Overentrant Swelling Behaviour in Poly(potassium, 3-sulfopropyl acrylate-acrylic acid) Hydrogels

Polymer gels swell in suitable solvents but cannot dissolve because of their network structure. Gels can be classified into two main groups: hydrogels and organogels [1].When a polymer gel is placed in a swelling medium composed of two miscible solvents, several phenomena may be observeddepending on the polymer characteristics. Straightforward swelling and collapsing are the most usual behaviours, while co-solvency, co-nonsolvency, re-entrant and overentrant phenomena are moderately rare [2]. Overentrant is referred to an unusual swelling behaviour in which swelling in mixed solvents is higher than in the solventwhich has higher dielectric constant. Reentrant is referred to swelling behaviour in which swelling initially decreases withadding solvent with a lower dielectric constant and then increases with further addition of a same solvent. In the present work, we synthesized a series of copolymeric gels based on potassium, 3-sulfopropyl acrylate(KSPA) and acrylic acid(AA), and studied their swelling in water/organic solvent.