Physical Studies of Homologous 4-Cyanophenyl Esters of 4′- n-Alkylcinnamic Acids

The mean polarizabilities of homologous series of nematic liquid crystals of 4-cyanophenyl esters of 4′- n-alkylcinnamic acids are evaluated by using the MLδP method. From these polarizabilities the mean diamagnetic susceptibilities of the liquid crystals are also calculated. The orientational order parameters of these compounds are also estimated using the Vuks and Neugebauer methods. The variation of the order parameter with temperature is discussed.     

Synthesis and Some Properties of 3-Fluoro-4-Cyanophenyl 4′-n-alkylbenzoates

A series of 3-fluoro-4-cyanophenyl 4′-n-alkylbenzoates, which show monotropic nematic phases, was prepared and their transition temperatures and melting enthalpies were measured. The 3-fluoro-4-cyanophenyl 4′-n-propylbenzoate, 3-chloro-4-cyanophenyl 4′-n-propylbenzoate and 4-cyanophenyl 4′-n-propylbenzoate were mixed with a nematic mixture (A) of 4-n-alkoxyphenyl 4′-n-alkylcyclohexane-1′-carboxylates. 3-Fluoro-4-cyanophenyl 4′-n-propylbenzoate decreases the N-1 transition temperature less, increases the birefringence more, and increases the bulk viscosity less than 3-chloro-4-cyanophenyl 4′-n-propylbenzoate, and reduces the threshold voltage to the greatest extent. The dielectric anisotropies of 3-fluoro-4-cyanophenyl 4′-n-propylbenzoate and 4-cyanophenyl 4′-n-propylbenzoate determined from a series of solutions of the compounds in nematic mixture (A) are 35.9 and 29.6, respectively.     

The Synthesis of Fluorine Containing Phenyl Benzoates and Their Properties as Liquid Crystals

A new series of fluorine containing phenyl benzoates has been synthesized and the transition temperatures of these compounds have been determined. A series of 4-trifluoromethylphe 4nyl 4-n-alkybenzoates showed no liquid crystalline behaviour, but the 4-trifluoromethylphenyl 4-n-alkoxybenzoates series, with six carbons or more in alkoxy chain, was mesomorphic. The 4-cyanophenyl 4-perfluoroalkylbenzoates showed smectic liquid crystalline properties.     

Synthesis and Structural Analysis of 2-Cyanophenyl Phenacyl Ether

Crystallography Reports - Molecular and crystal structure of 2-cyanophenyl phenacyl ether, C15H11O2N, have been determined by single crystal X-ray diffraction study. The title compound is...     

Phase Diagrams of New Compounds with Nematic Reentrant Mesophases

Two new series of compounds exhibiting nematic and smectic reentrant mesophases are presented here; the first one is 4-n-alkoxy benzoyloxybenzylidene 4'-cyanoaniline series the second one the 1-(4-n-alkylbenzoyloxyphenyl) 2-(4'-cyanophenyl) ethane series. Isobaric binary phase diagrams are plotted for each compound by means of the contact method and the mesophases so identified.     

Nematogens for Matrix-Addressed Twisted Nematic Displays - I

Nematogens with small Δσ/σ₁ for matrix-addressed TN-displays were synthesized. The effect of introducing lateral cyano groups on the dielectric constants and the thermodynamic stability of the mesophase of 4-cyanophenyl esters is described. Fluoro-PCH's suitable for matrix addressing were prepared and the effect of the fluoro substituent on the clearing point was studied.     

The Structure of 4-n-Hexyle-6-(4-cyanophenyl)-1,5-diazobicyclo [3.1.0]-hexanone-(2), C17H21N3O

M_r = 283.2; monoclinic, P 2₁/c, a = 9.631(7), b = 21.268(16), c = 8.488(8) Å, β = 107.13(9)°, Z = 4, V = 1661.8(9) ų, D_x = 1.42 Mg m⁻³, final R = 0.134 for 605 independent reflections excluding those with |F_o| < 3σ|F_o|). Intensities were measured with an automatic diffractometer. The compound is a product of a photoreaction. The five membered ring and the three membered ring of the bicyclic diaziridine group and the six membered ring of the 4-cyanophenyl group are nearly perpendicular one to another. The 4-cyanophenyl group is in exo-position to the five membered ring of the bicyclic diaziridine group. The C(4) atom and the aliphatic hexyle group are in respect to the five ring in trans-position.     

Synthesis and crystal structure elucidation of 1-(4-fluorobenzyl)-2-(4-cyanophenyl)-1H- benzimidazole-5-carbonitrile

The synthesis and spectral identification of 1-(4-fluorobenzyl)-2-(4-cyanophenyl)-1H-benzimidazole-5-carbonitrile (1) have been reported. IR, ¹H NMR, and EI mass spectral analysis were used for its spectral identification. The structure of 1 was confirmed by X-ray crystallographic studies. Intramolecular hydrogen bond occurs between the imidazole nitrogen and one of hydrogen of the florobenzene. The crystal packing is governed by C–HN intermolecular hydrogen bonds. The molecular structure observed in crystal and the optimised geometries at the HF level by doing semi-empirical and ab initio calculations were compared.     

The Order Parameters of Some Nematic Liquid Crystals Measured by the Resonance Raman Effect and Its Relevance to the Nematic-Isotropic Phase Transition

The second and fourth order parameters of nematic MBBA and 5CB have been determined near the nematic-isotropic transition temperatures by means of resonance Raman measurements on β-carotene dissolved as an orientational probe. The limiting behaviour of the second order parameter of MBBA near the transition point has been investigated on the basis of its fluctuation, which is deduced from the 2nd and 4th order parameter values.     

X-Ray Studies of Cyanophenyl Pyrimidines Part II The Crystal and Molecular Structure of 5-(4-Ethylcyclohexyl)-2-(4-Cyanophenyl)Pyrimidine

The crystal and molecular structure of 5-(4-ethylcyclohexyl)-2-(4-cyanophenyl)pyrimidine (ECCPP), C₁₉H₁₈N₃, has been determined at room temperature by means of direct methods. The crystals belong to the monoclinic space group P2₁/n, a = 15.959(2), b = 33.469(3), c = 6.210(3) Å β = 90.335(7)° with 8 molecules in the unit cell. Refinement converged to an R value of 0.086. One of the two independent molecules in the unit cell exhibits disorder in the cyclohexane ring. The molecules extend roughly in the [010] direction and form a rather complicated structure in which dipolar interactions play a role.     

Single Crystal,DFT and Docking Studies of a Benzimidazolium Salt

Crystallography Reports - A single-crystal of (C18H18N3)+Br–, namely, 3-[(2-cyanophenyl)methyl]-1-propyl-1H-benzo[d]imidazol-3-ium bromide, was studied using X-ray diffraction techniques....     

Order Parameters of β-Substituted Anthraquinone Dyes I: 1-Amino-4-Hydroxyanthraquinone Derivatives

A study is presented of the optical order parameters and spectroscopic properties of I-amino-4-hydroxyanthraquinone derivatives containing various substituents in the 2-position in a nematic liquid crystalline mixture composed of cyanophenylcyclohexane derivatives. The results are discussed in terms of the effects of the dye structure on the order parameters. By introducing a-SCH₂-group into the 2-position, magenta dyes have been obtained which show high order parameters and solubilities. In addition, preliminary data on the solubility and photostability of the dyes are reported.     

Magnetic and Electric Birefringence in the Isotropic Phase of a Nematic of Large Positive Dielectric Anisotropy

Abstract

Magnetic (Δn_H ) and electric birefringence (Δn_E ) in the isotropic phase of strongly positive (Δ 8)trans-p-n-octyloxy α-methyl-p'-cyanophenyl cinnamate (8 OMCPC) have been measured. It is established that they both exhibit a (T - T*)^?1 dependence, T _NI - T* being 1.4 K. Also, the induced birefringence is found to be proportional to the square of the applied field, magnetic or electric.     

Optical Anisotropy of Dodecyl Benzene Sulfonic Acid

The order parameters of a number of novel 2-aryl-l,4-naphthoquinone dyes dissolved in a mixed cyanobiphenyl-terphenyl nematic liquid crystal system (Type E43, B.D.H. Chemicals Ltd.) have been determined. Observed values range from 0.80 to 0.09, and can be interpreted qualitatively by consideration of the w-dipole moment and transition moment directions of the dyes calculated by the PPP-SCF-CI MO method.     

Liquid Crystals: A Bibliography for 1975

Abstract

The static dielectric constants of biphenyl-4-p-n-alkoxybenzoates have been measured as functions of temperature. The dielectric anisotropy (δ?) for the successive homologues (hexyl to undecyl) shows an alternation similar to that exhibited by the nematic-isotropic transition temperature (T _NI). The dispersion of ?_∥ in the frequency range of 0.1-15 MHz has been studied for four successive members of biphenyl-4-p-n-alkoxybenzoates (heptyl to decyl derivatives) as well as of trans-p-n-alkoxy-α-methyl-p'-cyanophenyl cinnamates (eighth to eleventh members). For both series the relaxation frequency (f _R) and the frequency of dielectric isotropy (f _o) evaluated at a common relative temperature show an alternation similar to T _NI. For any given compound the Arrhenius plots for f _R and f _o give the same value of the activation energy (W). In the case of the biphenyl esters the vaue of W is the same for the seventh and eighth members, but increases for the higher members which exhibit a smectic phase at lower temperatures. On the contrary for cinnamic acid esters W is found to be the same for all homologues irrespective of whether the nematic phase is preceded by a smectic phase or not.     

Molecular Properties and Order Parameters of Schiff's Base Compounds

The refractive indices n_o, n_c and the order parameters are measured as a function of temperature for the Schiffs base compound PBBA. From the experimental data the molecular polarisabilities and its anisotropies at different wavelengths are calculated using different internal field models. The merits of each model are discussed. Order parameters (P ₂), (P ₄) and other molecular parameters of PBBA and EBBA are also calculated using X-ray diffraction techniques at different temperatures. Comparison with theoretical values shows the relative merits of different experimental techniques. The (P ₂) and (P ₄) values of other members of the Schiff's base compounds, already reported from our laboratory, have been given herewith to show the disagreement with the simple mean field theory. Possible causes for such disagreement have been discussed.     

Progress in the growth of CaCu3Ti4O12 and related functional dielectric perovskites

Calcium copper titanate, CaCu₃Ti₄O₁₂, (CCTO), a potential electro-ceramic is a member of a very important perovskite family and has been found to a show dielectric constant of the order of 10⁴–10⁵. It has a remarkable ability to undergo a series of cationic exchange reactions resulting in corresponding isomorphs. In the past decade there has been immense activity in the search of an isomorph of CCTO with high dielectric constant and low loss which enables its use as capacitor material for the storage of energy and miniaturization of electronic based equipment. Despite intensive research in the area there is no source of any literature that gives all the possible relevant information regarding various synthetic methods, characterizations, effect of sintering parameters (temperature, duration, and atmosphere). This review article is an effort to review the synthesis, grain growth, morphological evolution, effect of impurities, substitution and interface anisotropy on the dielectric constant, resistivity and other materials parameters.     

Molecular Ordering in Liquid Crystals and the Effect of End-Chains on the Even-Odd Effect

The second and fourth orientational order parameters [Pbar]₂, [Pbar]₄ of the homologous series of 4-n-alkyl-4′-cyanobiphenyls (nCB, n = 5 ～ 8) in the nematic liquid crystalline state have been determined from the Raman depolarization ratios by the resonance Raman probe method. It was found out that not only [Pbar]₂ but also [Pbar]₄ exhibits evident even-odd effect when they are compared at the same reduced temperature. For understanding the mechanism of the even-odd effect, a theoretical calculation has been carried out on the basis of the mean field theory of Marcelja, in which the effect of the end alkyl-chain on the liquid crystalline state is taken explicitly into consideration. The observed trend in [Pbar]₂, [Pbar]₄, nematic-isotropic transition temperature were well reproduced. Detailed inspection of the results shows that the presence of anisotropic molecular field plays an important role in the appearance of the even-odd effect. The anisotropic molecular field produces redistribution of the statistical weight of various conformers in such a way that the end chains of odd-members align better along the direction of the rigid core part than those of even-members.