New compounds with a TGBA-TGBC-SmC* phase sequence

Abstract

A new series of lactic acid derivatives has been prepared with molecular cores consisting of two laterally substituted biphenyls connected by an ester group. The compounds exhibited the TGBA phase in a broad temperature range. In addition, for some compounds, a narrow blue phase was found above the TGBA phase on cooling from the isotropic phase. Except for the compound with the shortest chain, the TGBC phase appeared below the TGBA phase. The low temperature SmC* phase existed within the interval up to 80 K, including the overcooled state, which was down to room temperature. In the compounds studied a strong pre-transitional phenomenon took place manifested as a broad peak on the differential scanning calorimetry plot in the isotropic phase. The phases were established on the basis of a planar sample and free-standing film microscope observation. Small angle X-ray diffraction measurements provided information about layer spacing, d, and confirmed the phase assignment. Dielectric spectroscopy revealed the soft and Goldstone modes in the respective TGBA and SmC* phases.

Effect of Molecular Structure and Thermal Treatment on Photo‐optical Properties of Photochromic Azobenzene‐containing Polymer Films

“…(S)-2-methylbutyl-(S)-lactate 5 was prepared according to a method described elsewhere. [19] The reaction mixture was poured into water, extracted using diethylether, washed with dilute hydrochloric acid and evaporated. The product was stirred in a mixture of tetrahydrofuran and ammonia at room temperature.…”

Frustrated smectic liquid crystalline phases in lactic acid derivatives

“…[23] It can be supposed that both soft and Goldstone modes are active in the individual smectic blocks forming the TGB superstructure, but these modes are not homogeneous within the blocks, as they are clamped at the grain boundaries limiting the blocks. [14,15,24] The clamping results in increase of relaxation frequencies and decrease of the dielectric strength compared to those typical for homogeneous SmA and SmC Ã phases. The difference might reach two orders for each quantity.…”

“…It indicates that the helical superstructure adopts the role of layers in smectic phases. [14] In both these sample geometries the filament texture takes place.…”

“…Temperature dependences of both quantities exhibit either no or small anomalies at the TGBC À SmC Ã transition, depending on value of the applied electric field (see Figure 9). [14,15] It may happen that in the TGBC phase the P value cannot be evaluated because the ferroelectric switching is not complete due to very high coercive field.…”

“…The length of the non-chiral chain expressed by n number of carbon atoms has been varied. [14,15] The lactate has been employed because of its strong chirality. Besides the lactates, additional chiral centre is present in the metylbutyl chain, all chiral centres having the same S configuration.…”