Morphology control of stimulus-responsive fluorescence-enhanced supramolecular aggregates based on pillar[5]arenes

Abstract

The rational functionalization of pillar[n]arenes enables unprecedented properties, establishing it as a pivotal strategy for constructing advanced functional materials. In this study, we synthesized a series of asymmetrically functionalized pillar[5]arene derivatives H₁, H₂, and H₃, whose molecules were terminated with ester, carboxylate, and carboxylate groups, respectively. The morphological study of these molecular assemblies indicated that different molecular termini significantly influence self-assembly of nanostructures, which leads to the formation of nanospheres, nanosheets, and cross-linked nanomicelles, respectively. Furthermore, the host–guest complexes H₂G and H₃G, formed by molecule G containing a tetraphenylethylene (TPE) core and molecules H_2–3, self-assemble into dendritic and feather-like aggregates in aqueous solution, respectively. The experimental results revealed that the intermolecular interaction of the rigid building block, the hydrophilic/hydrophobic effect, and the structure of the terminal groups synergistically affect the morphology of the supramolecular assemblies. Interestingly, a pH-sensitive reversible morphological conversion between H₂G and H₃G was established, which could be utilized for fluorescence information encryption. The findings of this study provide not only a new design strategy for functionalized pillar[5]arenes but also a novel approach for constructing advanced stimulus-responsive supramolecular materials.