The influence of the complexation of sodium and lithium triflate on the self-assembly of tubular-supramolecular architectures displaying a columnar mesophase based on taper-shaped monoesters of oligoethylene oxide with 3,4,5-tris[p-(n-dodecan-1-yloxy)benzyloxy]benzoic acid and of their polymethacrylates

Abstract

The monoesters of mono-(1a), di-(1b), tri-(1c) and tetra-(ld) ethylene glycol with 3,4,5-tris[p-(n-dodecan-1-yloxy)benzyloxy]benzole acid (1), the polymethacrylates derived from them (2) and the complexes of both 1 and 2 with LiCF₃SO₃ and NaCF₃SO₃ self-assemble into cylindrical supra-molecular architectures which exhibit a hexagonal columnar (Φ_h) mesophase. The generation of the Φ_h mesophase depends on the stabilization of this assembly by endo-recognition in the core of the cylinder (H-bonding and ionic interactions) and exo-recognition that occurs between the tapered groups and also between the cylinders (i.e., the hexagonal arrangement of the columns). The low molecular weight compounds 1 are able to complex more salt in the Φ_h mesophase and have larger increases in Φ_h–isotropic transition temperature (T_Φh–i) per increase in salt concentration than the corresponding polymethylcrylates 2 derived from them. Molecular modelling appears to indicate that positional and conformational restrictions imposed by both the tapered side groups and the polymer backbone are responsible for these results. Both the polymers and the low molar mass compounds have their T_Φh–i shifted to lower temperatures and allow more LiCF₃SO₃ to be complexed with the increase in the number of oxyethylene segments present in the flexible spacer. A comparison of the difference in the effectiveness of the Li cation versus the Na cation in providing increased stabilization of the Φ_h mesophase does not show any significant differences between the two cations.