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)2PNSiMe3 (R = Ph,
MeOPh, C10H7, BOC−NH−CH2CH2, t-BuMe2SiO(CH2)5, C8H11, and CH2CH−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)2PN]
n
−P(OCH2CF3)3OR, were prepared by terminating living poly(dichlorophosphazene) chains,
[Cl3PN−(Cl2PN)
n
−PCl3]+[PCl6]-, with these alkoxy or aryloxy phosphoranimines. Alternatively,
monotelechelic polyphosphazenes were produced through the termination of the polymer [(CF3CH2O2)3PN−(Cl2PN)
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.
A series of poly(fluoroalkoxyphosphazenes) containing a mixture of 2,2,3,3,4,4,5,5-octafluoropentoxy and 2,2,2-trifluoroethoxy substituents was synthesized. The series included polymers with 25-94% incorporation of the trifluoroethoxy substituent, as well as single-substituent polymers with 100% octafluoropentoxy or trifluoroethoxy side groups. Polymers were analyzed by multinuclear NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis, and were subjected to limiting oxygen index and microtensile testing. It was found that the T g and T d values among the cosubstituted polymers varied little with changes in composition, but the mechanical properties varied over a wide range.
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