SYNTHESIS OF POLYPHOSPHAZENES WITH ISOTHIOCYANATO, THIOURETHANE, AND THIOUREA SIDE GROUPS

The isothiocyanatophosphazene, [NP(NCS)2]3, undergoes ring-opening polymerization when heated at temperatures above 100-degrees-C to form a low molecular weight polymer, [NP(NCS)2]n. the copolymerization of [NP(NCS)2]3 and [NPCl2]3 was examined, and mechanistic implications for cyclophosphazene polymerization are discussed. High molecular weight [NP(NCS)2]n was prepared by the metathetical exchange reaction of (NPCl2)n with potassium thiocyanate. Treatment of [NP(NCS)2]n with alcohols and amines to form thiourethane and thiourea derivatives was examined. Steric and electronic effects prevented full reaction of the isothiocyanato side groups with alcohols. However, thiourea derivatives, [NP-(NHCSNHR)2]n, were prepared by the reactions of [NP(NCS)2]n with amines. Mixed-substituent thiourethane and thiourea phosphazene polymers with trifluoroethoxy or 2-(2-methoxyethoxy)ethoxy cosubstituent groups were also synthesized. The characterization and properties of the thiourethane and thiourea phosphazene polymers are described.