Ternary interpenetrating networks of polyurethane-poly(methyl methacrylate)-silica: Preparation by the sol–gel process and characterization of films

Novel organic/inorganic interpenetrating networks composed of polyurethane (PU), poly(methyl methacrylate) (PMMA) and silica generated from tetraethoxysilane (TEOS), were prepared by in situ bulk polymerization. Optically transparent films were successfully synthesized using 3-(trimethoxysilyl)propyl methacrylate (TMSPM) and isocyanatopropyl triethoxysilane (IPTES) as dual coupling agents. An experimental protocol was established to minimize undesirable side-reactions. According to infrared spectroscopic analysis and thermogravimetric studies of the hybrid materials, the degree of silica condensation was unfavorably affected by the presence of the organic components. Consequently, storage modulus (E′) at 25 °C, and hardness of the films decreased with increasing silica content.