Polynorbornenes bearing pendent cyclotriphosphazenes with oligoethyleneoxyside groups: Behavior as solid polymer electrolytes

Three different polynorbornenes (PNB) with pendent cyclotriphosphazene side units that bear different short-chain oligoethyleneoxy side groups were sy nthesized via ring-opening metathesis polymerization (ROMP). Polymers with methoxyethoxy (-OCH2CH2)(n)OCH3 (n = 1); di(ethylene glycol) methyl ether ( n = 2), and tri(ethylene glycol) methyl ether (n = 3) were synthesized and characterized by multinuclear NMR, GPC, DSC, and elemental analysis. The so lid polymers were complexed with LiSO3-CF3 and LiN(SO2CF3)(2) (10-60% molar ratios), and the ionic conductivities were measured by impedance analysis as a function of temperature. The polymers with methoxpethoxy side units sh owed no detectable ambient temperature conductivities within the limitation s of the impedance analyzer. The conductivities of the other polymer electr olytes increased as the concentration of salt was increased, with similar m aximum conductivities found for the di(ethylene glycol) and tri(ethylene gl ycol) systems (2.1 x 10(-5) S/cm at 30 degreesC with the use of 40 mol % Li N(SO2CF3)(2) in both cases). The conductivities showed non-Arrhenius temper ature dependence. No melting or crystallization transitions were detected a t temperatures above 25 degreesC for any of polymer-salt complexes tested. Modification of one polymer with -O(CH2CH2O)(3)CH3 side chains was carried out by epoxidation of the backbone C=C bonds.