The effect of the shape of the mesogenic group on the structure and phase behavior of 2,3,4-tris(dodecyloxy)benzenesulfonates with alkaline cations

Abstract

Synthesis and mesophase structure characterisation are reported for a group of alkali salts of 2,3,4-tris(dodecyloxy)benzenesulfonic acid. As revealed by a combination of polarizing optical microscopy, differential scanning calorimetry and X-ray scattering, variation of the effective mesogen shape due to changes of the cation size leads to systematic transformation of the materials' phase behaviour. Thermotropic mesophases of different types and dimensionalities were observed: 1D (smectic bilayers), 2D (ordered and disordered columnar phases), and 3D (high-temperature micellar mesomorphic phase, low-temperature crystalline one). Cubic packing prevails when the cation size is small and, thus, the effective mesogen shape is close to the conic one. With increasing ion size, the mesogen shape becomes more tapered, and columnar mesophases appear to be more stable.

Molecular ejection transition in liquid crystal columns self-assembled from wedge-shaped minidendrons

“…These have their counterparts in metals and are either cubic such as Pm3n (A15) 5 and body-centered cubic (BCC) 6 , or tetragonal (α-phase) 7 or even quasicrystalline 8,9 . Interestingly, all phases observed so far in these series of compounds can be seen in the simplest of them, known as 'minidendrons' [10][11][12] (see e.g. Figure 1a).…”

Added Alkane Allows Thermal Thinning of Supramolecular Columns by Forming Superlattice—An X-ray and Neutron Study

“…While dendrons of this type up to fifth generation have been synthesized and studied, it turned out that most LC phases are observed already with the simplest tapered mesogens, the so-called “minidendrons”, containing just one benzene ring, a weekly interacting group at the apex (1-position) and three or two flexible chains attached to positions 3, 4 and/or 5. The group at the apex could be carboxylate salt , sulfonate salt, an onium group , or other.…”

The effect of aliphatic chain length on the self-assembly of wedge-shaped cesium 3,4,5-tris(alkyloxy)benzenesulfonates

“…Furthermore, order–disorder transition in the cylinders of the columnar phase is accompanied by a significant redistribution of relative intensity of crystallographic reflections and therefore electron density in columns. 62 A rise of temperature causes a change of the potassium and sodium 2,3,4-tris(dodecyloxy)benzenesulfonate dendron shape and leads to the formation of a plastic type cubic phase. For cesium 2,3,4-tris(dodecyloxy)benzenesulfonate, only ordered and disordered columnar phases are observed.…”