Syntheses and mesomorphic properties of di-, tri- and tetrafluorosubstituted 4'-(4-alkylphenyl)-4-isothiocyanatotolanes are described. Four fluorine substituted compounds in the position 2', 3', 3, and 5 show stronger nematic character than difluorosubstituted ones in the position 3, 5 or 2', 3'. Example of high birefringence nematic mixture and its properties are given.
3
Dostęp do pełnego tekstu na zewnętrznej witrynie WWW
Mesomorphic and dielectric properties of three homologous series of two and three ring fluorosubstituted esters are described. They are 4-cyano-3-fluorophenyl 4-alkyloxy-2-fluorobenzoates, 4-cyano-3-fluorophenyl 4-(4-alkylbenzoyloxy)-2-fluorobenzoates and 3-fluoro-4-cyanophenyl, or 3-fluoro-4-isothiocyanatophenyl or 3,4-difluorophenyl 4'-alkyl-2,3-difluoro-biphenyl-4-carboxylates. The compounds exhibit the nematic mesophase accompanied by the smectic A or smectic C mesophase in some cases. Most of them show strong dependence of the dielectric anisotropy Δ ε upon frequency, at low frequencies Δ ε reaches a value ∼ 200, while at high frequencies a small negative dielectric anisotropy appears.
4
Dostęp do pełnego tekstu na zewnętrznej witrynie WWW
Novel chiral esters with partially fluorinated alkoxyalkoxy terminal chains are described. Their phase transition temperatures, enthalpies, and electrooptical properties are reported. A helical pitch in pure compounds and their mixtures based on selective reflection of light is also characterized.
5
Dostęp do pełnego tekstu na zewnętrznej witrynie WWW
Compounds with moderate and large negative dielectric anisotropy (Δ ε ) are very attractive liquid crystal (LC) for vertical alignment mode (VA). Materials with such properties can be achieved by lateral substitution of a polar group into a mesogenic molecule. We synthesized some new LC materials with a negative value of Δ ε, a moderately high birefringence (Δ n), and a low viscosity. The mesomorphic and physical behaviour of the novel biphenyls, terphenyls and quaterphenyls fluorosubstituted in the rigid core and also with fluorinated alkyl and alkoxy chains are investigated. The prepared series of four LC compounds are promising for new LC mixtures for various applications. Examples of nematic mixtures with Δ ε ∼ -3.25 will be presented.
6
Dostęp do pełnego tekstu na zewnętrznej witrynie WWW
Three homologous series of orthoconic (45 degree tilt) antiferroelectric liquid crystals containing either naphthyl or terphenyl groups as mesogenic unit have been synthesized and their mesomorphic behaviour investigated by DSC and polarized light microscopy, and their properties discussed. X-ray difraction studies have shown the presence of a de Vries-type smectic A phase which does not exhibit a layer shrinkage on transition to the ferroelectric smectic C phase. Mixtures of the new materials have been formulated and their electro-optical properties investigated for their use in surface stabilized orthoconic antiferroelectric liquid crystal (SSOAFLC) devices.
8
Dostęp do pełnego tekstu na zewnętrznej witrynie WWW
Two types of fast switching mixtures with high positive dielectric anisotropy were described. The first type, with a birefringence below 0.3, was designed for devices operating at room or lower temperatures and the second one, with a birefringence higher than 0.3 for devices operating at elevated temperatures.
9
Dostęp do pełnego tekstu na zewnętrznej witrynie WWW
W pracy opisano syntezę 4-propylo-, 4-hektylobicyklo[2,2,2]oktano-1-karboksylanów 2-chloro-4-heptylofenylu. Zmierzono ich lepkość dynamiczną, gęstość, współczynniki załamania światła i przenikalność elektryczną w różnych temperaturach. Związki te są nematykami o ujemnej anizotropii dielektrycznej i niskiej temperaturze topnienia. Sugeruje się, że związki te mogą być stosowane jako modelowe w badaniach podstawowych dotyczących różnych właściwości związków ciekłokrystalicznych i efektów elektrooptycznych zamiast mniej trwałego MBBA, a także mogą być wykorzystywane jako anizotropowe rozpuszczalniki w badaniach spektroskopowych lub kinetycznych.
EN
2-chloro-4-heptylphenyl 4-alkylbicyclo[2,2,2]octane-1-carboxylates have been synthesized. They are low melting stable nematic compounds with a negative dielectric anisotropy. The temperature dependence of the bulk viscosity, density, optical indices, dielectric constants and elastic constants have been measured. It is suggested that these compounds may be used instead of MBBA for testing and demonstrating of different liquid crystalline properties and effects. They may be useful also as anisotropic solvents in spectroscopic studies.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.