GRAFT COPOLYMERIZATION OF VINYL ACETATE AND VINYL ACETATEMETHYL METHACRYLATE ONTO CELLULOSIC MATERIALS CONTAINING CARBONYL AND CARBOXYL GROUPS

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Graft copolymerization of vinyl acetate (VAc) and vinyl acetate-methyl methacrylate (MMA) mixtures onto cellulosic materials containing carbonyl and carboxyl groups were carried out using ceric salt as initiator.
Graft copolymerization of vinyl acetate:
The per cent grafting reached a maximum at a ceric salt concentration of approximately 2 mmol/l, and decreased in the order; cotton linter>periodate-oxidized cellulose>nitrogen dioxide-oxidized cellulose. The per cent grafting increased with monomer concentration in the absence of nitric acid. The initial rate of polymerization increased with reaction time and temperature, and the rate of increment decreased after 30-60 min, because the rate of termination of growing chains is higher than that of initiation. The per cent grafting and the number of apparent grafted chains decreased with increasing functional group (carbonyl and carboxyl) contents, or with decreasing the degree of polymerization in cellulosic materials. From these results, it is deduced that the grafting starts more easily at the hydroxyl groups at C(2) or C(3) of anhydro glucose units than at C(1) of the reducing end groups of cellulose molecules.
Graft copolymerization of vinyl acetate-methyl methacrylate:
The total conversion and the per cent grafting increased with methyl methacrylate content in the feed, and decreased in the order; cotton linter>period ate-oxidized cellulose>none.
The monomer reactivity ratios r₁ (MMA) and r₂ (VAc) obtained for ungrafted copolymers were as follows:
r₁=0.71, r₂=0.29 in the presence of cotton linter,
r₁=1.20, r₂=0.20 in the presence of HIO₄-oxidized cellulose,
r₁=1.86, r₂=0.03 in the absence of cellulose. From these results, it is supposed that the addition of MMA to VAc growing radicals occurs more easily in the absence of cellulosic materials than in the presence of cellulosic materials.