Splay and bend elastic constants in the nematic phase of some disulfide bridged dimeric compounds.

We report measurements of the temperature dependences of the splay (K11) and bend (K33) elastic constants of several homologues and a binary mixture of disulfide bridged symmetric dimers made of alkoxy cyanobiphenyl monomeric units. All of them have an even number m of carbon and sulfur atoms in the linking chain and expected to have linear conformations. Both K(11) and K(33) alternate depending on the parity of x which is the number of carbon atoms in the alkyl chain of a monomer.

Anomalous temperature dependence of elastic constants in the nematic phase of binary mixtures made of rodlike and bent-core molecules.

We report on two anomalous trends in the temperature dependences of the splay (K11) and bend (K33) elastic constants in the nematic (N) phase of mixtures of compounds with rodlike (R) and bent-core (BC) molecules: As the sample is cooled from the isotropic to N transition point, (i) K33 increases, attains a maximum value and then decreases, and (ii) close to the N to smectic A (SmA) transition point, K11 decreases sharply. At higher temperatures the bow axes of BC molecules are aligned along the director n, strongly favoring a bend distortion of n as the orientational order parameter is increased. Close to the N-SmA transition point the smecticlike short-range order builds up, and the arrow axes of BC molecules are aligned along n, facilitating a splay distortion of n.