ANISOTROPIC IONIC-CONDUCTION IN A MAGNETICALLY ALIGNED LIQUID-CRYSTALLINE POLYMER ELECTROLYTE

Sequentially ordered thermotropic main-chain liquid crystalline polyme rs based on modifications of terephthaloyl-bis-4-oxybenzoyl copolymeri sed with polyethylene glycol (TOB-PEG) have been synthesized. Material s of interest typically have a T-g below ambient, a crystalline melt t ransition around 100 degrees C, and exhibit a number of complex liquid crystalline phases with clearing ranges to isotropic in the region 12 0-180 degrees C. The variation of ionic conductivity with temperature of complexes formed with LiCF3SO3 is typically in the range 10(-9) S/c m at ambient to 10(-5) S/cm at 130 degrees C, and reveals discontinuit ies of slope which correlate with changes of phase in the material. Se lected unsalted materials have been aligned magnetically using a 7.1T superconducting magnet and show ordering at ambient temperatures chara cteristic of a smectic C type configuration. Polymer electrolytes form ed with LiCF3 SO3 (EO/Li in the range 30 to 75) have also been magneti cally aligned and bulk ionic conductivities measured parallel (sigma(p arallel to)) and perpendicular (sigma(perpendicular to)) to the alignm ent direction measured, aii is significantly reduced over the isotropi c polymer by a factor of more than;five due to the blocking smectic-ty pe layers. When heated to the onset of the melt, sigma(perpendicular t o) shows an unexpected increase attributed to the opening up of aligne d conduction channels of PEG. (C) 1998 Published by Elsevier Science L td. All rights reserved.