Comparative investigations of linear and cyclic siloxanes with a swallow-tailed liquid crystal as side chain

Abstract

Molecular ‘zip-fasteners’ consisting of short linear and cyclic siloxane backbones and the same swallow-tailed liquid crystal unit as side group were synthesized. The closing and opening mechanism was studied by dielectric measurements. Thereby an abrupt decrease of the static dielectric constant ε_0∥ was observed indicating the antiparallel order of the side groups in the ‘closed’ state. The dielectric relaxation frequencies of the δ- and α-relaxation for the respective oligomers do not depend on the degree of polymerization which could be the result of the high flexibility of the main chain and the relatively low mobility of the liquid crystalline unit.