The Physical and Molecular Properties of New Low Melting Nematics with Negative Dielectric Anisotropy

Abstract

The paper presents some basic physical properties (static electric permittivities, refraction indices, density and viscosity) of 2-chloro-4-n’-alkylphenyl esters of 4-n-alkylbicyclo[2,2,2] octane-1-carboxylic acids (n’=7, n = 5 and 7) which are, at room temperature, nematics with a negative dielectric an-isotropy. On the basis of temperature dependence of the principal static permittivities ε‖(T) and e⊥(T) of the nematics, using the Maier-Meier equations, the angle between the dipole moment vector and the long axis of mesogenic molecules, the apparent molecular dipole moment square pl μ2app(T), and the nematic order parameter S(T) were determined.

Analysis of the Dielectric Anisotropy of Typical Nematics with the Aid of the Maier-Meier Equations

“…[1-3,6-10]). However, only quite recently Jadzyn et al [9,10] have analysed (1) and (2) taking into account the experimental data on the permittivity and polarizability components of several nematics. These authors fitted the theoretical permittivity components to the experimental ones with ß, P" e f((T) and S(T) as adjustable parameters.…”

“…(l) and (2) (open points). molecular rotations around the long and short axes [13][14][15]28], The dielectric permittivities of four of the studied substances (5CB, 60CB, 7CP5BOC, and 7CP7BOC) were recently analysed by Jadzyn et al [9,10] with the aid of (1) and (2). The authors fitted the theoretical permittivity components to the experimental ones with ß, jU gff (T) and 5(7") as the adjustable parameters.…”

“…b [ 17], c [ 16], d according to [ 16], 0 [7],' [ 12], g [26], h [28], 1 [23], j [24], k [21 ], 1 unknown; we assumed the same compressibility value as was obtained for the N phase of 6CB [25], m [13], n [22], ° [10]. nents are by ca.…”

Synthesis of trans, trans-4-(2-Fluoro-3-isothiocyanato-4-propylphenyl)-4-alkylbicyclohexyl for Liquid Crystal Display

“…The reaction mixture of compound (9) (9.8 g, 17 mmol) and palladium on activated carbon (0.01 g) in methanol/THF (20 ml/10 ml) was maintained for 6 h under H 2 stream of 60 psi. After confirmate of complete reaction by 1 H NMR the Pd/C was filtered off and the residue was evaporated in vacuo to give (10) (6.5 g, 16.2 mmol). The pure white solid trans- (10) trans, trans-4-(2-Fluoro-3-isothiocyanato-4-propylphenyl)-4-hexylbicyclohexyl (11).…”

“…Compounds with negative dielectric constant (∆ε<0) is suitable for VA display mode. [1][2][3][4] In order to develop a nematic mesophase material which has a negative dielectric anisotropy, we designed and synthesized compounds with NCS group and F atom on bicyclohexylbenzene core unit and arrange those substituents toward the vertical to long axis of molecule. It is reported that liquid crystals with NCS group have low viscosity, nematic phase of wider range and the high stability to heat, [5][6][7][8][9][10] therefore, NCS group is regarded as an ideal substituent for nematic mesophase compound.…”