MEASUREMENT OF RHEOLOGICAL PROPERTIES FOR SMECTIC-A LIQUID CRYSTAL BY USING ULTRASONIC RHEOMETER AND ROTATIONAL VISCOMETER [Review]

摘要

The relationship between the rheological properties and the alignment direction of liquid crystals was studied using a rotational viscometer and an ultrasonic rheometer. 4-Cyano-4'-n-octylbiphenyl (8CB) was used for the sample. The measurements of viscosity for 8CB were carried out using the rotational viscometer having parallel plate geometry. The parallel plates were made from glass and covered by polyimide film with rubbing to align the liquid crystal molecules, The oriented structure of 8CB was examined using a polarizing microscope optical system which was built in the rotational viscometer. When the direction of shearing was perpendicular to the layers of smectic 8CB, the apparent viscosity was higher than that in the case of no-rubbing. Viscoelastic properties at ultrasonic frequency (3 MHz) were examined by the ultrasonic rheometer using a fused-quartz delay line. When the shear wave vibration was perpendicular to the smectic layers, G' was observed, However, when the shear wave vibration was parallel to the smectic layers, G' was not observed. (C) 1997 Elsevier Science S.A. [References: 13]