Gelation-induced phase separation of poly(vinyl alcohol) in mixed solvents of dimethyl sulfoxide and water

Takahashi, Nobuaki; Kanaya, Toshiji; Nishida, Koji*; Kaji, Keisuke*

Time-resolved light scattering measurements have been performed on poly(vinyl alcohol) (PVA) in mixed solvents of dimethyl sulfoxide (DMSO) and water with various mixing ratios after quenching from 100C to 25C to examine physical gelation process. A broad scattering peak characteristic to phase separation appeared in the light scattering profiles after a certain incubation time () and the peak position moved to higher with annealing time. The results contradict the theoretical predictions and experimental observations for usual phase separation systems, suggesting effects of gelation (or network formation) on the phase separation. The growth kinetics significantly depend on the mixing ratio of DMSO and water, showing that the solvent quality is also a factor to affect the phase separation kinetics during the physical gelation process. The unusual phase separation kinetics is discussed in terms of gelation-induced phase separation.