Amphiphilic pillar[5]arenes: influence of chemical structure on self-assembly morphology and application in gas response and λ-DNA condensation

Abstract

In order to investigate the influence of chemical structures on self-assembly morphology, six amphiphilic pillar[5]arenes C1, C2, C3, C4, D, and E with different hydrophilic and hydrophobic groups were synthesized. When they were dissolved in water, they all self-assembled into vesicles first. The amine groups on C1 and C2 can reversibly react with CO₂ in water, so vesicles self-assembled from them could reversibly transform into micelles by bubbling CO₂ and N₂. More interestingly, C1, C2, C3, and C4 with the same N-(2-aminoethyl)acetamide units as the hydrophilic groups all further self-assembled into microtubes, on the other hand, E with acetohydrazide units as the hydrophilic groups further self-assembled into nanosheets in water. Amphiphilic pillar[5]arene D could not further self-assemble into any other morphology in water itself, but the carboxylate groups on D can coordinate with silver ions so it could further self-assemble into dendritic structures in water. Dynamic light scattering, transmission electron microscopy, scanning electron microscopy, UV-Vis spectroscopy, and FT-IR spectroscopy were employed to characterize the self-assembly processes of these six amphiphilic pillar[5]arenes and the resultant self-assemblies. The acidified microtubes, which have ammonium ions on their surfaces, could capture negatively charged DNA through electrostatic interactions in water.