AC-IMPEDANCE ANALYSIS ON DUAL-PHASE POLYMER ELECTROLYTES PREPARED FROM SBR NBR MIXED LATICES/

Dual-phase polymer electrolytes (DPE) are analyzed by ac impedance spe ctroscopy. DPE is prepared from an NBR/SBR latex mixture in the follow ing process: the latex mixture is dried to produce a polymer matrix fi lm, and the polymer matrix is then impregnated with a lithium salt sol ution as a plasticizer, which selectively permeates into the NBR phase . When a polymer matrix is impregnated with 1M LiClO4/gamma-butyrolact one and its NBR content is small, a distorted complex impedance spectr um, composed of overlapping two semicircles, is observed. The analysis based on an equivalent circuit indicates that isolated fragments of t he conductive NBR phase are formulated in addition to the continuous c onductive pathways. With increasing content of NBR, the two semicircle s get merged. This suggests that the isolated conductive phase comes t o be integrated into the continuous ionic pathways. The impregnation p rocess of DPE with a less polar plasticizer was followed by analyzing the complex impedance and modulus spectra. According to this analysis, secondary conductive pathways are formed along the SBR particle bound aries in addition to the NBR conductive phase. Swelling of NBR particl es progresses in the secondary conductive pathways, and the NBR partic les are finally linked to form continuous ionic pathways between the e lectrodes.