Self-assembly of L-glutamate based aromatic dendrons through the air/water interface: morphology, photodimerization and supramolecular chirality

A series of dendrimers containing focal aromatic rings, ranged from phenyl, naphthyl, anthryl to pyrenyl, and the L-glutamate peripheral groups were designed and their self-assembly through the air/water interface was investigated. It has been found that although these dendrimers have no long alkyl chains, some of the dendrimers could form stable monolayers at the air/water interface due to an appropriate balance between the hydrophobic core and the hydrophilic peripheral group. Nanofibers were observed for the monolayers of the dendrimer containing a 2-anthryl group, while nanostrips were observed for that containing a pyrenyl group. In contrast to the dendrimers in solution, the molecular chirality at the chiral center of L-glutamate was transferred to the supramolecular assemblies in the films, indicating the effect of the interfacial assembly. For the dendrimers containing an anthryl core, photodimerization occurred. The photoirradiation was carried out under different conditions such as in solution, in a floating monolayer and in the transferred LB films. Different morphologies were obtained. These results indicated that the photoreaction of an anthryl dendrimer can be regulated through the interfacial organization, which leads to different packing as well as the subsequent photoreaction.