Novel photo-reactive acrylamide-based copolymers instantly gave the sensitive stimuli-responsive hydrogels

Novel photo-cross-linkable polymers were synthesized for the preparation of the hydrogels with both pH- and temperature-responsive properties. Photo-reactive 4-aminobenzophenone (BP) was introduced into the side groups of poly(N-isopropylacrylamide-co-2-carboxyisopropylacrylamide). This starting copolymer was designed for the highly random sequences of comonomers. The introduction degree of BP was controlled by changing the ratio between the BP and the carboxyl groups. The cylinder-shaped hydrogel was easily prepared by UV irradiation for a few minutes. The photo-cross-linked hydrogels exhibited clear volume phase transitions in response to both pH and temperature changes and expected to be used for drug delivery systems.