Network formation and swelling behavior of photosensitive poly(vinyl alcohol) gels prepared by photogenerated crosslinking

Poly (vinyl alcohol) with pendent styrylpyridinium groups (SbQ) is insolubilized by photoirradiation. An association takes place in SbQ groups. The association of polymer chains becomes marked with increasing the number of SbQ groups. Mainly intermolecular crosslinks were formed. Transparent and homogeneous macrogels consisting of several intermolecular 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 in conversion of photodimerization of SbQ groups, x=0.27-0.58. The water uptake after swelling of the gels in water increased 6-27 times compared to the original weight at pH=7. The higher the degree of photocrosslinking, the lower was the degree of swelling. The water diffusion coefficients, 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 get increased discontinuously about 10-fold for the 99% saponified PVA with 0.096 mol% SbQ and 51% water (49% acetone). The acetone concentration at the transition decreased with increasing the degree of saponification of the PVA.