Polyether/salt hybrid .4. Effect of benzenesulfonate group(s) and PEO molecular weight on the bulk ionic conductivity

Benzenesulfonate (Bs) groups were introduced to the terminal of poly(ethylene oxide) (PEG) and poly(propylene oxide) (PPO) oligomers with molecular weight (MW) of 300-6000 to design an ion conductive amorphous matrix. The phase of these PEG-salt hybrids was mainly influenced by the MW of the polyethers. PEO oligomers having benzenesulfonate group(s) with MW less than 600 showed amorphous phase in the bulk in a wide temperature range (-120 similar to +150 degrees C). The ionic conductivity of these amorphous salts was considerably influenced by the glass transition temperature (T-g). The T-g of these PEG-salt hybrids was influenced by the fraction of salt group in the matrix. Among totally amorphous salts, the best ionic conductivity of 2.95 x 10(-5) S cm(-1), at 50 degrees C was obtained in the PEO(550)-BsCs. Though PEO(350)-BsM was also an amorphous salt, lower ionic conductivity was observed because of higher T-g than that of PEO(550)-BsM However, PEO(350)-BsM was useful as electrolyte in PEO oligomers because of excellent compatibility with the PEO oligomers. The ionic conductivity of PEO(350)-BsM in PEO(300) (MW of 300) was 40 times higher than that of PEO(350)-BsM in the bulk. Since PEG(350)-BsM was inherently ion conductive, the ionic conductivity for PEO(350)-BsM/PEO(300) was kept high regardless of the salt concentration. (C) 1997 Elsevier Science Ltd.