Three Classes of New Chiral Dopants: Synthesis and Physical Qualification as Dopants for Practical FLC-Mixtures

Abstract

Three classes of new chiral dopants were synthesized and their properties in a non-chiral host mixture were measured. An extremely large spontaneous polarization (77 nC/cm2 at 25°C) was induced by 10% dopant in one case. Molecular mechanics calculations reveal that such a high polarization is predominantly obtained by steric hindrance around the chiral center. This steric effect also influences other physical properties such as helical twisting power. In addition the relationship between electro-optical properties and spontaneous polarization (Ps) are studied. It is apparent that higher Ps does not always improve switching time and bistability.

Cristais Líquidos Ferroelétricos - CLF. Uma abordagem sintética

“…Dübal e colaboradores 33 A análise do comportamento mesomórfico para os 14 compostos sintetizados revela que, de um modo geral, predomina a mesofase nemática quiral e alguns mostram mesofase S A e ausência de S C *. As propriedades eletroópticas para estes compostos, tais como, polarização, ângulo de inclinação, passo da hélice, etc, foram medidas usando-se misturas de pirimidinas e ésteres padrões como hospedeiro quiral Sc7 1007, em 15 o C abaixo da transição S C *.…”

New monomer liquid crystals containing a chiral 2,2- or 2,3-disubstituted oxirane ring

“…The solution was diluted with 40 ml of water and 120 ml of dichloromethane, and the organic phase was then separated, dried over Na 2 SO 4 , and evaporated to dryness. The solid residue was crystallized from methanol, giving (4)(5)(6)(7)(8)(9)(10)(11). A suspension of 1.01 g (2.12 mmol) of 26-11, 0.26 g (2.13 mmol) of potassium t-butoxide, and 1.95 g of powdered molecular sieves (4 Å) in 70 ml of dimethyl sulfoxide was vigorously stirred for 1 h. A solution of 1.10 g (3.53 mmol) of 21 in 30 ml of dimethyl sulfoxide was then added in 20 min at room temperature.…”

“…A great diversity of chiral groups have been used in combination with mesogenic cores to induce chirality in liquid crystals. Comparatively little attention has been devoted to the oxirane ring as a chiral building block [9][10][11][12][13][14][15][16]. 2,3-Disubstituted and 2,2-disubstituted oxirane rings (I and II, respectively) present distinct structural features.…”