Reversible morphological changes of assembled supramolecular amphiphiles triggered by pH-modulated host–guest interactions

Abstract

Reversible template-directed micellar-size and shape modulation by virtue of host-guest reversible docking of molecular templates at the micellar-solvent interface was achieved in water. By combining a π-electron deficient bipyridinium-based gemini amphiphile which is capable of binding and aligning with a π-electron rich tri(ethylene glycol)-disubstituted 1,5-diaminonaphthalene, a switchable detergent system which operates through the pH-responsive formation of bisammonium dications was realised. The binding of the 1,5-diaminonaphthalene guest to the bipyridinium-based micellar aggregate superstructure can be actuated by the addition of acid and base. Upon the addition of acid, protonation of the guest forming the dication deactivates molecular recognition with the charged head groups of the micellar aggregate by Coulombic repulsion. This process is completely reversible upon the addition of base, whereby the guest reintercalates into the superstructure -again forming donor-acceptor π-π stacks at the micellar-solvent interface amongst contiguous surfactant head groups. Synchrotron small angle X-ray scattering and dynamic laser light scattering confirm that this form of reversible directionally-templated micellisation results in an oblate spheroid-to-lamellar micelle morphological transition with a stabilising net decrease in the free energy of micellisation of 1.4 kcal mol(-1) per hydrophobic tail.

Poly-Lipoic Ester-Based Coacervates for the Efficient Removal of Organic Pollutants from Water and Increased Point-of-Use Versatility

“…This poly-lipoic ester, PLE1 , can be easily postfunctionalized via simple nucleophilic substitution. PLE1 was then reacted with monoundecylated bipyridine to afford a water-insoluble polymeric material, bipyridinium-functionalized poly-lipoic ester ( BPLE ). − Bipyridinium is a π-electron-deficient moiety that has been widely applied in various fields on account of its ability to engage in molecular recognition forming noncovalent donor–acceptor π-stacking interactions with π-electron-rich guest molecules. ,− Thus, based on our extensive work − with bipyridinium-based surfactants, we anticipated that the BPLE polymer, being comprised of a hydrophobic aliphatic poly-backbone and an amphiphilic π-electron-deficient functional side chain, would adsorb numerous types of π-electron-rich pollutants from water employing noncovalent interactions. , …”

Tunable Thermochromism of Multifunctional Charge-Transfer-Based Supramolecular Materials Assembled in Water

“…Supramolecular materials has become an emerging interdisciplinary research area that has attracted considerable attention from scientific communities on account of the modularity of their structural components, inherent reversibility, and overall versatility. 1−3 In recent decades, supramolecular self-assemblies that can respond to various external stimuli, such as changes in temperature, 4,5 pH, 6,7 and magnetic fields, 8,9 have been developed and used in a variety of applications in the areas of biomedical technology, 10−12 sensors, 13,14 energy storage, 15−17 and optical/electronic devices. 18−20 The utility of supramolecular materials undoubtedly stems from the reversible noncovalent interactions from which they are assembled, endowing them with dynamic properties that can be designed and controlled in a prescribed manner.…”

“…Supramolecular materials has become an emerging interdisciplinary research area that has attracted considerable attention from scientific communities on account of the modularity of their structural components, inherent reversibility, and overall versatility. − In recent decades, supramolecular self-assemblies that can respond to various external stimuli, such as changes in temperature, , pH, , and magnetic fields, , have been developed and used in a variety of applications in the areas of biomedical technology, − sensors, , energy storage, − and optical/electronic devices. − The utility of supramolecular materials undoubtedly stems from the reversible noncovalent interactions from which they are assembled, endowing them with dynamic properties that can be designed and controlled in a prescribed manner. The incorporation of π-donor–acceptor charge-transfer (CT) interactions into supramolecular materials brings to the table a multitude of advantages on account of the following: (i) their tunable optical properties through the adjustment of the frontier orbitals of the π-donors and/or acceptors; (ii) the directional nature of CT interactions that allow for the construction of anisotropic architectures; − and (iii) their compatibility with aqueous environments.…”

p-Sulfonatocalix[6]arene-dodecyltrimethylammonium Supramolecular Amphiphilic System: Relationship between Calixarene and Micelle Concentration

“…Supramolecular amphiphiles are, by definition, noncovalent complexes formed from hydrophilic and hydrophobic molecules. − In practice, most of the reported examples of supramolecular amphiphiles are composed of an amphiphilic molecule that upon interaction with a second species forms a supramolecular complex with superior (or distinct) amphiphilic properties. Several strategies can be used to devise supramolecular amphiphiles including host–guest, hydrogen bonding, charge-transfer, π-stacking, and Coulombic interactions, to give some examples. − …”