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Ferroelectric liquid-crystalline side chain polymers containing polyacrylate or polysiloxane main chains, a mesogenic unit of three aromatic cores and chiral end groups were synthesized and characterized by D.S.C., optical microscopy, and X-ray diffraction. Polyacrylates with a flexible spacer of eleven methylene groups exhibit fast bistable switching in oriented samples (2 to 4μm cells) with response times of some ms at low D.C. voltages, making these polymers interesting for the fabrication of electrooptical devices. Somewhat longer response times were found for the first switchable polysiloxanes. In this case some problems in obtaining well orientated samples have to be solved. 相似文献
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S. U. Vallerien F. Kremer G. Scherowsky A. Schliwa K. Kü hnpast E. W. Fischer 《Liquid crystals》1990,8(5):719-725
Broadband dielectric spectroscopy (10-1 to 107Hz, 100 to 450 K) has been applied, for the first time, to investigate the molecular dynamics of recently synthesized fast switching ferroelectric side group polymers. The softmode could be studied in detail in the Sc* phase and in the S1* phase. At the transition a pronounced increase of the relaxational strength was found whereas its relaxational frequency remains constant The softmode is the molecular basis for the electroclinic effect which has high application potential for ferroelectric liquid crystal polymers. 相似文献
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Abstract We have reported in a previous paper the synthesis, characterization, structural and electro-optic properties of a new family of chiral mesomorphic side chain polyacrylates. The most salient finding was that many of these polymers presented two S*C phases of similar structure, but differing in their switching properties. In addition, two unusual mesophases called U1 and U2 were also discovered in this family. We describe here in more detail the symmetries and molecular organizations for these U1 and U2 phases. We also discuss their relation, on the one hand, to the newly discovered antiferroelectric chiral S*CA and S*o phases, and, on the other hand, to the 2-dimensional fluid smectic à and smectic °C phases displayed by strongly polar low molar mass mesogens. The occurrence of chevron-like ordering in the U1 and U2 phases may give a clue to an understanding of this peculiar S*C polymorphism. 相似文献
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