Synthesis and characterization of ionically conducting alkoxy ether/alkoxy mixed-substituent poly(organophosphazenes) and their use as solid solvents for ionic conduction

A series of mixed-substituent poly(organophosphazenes) with the general structure {NP[OCH₂CH₂OCH₂CH₂OCH ₃]_x[O(CH₂)_yCH₃] _2-x}_n, where x = 1 and y = 2-9 was synthesized. These polymers are candidates for use as solid polymeric, ionic conduction media. The polymers were characterized by ¹H, ¹³C, and ³¹P nuclear magnetic resonance spectroscopy, gel permeation chromatography, elemental microanalysis, infrared spectroscopy, and differential scanning calorimetry. The polymers were complexed with LiSO₃CF₃ and ambient temperature (25°C) ionic conductivity studies were performed with the use of complex impedance analysis. The effect of changes in the length of the alkyl component of the alkoxy groups on conductivity was examined. A maximum conductivity as a function of the concentration of lithium triflate was found for each system. The conductivity decreased with an increase in the alkyl group side-chain length. These polymers were compared to the polyphosphazene single-substituent polymer [NP(OCH₂CH₂OCH₂CH₂OCH ₃)₂]_n, as well as to the n-alkyloxy single-substituent polymers {NP[O(CH₂)_xCH₃]₂}_n, where x = 2-9.