Supramolecular helical nanofibers assembled from a pyridinium-functionalized methyl glycyrrhetate amphiphile

Abstract

A glycyrrhetate-containing amphiphile, MGP (1-[2-(methyl glycyrrhetate)-2-oxoethyl]pyridinium bromide), has been synthesized, and found to assemble into supramolecular helical nanofibers in chloroform/aromatic solvents, which are primarily driven by π-π stacking, van der Waals forces, and hydrophobic interactions. During the assembly process, MGP stacked into J-aggregates resulting in the sequestration of the hydrophilic pyridinium cation within the interior with the concomitant projection of its hydrophobic skeleton on the outside surface. Ultimately, this protrusion generated a staggered angle due to the steric hindrance between stacked molecules. This staggered angle further led to molecular misalignments and the formation of helical fibrils, which could twist with each other to fabricate larger helical fibers. Consequently, a gel was formed by intertwining these nanofibers into three-dimensional networks. Using this strategy, we found that other triterpenoid-tailored pyridinium amphiphiles are also potential scaffolds for supramolecular helical structures. This work provides a facile approach for the fabrication of supramolecular macroscopic chiral nanostructures that originate from natural products.

Hydrogen bonding and thermoplastic elastomers – a nice couple with temperature-adjustable mechanical properties

“…3,4 Especially the variety of available non-covalent bonds which can be used to form transient connections and therefore supramolecular polymers and networks is nowadays large. This broad variety of different interactions includes p-p stacking, 5,6 metal-ligand interactions, [7][8][9][10] hydrophobic forces, 11,12 electrostatic effects, 13,14 and hydrogen bonding. 4,[15][16][17][18][19][20] Not only the functionalization of the precursor building blocks (telechelic units) for the polymer chains and networks is today synthetically quite feasible, 21,22 but also the post modification of a polymer along the chain.…”

Triterpenoid‐Based Self‐Healing Supramolecular Polymer Hydrogels Formed by Host–Guest Interactions

“…These features not only endow them with pharmacological properties, but also make them ideal building blocks for self‐assembling versatile supramolecular structures . Since the first supramolecular organogel based on a pentacyclic triterpenoid was reported by Bag and co‐workers in 2005, a series of pentacyclic triterpenoid‐based small molecules have been designed and synthesized to study their supramolecular gelation behavior . For example, Mezzenga et al.…”

“…reported that the right‐handed fibrillar networks in the hydrogel of glycyrrhizic acid could be utilized as scaffolds for hybrid nanomaterials in heterogeneous catalysis . We found that a pyridinium‐tailored glycyrrhetinic acid amphiphile could transfer and magnify its chirality at the supramolecular level, and consequently result in the formation of helical nanofibers . However, these low molecular weight gels have limitations in applications due to the participation of toxic organic solvents or weak mechanical properties.…”

“…[10][11][12][13] Since the first supramolecular organogel based on ap entacyclic triterpenoid was reported by Bag and co-workers in 2005, [14] as eries of pentacyclic triterpe-noid-based smallm olecules have been designed and synthesized to study their supramolecular gelation behavior. [15][16][17][18][19][20][21][22][23][24] For example, Mezzenga et al reported that the right-handedf ibrillar networks in the hydrogel of glycyrrhizic acid could be utilized as scaffolds for hybrid nanomaterials in heterogeneous catalysis. [15] We foundt hat ap yridinium-tailored glycyrrhetinic acid amphiphile could transfer and magnify its chirality at the supramolecular level,a nd consequently result in the formation of helical nanofibers.…”

“…[15] We foundt hat ap yridinium-tailored glycyrrhetinic acid amphiphile could transfer and magnify its chirality at the supramolecular level,a nd consequently result in the formation of helical nanofibers. [16] However,t hese low molecular weight gels have limitations in applications due to the participation of toxic organic solvents or weak mechanical properties. Thus,i t is necessary to explore polymeric hydrogels based on pentacyclic triterpenoids, which will may open an ew scenario for pentacyclic-triterpenoid-based biomaterials.…”