Using Lateral Substitution to Control Conformational Preference and Phase Behaviour of Benzanilide‐based Liquid Crystal Dimers. Issue 7 (30th December 2022)

• Record Type: Journal Article
• Authors: Strachan, Grant J.; Majewska, Magdalena M.; Pociecha, Damian; Storey, John M.D.; Imrie, Corrie T.
• Is Part Of: Chemphyschem. Volume 24:Issue 7(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-12-30
• Subjects: benzanilide -- conformational analysis -- liquid crystals -- nematic phase -- NMR spectroscopy; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.202200758
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: 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° 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° 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. Abstract : Turning back the amide : Tertiary benzanilides show a strong preference for the E amide conformation which tends to inhibit the formation of liquid crystal phases. Here we show that adding methyl substituents around the amide bond can promote mesophase formation by modifying the conformational preferences of the amide group.