Synthesis of thermotropic cellulose derivatives and their behaviour as ion conducting materials

Novel thermotropic cellulose derivatives containing poly(ethylene oxide) (PEO) side chains and pendant mesogenic side chains were synthesized and characterized. The PEO-350 groups were incorporated onto the cellulose backbone via ester or ether linkage, and the three products, including two highly substituted esters (COE-1 and HPCOE-1A) and a regioselective substituted ether (TPEOCELL), all exhibit thermotropic liquid crystallinity. Among them TPEOCELL forms a right-handed chiral nematic mesophase at room temperature, with the selective reflection in the wavelength of the visible range; the influence of salt on the cholesteric optical properties was examined. These three polymers were employed as polymer hosts for ranges of solvent-free polymer electrolytes, which also exhibit thermotropic liquid crystallinity. The effect of salt on ion conductivity, liquid crystallinity and morphology were investigated. Gel polymer electrolytes, prepared from a HPC ester partially substituted with PEO side chains (HPCOE-1B), propylene carbonate (PC) or a mixture of PC and ethylene carbonate (EC), and LiCF_3SO_3, were studied. The gels, containing 70 wt% PC or a mixture of PC and EC, were readily crosslinked to form films exhibiting moderate elastomeric properties and room temperature conductivities of #approx#10"-"3 S cm"-"1. These films are very promising candidates for practical applications. Three kinds of mesogenic units, 4-cyano-4'-oxybiphenyl group, 4-methoxy-4'- oxylbiphenyl group and 4-methoxyphenyl-4'-oxybenzoate group, were incorporated onto the cellulose backbone via a flexible spacer, respectively. The effects of the structure of the mesogenic groups and the length of spacer on the thermotropic liquid crystallinity of these polymers were investigated. (author)SIGLEAvailable from British Library Document Supply Centre-DSC:DXN051861 / BLDSC - British Library Document Supply CentreGBUnited Kingdo