The polymerization of [P(O2C12H8)(N3)] and the formation of soluble and insoluble poly(2,2′-dioxy-1,1′-biphenylphosphazene)

The phosphorus azide [P(O2C12H8)(N3)] [(O2C12H8) = 2,2′-dioxy-1,1′-biphenyl] undergoes a solid state polymerization at 30 °C giving a separable mixture of the polyphosphazene {[NP(O2C12H8)]}n with a Mw in the range of 104, together with a fraction of small and large cyclic spirophosphazene oligomers {[NP(O2C12H8)]}n, and an insoluble polymeric material with a very high char forming tendency, consisting very likely on a network of large interlooped cyclic oligomers and polymers of overall composition [NP(O2C12H8)]n. The reaction proceeds with smooth though irregular release of nitrogen at first but tending to abrupt accelerations ending in an explosion. The later outcome is more likely in scales of 10–50 g, and results in a decrease in the yield of the soluble polymer and a large increase in the yield of the polymeric matrix.