Telechelic polyphosphazenes: Reaction of living poly(dichlorophosphazene) chains with alkoxy and aryloxy phosphoranimines

A modification of the method for synthesis of well-defined mono- and ditelechelic polyphosphazenes via the living, cationic polymerization of phosphoranimines has been developed. This process provides access to phosphazene block, comb, and graft copolymers that contain organic or organosilicon macromolecules. Several alkoxy and aryloxy phosphoranimines, RO(CF3CH2O)(2)P=NSiMe3 (R = Ph, MeOPh, C10H7, BOC-NH-CH2CH2, t-BuMe2SiO(CH2)(5), C8H11, and CH2=CH-C6H4), were synthesized via the reaction between a bromophosphoranimine and the appropriate sodium alkoxide or aryl oxide. These species are potential initiators or terminators, useful for the synthesis of telechelic polyphosphazenes with etheric linkages rather than the amino linkages used previously. Ditelechelic polymers, RO[(CF3CH2O)(2)P=N](n)-P(OCH2CF3)(3)OR, were prepared by terminating living poly(dichlorophosphazene) chains, [Cl3P=N-(Cl2P=N)(n)-PCl3](+)[PCl6](-), with these alkoxy or aryloxy phosphorandmines. Alternatively, monotelechelic polyphosphazenes were produced through the termination of the polymer [(CF3CH2O2)(3)P= N-(Cl2P=N)(n)-PCl3](+)[PCl6](-) with the appropriate alkoxy or aryloxy phosphoranimines. In all cases, hydrolytically stable telechelic polymers with controlled molecular weights and low polydispersities were obtained in good yield after macromolecular replacement of labile chlorine atoms with sodium trifluoroethoxide.