Remarkable polymorphism in gels of new azobenzene bis-urea gelators

Azobenzenes substituted with two urea groups, and especially the 2,2‘-disubstituted azobenzenes, form thermoreversible gels with a wide range of organic solvents at concentrations which are in some cases even as low as 0.2 mM. Most remarkably, the 2,2‘-disubstituted azobenzene gelator can form two different morphs, which is governed by the properties of the solvent and kinetic factors.