Synthesis of Alkylphosphazene High Polymers via the Polymerization of Monoalkylpentachlorocyclotriphosphazenes

A new class of high molecular weight poly(organophosphazenes) of general formula [-(N=PC12)2-N=PClR-]n (VIII), where R = CH3, C2H5, n-C3H7, or n-C4H9, have been prepared by the thermal polymerization of monoalkylpentachlorocyclotriphosphazenes, N3P3C16R (VII). These are among the first high molecular weight polyphosphazenes with side groups linked directly to the skeleton through C-P bonds. Hydrolytically stable, elastomeric derivatives of formula [-N=P(OR')2)2-N=P(OR,)R-]n, were obtained by a replacement of the chlorine atoms in VIII with trifluoroethoxy or phenoxy groups. Bulky alkyl groups, such as i-C3H7 or t-C4H9, retard the polymerization process and sensitize the system to decomposition reactions during polymerization. The structures of the polymers were deduced by comparisons with cyclic trimeric phosphazene model compounds of formulas N3P3(OCH2CF3)5R and N3P3(OC6H6)6R, where R is CH3, C2H5, n-C3H7, n-C4H9, i-C3H7, or t-C4H9.