Effect of the dimeric H-bonded mesogens of chiral acids on the mesogenic and optical properties

ABSTRACT

A serial of chiral aromatic acid derivatives was systematically prepared to study the effect of dimeric H-bonded mesogens on liquid crystal (LC) and optical behaviours. The lateral fluoro-substituent and the chiral terminal chains were also studied for comparison. When the H-bonded mesogens changed from biphenyl or phenyl benzoate to naphthalene ring or benzene ring, the molecular length‒width ratio reduced greatly, which thus led the temperature range of mesophases reduced and the phase transition decreased. The lateral fluoro-substituent, a shorter or meta-substituted terminal chain, could make the mesophase range narrowed or disappeared. Besides the chiral nematic (N*) phase, twist grain boundary C (TGBC*) phase was found in the double aromatic-ring acids with a chiral para-substituted octan-2-yloxyl group. Interestingly, the TGBC* phase could scatter away most incident light in any surface anchoring condition, and the light scattering performance exceeded any other phases of low-molecular-weight LCs known. The unusual H-boned material could be used for preparing reversible optical switches without using any polariser and any surface alignment treatment.

Graphical Abstract

KEYWORDS:

• Hydrogen bond
• light scattering
• TGBC* phase
• liquid crystal

Disclosure statement

No potential conflict of interest was reported by the authors.

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Funding

This work was supported by the National Natural Science Foundation of China [grant number 61370048], [grant number 51333001], [grant number 51373024], [grant number 51473020]; the National Key Basic Research Program of China [grant number 2014CB931804]; and the Fundamental Research Funds for the Central Universities [grant number FRF-TP-15-003A3].