Weak polymer-electrolyte interaction revealed by Fermi resonance perturbed Raman bands

A detailed analysis of isotropic and anisotropic Raman spectra of carbonyl stretching vibrations of ethylene carbonate in different systems was conducted. The variation of Fermi resonance perturbed spectral profiles was used to investigate changes in local molecular surroundings in polymer gel-electrolyte systems as a function of their composition. In poly(methyl methacrylate)-based gels it is found that the matrix interacts very weakly with the solvent molecules, ethylene and propylene carbonates, mostly playing a role of a hydrogen bond-breaking agent. In gel systems containing lithium salt, however, a new type of coordination appears. Along with the solvent-solvent and solvent-cation couplings characteristic of liquid electrolytes, the spectra of gels demonstrate the presence of mixed states in which cations, solvent molecules and polymer segments take part. The importance of the mixed states for ionic conduction is discussed. Copyright (C) 2002 John Wiley Sons, Ltd.