Thermal and shear flow effects on microstructure of a thermotropic liquid crystalline polymer

The effects of annealing time and temperature on the texture and transient shear rheological behavior of a thermotropic liquid crystalline polymer were investigated. The texture evolution during annealing included two processes: the reduction of the defect density and the increase of the domain size but decrease of the domain number. We confirmed that the threaded texture caused the first shear stress peak and the shear stress minimum during shear flow startup. More importantly, using the wide-angle X-ray diffraction technique, we determined that the second shear stress peak during flow startup can be attributed to the evolution of the molecular orientation.