Effects of incorporating acrylolsobutyl polyhedral oligomeric silsesquioxane on the properties of P(N-isopropylacrylamide-co-poly(ethylene glycol) diacrylate) hybrid hydrogels

A novel system for enhancing the properties of P(N-isopropylacrylamide-co-poly(ethylene glycol)diacrylate) (P(NIPAM-co-PEGDA)) temperature-sensitive hybrid hydrogels by incorporating acrylolsobutyl polyhedral oligomeric silsesquioxane (MAPOSS) was developed in this study. Inorganic/organic hybrid P(NIPAM-co-PEGDA) hydrogels based on MAPOSS were synthesized via free radical polymerization. Environmental scanning electron microscopy images showed that hydrogels with different feed ratios exhibited significant changes in the porous structure and average pore size. The heterogeneous and irregular network was caused mainly by MAPOSS aggregation. The rigid cage-like nanostructure of MAPOSS had dual opposite effects on polymer thermal properties; this effect was proven through differential scanning calorimetry and thermogravimetric analysis. The mechanical behaviors of the swollen hydrogels investigated through compression test showed that MAPOSS incorporation enhanced the yield strength. Swelling, deswelling and reswelling behaviors of hydrogels with different feed ratios were systematically examined and compared. The increase in MAPOSS provided the hydrogels with improved deswelling rate because of its cage-like nanostructure and hydrophobicity.