Elastomeric comb-shaped high molecular mass poly(oxyethylene) for polymer electrolyte: Morphology and ionic conductivity

The morphology, dynamic mechanical properties and ionic conductivity of high molecular mass comb-shaped poly(oxyethylene)s with tri(oxyethylene) side chains (TECs) were investigated, when LiClO4 was doped at the concentration of [Li]/[-O-] = 0.05 similar to 0.15. The samples were TEC-11 and TEC-18, the contents of tri(oxyethylene) side chain of which were 11 and 18 mol%, respectively. With increasing salt concentration, the glass transition temperature increased and the melting temperature decreased followed by the disappearance of the melting point. By adding the salt at the concentration of [Li]/[-O-] = 0.10 or 0.15, an alternative structure was suggested to be formed although the poly(oxyethylene) matrix was completely amorphous. Due to the morphological characteristics of TECs and the concentration of the salt, both TEC-II and TEC-18 exhibit the high ionic conductivities of 10(-4) S/cm at 30 degreesC, when the salt was doped at the concentration of [Li]/[-O-] = 0.10. The high molecular mass, over 10(6), of TECs gave rubbery electrolyte films without chemically crosslinked structure. The addition of the salt to TECs decreased the shear storage modulus at room temperature and expanded the temperature range of the rubbery plateau region within the range of salt concentrations studied here.