Solvent‐Polarity‐Tuned Morphology and Inversion of Supramolecular Chirality in a Self‐Assembled Pyridylpyrazole‐Linked Glutamide Derivative: Nanofibers, Nanotwists, Nanotubes, and Microtubes

Abstract

The self-assembly of a low-molecular-weight organogelator into various hierarchical structures has been achieved for a pyridylpyrazole linked L-glutamide amphiphile in different solvents. Upon gel formation, supramolecular chirality was observed, which exhibited an obvious dependence on the polarity of the solvent. Positive supramolecular chirality was obtained in nonpolar solvents, whereas it was inverted into negative supramolecular chirality in polar solvents. Moreover, the gelator molecules self-assembled into a diverse array of nanostructures over a wide scale range, from nanofibers to nanotubes and microtubes, depending on the solvent polarity. Such morphological changes could even occur for the xerogels in the solvent vapors. We found that the interactions between the pyridylpyrazole headgroups and the solvents could subtly change the stacking of the molecules and, hence, their self-assembled nanostructures. This work exemplifies that organic solvents can significantly involve the gelation, as well as tune the structure and properties, of a gel.

Tuning Soft Nanostructures in Self‐assembled Supramolecular Gels: From Morphology Control to Morphology‐Dependent Functions

“…[ 64 ] An organogelator, N,N′ -bisoctadecyl-2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl)-L-glutamic amide (abbreviated as PPLG, 6 ) can self-assemble into various structures from nanofi bers to nanoribbons, nanotwists, nanotubes, and microtubes, depending on the solvents' polarity, their ability to donate (α) and accept hydrogen bonds (β) ( Figure 6 ). [ 37 ] Such Figure 5. The structure of organogelator 5 , and SEM images of 5 with different alkyl chain lengths, (a) n = 5, (b) n = 8, (c) n = 11.…”

“…Reprodued with permission. [ 36,37,53,57 ] Copyright 2010, 2013, 2012, and 2011, respectively, Wiley-VCH. Figure 2.…”

“…If there is a chiral center, the nanobelts frequently change into nanotwists or helical nanoribbon structures and hollow tubular structures. [ 36,37,44,45 ] For the tubes, various kinds of nanotubes with different parameters or shapes could be acquired. For the sphere structures, derived structures such as nanofl owers or cottonlike structures often appear, [ 39 ] which can be extended to micrometer sizes in many cases.…”

Enantioselective recognition of a fluorescence-labeled phenylalanine by self-assembled chiral nanostructures

“…22 In order to express the recognition using fluorescence, we modified the amino acids with a Dansyl group. Dansyl group is a typical fluorescence probe and is very sensitive to the environment and exhibits different fluorescence in a 40 hydrophobic or hydrophilic environment.…”

“…22 The structure of DNSP (Dansyl linked phenylalanine, abbreviated as DNSP, the reaction was shown in the Supporting Information), PPLG and PPLGOEt were shown in Figure 1. In the experiment, various nanostructures of PPLG were obtained through gelation with different organic solvents.…”