Self-organization Of Bolaamphiphiles: Towards Stable Supramolecular Nanostructures

In this dissertation, we try to explore the rules to govern the self-organization of bolaamphiphiles, and enhance the stability of the self-organized structures by introducing strong supramolecular interactions between molecules.To investigate the relationship between molecular structure of bolaamphiphile and its self-organized morphology, we designed and synthesized a series of molecules with different hydrophobic alkyl chain lengths, hydrophilic headgroups, mesogenic groups, and connectors between the alkyl chains and the mesogenic group. By studying the self-organization behavior of these bolaamphiphiles, some rules are summarized: (1) The molecules with alkyl chains longer than 10 methyl groups can form spaghetti-like surface micelles, while only those have 10 or 11 methyl groups can form stable surface micelles; (2) The types of headgroup and counterion have great effect on the morphology of the surface micelles; (3) When the carbonyl group is conjugated to the mesogenic groups, their influence to the interfacial self-organization behavior of bolaamphiphiles is small; otherwise, the influence is significant.To enhance the stability of the self-organized structures, a new type of bolaamphiphile which contains a DPP dye residue in the middle and carboxylic acid headgroups was synthesized, noted as DPP-11A. It is shown that self-organization of DPP-11A leads to the formation of supramolecular nanofibers. There are strongπ-πstacking interaction and hydrogen bonds between the molecules in the aggregates. The self-organization process is monitored by UV-vis spectra on the basis of the absorption change before and after the formation of the aggregates. In addition, the suprmolecular nanofibers can stand at least 130 oC without breakage of the intermolecular interactions, indicating a good thermal stability. We believe that this line of research may provide new approaches for fabricating supramolecular nanostructured materials.