IONIC-CONDUCTIVITY OF A NOVEL SMECTIC POLYMER ELECTROLYTE

Polymers having the following general formula have been synthesised [G RAPHICS} where R is a long chain alkyl substituent such as -C16H33. Th e number of skeletal oxygen atoms n = 5 or 6 (coded C1605 or C1606) so : that the helix formed by association of neighbouring side groups R, has 18 or 21 skeletal bonds per rotation and so imitates the PEO-Li+ o r PEO-Na+ 2(1) helix. Complexes with LiBF4 in stoichiometries of 1 mol salt per structural (helical) repeat unit and 0.5 mol per repeat have been prepared. Small-angle- and wide-angle X-ray diffraction, thermal analysis and hot stage polarised light microscopy have been used to s how that the complexes form smectic systems in the uncomplexed and com plexed forms. In the complexes, cations are enclosed within the helice s and the anions lie between planes of helices and the alkyl side chai ns so that the overall d spacing is 42.9 Angstrom. The -C16H33 side ch ains melt at ca. 40 degrees C in the complexed material, to give a liq uid crystal phase. The liquid crystal-isotropic transition varies slig htly according to polymer and stoichiometry and is 89 degrees C for C1 605:LiBF4 (1:1). The ionic conductivity-temperature relationship shows well-defined transitions at the phase changes and the complex impedan ce behaviour also reflects the several states of the system. The condu ctivity of the (1:1) complex is higher than the (1:0.5) complex and is comparable to P(EO)(6):LiBF4 in the crystal and istropic phases, but is somewhat lower over the temperature range of the liquid crystal pha se.