Copolycondensation of functional silanes and siloxanes in solution using tris(pentafl uorophenyl)borane as a catalyst in a view to generate hybrid silicones

Abstract

This paper proposes new ways of preparation of hybrid silicones, i.e. an alternated multiblock sequence of silicone and alkyl spacers, via a polycondensation process catalyzed by the tris(pentafl uorophenyl)borane, a water-tolerant Lewis acid, between methoxy and hydrogeno functionalized silanes and siloxanes at room temperature and in the open air. The protocol was first developed with model molecules which led to polydimethylsiloxane (PDMS) chains, in order to seize the best experimental conditions. Several factors were studied such as the contents of each reactants, the nature of the solvent or the rate of addition. The best conditions were then adapted to the synthesis of hybrid silicones, condensing alkylated oligocarbosiloxanes with methoxy or hydrogeno chain-ends and complementary small molecules. A systematic limitation in fi nal molar masses of hybrid silicones was observed and explained by the formation of macrocycles, which cannot redistribute or condense further while formed. © 2008 Springer Science+Business Media B.V.