ELECTRORHEOLOGICAL EFFECT OF LIQUID CRYSTALLINE POLYMERS

A series of side chain liquid crystalline polymers (LCPs) containing different spacer length and various terminal structures has been prepared and their electrorheological (ER) effect has been investigated. Although the LCP itself showed small ER effect, a mixture of the LCP with a plain polydimethylsiloxane (PDMS) oil was found to show a large increase in shear stress upon application of an electric field. The shear stresses under DC 2 kV/mm of an electric field were 14 to 4 times those without the application of an electric field over the temperature range of 30 to 160 °C for a 2:1 mixture (by weight) of a LCP containing an oxyethylene spacer and a mesogen based on 4-cyanophenyl benzoate with PDMS. Two mechanisms responsible for the generation of the ER effect was suggested from the investigation using phenyl-substituted PDMS and an analysis by DSC: oriented LC network induction, and phase separation between the LC base polymer and PDMS.