Cationic Polymerization of Hexamethylcyclotrisiloxane in Excess Water

Ring-opening ionic polymerization of cyclosiloxanes in dispersed media has long been discovered, and is nowadays both fundamentally studied and practically used. In this short communication, we show some preliminary results on the cationic ring-opening polymerization of hexamethylcyclotrisiloxane (D-3), a crystalline strained cycle, in water. Depending on the catalyst or/and surfactants used, polymers of various molar masses are prepared in a straightforward way. Emphasis is given here on experiments conducted with tris(pentafluorophenyl)borane (BCF), where high-molar polymers were generated at room temperature. In surfactant-free conditions, mu m-sized droplets are stabilized by silanol end-groups of thus generated amphiphilic polymers, the latter of which precipitate in the course of reaction through chain extension. Introducing various surfactants in the recipe allows generating smaller emulsions in size with close polymerization ability, but better final colloidal stability, at the expense of low small cycles' content. A tentative mechanism is finally proposed.

Automated summary

This study presents preliminary results on cationic ring-opening polymerization of hexamethylcyclotrisiloxane (D-3) in water, with a focus on experiments conducted using tris(pentafluorophenyl)borane (BCF) as the catalyst. By using different catalysts and surfactants, polymers of various molar masses can be prepared in a straightforward manner. The presence or absence of surfactants influences the size and stability of the emulsions generated during the reaction process, with a tentative mechanism proposed for the observed phenomena.