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 × 10 4 with polydispersities of 1.06−1.39). The diblock copolymers, {[N PCl 2 ] n [N PR(R‘)] m }, were synthesized by the cationic condensation polymerization of the phosphoranimines, PhCl 2 P NSiMe 3, Me(Et)ClP NSiMe 3, Me 2 ClP NSiMe 3, Ph 2 ClP NSiMe 3, and PhF 2 P NSiMe 3, at 35 °C initiated from the “living” end unit of poly(dichlorophosphazene), [Cl−(PCl 2 N) n -PCl 3 + PCl 6 - ] which was itself formed by the polymerization of Cl 3 P NSiMe 3 with small amounts of PCl 5 initiator in CH 2 Cl 2 at 25 °C. Halogen replacement reactions through the use of NaOCH 2 CF 3 and/or NaOCH 2 CH 2 OCH 2 CH 2 OCH 3 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, −{CH 2 NH(CF 3 CH 2 O) 2 P−N−PCl 3 + PCl 6 - } 2, first with Cl 3 P NSiMe 3 and second with Me(Et)ClP NSiMe 3, followed by halogen replacement with NaOCH 2 CF 3, to yield the triblock {[(Et)MeP N] m [(CF 3 CH 2 O) 2 P N] n −P(OCH 2 CF 3 ) 2 NHCH 2 CH 2 NH−(CF 3 CH 2 O) 2 P−[N P(OCH 2 CF 3 ) 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.