THE RHEOLOGY OF LAYERED LIQUIDS - LAMELLAR BLOCK-COPOLYMERS AND SMECTIC LIQUID-CRYSTALS

The frequency-dependence of the viscoelastic shear modulus at low frequencies in a lamellar polystyrene-polyisoprene block copolymer is qualitatively identical to that measured in small-molecule smectics, namely, the rodlike 4-cyano-4'-octylbiphenyl and the flexible n-nonyl-1-O-beta-D-glucopyranoside. All three materials were studied after quenching from the isotropic state, and during and after alignment by large-amplitude oscillatory shearing. The kinetics of aligning, as measured by changes in moduli during shearing, are similar, despite great differences in molecular characteristics. These moduli and the aligning process are evidently controlled by smectic fluctuations and defects, the dynamics of which have universal features.