Facile preparation of pH-sensitive poly(acrylic acid-co-acrylamide)/SiO2 hybrid hydrogels with high strength by in situ frontal polymerization

A series of poly(acrylic acid-co-acrylamide) (PAA)/SiO 2 hybrid hydrogels were prepared by in situ frontal polymerization. It was found that the increase in the concentration of SiO 2 nanoparticles could lead to the increase in front velocity ( V f ) and the highest front temperature ( T max ). This may be attributed to the fact that SiO 2 nanoparticles could increase the liquid viscosity of reaction mixture. The obtained PAA/SiO 2 hybrid hydrogels were characterized by SEM and Fourier transform infrared spectroscopy spectrum and swelling measurements. The pH-sensitive swelling behaviors showed that the prepared PAA/SiO 2 hybrid hydrogel had high pH sensitivity in different pH buffer solutions. Mechanical property test indicated that the PAA/SiO 2 hybrid hydrogels exhibited a high compressive strength while remaining a high swelling radio (SR). The maximum of compressive strength and SR of the hybrid hydrogel may reach 42.6 kPa and 17.8, respectively, which was much higher than that of pure PAA hydrogel.