Showing papers by "Krzysztof Czupryński published in 2006"

Synthesis and characterization of new ferroelectric liquid‐crystalline cyclic oligosiloxanes containing methyleneoxymethylene spacers

Abstract: The synthesis of side-chain liquid-crystalline oligocyclosiloxanes containing methyleneoxymethylene spacers, two different mesogenic cores (including biphenyl phenyl carboxylate or biphenyl fluorophenyl carboxylate groups) and chiral tails is presented. Differential scanning calorimetry, optical polarizing microscopy and X-ray diffraction measurements reveal liquid-crystalline properties for all of the synthesized monomers and oligomers. All cyclic oligosiloxanes exhibit enantiotropic smectic A and chiral smectic C phases. The mesogenic properties of the cyclic oligomers and side-chain liquid-crystalline precursor are discussed. Copyright © 2005 Society of Chemical Industry

Ferroelectric Compounds with Strong Polar Cyano Group in Terminal Position

Abstract: The synthesis, phase transition parameters, the temperature dependence of spontaneous polarization, tilt and pitch of (S)-(+)-4-(1-methylheptyloxycarbonyl)phenyl 4′-(cyanoacetoxy hexoxy)biphenyl-4-carboxylates and (S)-(+)-4-(1-methylheptyloxycarbonyl)biphenylyl 4′-(cyanoacetoxy)benzoate are described. These compounds exhibit the synclinic smectic C phase and are useful as the components of antiferroelectric mixtures with high tilt angle. The (S)-(+)-4-(1-methylheptyloxycarbonyl)phenyl 4′-(cyanoacetoxyhexoxy)biphenyl-4-carboxylate shows the ability to induce an antiferroelectric phase in mixtures based on the other ferroelectric components.

Pretransitional behavior in the isotropic phase of a nematic liquid crystal with the transverse permanent dipole moment

Abstract: The results presented give the evidence for the quasicritical, pretransitional behavior of dielectric properties in the isotropic phase of a rodlike nematic liquid crystal with the transverse permanent dipole moment. Studies were conducted in 2-cyano-4-pentylbiphenyl 4-(trans-4-pentylcyclohexyl) benzoate, focusing on the static-and ionic-dominated low-frequency (LF) regions. For the static dielectric permittivity [epsilon(')(T)] the application of the derivative analysis revealed the pretransitional anomaly associated with the specific heat exponent alpha approximately 0.5. For the LF domain the contribution to epsilon(')(T) from residual ionic impurities follows a linear temperature dependence on approaching the isotropic-nematic (I-N) transition. This dependence and pretransitional anomalies of electric conductivity and dielectric modulus can be associated with the influence of prenematic fluctuations. "Linear" dielectric studies were supported by the static nonlinear dielectric effect measurements, which delivered reliable estimations of the temperature of the hypothetical continuous phase transition T(*) and the discontinuity of the I-N transition DeltaT approximately 1.7 K.