Raman and Brillouin scattering measurements on hybrid inorganic-organic materials obtained from tetraethoxysilane and methacrylic monomers

Raman and Brillouin spectroscopies have been used for characterizing hybrid inorganic-organic macromolecular materials obtained from the polymerization of 2-hydroxy ethyl methacrylate (HEMA) or methyl methacrylate (MMA), modified by silicon tetraethoxide (TEOS). Different molar ratios r = [TEOS]/[HEMA], with r varying from 0.5 to 5, and [TEOS]/[MMA] = 0.05 have been considered. The Raman data have provided a qualitative evaluation of the interaction between inorganic and organic components. The data of Brillouin scattering suggest that pure polymers are stiffer than the hybrids, almost irrespective of the inorganic compounds amount. The refractive index of the hybrids is lower than the pure polymer, even in case of small amounts of inorganic compound. The results are tentatively explained on the basis of the structural change in the polymeric network, due to the presence of the inorganic domains.