Self-assembly of twin tapered bisamides into supramolecular columns exhibiting hexagonal columnar mesophases. Structural evidence for a microsegregated model of the supramolecular column

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Abstract
The 1,2-bis[3,4,5-tris(alkan-1-yloxy)benzamido] ethanes (DA-n , where n is the number of carbons in the alkanyl group) form a high temperature hexagonal columnar (ϕh) liquid crystalline phase when n ' 10, 11, 12, 14, 16 and 18. DA-n with n ' 4, 5, 6, and 7 show at elevated temperatures a distorted hexagonal crystal phase. X-ray diffraction data support a model for the ϕh phase consisting of a 2-D hexagonal lattice of self-assembled supramolecular columns in which the melted outstretching alkyl chains of DA-n occupy a space of constant density surrounding a rigid amide channel. A local ABAB stacking of layers along the column is proposed. Each layer contains two DA-n molecules. Layer B is rotated by 90[ddot] around the column axis relative to layer A. H-bonding between the amide groups is responsible for this mode of self-assembly.

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