CATIONIC RING-OPENING POLYMERIZATION OF HEXAMETHYLCYCLODISILAZANE - GENERAL-ASPECTS AND TENTATIVE MECHANISMS

The ring-opening polymerization of hexamethylcyclodisilazane (D2NMe), initiated by methyl triflate in 1,2-dichloroethane, forms in the first , fast kinetic step both linear polymer and cyclic dimer (D4NMe). Subs equently a slow depolymerization process occurs leading to exclusively cyclotrisilazane (D3NMe). On the basis of kinetic measurements carrie d out using an adiabatic calorimetric technique and complementary expe riments, mechanisms of both propagation, cyclization and back-biting r eactions are proposed. The influence of the reaction temperature was a lso studied; it is demonstrated that, at low temperature, polymerizati on does not lead to cyclic oligomer formation. In such conditions, the polymerization presents a' living' character.