PHOTO-RESPONSIVE HYDROGELS FOR POTENTIAL RESPONSIVE RELEASE APPLICATIONS

Two N-isopropylacrylamide hydrogels that include photoreactive azobenz ene groups were prepared, one copolymerized with monomer with an azobe nzene pendant group (4-methacryloylaminoazobenzene) and the other form ed with the crosslinker (4,4'-di(methacryloylamino)azobenzene. Azobenz ene is known to isomerize and to change its dimensions on UV irradiati on. Release of two model solutes (caffeine and poly(styrene sulfonic a cid)) from the hydrogels was measured upon UV irradiation. The results show that UV irradiation of hydrogels with azobenzene pendant groups increases the extent of release from the matrix, while irradiation of hydrogels with an azobenzene crosslinker results in a decrease.