Electrorheological effect of liquid crystalline polymers

✍ Scribed by A. Inoue; S. Maniwa

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 415 KB
• Volume: 55
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1995.070550112

✦ Synopsis

Large increases in shear stress upon application of a 2.0 kV/mm electric field were observed in homogeneous fluids composed of polysiloxane-based liquid crystalline polymers (LCPs) in dimethyl silicone at a shear rate of 200 s-*. The increase was largest (about 3,000 Pa at 50°C) with LCP consisting of a polysiloxane bearing mesogenic groups as side chains. With LCP having the mesogenic groups within the main chain, the maximum increase was about 1,300 Pa at 90°C. It was about 400 Pa at 30°C with LCP having the mesogenic groups at both ends only (biterminal), and several Pa a t 30°C with LCP having the mesogenic group at one end only (monoterminal). The increases were smaller with mesogenic groups of lower positive dielectric anisotropy in the side chain LCP. The side chain, biterminal, and monoterminal LCPs exhibited Newtonian flow in the electric field and shear stress yield at low shear rates in its absence. The complex dynamic modulus and viscosity of the side chain LCP in the electric field showed no dependence on strain at deformation displacements approaching 5", but in its absence were generally strain-dependent, and suggest the strong electrorheological effect of these homogeneous LCP fluids is related to a flexible-chain linkage between their crystalline domains. 0 1995 John Wiley & Sons, Inc.