Supramolecular tube

Upon addition of NaOTf, columnar hexagonal mesophases could be induced. For 68, 0.4 equiv. of salt were needed while for 67, only 0.2 equiv. of NaOTf were needed for mesophase induction. Upon complexation, the complexed crown ether moieties and the anions self-assemble within a supramolecular tube and the taper-shaped side groups stack over each other in the periphery. X-Ray scattering... 

Fig. 11 Molecular recognition directed self-assembly of NaOTf-67, NaOTf-68 to supramolecular discs which further self-assemble to supramolecular tubes. Reproduced by permission of The Royal Society of Chemistry from [85]...

The transport velocity of Li+ is faster than that of Na+ and K+ due to the size of the cation. The data are consistent with a hopping transport mechanism of the cations accompanied by a non-specific co-transport of the anions. The transport rates for N03 > Cl- > C104 are related to the adjacent hydrate shell and not yet fully understood. Anyway, a path in the center of the supramolecular tubes, where the crown ethers assemble, must exist and allow for the co-transport of the anions. By forming the membranes in the pores of track-etched membranes, the transport rates could be improved by an order of magnitude due to the orientation of the channels perpendicular to the membrane surface. 

Schappacher, M. Deffieux, A., Synthesis and Macrocyclic Copolymer Brushes and Their Self-Assembly into Supramolecular Tubes. Science 2008, 319, 1512-1515. 

Schappacher, M. and Defifieux, A. (2008a) Synthesis of macrocyclic copolymer brushes and their self-assembly into supramolecular tubes. Science, 319,1512-1515. 

Organoclay materials with higher-order organization can also be prepared by template-directed methods involving self-assembled supramolecular structures. In this approach, preformed organic architectures in the form of tubes, fibers, hollow shells, gyroids, helicoids, and so on are transferred into hybrid materials exhibiting structural hierarchy, complex form and ordered mesoporosity [47-55]. For example,... 

Yan D, Zhou Y, Hou J. Supramolecular self-assembly of macroscopic tubes. Science 2004 303 65-67. 

More detailed analyses of sapphyrin anion chelation in solution were made using a full range of tricks borrowed from the supramolecular field. Thus both spectroscopic techniques (e.g., NMR, UV-vis, fluorescence spectroscopy) and transport studies (carried out in a model Pressman type U-tube membrane system ) were employed. From these analyses, it became clear that sapphyrin does in fact bind various negatively charged substrates in solution, but does so both with variable affinity and oft-times remarkable selectivity. These findings/conclusions are detailed further in the paragraphs below. 

This chapter describes the structures and properties of supramolecular silver complexes with specific topologies such as cages, tubes, catenanes and polycate-nanes, rotaxanes and polyrotaxanes, and multidimensional frameworks, as synthesized by reactions of various silver salts with predesigned organic ligands. 

Fig. 6 Pseudo-phase diagram for supramolecular polymer 3 in toluene solutions. Transition between monomers and thin supramolecular filaments determined by calorimetry (ITC) ( ). Transition between thin filaments and thick tubes determined by ITC (A), vis-cosimetry ( ) and FTIR ( ). SANS characterization of the thin filaments (o) and thick tubes (A). Reprinted with permission from [40]...

Fig. 10 Transition temperature (T ) between the thin filaments and tubes for supramolecular polymer 3 solutions in aromatic solvents, versus length (L) and width (W) of the solvent molecules. The length (L), width (W) and thickness (Th) are defined as the respective dimensions of the smallest right-angled parallelepiped containing the molecule, such that L>W>Th. Reprinted with permission from [42]...

A great variety of self-assembled supramolecular structures can be found in supramolecular gels . Association of low molecular weight compounds in a topologically defined way yields long fibres with often well defined diameters [420], An amazing variety of very complex superstructures has been described, i.e. rods and tubes formed from concentric or would up lamellae, helices, or braid-like structures. In all cases we can assume a hierarchy of superstructures which ultimately link the molecular structure to the nanoscopic assembly. However, this has only been investigated in detail in a few cases so far. 

Fig. 15. Molecular structures and supramolecular assemblies obtained under different conditions, as described by Aida et al. SEM (a-d) and TEM (e-h) micrographs of the tubes are shown. Reproduced with the permission of Wiley-VCH 212).

There has been a number of examples of cylindrical (tubular) supramolecular structures reported over recent years. These encompass all-carbon structures as well as other inorganic and organic tubes (and columns) and include lipid-based systems. However, the majority of these tubes represent extended arrays (on a multi-nanometre or higher scale) and hence fall outside the scope of the present discussion - in any case, many were not obtained directly by self-assembly processes. Indeed, only a limited number of self-assembled, discrete cylindrical systems have been described. 

---