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Grafting Yield (grafting + yield)

Distribution by Scientific Domains

Polymers and Materials Science	100%

Selected Abstracts

Methacryloxyethyl phosphate-grafted expanded polytetrafluoroethylene membranes for biomedical applications

POLYMER INTERNATIONAL, Issue 12 2005
Edeline Wentrup-Byrne
Abstract Expanded polytetrafluoroethylene (ePTFE) membranes were modified by graft copolymerization with methacryloxyethyl phosphate (MOEP) in methanol and 2-butanone (methyl ethyl ketone (MEK)) at ambient temperature using gamma irradiation. The effect of dose rate (0.46 and 4.6 kGy h,1), monomer concentration (1,40 %) and solvent were studied and the modified membranes were characterized by weight increase, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). XPS was used to determine the % degree of surface coverage using the CF (ePTFE membrane) and the CC (MOEP graft copolymer) peaks. Grafting yield, as well as surface coverage, were found to increase with increasing monomer concentration and were significantly higher for samples grafted in MEK than in methanol solution. SEM images showed distinctly different surface morphologies for the membranes grafted in methanol (smooth) and MEK (globular), hence indicating phase separation of the homopolymer in MEK. We propose that in our system, the non-solvent properties of MEK for the homopolymer play a more important role than solvent chain transfer reactions in determining grafting outcomes. Copyright © 2005 Society of Chemical Industry [source]

Electrical properties of modified-grafted polypropylene

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007
Naeem M. El-Sawy
Abstract The electrical properties of polypropylene (PP), grafted polypropylene (PP- g -PVP), and modified-grafted PVP with ,-cyano-,-(2-thienyl) crotononitrile were investigated. Also, the electrical characteristic of the modified-grafted PVP subjected to ,-irradiation (60 kGy) was studied. The results show that the , of trunk polymer undergoing different degree of grafting generally increases as function of the grafting yield. The grafting yield between 64.1 and 149% resulted in a progressive decrease in ,E, value. Inclusion of sulfur-containing substrate in different films, having various grafting yields, leads to both increase and decrease in , values. A significant increase in , values is observed upon inclusion of sulfur-containing substrate having maximum grafting yield (149%). These changes are accompanied by fluctuation in , values. The exposure of sulfur-containing substrate in grafting film to a dose of 60 kGy results in a significant decrease in ,E, values for the films undergoing a grafting yield between 64.1 and 149%. The observed changes in ,E, of different films investigated could be attributed mainly to corresponding changes in , values. The observed improvement in electrical properties is mainly because of possible increase in concentration of charge carrier and/or their mobilities. The scanning electron micrographs of some selected films show significant changes in the morphology of the films investigated due to changing the grafting yield, inclusion of sulfur-containing substrate, and exposure to ,-irradiation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3797,3803, 2007 [source]

Synthesis of comb polymers via grafting-onto macromolecules bearing pendant diene groups via the hetero-Diels-Alder-RAFT click concept

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2010
Antoine Bousquet
Abstract Comb polymers were synthesized by the "grafting-onto" method via a combination of Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization and the hetero-Diels-Alder (HDA) cycloaddition. The HDA reactive monomer trans, trans-hexa-2,4-dienylacrylate (ttHA) was copolymerized with styrene via the RAFT process. Crosslinking was minimized by decreasing the monomer concentration,whilst keeping monomer to polymer conversions low,resulting in reactive backbones with on average one reactive pendant diene groups for 10 styrene units. The HDA cycloaddition was performed between the diene functions of the copolymer and a poly(n -butyl acrylate) (PnBA) prepared via RAFT polymerization with pyridin-2-yldithioformate, which can act as a dienophile. The coupling reactions were performed within 24 h at 50 °C and the grafting yield varies from 75% to 100%, depending on the number average molecular weight of the PnBA (3500 g mol,1 < Mn < 13,000 g mol,1) grafted chain and the reaction stoichiometry. The molecular weights of the grafted block copolymers range from 19,000 g mol,1 to 58,000 g mol,1 with polydispersities close to 1.25. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1773,1781, 2010 [source]

Spectroscopic study of the penetration depth of grafted polystyrene onto poly(tetrafluoroethylene- co -perfluoropropylvinylether) substrates.

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2002

Abstract This study concerns the radiation grafting of styrene onto poly(tetrafluoroethylene- co -perfluoropropylvinylether) (PFA) substrates and the penetration depth of the graft. Grafting was obtained by the simultaneous irradiation method, and the spectroscopic analysis was made with the micro-Raman technique. Effects of grafting conditions such as the type of solvent, dose rate, and irradiation dose on the grafting yield were investigated. Of the different solvents used, the most efficient in terms of increasing grafting yield were dichloromethane, benzene, and methanol, respectively. A mixture of methanol and dichloromethane used as a solvent for styrene achieved a higher degree of grafting and concentration of grafted polystyrene onto the surface of PFA substrates than solutions of the monomer in the separate solvents. The degree of grafting increased with increasing radiation dose up to 500 kGy, stabilizing above this dose. However, the grafting yield decreased with an increase in the dose rate. The increase in the overall grafting yield was accompanied by a proportional increase in the penetration depth of the grafts into the substrate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3191,3199, 2002 [source]

Graft copolymerization of methyl acrylate onto cellulose initiated by potassium ditelluratoargentate(III)

POLYMER INTERNATIONAL, Issue 10 2004
Yinghai 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]

Comparative study of the radiation-induced grafting of styrene onto poly(tetrafluoroethylene- co -perfluoropropylvinyl ether) and polypropylene substrates.

POLYMER INTERNATIONAL, Issue 5 2003
I: Kinetics, structural investigation
Abstract A comparative study has been made of the radiation grafting of styrene onto poly(tetrafluoroethylene- co -perfluoropropyl vinyl ether) (PFA) and polypropylene (PP) substrates, using the simultaneous irradiation method. Effects of grafting conditions such as monomer concentrations, type of solvent, dose rate and irradiation dose on the grafting yield were investigated. Under the same grafting conditions it was found that a higher degree of grafting of styrene was obtained using a mixture of dichloromethane/methanol solvents for PFA and methanol for PP and the degree of grafting was higher in PP than in PFA at all doses. However, the micro-Raman spectroscopy analysis of the graft revealed that, for the same degree of grafting, the penetration depth of the grafted polystyrene into the substrate was higher in PFA than in PP substrates. In both polymers the crystallinity was hardly affected by the grafting process and the degree of crystallinity decreased slightly with grafting dose. The dependence of the initial rate of grafting on the dose rate and the monomer concentration was found to be 0.6 and 1.4 order for PFA and 0.15 and 2.2 for PP, respectively. The degree of grafting increased with increasing radiation dose in both polymers. However, the grafting yield decreased with an increase in the dose rate. The increase in the overall grafting yield for PFA and PP was accompanied by a proportional increase in the penetration depth of the graft into the substrates. Copyright © 2003 Society of Chemical Industry [source]

Electrical properties of modified-grafted polypropylene

Radiation-grafted ion-exchange membranes: Influence of the initial matrix on the synthesis and structure

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2001
Nadia Walsby
Abstract A series of commercial fluoropolymer films was irradiated with an electron beam, grafted with styrene, and sulfonated. The influence of the initial fluoropolymer on the grafting yields and the properties of the grafted and sulfonated membranes were investigated. The same synthesis procedure can be followed for most fluoropolymers and samples with a similar degree of grafting, and a homogenous polystyrene distribution can be prepared by varying the absorbed dose. The main difference among different fluoropolymer-based membranes is the water uptake from liquid water that has a roughly linear dependence on the crystallinity of the sample. The more amorphous the initial material, the greater the water uptake. Mechanical properties of the membranes at 50% relative humidity differ less than those of the starting materials and are comparable to those of Nafion® 105. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3008,3017, 2001 [source]

Grafting of functionalized silica particles with poly(acrylic acid)

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2006
Jarkko J. Heikkinen
Abstract Two different methods to graft silica particles with poly(acrylic acid) (PAA) were studied. In the first method PAA was reacted with 1,1,-carbonyldiimidazole to give functionalized PAA. The resulting activated carbonyl group reacted easily with 3-aminopropyl-functionalized silica at low temperatures. In the second method 3-glycidoxypropyl-functionalized silica particles were reacted directly with PAA by using magnesium chloride as a catalyst. Different molecular weights of PAAs were used in order to investigate the effect of molecular weight on grafting yields in both methods. The grafting yields were determined with thermogravimetric analysis (TGA). All products were also investigated with IR. The results showed that the yields of reactions performed at ambient temperature by using 1,1,-carbonyldiimidazole-functionalized PAA were the same as with a direct reaction of unfunctionalized PAA and 3-aminopropyl-functionalized silica performed at 153°C. Also in reactions between 3-glycidoxypropyl-functionalized silica and PAA the yields were satisfactory. Copyright © 2006 John Wiley & Sons, Ltd. [source]