Effect of calix[6]pyrrole anion receptor addition on properties of PEO-based solid polymer electrolytes doped with LiTf and LiTfSI salts

In this article the impact of anion receptor (1,1,3,3,5,5-meso-hexaphenyl-2,2,4,4,6,6-meso-hexamethyl-calix[6]pyrrole) on physicochemical and ion transport properties of poly(ethylene oxide)-salt composites is discussed. Two salts, lithium triflate and lithium bis(trifluoromethane) sulfonamide, were tested. It is shown that addition of the anion receptor significantly increases glass transition temperature of the composite suggesting changes in the velocity of segmental motions of the polymeric matrix. Also some discrepancies between crystallinity of the electrolyte measured by means of DSC and the one measured by means of XRD for lithium triflate containing electrolytes are discussed. It is proved that the influence of the anion receptor on electrolyte properties depends on the coordinating properties of the anion. In consequence this two structurally similar anions are found to reveal opposite behavior. In systems containing LiTf significant changes in properties are observed upon receptor addition. Contrastively, LiTfSI does not interact with receptor and obtained samples exhibit non-homogenous structure with consequent receptor participation.