Synthesis and Characterization of Phosphazene Di- and Triblock Copolymers via the Controlled Cationic, Ambient Temperature Polymerization of Phosphoranimines

An advanced process for the synthesis of polyphosphazenes with controlled architectures has been investigated. By this method, a wide range of well-defined phosphazene di- and triblock copolymers with controlled molecular weights and narrow polydispersities have been synthesized (M n up to 4.8 × 104 with polydispersities of 1.06−1.39). The diblock copolymers, {[NPCl2] n [NPR(R‘)] m }, were synthesized by the cationic condensation polymerization of the phosphoranimines, PhCl2PNSiMe3, Me(Et)ClPNSiMe3, Me2ClPNSiMe3, Ph2ClPNSiMe3, and PhF2PNSiMe3, at 35 °C initiated from the “living” end unit of poly(dichlorophosphazene), [Cl−(PCl2N) n -PCl3 +PCl6 -] which was itself formed by the polymerization of Cl3PNSiMe3 with small amounts of PCl5 initiator in CH2Cl2 at 25 °C. Halogen replacement reactions through the use of NaOCH2CF3 and/or NaOCH2CH2OCH2CH2OCH3 on the diblock copolymers yielded fully organo-substituted macromolecules. In addition, the diblock copolymer {[NPMe(Et)] n [NPMe(Ph)] m } was formed by the block copolymerization of the two different organophosphoranimines. Triblock species were produced by the reaction of the “living” difunctional initiator, −{CH2NH(CF3CH2O)2P−N−PCl3 +PCl6 -}2, first with Cl3PNSiMe3 and second with Me(Et)ClPNSiMe3, followed by halogen replacement with NaOCH2CF3, to yield the triblock {[(Et)MePN] m [(CF3CH2O)2PN] n −P(OCH2CF3)2NHCH2CH2NH−(CF3CH2O)2P−[NP(OCH2CF3)2] n [NPMe(Et)] m }. The evidence for the formation of the di- and triblock copolymers includes NMR, GPC, elemental analysis, and solubility data.