Supramolecular assemblies from carbazole dendrimers modulated by core size and molecular configuration

Abstract

Different core moieties can modulate the self-assembly behaviors of second generation carbazole-based conjugated dendrimers with the same dendrons and surface groups in a solvent mixture of a good solvent and an anti-solvent. For TA-D2 with triphenylamine as the core, crystalline spherulites were formed since the more planar molecular configuration of TA-D2 can enhance the π–π interactions between the carbazole dendrimers. For G2 with the large-sized fac-Ir(PBI)₃ as the core, amorphous globular particles were obtained because the large core in G2 increases the distance between carbazole dendrimers and decreases the π–π interactions. While for TPO-D2 with triphenylphosphine oxide as the core with moderate size and a twisted molecular configuration, a supramolecular gel consisting of fibers was formed in the solvent mixture of aromatic solvent and alcohol solvent. The sol–gel conversion of TPO-D2 can be observed by simple heating and cooling. Fast cooling and ultrasonication are beneficial to get uniform TPO-D2 gel with small aggregates. The TPO-D2 xerogel shows three-dimensional networks with the nanofibers entangling and intersecting with each other. The moderate π–π interactions between the carbazole units modulated by the core may be the driving force for TPO-D2 to form the gel, the balance phase between the ordered crystal and amorphous precipitate.