A new type of square columnar liquid crystalline phases formed by facial amphiphilic triblock molecules

A series of three novel liquid crystalline amphiphilic molecules is reported which are composed of three incompatible molecular parts, a rigid terphenyl core, two lipophilic decyloxy chains in the terminal 4- and 4′′-positions, and a polar group in the lateral 2′-position. The polar group comprises a polyether chain, an amide group, and a polyhydroxyalkyl end group (1-acylamino-1-deoxy-D-sorbitol derivatives). The self-organization of these compounds was studied by polarized light microscopy, differential scanning calorimetry, and different X-ray diffraction techniques. These investigations confirm a novel liquid crystalline phase with a square 2D-lattice (square columnar mesophase, plane group p4mm). This structure is built up by a set of three distinct columns, namely columns containing the polar lateral groups, columns incorporating the alkyl chains, and ribbons of the rodlike terphenyl units. The calamitic cores form walls bounding square-shaped channels occupied by the microsegregated polar lateral chains. The lipophilic columns containing alkyl chains are at the corners interconnecting the aromatic rods end-to-end.