Structural Evolution During and After Cessation of the Shear Flow for a Side-Chain-Type Liquid Crystalline Polysiloxane Above the Isotropic-Liquid Crystalline Phase Transition Temperature

• Published in: Journal of macromolecular science. Physics 2003-01, Vol.42 (3-4), p.901-914
• Main Authors: Tanaka, Katsufumi, Yonetake, Koichiro, Masuko, Toru, Akiyama, Ryuichi
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Flow cessation; Inorganic and organomineral polymers; Liquid crystalline polymer; Phase transition; Physicochemistry of polymers; Properties and characterization; Shear flow; Shearing microscopy; Structural evolution
• ISSN: 0022-2348; 1525-609X
• DOI: 10.1081/MB-120021614

Evolution of the anisotropic texture during and after cessation of shear flow for a side-chain-type liquid crystalline polysiloxane (LCS) was studied by shearing microscopy at temperatures above the isotropic to liquid crystalline phase transition temperature ( T c =309.2 K if LCS is cooled from the isotropic phase in the quiescent state). The anisotropic texture of LCS during the shear flow was found at a temperature of 313 K and a shear rate of 50 s −1 . After cessation of the shear flow, the anisotropic texture disappeared. At a temperature of 311 K and a shear rate of 50 s −1 , LCS under shear flow also showed the anisotropic texture. It is noteworthy that the anisotropic texture was stable at this temperature, even after cessation of the shear flow. Furthermore, the evolution of the anisotropic texture was described quantitatively from the behavior of the birefringence as a function of time after cessation of the shear flow.