Poly[bis(adamantylamino-co-trifluoroethoxy)phosphazene], poly[bis(adamantyloxy-co-trifluoroethoxy)phosphazene] , and poly[bis(adamantylmethoxy-co-trifluoroethoxy)phosphazene] with different ratios of adamantyl to trifluoroethoxy groups were synthesized by macromolecular substitution. This work. was preceded by model compound studies with cyclophosphazene trimers and tetramers. Polymers in which all the side groups were adamantyl units could not be prepared because of the steric restrictions imposed by the side groups. However, the mixed-substituent polymers with trifluoroethoxy cosubstituents were accessible by sequential substitutions on poly(dichlorophosphazene). These reactions were complicated by some displacement of adamantyl groups by the second nucleophile-sodium trifluoro-ethoxide. The molecular and materials properties of the mixed-substituent polymers are described.