Formation Behavior and Optical Properties of Transparent Inorganic-Organic Hybrids Prepared from Metal Alkoxides and Polydimethylsiloxane

The formation behavior of the transparent inorganic-organic hybrids prepared from silanol-terminated polydimethylsiloxane (PDMS) and metal alkoxides of Al (III), Ti (IV), Zr (IV), Nb (V) and Ta (V) chemically modified with ethyl acetoacetate (EAcAc) has been investigated. EAcAc bonded to metal alkoxides remained in hydrolyzed solutions and gels to prevent the rapid growth of large inorganic particles. It is speculated that extremely small inorganic clusters are dispersed uniformly in PDMS, resulting in the transparent hybrids. The upper limit of M(OR)_n/PDMS ratio to obtain transparent hybrids was influenced by the inorganic source. As the number of remaining alkoxy groups in the modified alkoxide M(OR)_{n – x}(EAcAc)_x increased, the fabrication of transparent hybrids became difficult. The refractive index depended on the inorganic sources reflecting the difference in polarizability of the incorporated metallic ion and the molar volume of the hybrid. The refractive index increased in the order Al (III) < Zr (IV) Ti (IV) < Ta(V) Nb (V).