Ten isomeric five-ring bent-core mesogens: The influence of the direction of the carboxyl connecting groups on the mesophase behaviour

Abstract

In order to study the role of the direction of the connecting groups in bent-core mesogens we synthesized two series of ten possible achiral isomeric five-ring bent-core compounds in which all aromatic rings are connected by ester groups and each of which possesses the same length of the terminal chains (octyloxy or dodecyloxy, respectively). The structure of the isomers is distinguished by the direction of at least one ester group, only. The mesophase behaviour of the compounds has been studied by polarizing microscopy, differential scanning calorimetry, X-ray experiments and electro-optical measurements. We have found that in spite of the minor structural differences a variety of mesophases occur (SmCP A , Col rec , Col ob ) whereby the clearing temperatures vary from 121 to 193 uC (octyloxy isomers) and 112 to 189 uC (dodecyloxy isomers). Depending on the direction of the ester groups some of these isomers show interesting properties, such as field-induced inversion of chirality in SmCP A and columnar phases, the field-induced enhancement of the clearing temperature, a second-order phase transition Col ob A SmCP A or the reversible field-induced phase transition Col ob A SmCP F . The unexpectedly strong influence of the direction of the connecting groups is discussed on the base of theoretical calculations and molecular dynamics simulation on isolated molecules.

Dynamically self-assembled silver nanoparticles as a thermally tunable metamaterial

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Hockey stick-shaped azo compounds: effect of linkage groups and their direction of linking on mesomorphic properties

“…From our previous studies [22,23] as well as other reports, [24,25] it has been found that even a small change such as changing/reversing a linkage group in bent-core compounds may affect, to a great extent, the mesomorphic properties of the resulting compounds. Thus, to study such effects in hockey stickshaped azo compounds, we synthesised five new series of hockey stick-shaped azo compounds in addition to four compounds I, II, III and IV.…”

Electric‐ and Light‐Responsive Bent‐Core Liquid Crystals: From Molecular Architecture and Supramolecular Nanostructures to Applications

“…[102]. These isomeric bent-core molecules exhibit SmCP and/or Col phases [103]. The calculated dipole moments along the bend direction are all negative without an external E-field and change their signs from the negative to the positive upon applying a small E-field depending on the orientation of carboxylate groups.…”

“…6.7c and 6.7b) to illustrate layer chirality for compounds 3 and 4. [103], and the calculation was carried out with an external E-field (0.006 au in y direction) in a coordinate system as shown. The dipole direction points from the negative to the positive, as defined in physics.…”