Cyclohexane bis-urea compounds for the gelation of water and aqueous solutions

Abstract

A new class of efficient hydrogelators has been developed by a simple modification of the peripheral substituents of cyclohexane bis-urea organogelators with hydrophilic hydroxy or amino functionalities. These bis-urea hydrogelators were synthesised in two or three steps using an alternative procedure to the common isocyanate method. Gelation was obtained with organic solvents, water and strongly basic aqueous solutions like 25% ammonia. Hydrogelation was found to depend on a delicate balance between the hydrophobicity of the alkyl chains, hydrophilicity of the terminal substituents and the enantiomeric purity of the compound. The hydrogels consisted of a network of fibers, in which all urea groups are involved in intermolecular hydrogen bonding. Most likely, gelation is driven by hydrophobic interactions of the methylene units, whereas hydrogen bond formation between the urea groups provides the necessary anisotropy of the aggregation and the high thermal stability of the gels.

Supramolecular gels based on organic diacid monoamides of cholesteryl glycinate

“…The kinds of gelators reported in the literature had been specially designed and synthesized in complex ways (see Refs. [40][41][42][43][44][45] for examples). During the continuance of our previous work [33,34], we observed and were able to report two ambidextrous gelators which were obtained in a very simple way.…”

The Art of Building Small: From Molecular Switches to Molecular Motors

“…29 These compounds have a pronounced ability to self-assemble in a variety of fiber-like structures and can gelate a wide range of solvents at low concentrations. Hydrogels, 30 aerogels, 31 patterned surfaces, 32 and two-stage drug delivery systems 33 are just a few of a wide range of these soft materials, which we have developed. The introduction of light-switchable functions to synthetic LMW organogelators allows one to achieve reversible control over the selfassembly process.…”

Gelation by histidine-derived ureas

“…Amides 1-5 and ureas [5][6][7][8][9] are well-known classes of supramolecular gelators, capable of gelling water (hydrogels) and organic solvents (organogels) by means of highly directional NHO=C hydrogen bonding interactions. [10][11][12][13][14][15][16] This type of hydrogen bonded fibre formation is implicated in a range of important biological phenomena such as protein (mis)folding and amyloid formation.…”