Polyphosphazenes functionalized with sulfone or sulfoxide groups: Synthesis, characterization, and possible polymer electrolyte applications

A method for the introduction of sulfone or sulfoxide functional groups into the side groups of polyphosphazenes has been developed. This procedure involves the prior introduction of thioether-containing side groups into phosphazenes followed by oxidation of the sulfur atoms by H2O2 or m-chloroperbenzoic acid(MCPBA). This method was first explored at the level of model small molecule cyclic species as a prelude to the polymer oxidation reactions. The attractive forces generated by sulfone or sulfoxide functional groups produce alkyloxy-substituted polyphosphazenes with relatively high glass transition temperatures (up to +19 degrees C). The potential of these materials as polymer electrolytes, both in the solid state and in systems with added propylene carbonate, was explored by means of impedance analysis conductivity studies. The competition between the polymer and the solvent for lithium ions was also investigated.