QUANTITATIVE-ANALYSIS ON SWELLING BEHAVIOR OF IONIC GELS IN THE MIXED-SOLVENTS

Phase transition was observed in HSMA/PVA IPN gels having ionizable gr oups with 3-dimensional network structure in the mixed solvents such a s water-methanol, water-acetone or water-ethanol. In order to analyze this phenomena quantitatively, two adjustable parameters related to ge l properties were determined from the model based on Tanaka theory. On e was the number of dissociated counterions per effective chain (f), t he other was the interaction parameters (chi(ij)) between gel and wate r. As increasing the composition of water, swelling of the gels occurs in the mixed solvent; the gel was shrunk instead when the water conte nt was decreased, which was reversible regardless of the path of swell ing and shrinking. A degree of swelling or shrinking of the gel was de pendent upon these chi(ij) and f of the gel. With smaller chi(ij) and larger f, more rapid phase transition was observed. Additionally, swel ling and shrinking behavior of the gel in system of two solvents and o ne polymer was influenced not only by chi(ij) between gel and solvents but also by chi(ij) between two solvents.