화학공학소재연구정보센터
Macromolecules, Vol.52, No.9, 3165-3175, 2019
Structure and Thermodynamics of Hybrid Organic-Inorganic Diblock Copolymers with Salt
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, chi(eff), for the electrolytes. Unlike conventional systems, chi(eff) increases with increasing temperature. A simple expression is proposed to describe the dependence of chi(eff) on temperature and salt concentration. This enables the calculation of the segregation strength, chi N-eff, for both ordered and disordered electrolytes. The composition of the electrolytes is quantified by f(EO/LiTFSI), the volume fraction of the salt-containing poly(ethylene oxide)-rich phase. The morphology of electrolytes is presented on a chi N-eff versus f(EO/LiTFSI) phase diagram. Over the values of f(EO/LiTFSI) studied (0.61-0.91), only two ordered phases were found: lamellae and co-existing lamellae/hexagonally packed cylinders.