Chemical Structure of Poly(Vinyl Alcohol)-Methyl Methacrylate Graft Copolymer Prepared by Pre-Irradiatflon Technique

Poly(vinyl alcohol) (PVA) films were pre-irradiated in air to a dose of 1.0;(106r and graft copolymerization f methyl methacrylate (MMA) onto the films was carried out in methanol solution of the monomer which contained trichloroethylene to control the branch length. The graft copolymer was isolated from the grafting product by alternate extraction of the homoPMMA and the ungrafted PVA. The PVA part of the isolated graft copolymer was acetylated to make better the compatibility between the backbone and the branch and then fractionated into 13 fractions by addition of n-hexane to benzene solution of the ace-tylated graft copolymer. After acetyl groups in the fractionated graft copolymers were converted to hydroxyl groups again, 1,2-glycol bonds of backbone PVA was cleaved with periodic acid to separate the branch from the backbone polymer. The molecular weights of fractionated graft copolymers and the separated branches were measured by osmometry after acetylation of the PVA part. The chemical composition of each fraction was deter-mined by hydrolysis of acetyl groups in the graft copolymer. From the result obtained, it was found that the number of branch is only one per each graft copolymer molecule, while the backbone is formed from several mother PVA molecules, which are crosslinked. The chain length of homopolymer formed in the interior of the film was found to be appro-ximately equal to that of the branch