Water gelation by small organic molecules

A review of the small molecule organic hydrogelator literature over the past 20 years is given. This review presents a picture of the features necessary for effective gelation. While there appears to be no general rule for how to balance the hydrophobicity and hydrophilicity of a given molecule, such a distribution is essential for gelation to be preferred over fiber precipitation. Within families of structures, predictions can be made about the number of carbons per polar unit that are required to observe gel formation. Charged groups greatly facilitate gel formation and also provide a convenient trigger via pH modulation.