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.