CATIONIC MECHANISM FOR THE RING-OPENING POLYMERIZATION OF PHOSPHAZENES.

The polymerization of cyclophosphazenes to linear high polymers appears to proceed through mechanism that involves ionization of halogen atoms from phosphorus, followed by cationic attack by a phosphazenium ion on other trimeric or tetrameric molecules. These reactions involve ring-ring and ring-chain equilibria that are sensitive to the nature of the side groups. In addition, the presence of cyclosiloxanes in the polymerization system generates a series of phosphazenesiloxane interactions that reinforce the evidence for a cationic polymerization mechanism for phosphazenes.