Abstract
We report measurements of the temperature variations of physical parameters in ambient-temperature nematic liquid crystal mixtures of bent-core (BC) and rodlike molecules (5CB): birefringence ; static dielectric constants and ; splay and bend elastic constants; rotational viscosity ; and diffusion coefficients and of a microsphere. Both and decreases rapidly with increasing BC concentration, whereas remains almost constant. At a shifted temperature (e.g., C), increases by 50 and decreases by 80 compared to pure 5CB when the BC concentration is increased to 43 mol in the mixture. Viscosities parallel and perpendicular to the director, , , which are nearly equal to the Miesowicz viscosities and , respectively, were obtained by and using the Stokes-Einstein relation. Both the viscosities at room temperature increase by 60 and 50 times, respectively, whereas increases by 180 times (at 43 mol ) compared to the corresponding values of pure 5CB. The stiffening of and exorbitantly large enhancement in all the viscosities at a higher mol of BC indicate that the viscoelastic properties are highly impacted by the presence of smectic clusters of BC molecules that results from the restricted free rotation of the molecules along the bow axis in the nematic phase. A possible attachment model of smectic type clusters of BC molecules surrounding the microparticle is presented.
3 More- Received 21 October 2011
DOI:https://doi.org/10.1103/PhysRevE.85.011702
©2012 American Physical Society