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

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 H2-3, 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.