Synthesis of organic-inorganic hybrid gels by means of thiol-ene and azide-alkene reactions

Organic-inorganic hybrid gels have been synthesized from a multi-vinyl functional cyclic siloxane, 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (TVMCTS), or a cubic silsesquioxane, octavinyloctasilasesquioxane (PVOSS), and α,ω-dithiol compounds, 1,6-hexanedithiol (HDT), 1,10-decanedithiol (DDT), using thiol-ene reaction in toluene. The network structure of the resulting gels, mesh size and mesh size distribution, was quantitatively characterized by means of a scanning microscopic light scattering (SMILS). The gels obtained from TVMCTS-HDT formed homogeneous network structure with 1.5-1.6 nm mesh. Relaxation peaks derived from large clusters and/or micro gels were detected in the SMILS analysis of the TVMCTS-DDT, PVOSS-HDT, and PVOSS-DDT gels besides those from the small meshes. The organic-inorganic hybrid gels were also synthesized from TVMCTS, PVOSS with α,ω-diazide compounds, 1,6-hexanediazide (HDA), 1,10-decanediazide (DDA), using azide-alkene reaction in toluene. All the gels obtained with the azide-alkene reaction formed the homogeneous network structure. Enthalpy relaxation at the glass transition of the dried samples was detected by differential scanning calorimetry to study the network uniformity of the original gels. The gels synthesized by the azide-alkene reaction showed larger enthalpy than the gels synthesized by the thiol-ene reaction, indicating homogeneous network structure in the former gels.