Poly[(aryloxy)phosphazenes] with Phenylphenoxy and Related Bulky Side Groups. Synthesis, Thermal Transition Behavior, and Optical Properties

The effect of steric hindrance on the synthesis of poly[(aryloxy)phosphazenes] that bear bulky aryloxy substituents is discussed. The syntheses of poly[(aryloxy)phosphazenes] with the general formula [NP(OAr)_x(OAr^//)y]_n'where OAr' and OAr” are phenoxy, 2-methylphenoxy, 4-methylphenoxy, 2-phenylphenoxy, 3-phenylphenoxy, 4-phenylphenoxy, 4-benzylphenoxy, 4-cumylphenoxy, and 4-tert-butylphenoxy and x + y= 2, are described. These polymers were prepared by the interaction of the corresponding sodium aryloxide with poly(dichlorophosphazene) in dioxane at 150 °C in an autoclave. This procedure allows the synthesis of poly [ (aryloxy) phosphazenes] with bulky side groups while avoiding equilibration depolymerization. The influence of side group structural parameters on the thermal transition behavior of the polymers is discussed. The refractive indices of the polymers were measured by using a modified critical angle method at X = 632 nm and were found to vary between 1.561 and 1.686.