Thermosensitive PNIPA-based organic-inorganic hydrogels

Thermosensitive organic-inorganic (O-I) hydrogels have been synthesized by modification of poly(N-isopropylacrylamide) (PNIPA) gels with silica from tetramethoxysilane (TMOS) or with (3-(methacryloyloxy)propyl]trimethoxysilane (MPTMOS). Inorganic silica and silsesquioxane domains were formed in situ by sol-gel process within the organic matrix. Two methods of PNIPA-based get synthesis have been employed-polymerization under homogeneous and heterogeneous conditions. The hybrid hydrogels swollen in water exhibited swelling transition around 32 degrees C. Introduction of the inorganic phase into the PNIPA gels resulted in faster deswelling kinetics and better mechanical properties of the gels prepared under homogeneous conditions. Further acceleration of deswelling and swelling kinetics was achieved by applying heterogeneous conditions of synthesis above the lower critical solution temperature.