Chiro-optical properties of lyotropic ethyl cellulose derivatives

Novel derivatives of partially substituted ethyl cellulose (EC) were prepared and their chiro-optical properties studied as a function of degree of substitution. As had been previously reported for acetyl ethyl cellulose (AEC), the propanoate (PEC) and hexanoate (HEC) esters of EC undergo a degree of substitution dependant reversal of their chiral nematic (N*) helical twisting sense. The critical degree of substitution (DS*), above which this reversal of handedness takes place, was found to be considerably lower (DS*? 0.1) for these derivatives than that for the reversal of handedness of AEC (DS*? 0.18-0.21) lyotropic solutions in chloroform. This reversal of supra-molecular twisting sense was not observed for the benzoate ester of EC (BEC), rather these derivatives enter the compensated nematic state at low degrees of substitution (DS > 1.0) but no reversal of handedness is observed at higher DS. © 2000 Elsevier Science Ltd. All rights reserved.