The cyclic phosphazenes N3P3F6(CMe3), N3P3F6Ph, zion-gem-NaPaCUMea, non-gem-NaPaCUEta, (NPClMe)3, and (NPCIMeU have been polymerized to macromolecules of formula [(NPF2)2-NPFR]", [NPC12(NPC1R)2]", and (NPC1R)". Species (NPClMe)a and (NPClEt)a were copolymerized with (NPC12)3 to yield polymers of type [(NPCl2)x(NPClR)y]n. The halogen atoms in the high polymers were replaced by trifluoroethoxy groups to yield hydrolytically stable derivatives. The influence of the alkyl or aryl groups on the properties of the polymers is described. The new polymers are elastomers, with glass transition temperatures in the -40 to -60 °C range.The main method for the synthesis of stable polyphosphazenes involves the polymerization of hexachlorocyclotriphosphazene, (NPC12)3, to high molecular weight poly-(dichlorophosphazene), (NPC12)", followed by replacement of the halogen atoms in this polymer by alkoxy, aryloxy, or amino groups.1-4 In general, these polymers are microcrystalline materials if the side groups are OCH2CF3, OPh, or substituted phenoxy units and if only one type of side group is present along each chain. By contrast, polyphosphazenes with flexible side groups, such as OMe, OEt, or OCH2CH2OCH2CH2OCH3, are elastomers. However, polymers that bear two or more different fluoroalkoxy or aryloxy side groups attached to the same chain are elastomers.5-8 This is because the random distribution of different side groups along the chain prevents crystallization and allows the inherent flexibility of the polyphosphazene backbone to dominate the solid-state properties. Mixed-substituent fluoroalkoxyphosphazene polymers are used in technology as low-Tg solvent-, oil-, and oxidation-resistant elastomers.
