Using a facile experimental manipulation to fabricate and tune a polyoxometalate-cholesterol hybrid material

In this work, we describe how the toluene and DMF addition order influences the gelation behaviors and supramolecular structures of a self-assembled polyoxometalate-cholesterol hybrid. Morphological studies of the dried xerogel samples were performed with transmission electron microscopy and atomic force microscopy, revealing that the order of solvent addition directed the self-assembly of polyoxometalate-cholesterol hybrids toward the formation of organogels with different supramolecular structures. In the case of organogel 1, which was formed by adding DMF dropwise into a hybrid-containing toluene solution, the characteristic organogel morphology contained a three-dimensional fibrous network structure. Meanwhile, organogel 2, which was prepared by adding toluene dropwise into a hybrid-containing DMF solution, had a supramolecular structure made up of short ribbons. Based on these results, a mechanism is proposed to illustrate the distinctly different self-assembly mechanisms of hybrid molecules in the formation of organogels 1 and 2. Importantly, the order of solvent addition plays a central role in the aggregation process. This study provides a rational method for the construction of supramolecular soft materials, and can be extended to other self-assembled systems.