pH-reversible hydrogels. IV. Swelling behavior of the 2-hydroxyethyl methacrylate-co-acrylic acid-co-sodium acrylate copolymeric hydrogels

A series of 2-hydroxyethyl methacrylate (HEMA) and sodium acrylate (SA50) c opolymeric gels were prepared from HEMA and the anionic monomer SA50 with v arious molar ratios. The influence of SA50 on the copolymeric gels on their swelling behavior in deionized water at different temperatures and various pH buffer solutions was investigated. Results indicated that the poly(2-hy droxyethyl methacrylate) (PHEMA) hydrogels exhibited an overshooting phenom enon in their dynamic swelling behavior. The maximum overshooting value dec reased with increasing of the temperature. The same results were also found in the HEMA/SA50 copolymeric gels with a lower SA50 content. On the contra ry, the overshooting phenomenon for HEMA/ SA50 copolymeric gels with a high er content of SA50 was exhibited only under higher temperature (over 35 deg reesC). These copolymer gels were used to assess drug release and drug deli very in this article. (C) 2001 John Wiley & Sons, Inc.