Graft Polymerization (graft + polymerization)

Distribution by Scientific Domains


Selected Abstracts


Post-Synthesis Functionalization of (Meth)acrylate Based Monoliths via Electron Beam Triggered Graft Polymerization

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2008
Matthias J. Beier
Abstract Porous polymeric monoliths were prepared via electron beam triggered free radical polymerization of (meth)acrylates. Post-synthesis functionalization of these supports was accomplished via electron beam initiated free radical graft polymerization of methacryloyl-substituted NHC precursors. The grafted precursors were converted into the corresponding copper complexes. Cu-loadings were between 1.3 mg,,g,1 and 1.5 mg,,g,1. These supported catalysts were used in selected CO hydrosilylation and cyanosilylation reactions using a continuous flow setup. [source]


Surface Functionalization of Fe3O4 Magnetic Nanoparticles via RAFT-Mediated Graft Polymerization

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 19 2006
Wen-Cai Wang
Abstract Summary: Surface functionalization of Fe3O4 magnetic nanoparticles (MNP) via living radical graft polymerization with styrene and acrylic acid (AAc) in the reversible addition-fragmentation chain transfer (RAFT)-mediated process was reported. Peroxides and hydroperoxides generated on the surface of Fe3O4 nanoparticles via ozone pretreatment facilitated the thermally initiated graft polymerization in the RAFT-mediated process. A comparison of the MNP before and after the RAFT-mediated process was carried out using transmission electron microscopy (TEM) analysis, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). Gel permeation chromatography (GPC) was used to determine the molecular weight of the free homopolymer in the reaction mixture. Well-defined polymer chains were grown from the MNP surfaces to yield particles with a Fe3O4 core and a polymer outer layer. The resulting core,shell Fe3O4 - g -polystyrene and Fe3O4 - g -poly(acrylic acid) (PAAc) nanoparticles formed stable dispersions in the organic solvents for polystyrene (PS) and PAAc, respectively. Schematic illustration of thermally induced graft polymerization of styrene and AAc with the ozone-treated Fe3O4 MNP. [source]


Kinetics and Modeling of Vinyl Acetate Graft Polymerization from Poly(ethylene glycol)

MACROMOLECULAR REACTION ENGINEERING, Issue 4 2008
Xiaoxiang Zhu
Abstract A kinetic model for the graft polymerization of VAc from PEG was developed using the method of moments. Experiments were carried out to verify the model. The effect of various parameters, such as initiator concentration, temperature, and PEG molecular weight on the polymerization kinetics was examined. Polymerization rate, grafting efficiency, graft copolymer molecular weight, and PEG grafted ratio were measured. The model was in good agreement with the experimental data. No gel effect was observed at the studied PEG/VAc weight ratio of 1:1. The chain transfer constant to PEG was correlated to be . The model was also applied in a semi-batch reaction and compared with the experimental results. [source]


Novel negatively charged tentacle-type polymer coating for on-line preconcentration of proteins in CE

ELECTROPHORESIS, Issue 4 2009
Liang Xu
Abstract A novel negatively charged tentacle-type polymer-coated capillary column was fabricated and applied for on-line extraction and preconcentration of proteins. The polymer coating was prepared by glycidyl-methacrylate graft polymerization in a silanized capillary column and the following sulfonic acid group functionalization. It had high surface area and offered high phase ratio for protein adsorption. In addition, the polymer-coated capillary column provided more stable EOF than a bare uncoated capillary. These features of the polymer coating facilitated the extraction of proteins through electrostatic interactions. This was used to extract proteins. The extracted analytes were then desorbed and focused by EOF in the direction opposite to the sample injection flow for subsequent CE. With this procedure, over 1500-fold sensitivity enhancement was realized for myoglobin (MB) as compared with a normal capillary zone electrophoresis. By comparison of the peak areas of the enriched protein, it was found that the polymer-coated column could capture proteins about 30 times more than the uncoated column. In addition, the separation of a protein mixture containing 0.4,,g/mL of MB and 0.4,,g/mL of insulin was demonstrated by the on-line preconcentration and electrophoretic separation with the polymer-coated column. [source]


Thermally Responsive Biomineralization on Biodegradable Substrates,

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2007
J. Shi
Abstract Biomineralization offers an elegant example of how nature can design complex, hierarchical, and structurally/morphologically controllable materials. In this work, the surface of bioactive substrates prepared from poly(L -lactic acid) and reinforced with Bioglass are modified by the graft polymerization of poly(N -isopropylacrylamide), (PNIPAAm) after plasma activation. It is found that such treatment, together with temperature, could trigger the formation of apatite on the biodegradable substrate upon immersion in simulated body fluid above the PNIPAAm lower critical solution temperature (LCST); in contrast, no apatite is formed at room temperature. A control experiment on a material that is not subjected to surface treatment does not show any evidence of mineral deposition at the two analyzed temperatures. This "smart" biomineralization concept is combined with patterning methodologies to control the microstructure of the surface onto which PNIPAAm is grafted. In this case, the apatite is formed at 37,C in the modified regions. We suggest that this concept could be extended in the biomimetic production of other minerals, where it would be triggered by another kind of stimulus (e.g., pH or ionic strength) in substrates with more complex geometries. [source]


Plasma-induced graft polymerization of poly(ethylene glycol) on poly(methyl methacrylate) surfaces for improving antistatic property

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2010
Yanlin Wei
Abstract Ar plasma-induced graft polymerization of poly(ethylene glycol) (PEG) on Ar plasma pretreated poly(methyl methacrylate) (PMMA) surfaces was carried out to improve the antistatic properties. The surface composition and microstructure of the PEG-grafted PMMA surfaces from plasma induction were characterized by attenuated total reflectance Fourier transfer infrared (ATR-FTIR) spectroscopy, water contact angles (CA), and atomic force microscopy (AFM) measurements. The measurements revealed that the antistatic properties can be remarkably improved with the surface resistivity of PEG-grafted PMMA surface decreasing significantly by 3,6 orders of magnitude, with the optimum condition for polymerization grafted onto the Ar plasma pretreated PMMA surface being 40 W for RF power and 3 min for glow discharge time. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]


Chemical modification of polyethersulfone nanofiltration membranes: A review

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009
B. Van der Bruggen
Abstract Polysulfone (PS) and poly(ether)sulfone (PES) are often used for synthesis of nanofiltration membranes, due to their chemical, thermal, and mechanical stability. The disadvantage for applying PS/PES is their high hydrophobicity, which increases membrane fouling. To optimize the performance of PS/PES nanofiltration membranes, membranes can be modified. An increase in membrane hydrophilicity is a good method to improve membrane performance. This article reviews chemical (and physicochemical) modification methods applied to increase the hydrophilicity of PS/PES nanofiltration membranes. Modification of poly(ether)sulfone membranes in view of increasing hydrophilicity can be carried out in several ways. Physical or chemical membrane modification processes after formation of the membrane create more hydrophilic surfaces. Such modification processes are (1) graft polymerization that chemically attaches hydrophilic monomers to the membrane surface; (2) plasma treatment, that introduces different functional groups to the membrane surface; and (3) physical preadsorption of hydrophilic components to the membrane surface. Surfactant modification, self-assembly of hydrophilic nanoparticles and membrane nitrification are also such membrane modification processes. Another approach is based on modification of polymers before membrane formation. This bulk modification implies the modification of membrane materials before membrane synthesis of the incorporation of hydrophilic additives in the membrane matrix during membrane synthesis. Sulfonation, carboxylation, and nitration are such techniques. To conclude, polymer blending also results in membranes with improved surface characteristics. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]


Preparation and applicability of functionalized polyethylene with an ethylene/1,7-octadiene copolymer

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008
Eun-Soo ParkArticle first published online: 3 JUN 200
Abstract The copolymerization of ethylene and 1,7-octadiene was carried out to synthesize polyethylene with unreacted vinyl groups. The prepared copolymer [poly (ethylene- co -1,7-octadiene) (PEOD)] was epoxidized with peracetic acid, m -chloroperbenzoic acid, or formic acid/H2O2. Of these, peracetic acid gave the best results. Epoxidized PEOD was subjected to a reaction with 2-mercaptobenzimidazole and poly(L -lactic acid). The bromination of PEOD was also performed in the presence of a Br2/HBr solution at room temperature. The brominated poly(ethylene- co -1,7-octadiene) (PEOD-Br) was used as a macroinitiator for atom transfer radical polymerization. The polymerization of styrene, butyl methacrylate, and glycidyl methacrylate was performed in bulk or solution at 120C with a PEOD-Br/CuBr/2,2,-dipyridyl initiator system. The thermal properties of the graft copolymers and the efficiency of the graft polymerization were investigated. These graft copolymers have potential applications as interfacial modifiers. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


Physicochemical and biological evaluation of plasma-induced graft polymerization of acrylamide onto polydimethylsiloxane

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008
A. Parvin
Abstract Polydimethylsiloxane (PDMS) rubbers exhibit good mechanical properties for biomedical and industrial applications, but their inherently high hydrophobicity limits biomedical applications of this material despite its favorable mechanical properties. In this work, surface modification of PDMS by radio-frequency glow discharge and subsequently graft polymerization of acrylamide was studied. PAAm-grafted, oxygen plasma-treated, and control (untreated) PDMS rubbers were characterized using attenuated total reflectance Fourier transform infrared, scanning electron microscopy, dynamic mechanical thermal analyses, zeta potential, and contact angle techniques. Fibroblast (L929) cell attachment and growth onto these surfaces were examined by optical microscopy. The data from in vitro assays showed that cell attachment onto control surface was very negligible while significant cell attachment and growth was observed onto oxygen plasma-treated and PAAm-grafted PDMS surfaces. The method developed in this work offers a convenient way of surface modifications of biomaterials to improve attachment of cells onto substrates. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [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 2007
Libin 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]


Urease immobilization on an ion-exchange textile for urea hydrolysis

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2006
Kyeong-Ho Yeon
Abstract Ion-exchange textiles are used as organic supports for urease immobilization with the aim of developing reactive fibrous materials able to promote urea removal. A non-woven, polypropylene-based cation-exchange textile was prepared using UV-induced graft polymerization. Urease was covalently immobilized onto the cation-exchange textile using three different coupling agents: N -(3-dimethylaminopropyl)- N,-ethylcarbodiimide hydrochloride (EDC), N -cyclohexyl- N,-(b -[N -methylmorpholino]ethyl)carbodiimide p -toluenesulfonate (CMC), and glutaraldehyde (GA). The immobilized biocatalyst was characterized by means of FT-IR spectrometry, SEM micrographs, dependence of the enzyme activity on pH and temperature, and according to the kinetic constants of the free and immobilized ureases. The biotextile prepared with EDC in the presence of N -hydroxysuccinimide performs best. The optimum pH was 7.2 for the free urease and 7.6 for the immobilized ureases. The reactivity was maximal at 45 C for free urease, 50 C for biotextiles prepared using EDC or CMC, and 55 C for biotextiles prepared with GA. The activation energy for the immobilized ureases was 4.73,5.67 kcal mol,1, which is somewhat higher than 4.3 kcal mol,1 for free urease. The urea conversion for a continuous-flow immobilized urease reactor is nearly as good as a continuously stirred tank reactor having a much longer residence time, suggesting that the packed bed reactor had sufficient diffusive mixing and residence time to reach nearly optimal results. Urease immobilized on a biotextile using EDC has good storage and operational stability. Copyright 2006 Society of Chemical Industry [source]


High throughput synthesis and screening of new protein resistant surfaces for membrane filtration

AICHE JOURNAL, Issue 7 2010
Mingyan Zhou
Abstract A novel high throughput method for synthesis and screening of customized protein-resistant surfaces was developed. This method is an inexpensive, fast, reproducible and scalable approach to synthesize and screen protein-resistance surfaces appropriate for a specific feed. The method is illustrated here by combining a high throughput platform (HTP) approach together with our patented photo-induced graft polymerization (PGP) method developed for facile modification of commercial poly(aryl sulfone) membranes. This new HTP-PGP method was validated by comparison with our previous published results obtained using a bench-scale filtration assay of six well-studied monomers. Optimally-performing surfaces for resisting a model protein, bovine serum albumin (BSA), were identified from a library of 66 monomers. Surfaces were prepared via graft polymerization onto poly(ether sulfone) (PES) membranes and were evaluated using a protein adsorption assay followed by pressure-driven filtration. Bench-scale verification was conducted for selected monomers using HTP-PGP method; a good correlation with HTP-PGP results was found. 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]


Microwave-assisted graft polymerization of ,-caprolactone onto magnetite

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2009
Alexandrina Nan
Abstract The graft polymerization of ,-caprolactone (,-CL) onto magnetite was carried out under microwave irradiation in the presence of tin(II) 2-ethylhexanoate. The molar ratio of ,-CL to tin(II) 2-ethylhexanoate was 300, whereas the molar ratio of ,-CL to magnetite was 5. The chemical structures of the obtained poly(,-caprolactone) coated magnetic nanoparticles were characterized by FTIR and XPS spectroscopy. These magnetic-polymer hybrid nanostructures were further investigated by X-ray diffraction and magnetization measurements. The morphology of the magnetic core-shell nanostructures were determined by TEM. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5397,5404, 2009 [source]


Anionic grafting polymerization of propylene sulfide onto human hair in water

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2006
Hisatoyo Morinaga
Abstract Natural human hair was modified by the graft polymerization of propylene sulfide in an aqueous medium. The amount of the polymer grafted onto the reduced hair was 0.15,0.19 g on 1.0 g of hair. The grafted polymer was isolated by the hydrolysis of the hair in the polymer-grafted hair under basic conditions and was confirmed to be poly(propylene sulfide) by 1H NMR, 13C NMR, and Fourier transform infrared spectra. The number-average molecular weights of the isolated polymers from the grafted products were 10,000,12,000. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3778,3786, 2006 [source]


Reversible addition,fragmentation chain-transfer graft polymerization of styrene: Solid phases for organic and peptide synthesis

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2002
Leonie Barner
Abstract The ,-initiated reversible addition,fragmentation chain-transfer (RAFT)-agent-mediated free-radical graft polymerization of styrene onto a polypropylene solid phase has been performed with cumyl phenyldithioacetate (CPDA). The initial CPDA concentrations range between 1 10,2 and 2 10,3 mol L,1 with dose rates of 0.18, 0.08, 0.07, 0.05, and 0.03 kGy h,1. The RAFT graft polymerization is compared with the conventional free-radical graft polymerization of styrene onto polypropylene. Both processes show two distinct regimes of grafting: (1) the grafting layer regime, in which the surface is not yet totally covered with polymer chains, and (2) a regime in which a second polymer layer is formed. Here, we hypothesize that the surface is totally covered with polymer chains and that new polymer chains are started by polystyrene radicals from already grafted chains. The grafting ratio of the RAFT-agent-mediated process is controlled via the initial CPDA concentration. The molecular weight of the polystyrene from the solution (PSfree) shows a linear behavior with conversion and has a low polydispersity index. Furthermore, the loading of the grafted solid phase shows a linear relationship with the molecular weight of PSfree for both regimes. Regime 2 has a higher loading capacity per molecular weight than regime 1. 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4180,4192, 2002 [source]


Self-initiating performance of maleic anhydride on surface photografting polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2001
Jian-Ping Deng
Abstract Maleic anhydride (MAH) was photografted onto low-density polyethylene (LDPE) films with a grafting efficiency of about 70% in the absence of a photoinitiator. The self-initiating performance was attributed to a mechanism of abstracting hydrogen atoms from LDPE chains by excited MAH dimers. The supporting experimental results were as follows: (1) the far-UV radiation (200,300 nm) was indispensable for the graft polymerization and 2) the crosslinking reaction of LDPE inevitably accompanied the grafting of MAH. In addition, the initiation performance of MAH was further confirmed by surface photografting of acrylic acid in the presence of MAH, where MAH was used as the photoinitiator. 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3246,3249, 2001 [source]


Preparation of a sorbitol methacrylate grafted silica as stationary phase for hydrophilic interaction chromatography

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2008
Jonas Persson
Abstract A new highly hydrophilic stationary phase based on graft polymerization of sorbitol methacrylate from the surface of Kromasil silica particles is described. Polymerization was initiated by thermal cleavage of tert -butyl hydroperoxide covalently attached to the silica particle surface. Due to the highly amphiphilic properties of the monomer, an extensive search was needed to find solvent conditions that enabled surface-initiated polymerization. This was finally solved by using a mixture of solvents that only partially dissolved the monomer. The graft polymerization was confirmed by Fourier transform infrared spectroscopy and elemental analysis. The resulting stationary phase was evaluated by HPLC and exhibited a selectivity markedly different from that of commercially available columns and of neat silica. [source]


Chromatographic separation of cytidine triphosphate from fermentation broth of yeast using anion-exchange cryogel

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 4 2008
Lianghua Wang
Abstract A novel separation method was developed to isolate directly cytidine triphosphate (CTP) from fermentation broth of yeast using anion-exchange supermacroporous cryogel. The anion-exchange cryogel with tertiary amine groups was prepared by graft polymerization. The breakthrough characteristics and elution performance of pure CTP in the cryogel bed were investigated experimentally and the CTP binding capacity was determined. Then the separation experiments of CTP from crude fermentation broth of yeast using the cryogel column were carried out using deionized water and 0.01 M HCl as washing buffer, respectively. The chromatographic behavior was monitored and analyzed. The purity and concentration of the obtained CTP in these processes were determined quantitatively by HPLC. The maximal purity of CTP obtained at the condition of 0.01 M HCl as washing buffer and 0.5 M NaCl in 0.01 M HCl as elution buffer reached 93%. [source]


A Novel N -Succinylchitosan- graft -Polyacrylamide/Attapulgite Composite Hydrogel Prepared through Inverse Suspension Polymerization

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2007
Ping Li
Abstract A novel N -succinylchitosan- graft -polyacrylamide/attapulgite composite hydrogel was prepared by using N -succinylchitosan, acrylamide and attapulgite through inverse suspension polymerization. The result from FTIR spectra showed that OH of attapulgite, OH and NHCO of N -succinylchitosan participated in graft polymerization with acrylamide. The introduced attapulgite could enhance thermal stability of the hydrogel. Scanning electron microscopy observation indicates that the composite hydrogel has a microporous surface. The volume ratio of heptane to water, weight ratio of acrylamide to N -succinylchitosan and attapulgite content have great influence on swelling ability of the composite hydrogel. The composite hydrogel shows higher swelling rate and pH-sensitivity compared to that of without attapulgite. [source]


Post-Synthesis Functionalization of (Meth)acrylate Based Monoliths via Electron Beam Triggered Graft Polymerization

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2008
Matthias J. Beier
Abstract Porous polymeric monoliths were prepared via electron beam triggered free radical polymerization of (meth)acrylates. Post-synthesis functionalization of these supports was accomplished via electron beam initiated free radical graft polymerization of methacryloyl-substituted NHC precursors. The grafted precursors were converted into the corresponding copper complexes. Cu-loadings were between 1.3 mg,,g,1 and 1.5 mg,,g,1. These supported catalysts were used in selected CO hydrosilylation and cyanosilylation reactions using a continuous flow setup. [source]


Surface Functionalization of Fe3O4 Magnetic Nanoparticles via RAFT-Mediated Graft Polymerization

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 19 2006
Wen-Cai Wang
Abstract Summary: Surface functionalization of Fe3O4 magnetic nanoparticles (MNP) via living radical graft polymerization with styrene and acrylic acid (AAc) in the reversible addition-fragmentation chain transfer (RAFT)-mediated process was reported. Peroxides and hydroperoxides generated on the surface of Fe3O4 nanoparticles via ozone pretreatment facilitated the thermally initiated graft polymerization in the RAFT-mediated process. A comparison of the MNP before and after the RAFT-mediated process was carried out using transmission electron microscopy (TEM) analysis, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). Gel permeation chromatography (GPC) was used to determine the molecular weight of the free homopolymer in the reaction mixture. Well-defined polymer chains were grown from the MNP surfaces to yield particles with a Fe3O4 core and a polymer outer layer. The resulting core,shell Fe3O4 - g -polystyrene and Fe3O4 - g -poly(acrylic acid) (PAAc) nanoparticles formed stable dispersions in the organic solvents for polystyrene (PS) and PAAc, respectively. Schematic illustration of thermally induced graft polymerization of styrene and AAc with the ozone-treated Fe3O4 MNP. [source]


Kinetics and Modeling of Vinyl Acetate Graft Polymerization from Poly(ethylene glycol)

MACROMOLECULAR REACTION ENGINEERING, Issue 4 2008
Xiaoxiang Zhu
Abstract A kinetic model for the graft polymerization of VAc from PEG was developed using the method of moments. Experiments were carried out to verify the model. The effect of various parameters, such as initiator concentration, temperature, and PEG molecular weight on the polymerization kinetics was examined. Polymerization rate, grafting efficiency, graft copolymer molecular weight, and PEG grafted ratio were measured. The model was in good agreement with the experimental data. No gel effect was observed at the studied PEG/VAc weight ratio of 1:1. The chain transfer constant to PEG was correlated to be . The model was also applied in a semi-batch reaction and compared with the experimental results. [source]


Synthesis of sub-micrometer core,shell rubber particles with 1,2-azobisisobutyronitrile as initiator and deformation mechanisms of modified polystyrene under various conditions

POLYMER INTERNATIONAL, Issue 10 2009
Rujun Dai
Abstract BACKGROUND: Sub-micrometer core-shell polybutadiene- graft -polystyrene (PB- g -PS) copolymers with various ratios of polybutadiene (PB) core to polystyrene (PS) shell were synthesized by emulsion grafting polymerization with 1,2-azobisisobutyronitrile (AIBN) as initiator. These graft copolymers were blended with PS to prepare PS/PB- g -PS with a rubber content of 20 wt%. The mechanical properties, morphologies of the core-shell rubber particles and deformation mechanisms under various conditions were investigated. RESULTS: Infrared spectroscopic analysis confirmed that PS could be grafted onto the PB rubber particles. The experimental results showed that a specimen with a ,cluster' dispersion state of rubber particles in the PS matrix displayed better mechanical properties. Transmission electron micrographs suggested that crazing only occurred from rubber particles and extended in a bridge-like manner to neighboring rubber particles parallel to the equatorial plane at a high speed for failure specimens, while the interaction between crazing and shear yielding stabilized the growing crazes at a low speed in tensile tests. CONCLUSION: AIBN can be used as an initiator in the graft polymerization of styrene onto PB. The dispersion of rubber particles in a ,cluster' state leads to better impact resistance. The deformation mechanism in impact tests was multi-crazing, and crazing and shear yielding absorbed the energy in tensile experiments. Copyright 2009 Society of Chemical Industry [source]


Study of oxidation after monoacrylate grafting on polyethylene

POLYMER INTERNATIONAL, Issue 8 2008
Ourida Iguerb
Abstract BACKGROUND: The surface properties of high-density polyethylene and linear low-density polyethylene were modified by grafting urethane monoacrylate monomer under UV irradiation. This graft polymerization was carried out on native substrates and on substrates pre-treated by wet oxidation, for different oxidation times. RESULTS: As the urethane monacrylate layer is crosslinked, its grafting efficiency was checked by dissolving the polyethylene substrates in hot toluene. Grafting was evidenced by Fourier transform infrared spectroscopy of the obtained residues, which showed that both the characteristic urethane acrylate (3350 cm,1) and polyethylene (2920, 730 and 720 cm,1) bands were observable for any polyethylene oxidation time. For an oxidation time longer than 10 hours, acrylate grafting was homogeneous and the grafted surface was smooth with a roughness of less than 10 nm. In addition, X-ray photoelectron spectroscopy analysis of the residues revealed that O/C had an average value of 0.19, which is lower than the value corresponding to pure acrylate (0.42), whereas N/C had an average value of 0.068, also lower than that of pure acrylate (0.09), thus confirming the grafting. CONCLUSION: A urethane monoacrylate layer was grafted on native and oxidized polyethylene films. For highly oxidized films, the grafted surfaces are smooth and homogeneous. Copyright 2008 Society of Chemical Industry [source]


A facile approach to surface graft vinyl acetate onto polyolefin articles

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2004
Lin Tan
Abstract A facile and environment friendly approach was developed to graft vinyl acetate (VAc) onto plastic articles in an aqueous solution using tert -butyl alcohol (TBA) as a compatiblizer and benzoyl peroxide (BPO) as an initiator. In a novel setup, excessive monomer suspended in a water phase, VAc could be conveniently grafted on the model substrate of low-density polyethylene (LDPE) film and the graft percentage (GP) could be developed up to 7.3%. Reaction temperature could increase GP significantly, while adding monomer over a critical volume did not influence GP. By adding some paradioxybenzene, i.e. 0.06,0.08% in VAc phase, homopolymer PVAc could be avoided practically, while graft polymerization proceeded favorably in aqueous solutions. It was proved by attenuated total reflection-infrared (ATR-IR) spectroscopy that grafted VAc was located mainly at the surface of the LDPE film and hydrophilic nature of both grafted and alcoholyzed films were improved via contact angle measurements. Copyright 2004 John Wiley & Sons, Ltd. [source]


Modified chitosan III, superabsorbency, salt- and pH-sensitivity of smart ampholytic hydrogels from chitosan-g-PAN

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 4 2004
G. R. Mahdavinia
Abstract Polyacrylonitrile (PAN) grafted chitosan was prepared by ceric-initiated graft polymerization of acrylonitrile onto chitosan in a homogenous medium. The copolymer chitosan-g-PAN product was then hydrolyzed to yield a novel smart hydrogel (H-chitoPAN) with superabsorbing properties. The influence of add-on values as well as temperature and time of hydrolysis of the initial chitosan-g-PAN on swelling behavior of the hydrogel was evaluated in water and various salt solutions. The swelling kinetics of the superabsorbing hydrogel was studied as well. The hydrogels exhibited ampholytic and pH-sensitivity characteristics. Several sharp swelling changes were observed in lieu of pH variations in a wide range (pH 2,13). The swelling variations were explained according to swelling theory based on the hydrogel chemical structure. Superabsorbency, pH- and salt-sensitivity of the chitosan-based hydrogel was briefly compared with the classical starch-based superabsorbent, H-SPAN. The pH-reversibility and on,off switching behavior of the intelligent H-chitoPAN hydrogels makes them good candidates for considering as potential drug carries. Copyright 2004 John Wiley & Sons, Ltd. [source]