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The photodimerization reaction of pendant styrylpyridinium (SbQ) groups in poly(vinyl alcohol), PVA, and poly(vinyl alcohol-b-acrylic acid) block copolymers, P(VA-b-AA), was evaluated by a spectrophotometric measure-ment. The thermal properties of polymer films were analyzed by evaluating the differential scanning calorimetiy (DSC) and the dynamic mechanical thermal analysis (DMA) curves.The degree of dimerization of SbQ groups during the photoreaction was ultimately inclined to constant at about 0.7mol% SbQ in both P(VA-b-AA)-SbQ and PVA-SbQ films. The rate of cyclodimer formation of SbQ groups depended on the pH in casting solution of films. The rate in a P(VA-b-AA)-SbQ film was faster than that in a PVA-SbQ film. The number of cross-linked SbQ groups per polymer chain, Nc, deviate from linearity with increasing the degrees of polymerization of PVAs. The numbers of cross-linked SbQ groups per vinyl alcohol repeat unit, Nu, have the highest value for the polymer with degrees of polymerization of 2500. The P(VA-b-AA)-SbQ film has higher dynamic storage modulus than that of a PVA-SbQ film. The free volume fraction of the amorphous region in a P(VA-b-AA)-SbQ film has larger than that in a PVA-SbQ film. The Tm decreased slightly with increasing the degree of polymerization of the PVAs. The films having higher degree of polymerization exhibited lower crystallinity. The degree of crystallinity in the films after photoinadiation was lower than that in the films before photoirradiation.

Reactivities and Thermal Mechanical Properties of Poly(vinyl alcohol) and Poly(vinyl-b-acrylic acid) with Pendant Styrylpyridinium Groups.