Vibrational Spectroscopy Analysis of Ion Conduction Mechanism in Dispersed Phase Polymer Nanocomposites

A novel combination of dispersed phase polymer nanocomposite electrolyte based on PEO8-LiClO4 + x wt % nano-CeO2 has been investigated. A model for ion transport mechanism has been proposed to account for substantial enhancement of its electrical conductivity by similar to 2 orders of magnitude at low volume fraction of the filler reinforcement in the polymer nanocomposite films. The strength of the proposed model is based on unambiguous evidences from FTIR, TEM, and conductivity analysis. The FTIR results provide clear role of nanofiller concentration on ion-ion interaction quantified in terms of the fraction of free anion and ion-pairs present in the nanocomposite films and its excellent correlation with conductivity versus filler concentration. The presence of asymmetry in the nu(4)(ClO4-) band observed at 625 cm(-1) is attributed to its resolved degeneracy suggesting the presence of both uncoordinated and cation-coordinated ClO4- anion in the matrix due to ion-ion and ion-filler interactions assisted by Lewis acid-base interaction. The enhancement in conductivity at low concentration is possibly due to direct interaction of nano-CeO2 with both polymer host and anions resulting in the release of ionic charges. Drastic conductivity reduction at higher concentration is related to charge immobilization because of ion/ion-pair entrapment by local clusters of filler as evidenced in TEM. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 60-71, 2009