Reaction kinetics for the anionic ring-opening polymerization of tetraphenyltetramethylcyclo-tetrasiloxane using a fast catalyst system

It is well known that the rate of polymerization for an anionic mechanism is dependent on the ability of the bulk material or solvent system to disassociate the ion pair at the propagating chain red. In the anionic ring-opening polymerization of cyclic organosiloxanes in particular, the larger and softer the counter ion, the more rapid the reaction proceeds. A recently developed phosphazene catalyst system provides a large, soft counter ion relative to other traditional catalyst used for the polymerization of poly(demithylsiloxane) (PDMS). This novel catalyst system was used in this investigation for the ring-opening polymerization of tetraphenyltetramethylcyclo-tetrasiloxane and the reaction kinetics under buld and solution conditions were investigated. The nes catalyst system showed a dramatic increase in the rate of polymerization over the potassium hydroxide that is typicall used for this system.