DUAL-PHASE STRUCTURE OF POLYMER ELECTROLYTES COMPRISED OF NBR SBR LATEX FILMS SWOLLEN WITH LITHIUM SALT SOLUTION/

Dual-phase polymer electrolytes (DPE) that have high ionic conductivit y (> 10(-3) S/cm) and good mechanical strength were prepared by mixing NBR and SBR latices and casting films. The latex films absorbed large quantities of lithium salt solution (e.g., 1M lithium perchlorate in gamma-butyrolactone) to obtain DPE films but did not dissolve with swe lling. The NBR phase is polar and was impregnated selectively with the polar lithium salt solution, whereas the SBR phase is nonpolar and fo rmed a mechanically-supportive matrix. Transmission electron microscop ic (TEM), electron energy loss spectral (EELS), and energy-dispersive x-ray (EDX) analyses showed microscopically the dual-phase structure. Evidence for swelling by lithium salt solution was found only in the N BR phase and not in the SBR phase by EDX microanalysis. Ionic conducti vity as a function of NBR content or swelling degree showed clearly th at a percolation threshold for ionic conductivity exists. (C) 1994 Joh n Wiley & Sons, Inc.