Investigation of swelling and controlled-release behaviors of hydrophobically modified poly(methacrylic acid) hydrogels

Using hydrophobic acrylic acid-2-ethylhexyl ester (AAEHE) as a comonomer of methacrylic acid (MAA), a series of hydrophobically modified (HM) poly(methacrylic acid) (PMAA) (HMPMAA) hydrogels were prepared by UV solution copolymerization and studied as controlled-release matrices. The result indicates that swelling degree of the HMPMAA hydrogels can sensitively respond to change in pH. However, the presence of hydrophobic AAEHE segments influences swelling kinetics of PMAA hydrogel evidently. Using p-hydroxyanisole (PHAS) as a model molecule, controlled-release behaviors of the HMPMAA hydrogels were investigated. It is found that the presence of hydrophobic AAEHE segments can markedly slow down the release rate of PHAS from PMAA-based hydrogels regardless of pH 1.4 or 7.4.