and N -acryloylmorpholine. Proper monomer ratio and atapulgite content could form a loose surface, and improve reswelling ability and initial swelling rate. The buffer action of the COOH and COO, groups in the superabsorbent composite keeps the water absorbency a rough constant in the pH range of 4.4,9.6. Both polarity and structure of an organic solvent are responsible for the phase transition point of the superabsorbent composite. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] The influence of fiber surface modification on the mechanical properties of coir-polyester compositesPOLYMER COMPOSITES, Issue 4 2001J. Rout Coir, an important lignocellulosic fiber, can be incorporated in polymers like unsaturated polyester in different ways for achieving desired properties and texture. But its high level of moisture absorption, poor wettability and insufficient adhesion between untreated fiber and the polymer matrix lead to debonding with age. In order to improve the above qualities, adequate surface modification is required. In our present work, fiber surface modification was effected through dewaxing, alkali (5%) treatment, aqueous graft copolymerization of methyl methacrylate (MMA) onto 5% alkali treated coir for different extents using CuSO4 , NaIO4 combination as an initiator system and cyanoexhylation with a view to improve the mechanical performance of coir-polyester composites. Mechanical properties like tensile strength (PS), flexural strength (ES) and impact strength (IS) of the composites as a function of fiber loading and fiber surface modification have been evaluated. Composites containing z5 wt% of fiber (untreated) improved tensile and flexural strength by 30% and 27% respectively in comparison to neat polyester. The work of fracture (impact strength) of the composite with 25 wt% fiber content was found to be 967 J/m. The elongation at break of the composites exhibits an increase with the introduction of fiber, All types of surface modification result In improved mechanical properties of the composites. Significant improvement in mechanical strength was also observed for composites prepared from 5% PMMA grafted fiber. [source] | |||||||||||||