THERMOREVERSIBLE GELATION OF POLY(VINYLIDENE FLUORIDE) IN GAMMA-BUTYROLACTONE SOLUTION

Poly(vinylidene fluoride) gels were formed in gamma-butyrolactone; the critical polymer concentration for gel formation was 4.5 g per 100 cm3. Gelation was caused by liquid-liquid phase separation, even if solid-liquid phase separation by crystallization occurred in the late stage of gelation, as shown by the formation of transparent gel, a relatively small enthalpy of gel formation and the existence of two types of crystal structures. In the dried gel films many spherulites connected by tie molecules were observed by scanning electron microscopy; the existence of such tie molecules is likely to make the formation of the gel films possible.