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

A series of the 2-hydroxyethyl methacrylate/N,N'-dimethyl-(acrylamido propy l) ammonium propane sulfonate (HEMA/DMAAPS) copolymeric gels has been prepa red 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 sw elling ratio (Q(eq)), the PHEMA hydrogel exhibited a minimum Q(eq) at 55 de grees C, Then, the minimum Q(eq) was more obvious when higher zwitterionic monomer, DMAAPS, content was added into the HEMA/DMAAPS copolymeric gels. I n the saline solution, the swelling ratios of HEMA/DIMAAPS copolymer gels i ncreased rapidly with increasing concentration of the salt, and with smalle r 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 decreas es with increase in temperature. (C) 1999 Elsevier Science Ltd. All rights reserved.