Synthesis of Poly(dichlorophosphazene) by the Melt Phase Polymerization of P-Trichloro-N-(dichlorophosphoryl)monophosphazene

A major barrier to commercialization of any of the many exciting applications of the poly(phosphazenes) has been the cost and ease of preparation of the most widely utilized starting polymer, poly(dichlorophosphazene) (Cl₂PN)_n (1). One attractive route is the thermal polycondensation reaction of P-trichloro-N-(dichlorophosphoryl)monophosphazene, Cl₃P=N–P(O)Cl₂ (2). We are reporting a modified bulk polymerization of 2 which represents a convenient route to laboratory scale amounts of (NPCl₂)_n with moderate molecular weights and polydispersity. GPC characterization data were obtained on the corresponding phenoxy derivatives, [(PhO)₂PN]_n. We also have developed a one pot synthesis of 1 from ammonium sulfate and phosphorus pentachloride which are the starting materials for the synthesis of 2 and examined the major variables, time and temperature, for this process. The resulting poly(phosphazene) exhibits more branching than the product of bulk polymerization of 1.