Synthesis of Mixed Ladder-Like Polysilsesquioxanes by Copolymerization of 2-(3,4-Epoxycyclohexyl)ethyltrimethoxysilane and Dodecyltrimethoxysilane

Abstract

Epoxycyclohexyl- and dodecyl-bearing ladder-like polysilsesquioxanes (EDLASQs) are synthesized through the hydrolysis and co-condensation of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (ECTMS) and dodecyltrimethoxysilane (DTMS). Such copolymerization reactions are traditionally conducted in tetrahydrofuran and water containing K2CO3 as catalyst. The differing water compatibilities of the two monomers cause their reaction rates to differ drastically, making their random copolymerization impossible. In this work, we demonstrate that sodium dodecyl sulfate, a surfactant, can be used to improve water dispersion in monomers, thus increasing the area of the monomer/water interfaces and the reaction rates of the more hydrophobic DTMS monomer. This study presents results of polymerization kinetics from varying conditions and compositions as well as characterization data for the synthesized EDLASQs. Cured coatings of EDLASQs at E/D molar ratios of 8/1 and 6/1 exhibit both high hardness (> 1.0 GPa) and enhanced water repellency. The proposed method should be useful for synthesizing other co-LASQs.