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

• Published in: Macromolecules 2011-08, Vol.44 (15), p.6085-6093
• Main Authors: Naidu, Sudhakar, Ahn, Hyungju, Gong, Jinsam, Kim, Bokyung, Ryu, Du Yeol
• Format: Article
• Language: English
• Subjects: Applied sciences; Electrical, magnetic and optical properties; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma200429v

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 the samples quenched from the different structures is morphology-independent, while it increases with increasing salt concentration.