Ionic conductivity in polyphosphazene polymer electrolytes prepared by the living cationic polymerization

Two polyphosphazene-based electrolytes were synthesized. The first was the polymer electrolyte poly [bis(methoxy-ethoxy-ethoxy-) phosphazene] (MEEP) with lithium triflate, the second was sodium salt of sulfonated poly[bis(phenoxyethoxy)phosphazene] (PhEP) as a polyelectrolyte. The living cationic polymerization of the monomer Cl3P-NSi(CH3)(3) was used to obtain the polymer precursor poly(dichlorophosphazene). The final polymers were obtained from the precursor by nucleophilic substitution. The monomer was synthesized via a recently reported route. The emphasis lied on testing the accessability and properties of electrolyte materials obtained by the newer synthetic techniques. The chosen synthetic approach proved to be a suitable and straightforward access to functionalized polyphosphazenes and therefore to corresponding polymer-based electrolytes. The ionic conductivity was studied by impedance spectroscopy in the temperature range between 20 and 70degreesC. The temperature dependence of the conductivity of MEEP/LiCF3SO3 is described by the Vogel-Tamman-Fulcher (VTF) equation. At 25degreesC, its conductivity was 10(-5) S cm(-1). The conductivity of the sodium salt of sulfonated PhEP was especially sensitive to a changing water partial pressure and is useful as humidity-sensitive sensor. In the presence of a water-saturated atmosphere, sulfonated PhEP showed a conductivity of 4.7 x 10(-2) at 25degreesC. (C) 2004 Elsevier B.V. All rights reserved.