Low molecular-mass organic gelators
Low molecular-mass organic gelators (LMOGs) are the monomeric sub-unit which form self-assembled fibrillar networks (SAFINs) that entrap solvent between the strands.
The propensity of a low molecular weight molecule to form LMOGs is classified by its Minimum Gelation Concentration (MGC).
A lower MGC is desired to minimize the amount of gelator material needed to form gels.
LMOGs were first reported in the 1930s, but advances in the field were more often than not discoveries of chance; as there existed little theoretical understanding of gel formation.
[3] Interest in the field dwindled for several decades until the mid-1990s when Hanabusa, Shinkai, and Hamilton designed numerous LMOGs which form thermoreversible intermolecular amide-carbonyl hydrogen bonds.
From these earliest studies and screening numerous compounds, it was determined that for thermoreversible gels based on the amide-carbonyl hydrogen bond, amino acid structure, enantiopurity, hydrophilic-lypophilic ratio, and increasing peptide substitution greatly affected the gelling ability of various new compounds.
The aforementioned principles that developed in this field's infancy have proved successful in allowing researchers to tune LMOGs for different functions.
This newfound functional diversity has led to a wide range of possible applications for LMOGs in agriculture, drug delivery, pollutant/heavy metal remediation, luminescent devices, and chemical sensing.
The majority of LMOGs can be triggered to form by manipulating the systems' properties, such as the pH, solvent, exposure to light, or by introducing oxidizing or reducing reagents.
However, it has recently been shown that non-liquid crystalline gelators, composed of (R)-18-(n-alkylamino)octadecan-7-ols (HSN-n), undergo first order gel-to-gel phase transitions; leading to different morphologies of the gel in carbon tetrachloride (CCl4).
Scanning Electron Microscopy is a useful means for researchers to determine the structural properties of a low molecular-mass weight gel.
To address these functional issues a sugar alcohol-based amphiphilic super-gelator, mannitol dioctanoate (M8), has been developed that efficiently gelled the pheromones, 2-heptanone and lauryl acetate.
The prepared organic salts produced gel in many non-protic solvents[24] and can release sex pheromone slowly.
Researchers have been exploring LMOGs belonging to a class of molecules called cyclohexane trisamides due to their ability to form hydrogels.
They developed a class of LMOGs that were capable of gelling diesel, gasoline, pump, mineral, and silicone oils.
Being able to visually detect a color change in the presence of a dilute analyte is a promising field application of LMOG materials.
A supramolecular gelator, namely dicyclohexyammonium Boc-glycinate produced gel in nitrobenzene and exhibited self-healing and load-bearing property.
