Polymers with Sulfur(VI)−Nitrogen−Phosphorus Backbones: Synthesis, Characterization, and Properties of Atactic Poly[(amino)thionylphosphazenes]

Aminolysis of the halogenated poly(thionylphosphazene) [NSOCl(NPCl 2 ) 2 ] n ( 2a ), which possesses a novel S(VI)−N−P backbone, with a series of primary amines NH 2 R (R = Me, Et, n Pr, allyl, n Bu, n Hex, and Ph) afforded the hydrolytically stable poly[(amino)thionylphosphazenes] [NSO(NHR){NP(NHR) 2 } 2 ] n 4 ( a, R = Me; b, R = Et; c, R = n Pr; d, R = allyl; e, R = n Bu; f, R = n Hex; g, R = Ph) in which both the chlorine substituents at the phosphorus center and at sulfur were replaced. Treatment of 2a with a mixture of amines, NH 2 R (R = allyl and n Bu), yielded a series of mixed substituent copolymers 5a − 5c of which 5a and 5b were thermally and UV cross-linkable. These new polymers were structurally characterized by 31 P, 1 H, and 13 C NMR and IR spectroscopy and by elemental analysis. The stereochemistry of the poly[(amino)thionylphosphazenes] was investigated by 31 P NMR which indicated the polymers are atactic. Molecular weights of the polymers 4a − 4g and 5a − 5c were in the range M w = 5.0 × 10 3 to 1.3 × 10 5, M n = 3.3 × 10 3 to 7.4 × 10 4 according to GPC analysis in THF versus polystyrene standards. An absolute value of M w = 1.0 × 10 5 was obtained by low-angle laser light scattering for 4e, which was approximately double that obtained by GPC ( M w = 4.9 × 10 4 ). The thermal transition behavior of the polymers was investigated by DSC. Glass transition temperatures ( T g 's) of the poly[(amino)thionylphosphazenes] 4a − 4g and 5a − 5c were in the range of −40 to +82 °C. No melt transitions were detected and wide-angle X-ray scattering studies also indicated that poly[(amino)thionylphosphazenes] were amorphous. TGA analysis showed that the poly[(amino)thionylphosphazenes] were stable to weight loss up to 200−250 °C under nitrogen at a heating rate of 10 °C/min.