Phase Behavior and Ionic Conductivity of Lithium Perchlorate-Doped Polystyrene-b-poly(2-vinylpyridine) Copolymer

Abstract

The phase transitions of lithium perchlorate (LiClO4)- doped polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) were studied as a function of temperature and ion salt concentration using in situ small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Incorporation of LiClO4 into an asymmetric, disordered PS-b-P2VP copolymer produced temperature-dependent order–disorder (ODT) and order–order transitions (OOTs) from spherical to lamellar microphases. The effective interaction parameter (χeff) between two block components was evaluated for low molecular weight LiClO4-doped PS-b-P2VP in a disordered state. With increasing quantities of LiClO4, a remarkable increase in χ along with a volumetric change produced by the selective coordination of LiClO4 to the ionophilic P2VP block led to morphological transitions from disordered (DIS) to body-centered cubic spherical (BCC) to hexagonally packed cylindrical (HEX) to lamellar (LAM) structures. We also demonstrate that the ionic conductivity in ...