Electrooptical properties of liquid crystalline side chain polymers with laterally attached mesogenic units

Abstract

The electrooptical properties of side-chain liquid crystalline polymers were investigated for the case that the mesogenic units were attached laterally rather than longitudinally to a flexible chain backbone via flexible spacer units. The experimental finding is that these polymers display unusual electrooptical properties within the isotropic phase in the neighborhood of the transition into the nematic phase.The polymers are characterized by the occurrence of a fast and a slow electrooptical response both of which show a critical divergence of the Kerr constant and the Kerr relaxation time. In addition, they show dmiations between the rise and the decay values of the Kerr constants and in certain cases also of the Kerr relaxation times. Finally an overshoot of the induced birefringence following a sudden s t v i s e increase of the applied electric field has been found for one of these polymers. All these features can be accounted for on fhe basis of a newly developed theoretical approach that considers the particular dipolar and optical polarization configurations of these polymers. 1042-7147/90/01W93-09$05.~

Near-critical behavior of the dynamic stress-optical coefficient in liquid crystalline elastomers

“…In dynamical Kerr effect measurements on liquid crystalline side group polymers of the same general type also two relaxation processes have been reported. 18 The existence of the two processes probably originates from the fact that due to the lateral coupling of the spacer to the mesogen the two short molecular reorientation axes are no longer equivalent. The mesogens behave in a "dynamically biaxial" manner.…”