Synthesis and characterization of acrylic acid-based SiO2 nanocomposite hydrogels

Acrylic acid (AA) nanocomposite hydrogels (NCH) containing different kinds of SiO2 nanoparticles were prepared by way of free radical polymerization. The polymerization conditions were optimized considering the initiator and monomer concentrations in the mixture, as well as the reaction temperature and time. SiO2 nanoparticles were used in original (neutral), NH2 modified (hydrophilic) and perlite forms. Nanocomposite hydrogels that contain NH2 modified nano-SiO2 were found to present swelling values higher than those of the original acrylic acid nanocomposite hydrogel and the nanocomposite hydrogel that contain original SiO2. AA-perlite nanocomposite hydrogels were used to achieve the best thermal stability, although the perlite-doped hydrogels exhibit less swelling due to the large particle size of perlite and its lower SiO2 content. FESEM and mapping analyses were conducted to verify the incorporation of SiO2 nanoparticles into the hydrogel structure. Amorphous structures were determined by an XRD analysis. Thermal stability of hydrogels was measured by TG-DTA. The thermal stabilities of NH2-modified SiO2- and perlite-doped nanocomposite hydrogels were found to be higher than those of plain hydrogel and original SiO2-doped nanocomposite hydrogels.