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Lateral fluoro-substitution and chiral effects on supramolecular liquid crystals containing rod-like and H-bonded bent-core mesogens†
Chun-Chieh Han,Li-Han Yang,Putikam Raghunath,Ming-Chang Lin,Rohit Kumar,Hong-Cheu Lin
RSC Advances Pub Date : 11/11/2016 00:00:00 , DOI:10.1039/C6RA19266A
Abstract

The first series of liquid crystalline supramolecular diads C/D containing asymmetric rod-like and H-bonded bent-core mesogens were designed and synthesised, among which supramolecular diad Image ID:c6ra19266a-t3.gif/Image ID:c6ra19266a-t4.gif with two chiral centers on both the H-acceptor/H-donor and non-lateral fluoride substitution possessed a wide blue phase (BPI) range of 13.7 °C. According to the molecular modeling, a large biaxial parameter (≥3.2) and an appropriate HTP value (4.2–4.8 μm−1) are the most important factors to stabilize the double twisted cylinder structure (i.e., BPI) in supramolecular diads. Moreover, the bent angles, biaxial parameters and dipole moments of supramolecular diads are mainly affected by the locations and numbers of H-bonds and chiral centers. Not only larger bent angles and biaxial parameters but also smaller dipole moments and HTP values were obtained by removing the lateral fluoride substitution on supramolecular diads to achieve the blue phase of Image ID:c6ra19266a-t5.gif/Image ID:c6ra19266a-t6.gif (without lateral fluoride substitution). Finally, the special optimal 1 : 1 molar ratio of supramolecular diad Image ID:c6ra19266a-t7.gif/Image ID:c6ra19266a-t8.gif (i.e., H-donor = 50 mol%) with the widest blue phase range is mainly attributed to its rod-like and H-bonded bent-core mesogens, rather than H-donor = 75 mol% in most supramolecular complexes containing linear H-bonded rod-like mesogens.

Graphical abstract: Lateral fluoro-substitution and chiral effects on supramolecular liquid crystals containing rod-like and H-bonded bent-core mesogens
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