IONIC-CONDUCTIVITY AND COMPATIBILITY STUDIES OF BLENDS OF POLY(METHYL METHACRYLATE) AND POLY(PROPYLENE GLYCOL) COMPLEXED WITH LICF3SO3

Stable to atmospheric moisture, adhesive and transparent polymer electrolytes have been prepared by blending poly (methyl methacrylate) (PMMA) with poly (propylene glycol)-425/LiCF3SO3 complexes. The blending of the polymers has been achieved by a method developed in our laboratory: free radical polymerization of methylmethacrylate in the polyether/salt matrix. A series of polymer blend complexes varying in PMMA content (up to 20% by weight) and oxygen /metal ratios (25, 16, and 8) have been synthesized and their properties studied. All the samples prepared in this study were found to be optically clear unlike the higher molecular weight poly (propylene glycol)-2000 (PPG-2000) system which required a minimum salt concentration to compatibilize a specific amount of PMMA with PPG. The mechanisms by which the salt holds the otherwise incompatible polymers together in a single phase have been investigated by FT-IR. Our studies show a weak coupling of the ether oxygens in the PPG with the ester groups of the PMMA through the lithium cations. Discrete changes has been observed in the FT-IR spectrum of PMMA when doped with the lithium salt hitherto unnoticed with other dopants. Gel permeation chromatography results of the PMMA samples isolated from the solid electrolytes indicate the molecular weight to vary between 43000 and 121000 with relatively narrow distributions, 1.6-2.0. The ionic conductivities of the polymer blend electrolytes were fairly high (10(5) S/cm) at room temperature. The PMMA neither significantly influenced the T(g) of the blend complexes nor effected the ionic conductivities drastically. The ionic conductivity as a function of temperature followed the empirical Vogel-Tammann-Fulcher equation. The blending of PMMA with PPG/LiCF3SO3 complexes was found to impart good adhesiveness to the solid electrolytes while making them stable to atmospheric moisture.