Study of ion solvation and ion association in polymer gel electrolyte with polyethylene oxide-co-polypropylene oxide as a plasticizer

Using a molal conductance method, ion solvation and ion association in polytriethylene glycol dimethacrylate (PTREGD)–LiClO₄ gel electrolytes with amorphous ethylene oxide-co-propylene oxide (EO-co-PO, M̄_n = 1750) as the plasticizer were investigated. It was found that the fraction of solute existing as single ions (α_i) and ion pairs (α_p) decreases, while that of triple ions (α_t) increases linearly with increasing salt concentration. The dependence of these fractions on molecular weight of plasticizer was also examined. It was shown that α_i and α_t increase and α_p decreases with increasing molecular weight. The result of temperature dependence of these fractions was very interesting: when the temperature is lower than 55°C, α_i increases while α_p and α_t decrease with increasing temperature; however, when the temperature is higher than 55°C, the reverse is true.