Enhanced Elasticity and Soft Glassy Rheology of a Smectic in a Random Porous Environment

Abstract

We report studies of the frequency dependent shear modulus, $G^{\ast }(\omega )=G^{\prime }(\omega )+i{G}^{\prime \prime }(\omega )$, of the liquid crystal octylcyanobiphenyl (8CB) confined in a colloidal aerosil gel. With the onset of smectic order, $G^{\prime }$ grows approximately linearly with decreasing temperature, reaching values that exceed by more than three orders of magnitude the values for pure 8CB. The modulus at low temperatures possesses a power-law component, $G^{\ast }(\omega )\sim {\omega }^{\alpha }$, with exponent $\alpha$ that approaches zero with increasing gel density. The amplitude of $G^{\prime }$ and its variation with temperature and gel density indicate that the low temperature response is dominated by a dense population of defects in the smectic. In contrast, when the 8CB is isotropic or nematic, the modulus is controlled by the elastic behavior of the colloidal gel.

4 pages, 4 eps figures; accepted for publication in Phys Rev Lett

References in corpus (6)

• Rheology of Soft Glassy Materials
• Smectic Liquid Crystals in Random Environments
• Smectic ordering in liquid crystal - aerosil dispersions I. X-ray scattering
• Smectic ordering in liquid crystal - aerosil dispersions II. Scaling analysis
• Structure and Rheology of the Defect-gel States of Pure and Particle-dispersed Lyotropic Lamellar Phases
• Mean-Field Nematic--Smectic-{\sl A} Transition in a Random Polymer Network

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• Novel Experimentally Observed Phenomena in Soft Matter
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