Dielectric relaxations in side-chain liquid crystalline polymers

Side-chain liquid crystalline polymers represent a novel class of mesogenic materials which exhibit electro- and magneto-optical properties that are similar to those observed for the low-molecular-weight liquid crystals, whilst also having the good film-forming qualities that are characteristic of the high molar mass polymers. From the rotational dynamic theory, four relaxation modes which are dielectrically active arise from combinations of certain time-correlation functions for the angular motions of the dipolar groups in the local (nematic) potential. The practical dielectric relaxation spectroscopy over a wide frequency range shows two typical relaxation processes of the mesogenic side chain when the environmental temperature is above the polymer's glass transition (;Influences of the molecular weight and the spacer length on the dielectric relaxation have been investigated for a smectic polyvinylether containing cyanobiphenyl side group. Both homogeneous and homeotropic alignments were achieved with an 8-Tesla magnetic field by slowly cooling the sample down from the isotropic phase to room temperature. The low-frequency ;The dielectric results of a nematic polymethacrylates containing a constitutional isomeric methoxy-methylstilbene mesogen (4-6-PMA and 4...