Mesh size control of organic-inorganic hybrid gels by means of a hydrosilylation co-gelation of siloxane or silsesquioxane and α,ω-non-conjugated dienes

Abstract

Organic-inorganic hybrid gels have been synthesized by means of co-gelation of multi-functional cyclic siloxane, 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS), or cubic silsesquioxane, 1,3,5,7,9,11,13,15-octakis(dimethylsilyloxy) pentacyclo-[9,5,1,1,1,1]octasilsesquioxane (POSS), as crosslinking reagents with α,ω-non-conjugated dienes, a hexa-1,5-diene (HD) and deca-1,9-diene (DD) mixture, using hydrosilylation reaction with Pt catalyst. Network structures of the resulting co-gels have been quantitatively characterized by means of a novel scanning microscopic light scattering system. The feed ratio of HD to DD strongly affects the gelation and mesh size of the co-gels. The critical concentration of gelation has maximum values in the co-gelation with a feed ratio of [HD]/[DD] = 1. The mesh-size of the resulting co-gels underwent changes with the [HD]/ [DD] ratio in the feed, and the structure (geometry) of the crosslinking reagents affect the trend of the mesh size change. The TMCTS-HD/DD co-gel obtained with a feed ratio of [HD]/[DD] = 1, showed the minimum mesh size. Whereas the mesh size of the POSS-HD/DD co-gel increased with an increase of DD in the feed ratio. The mesh-size distribution of the co-gels was narrower than the gels synthesized from single α,ω-non- conjugated dienes. Co-gelation of a TMCT/POSS-DD system was also investigated, and the critical gelation concentration showed maximum values for the co-gelation with a feed ratio of [TMCTS]/[POSS] = 1. The mesh size of the co-gel increased with increasing POSS ratio in the feed. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.