Dielectric studies of tolane derivatives exhibiting the E and K phases

Abstract

Results of dielectric studies for three tolane derivatives containing the isothiocyanato (NCS) and alkyl or alkoxy groups in the terminal positions are presented. A relaxation process associated with molecular rotations around the short axes has been observed in the crystal‐like smectic phases (B, E, K). The K phase was characterized for the first time by dielectric spectroscopy. The results are discussed by taking into account the dielectric relaxation data obtained recently for the biphenyl analogues in the E phase. The available X‐ray data allow us to calculate the so‐called packing parameter which characterizes the free volume of the molecules in the unit cells.