Polymerization of hexamethylcyclotrisiloxane with a biscatecholsiliconate. I. Nature of polymerization

Abstract

AbstractPolymerization behavior of hexamethylcyclotrisiloxane (D3) in toluene solution with the use of benzyltrimethylammonium bis(o‐p;henylenedioxy)phenylsiliconate as a catalyst, dimethyl sulfoxide as promoter, and adventitious moisture as initiator was investigated. The polymerization system gives a linear difunctional polymer, HO(Me2SiO)xH, with a molecular weight which is inversely proportional to the amount of water reacted rather than to the amount of catalyst employed. The polymerization in the presence of H2O gives rise to molecular weight distributions very close to Poisson distributions. The normalized experimental GPC curve agrees very well with the theoretical GPC curve calculated from the polymerization scheme: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm H}_2 {\rm O} + ({\rm Me}_2 {\rm SiO})_3 \to {\rm HO}({\rm Me}_2 {\rm SiO})_3 {\rm H}} \\ {{\rm HO(Me}_{\rm 2} {\rm SiO)}_{\rm 3} {\rm H} + {\rm N(Me}_{\rm 2} {\rm SiO)}_{\rm 3} \to {\rm HO}({\rm Me}_2 {\rm SiO})_{3(n + 1)} {\rm H}} \\ \end{array} $$\end{document} Polymerization carried out in the combined presence of H2O and ROH, where R is Me or Me3Si, gives rise to bimodal molecular weight distributions. The resulting polymers consist of HO(Me2SiO)2xH and RO(Me2SiO)xH. The molecular weight of the former is twice that of the latter, and their proportion depends on the ratio of H2O to ROH. The system is a special type of “living” polymer.