Supramolecular liquid crystals from the dimer of L-shapedmolecules with tertiary amide end groups

Supramolecular liquid crystals(SLCs)are attractive materials for fabricating devices with new optoelectronic functions.Conventional SLCs are made from hydrogen-bonded mesogens.However,these mesogens suffer from high melting points,and the types of formable aggregates are limited owing to the directionality of the hydro-gen bonding.Therefore,to fabricate non-hydrogen-bonded SLCs,we hypothesized that the introduction of tertiary amide groups into calamitic molecules would be advantageous because they have an L-shaped structure with N-or C-alkyl side chains not aligned along the long axis and theflexibility to undergo cis–trans isomeriza-tion.In this study,we developed a novel non-hydrogen-bonded SLC by assembling an L-shaped dimer composed of calamitic molecules(phenyltolanes)with tertiary amides at their ends.These molecules exhibited a smectic B phase.The phase tran-sition temperature of the SLCs from crystal to liquid crystal phase was low despite the longπ-conjugated core.Wide-angle X-ray diffraction and variable-temperature Fourier-transform infrared measurements revealed dimer formation by weak inter-molecular interactions,that is,the molecular recognition of L-shaped molecules,and mobility of the alkyl groups attached to amide driven by cis–trans isomerization in the liquid crystal phase.Thus,cis–trans isomerization of tertiary amides contributed enormously to the formation and lower clearing points of this SLC.The developed method can be used not only to develop non-hydrogen-bonded SLCs but also to develop novel soft matter with controlled properties by incorporating the SLCs,as the aggregates can be controlled to impart desired functionalities.