The Thermally-Induced Bulk Polymerization of Hexachlorocyclotriphosphazene to Polydichlorophosphazene by First-Principles Simulations

In this paper we report first principles calculations using the Car-Parrinello molecular dynamics approach in order to clarify the mechanism of the ring-opening polymerization of hexachlorocyclotriphosphazene, N3P3Cl6 to polydichlorophosphazene (NPCl2) (n) . In particular, we highlight the key role played by the cyclophosphazene phosphorus cation N3P3Cl5 (+) generated from the heterolytic cleavage of the P-Cl bond as the main component in the polymerization process. Moreover, the generation of the maximally localized Wannier functions, together with the Mulliken population analysis, allows us to clarify some basic issues of the investigated reaction. The activation energy, mainly due to the formation of phosphazenium cation, is found to be in good agreement with experiments. Structural and electronic analysis of the molecules involved is also reported.