N-메틸-2-피롤리돈/염화칼슘 용매계에서 Poly(2- cyano-p-phenylene terephthalamide)의 네마틱 액정거동

Abstract

The liquid crystalline behavior of poly(2-cyano-p-phenylene terephthalamide) (CY-PPTA) in a solvent system of N-methyl-2-pyrrolidone (NMP) and calcium chloride (CaCl2) was investigated by rheological methods. In the dilute concentration range, the intrinsic viscosity decreased with increasing temperature. Over the overlap concentration, in the semi-dilute regime, the reduced viscosity displayed a rapid increase at 60 oC with concentration. In the concentrated region in which intermolecular interaction are more dominant, lyotropic liquid crystalline behavior was observed with increasing concentration. Temperature increase lead to clearer Bingham behavior and lower values of power law index. In addition, the viscosity curves followed the Onogi and Asada model, which was proposed for liquid crystal polymers. The critical concentration was found to be 5 wt%, 4 wt%, and 3 wt%, at 30 oC, 45 oC, and 60 oC, respectively. Schlieren texture from nematic droplets of CY-PPTA was observed by polarized optical microscopy at 10 wt% for 30 oC and 9 wt% for 45 oC and 60 oC.