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

Abstract

Wedge-shaped dendrons based on benzenesulfonic acid form a variety of liquid crystal mesophases, such as ordered and disordered columnar hexagonal ones, micellar cubic Pm3n, etc. Among the factors affecting the phase behavior of such materials are the size and nature of focal groups. Another important factor – the length of aliphatic tails, influencing the temperature dependence of phase formation due to the change of both the mesogenic group shape and the aromatic to aliphatic relative volume ratio, became the focus of our paper. It was revealed that the 2D columnar ordered hexagonal mesophase, formed by cesium salts of 3,4,5-tris(alkyloxy) benzenesulfonic acid with varied lengths of aliphatic endings, can be described as three annuli: the central channel, virtually hollow channel and rigid aromatic part enveloped by an aliphatic matrix whose widths depend on the specific chemical structure of a dendron. The diameter of the central channel varies in the range of 0.9–1.15 nm. The transition to a columnar disordered hexagonal phase leads to ion channel closure because of the disruption of stacking in rigid parts of dendrons and therefore their ordered arrangement as well as possible molecular ejection. The abovementioned facts make the studied material promising for creating temperature-controlled ion-selective membranes.