Using Lateral Substitution to Control Conformational Preference and Phase Behaviour of Benzanilide-based Liquid Crystal Dimers

The inclusion of secondary and tertiary benzanilide-based mesogenic groups into liquid crystal dimers is reported as a means to develop new materials. Furthermore, substitution at the nitrogen atom is shown to introduce an additional synthetic 'handle' to modify the molecular structure of the tertiary materials. The design of these materials has proved challenging due to the strong preferences of 3 degrees benzanilides for the E amide conformation. In this work, lateral substitution is used to modify the conformational preferences of the amide linkage and promote liquid crystallinity for a series of N-methyl benzanilide dimers. As the proportion of the E conformer decreases, the nematic-isotropic transition temperatures increase, and enantiotropic nematic behaviour is observed. We also report the synthesis and characterisation of the analogous 2 degrees benzanilide-based materials, which show nematic and twist-bend nematic behaviour. This approach highlights the effects that seemingly small structural modifications, such as the inclusion and position of a methyl group, can have on molecular shape and hence, liquid crystalline behaviour.

Automated summary

The study reports the development of new materials by incorporating benzanilide-based mesogenic groups into liquid crystal dimers. The addition of a substituent at the nitrogen atom allows for further modification of the tertiary materials. Lateral substitution is used to modify the conformational preferences of the amide linkage, resulting in liquid crystallinity for a series of N-methyl benzanilide dimers. Structural modifications, such as the inclusion and position of a methyl group, can greatly affect molecular shape and liquid crystalline behavior.