Elastic Deformations of Liquid Crystalline Polymers and Their Monomers in Magnetic and Electric Fields

Abstract

A thermotropically mesogenic aromatic polyester and its low molecular weight analogue (“monomer”) in the nametic phase in thin layers form hometropic textures which can be deforemed under the influence of magnetic or electric fields. The elastic orientational deformations generated here are of the thereshold character (Freederiksz's transition) and are used for the determination of bend elastic constants, K₃, of the polymer and low molecular weight nematics. The optical anisotropies, n^e–n^o, of the samples investigated were detemied from the polerized-microscopic patterns of the deformed layers. The values of n^e-n^o for the polymeric and the low molecular weight nematics virtually coincide and over the investigated temperature range vary form 0.08 to 0.17. The bend constants k³ are close in the order of magnitude for the polymer and the monomer and vary with temperature in the ranges (5–20) ^.10⁻⁷ dyn, respectively. The orientation of molecules of the polymer nametic inmagetic and electic fields followes the mecanism of local smallscale chain motion.