Poly(2-hydroxyethyl methacrylate-co-sulfobetaine)s hydrogels: 3. Synthesis and swelling behaviors of the [2-hydroxyethyl methacrylate-co-N,N′-dimethyl (acrylamido propyl) ammonium propane sulfonate] hydrogels

Abstract

A series of the 2-hydroxyethyl methacrylate/N,N′-dimethyl-(acrylamido propyl) ammonium propane sulfonate (HEMA/DMAAPS) copolymeric gels has been prepared from various molar ratios of HEMA and the zwitterionic monomer DMAAPS. The influence of the amount of zwitterionic monomer in the copolymeric gels on the swelling behaviors in water, various saline solutions, and various temperatures was investigated. Results indicated that in the equilibrium swelling ratio (Qeq), the PHEMA hydrogel exhibited a minimum Qeq at 55°C. Then, the minimum Qeq was more obvious when higher zwitterionic monomer, DMAAPS, content was added into the HEMA/DMAAPS copolymeric gels. In the saline solution, the swelling ratios of HEMA/DMAAPS copolymer gels increased rapidly with increasing concentration of the salt, and with smaller ratio of charge/radius. In dynamic swelling behaviors, the PHEMA hydrogel (DM0) and the HEMA/DMAAPS copolymeric gels with lower DMAAPS content (DM1 and DM2) exhibited overshoot phenomena. The maximum overshoot value decreases with increase in temperature.