RHEOLOGY OF REGION-I FLOW IN A LYOTROPIC LIQUID-CRYSTAL POLYMER - THEEFFECTS OF DEFECT TEXTURE

A thorough rheological investigation into the region I flow of liquid- crystalline hydroxypropylcellulose in water is reported. At low shear rates a region of shear thinning with a power-law exponent 1/2 is obse rved over two decades in shear rate. Anomalous transient behavior is s een for applied stresses below the critical stress at the region I-II turnover such that the strain required to reach steady state increases as stress decreases. Recoil measurements show large recoverable strai n and similar pseudostrain scaling in both regions I and II. The activ ation energy for the viscosity is also the same in regions I and II. T his rheology combined with in situ flow-small-angle light scattering m easurements of the defect texture size show the qualitative and quanti tative accuracy of the defect texture stress balance previously propos ed to explain region I flow.