Anisotropic sol-gel transition: the influence of sample thickness, pressure and strain.

Abstract

We demonstrate an unprecedented influence of sample thickness (<i>d</i>) and pressure (<i>P</i>) on the gelation of a liquid crystalline nematic host. The temperature at which the anisotropic nematic sol transforms into a nematic gel is weakly dependent on '<i>d</i>' down to its certain value, but surprisingly exhibits a precipitous drop below about 30 μm thickness. Temperature-dependent laser transmission exhibits characteristics of approach to a tricritical point, when <i>d</i> is varied. While the strain dependence of storage and loss moduli exhibit Payne effect/weak strain overshoot, the magnitudes of the moduli and their thermal variation present explicit dependence on <i>d</i>, both behaviours being well described by power-law expressions. Studies at elevated pressures also corroborate the observations of <i>d</i>-dependence with the nematic sol thermal range increasing with <i>P</i>, suggesting reduced favour for network formation. We strongly believe that these experiments pave a new pathway to realize the formation of gel fibres.