Characterization of supramolecular gels

Abstract

Supramolecular gels are a fascinating class of soft materials. Their gelators can self-assemble into nano- or micro-scale superstructures, such as fibers, ribbons, sheets and spheres in an appropriate solvent, thereby resulting in the formation of 3D networks. The dynamic and reversible nature of the non-covalent interactions that contribute to the formation of these network structures together gives these supramolecular gels the inherent ability to respond to external stimuli. However, the dynamic nature of supramolecular gels, which endows them with unique properties, makes their characterization diversified at the same time. Therefore, we present here a review summarizing various methods for characterizing supramolecular gels, including nuclear magnetic resonance spectroscopy, computational techniques, X-ray techniques, microscopy techniques, dynamic light scattering, thermal analysis, and rheology. Based on the gelation mechanisms and influencing factors of supramolecular gels, suitable and sufficient characterization methods should be carefully employed to make full use of their respective advantages to better investigate these materials.

A CuI‐Based Metallo‐Supramolecular Gel‐Like Material Built from a Library of ­Oligomeric Ligands Featuring Exotopic 1,10‐Phenanthroline Units

“…Such behavior is in stark contrast to typical supramolecular gels, in which a temperature increase causes disaggregation and the subsequent transformation of gels into solutions. [27] As expected, treatment of the gel-like material with Et 4 NCN (ten-fold excess) restored a free-flowing solution due to the sequestration of Cu I (see Figure S8 in the Supporting Information). As predicted by J-S theory and actually found in real systems, the equilibrium concentration of the C i oligomers declines progressively with increasing i.…”

Low-Molecular-Weight Gels: The State of the Art

“…To understand the molecular packing, techniques such as nuclear magnetic resonance (NMR) spectroscopy, infrared spectroscopy, circular dichroism, fluorescence, and X-ray diffraction are used. 49,50 Although all of these can be informative, there are always caveats. Circular dichroism, for example, is very sensitive to concentration, and so good-quality data can often only be collected at concentrations lower than the mgc.…”

Metal ‘turn-off’, anion ‘turn-on’ gelation cascade in pyridinylmethyl ureas

“…Plateau storage moduli (G′) values at low stress are 40 kPa, 72 kPa and 20 kPa, and are approximately an order of magnitude higher than the loss moduli, G′′ as expected for solid-like gel phase materials. 5,29,30 Gels of L2 proved somewhat less robust with lower G′ and yield stress values. Gels were also characterised by SEM as the dried xerogels.…”

“…[1][2][3][4][5][6] The ease with which these low molecular weight gelators (LMWG) can be synthesised and the fact the properties of their gels can be modified by light, pH, redox or chemical stimuli suggests potential applications in areas such as drug delivery, biomedicine and pharmaceutical solid form control. 3,[7][8][9][10] N-pyridyl ureas have attracted considerable attention because their competitive hydrogen bonding properties allow particularly well-controlled gelation behaviour.…”