Sol-gel derived polysiloxane-oxide materials:extent of phase interaction

Polymethylsiloxane-oxide hybrid materials can be easily prepared by co-hydrolysis of diethoxydimethylsilane, (DEDMS) and methyltriethoxysilane (MTES) and Ti, Zr and Al alkoxides. The molar ratio between precursors and the nature of metal alkoxides strongly influence the chemical reactions in solution and thus the chemical homogeneity of the gel network. This aspect depends on the degree of co-condensation obtained by the formation of oxygen bridged heterometallic bonds, and affects the structure and properties of polysiloxane-oxide materials. This paper presents the recent results obtained on polymethylsiloxane-oxide materials by equilibrium swelling experiments, dynamic mechanical thermal analysis (DMTA) and mechanical properties measurements. The results highlight the influence of nature and load of the metal oxide precursor on the extent of phase interaction in the hybrid gels. The ability to promote the silanol condensation in DEDMS-derived gels is pointed out by the determination of the soluble fraction of the hybrids and the average molecular weight of the polydimethylsiloxane chains.