POLYPHOSPHAZENES BEARING BRANCHED AND LINEAR OLIGOETHYLENEOXY SIDE-GROUPS AS SOLID SOLVENTS FOR IONIC-CONDUCTION

A new series of solid polymer electrolyte materials based on the poly( organophosphazene) system has been designed and synthesized. The new p olymers contain linear or branched oligoethyleneoxy side chains. The p olymers were characterized by P-31, C-13, and H-1-NMR spectroscopy, ge l permeation chromatography, differential scanning calorimetry, and el emental analysis. The ambient temperature (25 degrees C) ionic conduct ivities of the polymers complexed with lithium triflate were measured by complex impedance analysis. The polymers that bear linear oligoethy leneoxy side chains [NP{O(CH2CH2O)(n)CH3}(2)], have low glass transiti on temperatures that range from -84 to -75 degrees C. These polymers h ave properties that are similar to those of the classical counterpart poly [bis(2-(2-methoxyethoxy)ethoxy)phosphazene. They have low dimensi onal stabilities and undergo viscous flow even at room temperature. Th e polymers with branched oligoethyleneoxy side chains (podands) have s imilar glass transition temperatures, in the range of -82 to -79 degre es C. However, the bulk dimensional stabilities of the branched polyme rs are significantly higher than those of the corresponding linear sid e chain series. The branched side chain polymers resist viscous flow a nd readily form thin, free-standing films. The podand polymers also di ssolve lithium triflate to form ionically conducting materials with co nductivity levels similar to those of the polymers bearing linear side chains.