Preparation of polypseudorotaxane composed of linear and cyclic polyethylene oxides and its application to solid polymer electrolyte

The mixture of linear polyethylene glycol with molecular weight of 20,000 (l‐PEG20K) and cyclic polyethylene glycol with molecular weight of 1,000 (c‐PEG1K) was ultrasonicated in acetonitrile. After evaporating the solvent, the residue was analyzed by DSC to show a remarkable decrease of crystallization temperature. Such a large crystallization suppression was not observed when linear polyethylene glycol with molecular weight of 1,000 (l‐PEG1K) was added instead of c‐PEG1K. Further, the mixture of cyclic polyethylene glycols (c‐PEG6K and c‐PEG1K) did not exhibit a significant crystallization suppression. These experimental results indicated that formation of polypseudorotaxane through ultrasonication‐assisted ring penetration played an important role in the crystallization suppression. Ionic conductivities of the polypseudorotaxane‐based polymer electrolytes prepared from polyethylene oxide with molecular weight of 600,000 (PEO600K) and c‐PEG1K showed conductivity enhancement especially at low Li salt concentration. Polyethylene oxide (PEO)‐based solid polymer electrolyte is still the most widely investigated system, and decreasing the degree of its crystallinity is important in the practical viewpoint. This work reports a new strategy for the crystallization suppression by forming polypseudorotaxane containing both linear and cyclic PEOs due to ultrasonication‐assisted ring penetration. Polypseudorotaxane‐based solid polymer electrolyte has higher ionic conductivity especially at low Li salt concentration.