Structure and Thermodynamics of Hybrid Organic–Inorganic Diblock Copolymers with Salt

Abstract

We examine the phase behavior of a hybrid organic–inorganic diblock copolymer/salt mixtures. The experimental system comprises poly(ethylene oxide)-block-polyhedral oligomeric silsesquioxane (PEO–POSS) mixed with a lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) salt. Although the diblock copolymers without salt exhibit a classical order-to-disorder transition behavior with increasing temperature, the PEO–POSS/salt mixtures exhibit disorder-to-order transitions with increasing temperature. The analysis of a small-angle X-ray scattering data from the disordered state using Leibler’s random phase approximation enables the determination of an effective Flory–Huggins interaction parameter, χeff, for the electrolytes. Unlike conventional systems, χeff increases with increasing temperature. A simple expression is proposed to describe the dependence of χeff on temperature and salt concentration. This enables the calculation of the segregation strength, χeffN, for both ordered and disordered electrolytes. T...