Effect of baking treatment and materials composition on the properties of bulky PMMA–silica hybrid sol–gel materials with low volume shrinkage

Abstract

AbstractA series of bulky PMMA–silica hybrid sol–gel materials had been successfully prepared through the conventional HCl‐catalyzed sol–gel approach with 2‐hydroxyethyl methyl methacrylate (HEMA) as coupling agent under pumping pretreatment (i.e., exhaustive vacuum evacuation). In this work, the hydroxyl groups of HEMA monomers were first cohydrolyzed with various contents of tetraethyl orthosilicate (TEOS) to afford chemical bonding for the forming silica networks by removal of solvent and byproduct of sol–gel reactions through pumping pretreatment before gelation reactions. Subsequently, the resultant viscous solution was then copolymerized with methyl methacrylate (MMA) monomers at specific feeding ratios by using benzoyl peroxide (BPO) as free‐radical initiator. Eventually, transparent bulky organic–inorganic hybrid sol–gel materials loaded with different silica content were always achieved. The obtained bulky hybrid sol–gel materials were found to be transparent, crack‐free, and of relatively low volume shrinkages even in high silica content. The as‐prepared bulky hybrid sol–gel materials were then characterized through silicon element mapping studies of energy‐dispersive X‐ray (EDX) and transmission electron microscopy (TEM). Effect of heating process at 150°C for 5 h after polymerization and material composition on the thermal properties, mechanical strength, and optical clarity of a series of bulky PMMA–silica hybrid sol–gel materials was investigated and compared by thermogravimetric analysis (TGA), thermomechanical analysis (TMA), hardness test, dynamic mechanical analysis (DMA), and UV–vis transmission spectroscopy, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1151–1159, 2006