Characterization and optical properties of sol-gel processed PMMA/SiO2 hybrid monoliths

Organic-inorganic hybrid monoliths consisting of poly(methyl methacrylate) and SiO₂ were synthesized by the sol-gel process. Three PMMA/TEOS ratios by weight were prepared, namely PMMA/TEOS = 80/20, 50/50 and 20/80. The effects of the ratio of PMMA/TEOS on thermal stability, microstructure, morphology and optical properties were systematically studied. In particular, scanning electron microscopy (SEM) demonstrated morphological variation corresponding to the degree of miscibility between organic and inorganic components. Energy dispersive spectroscopy (EDS) clearly revealed that the SiO₂ was more uniformly distributed in the hybrids with increasing PMMA content. The refractive index could be adjustable in the range of 1.474-1.486. The 80/20 monolith had the similar transparency to pure PMMA in the visible region and lower absorption than PMMA in the near infrared region, suggesting its potential applications for optical devices.