MOLECULAR AND IONIC INTERACTIONS IN POLY(ACRYLONITRILE)-BASED AND POLY(METHYLMETHACRYLATE)-BASED GEL ELECTROLYTES

Vibrational Raman and Fourier transform IR (FTIR) spectroscopy has bee n used to determine molecular and ionic interactions in poly(acrylonit rile)-(PAN) and poly(methylmetacrylate)(PMMA) based gel electrolytes, containing LiClO4 salt and a mixture of ethylene carbonate (EC) and pr opylene carbonate (PC) as a gelating agent. A number of model systems, representing different stages of gel preparation, as well as the pure components, have also been studied. Vibrational spectra reveal interac tions between EC and PC molecules in EC-PC mixture via electric dipole s located on C=O groups. In the salt-doped EC-PC system, additional ba nds close to the ring breathing and bending fundamentals of the carbon ate ring of EC and PC, respectively, are attributed to solvent molecul es interacting with the cations via Coulombic forces, the satellite ba nd frequencies being well correlated to the cationic potentials. In th e PMMA-based gels, no spectroscopically detectable interactions betwee n the polymer matrix and the electrolyte were observed. In the PAN-bas ed systems, in contrast, C=N groups of PAN serve as attractive sites f or both the solvent molecules and the cations, the preferable interact ion being that between PAN and the solvent. (C) 1998 American Institut e of Physics. [S0021-9606(98)52341-0].