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

The frequency-dependence of the viscoelastic shear modulus at low freq uencies in a lamellar polystyrene-polyisoprene block copolymer is qual itatively identical to that measured in small-molecule smectics, namel y, the rodlike 4-cyano-4'-octylbiphenyl and the flexible n-nonyl-1-O-b eta-D-glucopyranoside. All three materials were studied after quenchin g from the isotropic state, and during and after alignment by large-am plitude oscillatory shearing. The kinetics of aligning, as measured by changes in moduli during shearing, are similar, despite great differe nces in molecular characteristics. These moduli and the aligning proce ss are evidently controlled by smectic fluctuations and defects, the d ynamics of which have universal features.