Gels are formed when a compound present in a solution self-assembles to form a highly cross-linked fibrillar network in which the solvent molecules remain entrapped. The resulting material has properties that are intermediate between those of liquids and solids. Usually, gels are classified according to the nature of the solvent involved. Thus, hydrogels refer to gels formed in the presence of water, while organogels are those in which organic solvents are involved.
Many different types of compounds have been developed and used either as hydrogelators or as organogelators; according to the foods industry, natural and nonnatural polymers originally were tested for the formation of gels. Nevertheless, the use of low molecular weight gelators has gained increasing importance in recent years. Since low molecular weight compounds possess a well-defined structure, their properties including self-assembling behavior can be more easily studied, which allows for the more efficient design and fine-tuning of gelating agents. As a consequence, a large number of technological applications have recently been reported for gels formed either in water or organic solvents through the use of low molecular weight molecules.
In particular, gel formulations are used as penetration enhancers for drug and cosmetic actives release. This is due to the fact that incorporating the active component in a gel matrix can control its release rate, increasing the application time and consequently, the corresponding activity. The appropriate selection of structural components, reviewed herein, shows how to produce gels with tailored properties, including high thermal stability.
This is an excerpt of an article from GCI Magazine. The full version can be found here.