Synthesis and characterization of temperature sensitive poly(organophosphazene) hydrogels

Poly(organophosphazene)s bearing a hydrophilic group, 2-(2-methoxyethoxy)ethoxy and a Hydrophobic group such as methyl ester of alanine, 2,2,2-trifluoroethoxy, benzyloxy and p-(2-(2methoxyethoxy)ethoxyphenyl)phenoxy were synthesized and characterized by NMR spectroscopy, differential scanning calorimeter, gel permeation chromatography, and elemental analysis. These polymers were crosslinked by irradiating UV light in the presence of benzophenone or irradiating gamma ray (3M rad). Gamma radiation crosslinked the polymers but significant decomposition took place simultaneously. Polymers crosslinked by UV irradiation formed integrate hydrogels when swollen with water. Polymers containing hydrophobic groups in high fractions formed hydrogels without crosslinking. All the hydrogels prepared in this study had lower critical solution temperatures as the hydrogels became cloudy as the temperature was raised. The volume change at the clouding point varied depending on the nature of the side groups, composition, and the amount of water in the hydrogel. The volume change at the clouding point was negligible for most hydrogels investigated in this study.