Polymer electrolyte complexes of LiCIO₄ and comb polymers of siloxane with oligo‐oxyethylene side chains

Abstract

Abstract Polysiloxanes with oligo‐oxyethylene side chains of the type —O(CH 2 CH 2 O) 7 CH 3 and —(CH 2 ) 3 O(CH 2 CH 2 O) n CH 3 (average n ≈ 7 and 11) were synthesized from poly(hydrogenmethylsiloxane) and characterized by 1 H n.m.r., 29 Si n.m.r., i.r. and g.p.c. Cyclic analogues were used as model compounds and synthesized from tetramethylcyclotetrasiloxane. Polymer electrolyte complexes were made from the comb polymers and LiClO 4 by solvent‐casting from THF, and their conductivities measured as a function of temperature and studied by differential scanning calorimetry and correlated with their conductivity behaviour. Maximum conductivities close to 10 −4 S cm −1 were achieved at room temperature and at ethylene oxide units to Li + ratios of about 25. Cross‐linking or blending with high molecular weight poly(oxyethylene) lowers the conductance somewhat but vastly improves the mechanical properties of the complexes, and the blends with PEO can be cast into thin, flexible and tough films with good conducting properties.