NETWORK FORMATION AND SWELLING BEHAVIOR OF PHOTOSENSITIVE POLY(VINYL ALCOHOL) GELS PREPARED BY PHOTOGENERATED CROSS-LINKING

Poly (vinyl alcohol) with pendent styrylpyridinium groups (SbQ) is ins olubilized by photoirradiation, An association takes place in SbQ grou ps. The association of polymer chains becomes marked with increasing t he number of SbQ groups. Mainly intermolecular crosslinks were formed. Transparent and homogeneous macrogels consisting of several intermole cular crosslinks are obtained. The proportion of the free water to the bound water in PVA-SbQ gels was 3.3-2.9 despite of the large change i n conversion of photodimerization of SbQ groups, x=0.27-0.58. The wate r uptake after swelling of the gels in water increased 6-27 times comp ared to the original weight at pH=7. The higher the degree of photocro sslinking, the lower was the degree of swelling. The water diffusion c oefficients, D, were (2.2-5.8)x10(-5) cm(2) s(-1) for a 88% saponified PVA with 1.3 mol% SbQ groups. The volume of the gel increased discont inuously about 10-fold for the 99% saponified PVA with 0.096 mol% SbQ and 51% water (49% acetone). The acetone concentration at the transiti on decreased with increasing the degree of saponification of the PVA.