Control of the Swelling Rate of Superporous Hydrogels

Abstract

Superporous hydrogels (SPHs) have a fast swelling property because of the presence of interconnected pores. While the fast swelling property is an advantage, sometimes it is necessary to control the swelling rate. A method of coating the SPH surface with a polymer layer was studied to control the swelling kinetics of SPHs in aqueous solutions. Poly(ethylene glycol-b-tetramethylene oxide) (PEGTMO), an amphiphilic block copolymer, dissolved in ethanol was used. The coating was done by dipping and equilibrium soaking in PEGTMO solutions. The delay in swelling of PEGTMO-coated SPHs was dependent on the PEGTMO concentration used. Poly(acrylamide-co-acrylic acid)-SPHs coated with a PEGTMO film showed lower hydrophilicity as measured by contact angle. SEM analysis revealed that the number of surface pores of SPHs was decreased by coating with PEGTMO. It appears that the PEGTMO coating reduced the surface hydrophilicity as well as the porosity, leading to slower swelling in aqueous solution.