Synthesis of a Bis‐Urea Dimer and Its Effects on the Physical Properties of an Amphiphilic Tris‐Urea Supramolecular Hydrogel

Abstract

The successful development of stiff supramolecular gels is an important goal toward their practical application. One approach to stiffen supramolecular gels is to introduce covalent cross-links. The bis-urea dimer 2, having a structure similar to that of the low-molecular-weight gelator 1, was synthesized. Supramolecular hydrogels were formed from mixtures of 1 and 2 in appropriate ratios, with 2 acting as a covalent cross-linker to connect the fibrous aggregates formed by the self-assembly of 1. The introduction of these covalent cross-links greatly influenced the dynamic viscoelasticity of the supramolecular hydrogels. In the supramolecular hydrogel of 1 mixed with 5 % 2, the storage modulus was 1.35 times higher than that of the supramolecular hydrogel of 1 alone, and the crossover strain was extended from 5 % to over 20 %. The supramolecular hydrogel of 1 and 2 was free-standing and supported 13 times its own weight.

Metal Cation Triggered Peptide Hydrogels and Their Application in Food Freshness Monitoring and Dye Adsorption

“…The hydrogel was self-supporting and thermoreversible, with a Tgel of 107 • C. Thus, Tgel is higher than the boiling point of the solvent. This behaviour has been observed before in literature and can be ascribed to a remarkable stability of the 3D network [92][93][94][95]. The UV-Vis absorption spectrum of the gel showed the typical pyrene absorption band above 300 nm, but it was red-shifted, broader, and less structured when compared with the non-gelled sample (Figure 2a).…”

Urea-Based Low-Molecular-Weight Pseudopeptidic Organogelators for the Encapsulation and Slow Release of (R)-Limonene

“…Between the functional groups able to participate in the development of such supramolecular interactions, urea groups have played a relevant role according to their potential to develop topologically well defined hydrogen-bond networks. − This has allowed the development of a number of LMWGs based on bis-, tris-, and even tetrakis-urea derivatives, often based on the presence of a central polysubstituted aromatic core. In these systems the increasing number of urea functionalities was designed to modify the strength and morphology of the gels on the basis of the increased number of hydrogen-bonding sites. − …”

Urea Derivatives as Functional Molecules: Supramolecular Capsules, Supramolecular Polymers, Supramolecular Gels, Artificial Hosts, and Catalysts

“…These supramolecularh ydrogels can adsorbo rganic dyes efficiently, and their physicalp roperties can be adjusted by adding small amounts of ad imer having as imilar structure to tris-urea. [112,113] Polymer gels such as agarose and polyacrylamide are commonly used fore lectrophoresis of biopolymers, but Yamanaka et al developed electrophoresis methods using supramolecular hydrogels. [114] As upramolecular hydrogel of amphiphilic trisurea 23 (Figure 13) can be appliedt ot he electrophoresiso f denatured proteins.…”

“…Addition of terbium ions gives a luminescent supramolecular hydrogel. These supramolecular hydrogels can adsorb organic dyes efficiently, and their physical properties can be adjusted by adding small amounts of a dimer having a similar structure to tris‐urea [112, 113] …”