Preparation and properties of novel photoluminescent thermosensitive hydrogels containing a pyrene group

1-Acrylamidopyrene (AAP) was synthesized for the first time in this study. A series of thermosensitive copolymeric hydrogels were prepared by copolymerization of AAP and N-isopropyl acrylamide (NIPAAm) by UV irradiation. The effect of AAP content in the copolymeric hydrogels on the swelling ratio, mechanical properties, and drug release behavior of the hydrogels was investigated. The swelling ratios decreased from 6.5 to 4.9 (g/g) when the AAP content in the copolymeric hydrogels increased from 0.1 to 0.9 mol% owing to their increasing hydrophobicity. In addition, the thermosensitive behavior obviously diminished with increasing AAP content in the copolymeric hydrogels, but the mechanical properties and cross-linking densities of the hydrogels swollen in ethanol solution were enhanced with increasing AAP content. The swelling ratios of the hydrogels in different solvents were varied with increasing AAP content. The result of caffeine release in the hydrogels showed that when the content of AAP in the hydrogel increased, the caffeine-loading amount decreased; however, their fractional release increased. The corresponding copolymers of the NIPAAm/AAP copolymeric hydrogels were synthesized. The UV absorbance and photoluminescent (PL) behavior of AAP, NIPAAm/AAP copolymeric hydrogels, and their corresponding copolymers in some solvents with different polarities were investigated.