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SYNOPSISThe graft copolymerization of N-vinylpyrrolidone (VP) onto gelatin in aqueous medium, with a,d-azobisisobutylonitrile as initiator, has been studied. The effects of various reaction parameters such as temperature, reaction time, as well as the concentrations of initiator, monomer, and gelatin on the percentage of grafting and grafting efficiency were also studied. The chain-transfer constant of isopropanol in this system was calculated. Finally, the grafted samples were analyzed with IR, DSC, TEM, and SEM measurements. 0 1995 John

ABSTRACT:The graft copolymerization of N-vinylpyrrolidone (VP) onto gelatin was carried out by the following four different initiator systems: AIBN, K 2 S 2 O 8 , H 2 O 2 {Fe 2/ , and Ce 4/ {HNO 3 . The last one caused the monomer to lose the doublebond and polymerization ability due to the hydrolysis of the monomer. Using a,aazobisisobutyronitrile as an initiator, the graft copolymerization of gelatin and N-vinylpyrrolidone in aqueous medium was studied systematically. The relationships between the rate of grafting and the concentration of initiator, monomer, and gelatin were established experimentally. Meanwhile, the rate equation was also derived from the proposed reaction mechanism, and it was similar to the equation previously obtained experimentally. The apparent activation energies for homopolymerization ( E h ), graft copolymerization ( E g ), and over all polymerization (E p ) were calculated. The graft efficiency and molecular weight of the grafted PVP were measured by hydrolyzing the backbone with hydrochloric acid. The graft copolymers Gel-g-PVP were added into the coating films, and the physical properties of the films, such as hardening ability, dimensional stability, and wetting property were investigated.

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