Abstract
The methods of diffusion, sedimentation, viscometry and flow and electric birefringence in dilute solutions have been used for the investigation of the conformational properties of molecules of some thermotropic mesogenic aromatic polyesters (APE) differing in chain structure. The equilibrium rigidity and optical anisotropy of molecules of para-APE decrease markedly upon the introduction of alkyl, phenolphthalein, meta- and ortho-aromatic groups. However, the degree of hindrance to intramolecular rotations increases. Rigid-chain APE exhibit a strong molecular weight dependence of the Kerr constant K indicating the large-scale character of orientation of the polymer chain as a whole in the electric field. Elastic deformations in the nematic phase of some APE due to the action of magnetic and electric fields were investigated. These deformations are of the threshold type and make it possible to determine the elastic bend constant K 3 of the polymer nematic. The results show that, in the liquid-crystalline mass of the polymer, the reorientation of macromolecules in magnetic and electric fields follows the mechanism of a small-scale local motion of chain units.
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