Synthesis of trifluoromethyl- and methylphosphazene polymers: differences between polymerization and initiator/terminator properties

A new polyphosphazene, [N=PPh(CF₃)]_n, has been prepared via the PCl₅-induced cationic polymerization of Me₃SiN=P(CF₃)(Ph)Br. In addition, the cationic route has been used to produce [N= PPh(Me)]_n with controlled molecular weights and narrow polydispersities. By contrast, the new monomer Me₃SiN=P(t-Bu)(Ph)F failed to polymerize under any conditions but was used as an initiator and terminator to prepare both mono- and ditelechelic polymers. This monomer was also used to prepare [F(Ph)(t-Bu)P=N(PCl₂=N)P(t-Bu)(Ph)F]⁺, which was used as a substrate for reactions with alkoxy and aryloxy groups to yield the hydrolytically stable materials, [R(Ph)(t-Bu)P=N(PR₂=N)P(t-Bu)(Ph)R₂].