Rheology and Rheo-optics of Liquid Crystal Polymers

Abstract

Studies on deformations and flow mechanisms of polymer liquid crystals are expected to afford us fundamental knowledges to clarify the technologically important phenomena, including fiber formation in liquid crystal spinning. A rheological study alone, however, cannot tell the full story of deformation mechanisms of polymer liquid crystalline systems, because the systems usually form complicated super-structures or textures, the unstability of which have been prevented us from studing the relationship between the physical properties and structures. The author and his coworkers have developed new rheo-optical techniques and investigated the relations between structure and rheological properties of various liquid crystals, including liquid crystalline polymers. In this paper, these techniques and some recent experimental results are introduced.After a brief introduction to liquid crystals in general and their rheological properties, the rheology of liquid crystalline polymers is summarized by the three-region flow curve. And then rheo-optical properties of these liquid crystalline polymers are introduced. Spectro-photometric method is very effective for studing deformation and flow mechanism of cholesteric liquid crystals. Polarized-light method is expected to be developed for more general use. Both the rheo-optical and rheological properties of a liquid crystalline polymers may be interpreted by supposing three typical structural models for bulk structure of the polymer liquid crystalline system proposed before.