One-shot synthesis of a poly(N-isopropylacrylamide)/silica hybrid gel

Class I hybrid poly(N-isopropylacrylamide)/silica hydrogels, PNIPAM/SiO2, were prepared by a new one shot synthesis. In this approach, the free-radical polymerization of vinyl groups of N-isopropylacrylamide (NIPAM) and the hydrolysis-condensation of alkoxy groups of tetramethoxysilane (TMOS) are performed concomitantly using sodium persulfate and 3-(dimethylamino)-propionitrile, a well-known couple to initiate the organic polymerization. The cross-linker is N,N-methylenebisacrylamide. The kinetic study of mechanical properties from the sol-to-gel state for different ratios of TMOS/NIPAM was investigated by rheological ultrasonic measurements. The thermoresponse of hybrid materials was investigated by differential scanning calorimetry and the measurements showed that hybrid gels present a lower critical solution temperature, which is similar with one of single organic hydrogel.