Interfacial Assembiles Of Bolaamphiphilic Diacetylenes: Metal Ion Regulated Self-assembly And Supramolecular Chirality

The supramolecular polymers assembled at the interface have been studied extensively in current interface chemistry and polymer science. The assembly of supramolecular polymers rests on a variety of building blocks with the delicate design of molecular geometry and intermolecular interactions. Of all the building blocks, Polydiacetylenes(PDAs) derivatives obtained by the photopolymerized of well-ordered diacetylene(DA) monomers are particularly crucial because diverse PDA nanostructures have also been discovered, including nanorods, nanowires, helical nanoribbons and nanotubes. Although their aggregation behaviors of conventional PDA amphiphilic molecules with one polar headgroup at the air/water interface have been well studied, there are relatively few investigations on the interfacial assembly of PDA bolaamphiphiles with two hydrophilic ends, which covalently connected by hydrophobic alkyl spacers. Over the past years, self-organized structures of bolaamphiphiles have attracted increasing attention owing to their rich morphologies. Interfacial assembly through Langmuir as well as Langmuir-Blodgett techniques combining the dynamic and tunable characteristics provide an effective method to assemble PDAbolaamphiphiles in a two-dimensional way. In this paper, a series of organized supramolecular polymers have been fabricated from 10, 12-Docosadiynedioic acid(DDA) based on the air/water interface.Firstly, we have studied the self-assembly behaviors of DDA molecules on air/water interface. Surface-pressure isotherms were measured and it revealed that multilayer films were formed on the water surface. Then self-assembled twocomponent helical supramolecular structure based on the mixture of DDA and bolaamphiphilic D-Histidine(BolaH) formed at the air/water interface. FT-IR spectroscopies suggested that the hydrogen bond and ionic interactions among imidazole and carboxylic acid groups played important roles for the formation of the supramolecular structure. Depending on the mixing ratio(mol/mol) of DDA and BolaH, different morphology of LB films were observed. When the mixing ratio is 2:1, helical structure was found to form during the UV irradiation, which is also confirmed by the results of CD spectra. These results not only can help us to further understand the Interfacial assembly mechanisms of bolaamphiphile, but also provide an effect strategy for the fabrication of helical supramolecular structure at air/water interface.Secondly, different polymer behaviors were found in Bolaamphiphilic diacetylene LB film, which were induced by the presence in the subphase of Ag+, Cu2+, Zn2+, Cd2+ and Ni2+. The organized LB films of DDA showed different color changes after the UV irradiation. Special morphology was obtained by AFM. FT-IR data made it clear that metal ions in the subphase showed various types of interactions with the carboxylate groups. Those results indicated that adding metal ions in the subphase is a simple method to change the properties of bolaamphiphilic PDA films. The introduction of metal ions also provides some potential applications.