Chiral smectic-Aand smectic-Cphases with de Vries characteristics

Fluorenone imidazolium salts as novel de Vries materials

“…[26][27][28][29] De Vries materials have created much interest recently, because ferroelectric displays based on de Vries materials might overcome limitations of current nematic LC displays such as limited resolution and low optical efficiency. [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] One of the characteristic features of de Vries materials is their tilting transition without defect generation. These materials show no or only very low layer contraction upon the SmA to SmC phase transition, enabling ferroelectric displays without zig-zag defects caused by the chevron-like arrangement of the molecules in the mesophase.…”

“…These materials show no or only very low layer contraction upon the SmA to SmC phase transition, enabling ferroelectric displays without zig-zag defects caused by the chevron-like arrangement of the molecules in the mesophase. With regard to the design of calamitic liquid crystals displaying SmA and SmC phases and de Vries behaviour most previous work has focused on 5-phenylpyrimidines, 39,41,43,[48][49][50][51][52][53] 2phenylpyrimidines, [54][55][56][57][58] biphenyls, 40,44,[59][60][61][62][63][64] thiadiazoles, 54,65 aroylhydrazones 66 and bent-core mesogens. 37,[67][68][69][70][71][72][73][74] Lemieux and Ivanov have reported independently for non-charged liquid crystals 3-5 that a rigid uorenone core promotes formation of the SmC phase.…”

Nematic Phase of Polar Unsymmetrical Bent‐Core Molecules

“…The experimental data for complex permittivity were fitted to the Havriliak‐Negami equation to calculate the relaxation frequency and corresponding strengths of the relaxation modes. The Havriliak‐Negami equation is given by: [53,54] $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr {\varepsilon{} }^{{\rm ^{\ast}}}\left(\omega \right)={\varepsilon{} }^{{\rm { {^\prime}}}}-i{\varepsilon{} }^{{\rm { {^\prime}}}{\rm { {^\prime}}}}={\varepsilon{} }_{{\rm \infty }}+\sum _{k=1}^{2}{{\delta {\varepsilon{} }_{k}}\over{{\left[1+{\left(i\omega {\tau }_{k}\right)}^{{\alpha }_{k}}\right]}^{{\beta }_{k}}}}-{{i\sigma }\over{{\varepsilon{} }_{0}\omega }}\ \hfill\cr}}$$$ …”

“…The experimental data for complex permittivity were fitted to the Havriliak-Negami equation to calculate the relaxation frequency and corresponding strengths of the relaxation modes. The Havriliak-Negami equation is given by: [53,54] e…”

A chiral smectic phase induced by an alternating external field

“…The discovery of chiral liquid crystals can be traced back to the cholesteric liquid crystal formed by cholesterol, 1 which becomes the prelude to studies on chiral liquid crystals. A number of liquid crystalline phases possess the signature of chirality, such as cholesteric, 2 blue, [3][4][5][6] chiral smectic A (SmA*), 7 and chiral smectic C (SmC*). 8,9 The pitch of chiral liquid crystals sometimes can be selective to the wavelength of light that can be transmitted, and therefore they are often used as optical devices, such as novel displays, light shutters, polarization modulators, lasers and sensors.…”