Chemical microenvironment mediated formation of organic nanostructures from self-assembly of melamine and barbituric acid derivatives

The recent progresses on constructing organic nanostructures from the self-assembly of melamine and barbituric acid derivatives are reviewed. By mediating the chemical microenviron-ment during the self-assembly, the information contained in the molecular components can be expressed at different levels, thus resulting in the formation of different organic nanostructures. When the assembly is carried out in anhydrous chloroform, a kind of asymmetric layered structure with a d value of 4.1 nm is obtained. When a little amount of polar solvent such as alcohol is contained in the chloroform, organic nanotubes with diameter of 6 nm and length of several hundreds of nanometers are observed. After being treated by appropriate polar solvents, the nanotubes are induced into supercoils with diameter of about 300 nm and length of several tens of microns. The sensitivity of the self-assembly process origins from the weak noncovalent intermolecular interactions between the molecular components. The enthalpy change of such interactions is pretty small, so slight change of the molecular structure or microenvironment could affect the primary equilibrium, resulting in the rearrangement and transformation of the supramolecular structure.