Semi-interpenetrating polymer networks as solid polymer electrolytes: Effects of ion-dissociation, crosslink density and oligomeric entanglements on the conductivity behavior in poly(ethylene oxide)–polyurethane/poly(acrylonitrile) matrix

Abstract

The present study investigates into three aspects of tailoring and simple structural modifications on a promising solid polymer electrolyte system of poly(ethylene oxide)–polyurethane/poly(acrylonitrile) semi-interpenetrating polymer networks. Influence of the nature of salt solvated, cation/anion mobility, ion–polymer interaction and transient crosslink formation is evaluated using different solvated electrolytes and the conductivity achieved varied as LiClO4≥LiCF3SO3>NaBF4>NaClO4>KI. The role of optimum chain length between the crosslinks (crosslink density) necessary to attain better conductivity levels is appraised using PEG of different molecular weights (400, 2000, 4000, 10,000 and 35,000) for synthesis and the maximum conductivity was obtained for PEG-4000. The temperature dependence of ion conductivity shows an Arrhenius to VTF transition at ∼323K in these semi-IPNs, a general behavior independent of the nature of salt and the poly(ethylene glycol) chain length. Ternary composition of semi-IPN containing 30wt% PEGDME MW 500 yields a conductivity of ∼2×10−5Scm−1 at 35°C, an order of magnitude higher than that obtained without plasticizing component. VTF behavior is witnessed throughout the temperature window in the study for samples with oligomeric plasticization. Linear sweep voltammetry indicates significantly good electrochemical stability (∼4.6V) of the semi-IPN electrolyte matrix.