NATURE OF THE FLOW-INDUCED WORM TEXTURE OF THERMOTROPIC POLYMERS

Nematic polymers show at low shear rates the so-called worm texture which is characterized by a large density of defects. To study these defects, a specially designed cone-and-plate rheometer has been used for quenching the flowing worm texture of a thermotropic polymer. The preparation of samples involves ultramicrotoming and etching with sulfuric acid. The observations show that the defects are half-integer twist disclination loops lying in the shearing plane. The director is oriented along the flow direction inside the loop and along the vorticity axis outside.