Hydrogels Composed of Organic Amphiphiles and α‐Cyclodextrin: Supramolecular Networks of Their Pseudorotaxanes in Aqueous Media

Abstract

Mixtures of N-alkyl pyridinium compounds [py-N-(CH(2))(n)OC(6)H(3)-3,5-(OMe)(2)](+)(X(-)) (1bCl: n = 10, X = Cl; 1cBr: n = 12, X = Br) and alpha-cyclodextrin (alpha-CD) form supramolecular hydrogels in aqueous media. The concentrations of the two components influences the sol-gel transition temperature, which ranges from 7 to 67 degrees C. Washing the hydrogel with acetone or evaporation of water left the xerogel, and (13)C CP/MAS NMR measurements, powder X-ray diffraction (XRD), and scanning electron microscopy (SEM) revealed that the xerogel of 1bCl (or 1cBr) and alpha-CD was composed of pseudorotaxanes with high crystallinity. (13)C{(1)H} and (1)H NMR spectra of the gel revealed the detailed composition of the components. The gel from 1bCl and alpha-CD contains the corresponding [2]- and [3]pseudorotaxanes, [1b x (alpha-CD)]Br and [1b x (alpha-CD)(2)]Br, while that from 1cBr and alpha-CD consists mainly of [3]pseudorotaxane [1c x (alpha-CD)(2)]Br. 2D ROESY (1)H NMR measurements suggested intermolecular contact of 3,5-dimethoxyphenyl and pyridyl end groups of the axle component. The presence of the [3]pseudorotaxane is indispensable for gel formation. Thus, intermolecular interaction between the end groups of the axle component and that between alpha-CDs of the [3]pseudorotaxane contribute to formation of the network. The supramolecular gels were transformed into sols by adding denaturing agents such as urea, C(6)H(3)-1,3,5-(OH)(3), and [py-N-nBu](+)(Cl(-)).

Skeletal muscle contractile properties and proinflammatory cytokine gene expression in human endotoxaemia

“…In der Zeit zwischen Annahme und Veröffentlichung dieses Manuskripts sind weitere beachtliche Beiträge zu diesem Thema erschienen, z. B. über photoresponsive Pseudopolyrotaxan‐Hydrogele auf der Grundlage konkurrierender Wirt–Gast‐Wechselwirkungen,64 Hydrogele aus organischen Amphiphilen und α‐Cyclodextrin65 oder die lichtinduzierte Proteinfreisetzung aus einem supramolekularen Hydrogel 66…”

Formation of Linear Supramolecular Polymers That Is Driven by CH⋅⋅⋅π Interactions in Solution and in the Solid State

“…When the concentration is below the CPC, there is no significant change for the aggregation of 1. [16] In conclusion, based on easily available copillararene monomers, linear supramolecular polymers can be efficiently constructed driven by quadruple C À H···p interactions. This phenomenon indicated that temperature affects the aggregation of 1; when the temperature increases, the degree of polymerization decreases.…”

Formation of Linear Supramolecular Polymers That Is Driven by CH⋅⋅⋅π Interactions in Solution and in the Solid State

“…In chloroform, the positive entropy term (DS) resulting from exclusion of the solvent from the cavity should also augment the binding by reducing the free energy of the system (DG) (Supporting Information, Scheme S1 caption). [16] In conclusion, based on easily available copillararene monomers, linear supramolecular polymers can be efficiently constructed driven by quadruple C À H···p interactions. Only two steps were required to prepare copillararene monomer 1 from commerically available compounds.…”