SHEAR-INDUCED AND SOLIDIFICATION-INDUCED BAND TEXTURE FORMATION OF MAIN CHAIN NEMATIC POLYMERS

摘要

It is well known that both lyotropic and thermotropic liquid crystalline polymers(LCPs) have shown band texture under crossed polarizing microscope when subjected to shear or elongational flow. In the past decade, many experimental results regarding the structure and factors affecting band texture formation have been reported. It has been proved that the bands form during the relaxation after shear, depending on the shear rate, duration of the shearing, the layer thickness and the solution concentration (for lyotropic); the width of bands ranges from 0.5μm to 10μm, mainly depending on the nature of the polymer, apact from a few case being dependent of the shear rate. Even so the precise mechanism of band formation has not yet been satisfactorily explained.