Abstract
This study is to elucidate the process of network formation of a photosensitive poly (vinyl alcohol) with pendant styrylpyridinium groups. The fluorescence intensity ratio, I510 (excimer) /I427 (monomer) for the model compound as well as the 4-styrylpyridinium compound in solutions rapidly increases above a concentration of 5-8 X 10-2mol 1-1, whereas the values of surface tension decrease rapidly. The compounds in aqueous solution associate to form pre-micellar aggregates. In PVA-SbQ aqueous solution, the I510/I427 increases with increasing number of SbQ groups, and mainly intermolecular excimer is formed at a polymer concentration above 1.1g dl-1.
From observation on the UV-visible spectra of films (4μm) prepared by the solvent evaporation of 7wt% PVA-SbQ aqueous solution, the lower the drying temperature the higher is the probability of formation of dimers. This result suggests that the formation of ground-state aggregates or dimers is induced by slow-converting hydrophilic SbQ groups into hydrophobic SbQ groups.
The films having SbQ groups give a higher Tg than that of a PVA film because of an increase of molecular packing density of amorphous regions. The reason is believed to be caused by the formation of aggregates, and the tendency becomes progressively higher as the content of SbQ groups increases.
