Synthesis and characterization of ion conducting cellulose esters with PEO side chains

Cellulose esters with poly(oxyethylene) (PEO) side chains, denoted COE-1 and HPCOE-1A, were prepared through the homogeneous reactions between cellulose or hydroxypropylcellulose and a PEO monocarboxylic acid in the presence of N,N′-dicyclohexylcarbodiimide and 4-N,N′-dimethylamino-pyridine. The LiCF3SO3 complexes of the two polymers were prepared, and the effects of salt concentration on the liquid crystallinity, ionic conductivity and morphology were investigated. It has been found that the two kinds of complexes are both thermotropic liquid crystalline materials and exhibit clearing temperatures, Tc, that increase with increasing salt concentration. The increase in Tc for each system is compensated approximately by a rise in Tg, leaving the liquid crystalline temperature ranges fairly constant. A non-Arrhenius temperature dependence of ionic conductivity is predominant in both systems with the maximum conductivities occurring at [Li]/[O]≈0.07. The environmental scanning electron microscopy reveals a very rough, array-like internal structure for the COE-1 complex at this salt concentration.