Enhanced Self‐Assembly Abilities Coupled with Nano‐ and Microscale Non‐Equilibrium Phenomena in Flowing Microfields

Abstract Kinetically controlled self‐assemblies have the potential to produce unique supramolecules that are not accessible through conventional supramolecular strategies. However, this still remains a challenge for chemists owing to the lack of versatile and reliable methodologies. A straightforward way to control a kinetic process is to spontaneously change the micro‐environments surrounding the greater than thousands of self‐assembling molecules. Flowing solutions in microflow channels can provide fields for kinetically controlled self‐assemblies. So far, based on this concept, we have demonstrated that intermolecular interactions could be enhanced under rapid and uniform molecular diffusion environments in microflow channels. To show the generality of our developed self‐assembly system, herein, we have selected supramolecular polymerization of perylene bisimides (PBIs) dyes as a model. Amide‐appended PBI derivatives having various alkyl spacers (C n =3, 4, 5, 6) have been selected as an ideal model. These PBIs have the potential to form intramolecular hydrogen bonds at bisimide edges (closed form). Remarkably, in the case of PBI (C n =3), the closed form is less active toward self‐assembly due to steric hindrance of the peripheral dodecyl groups, while the non‐intramolecular hydrogen‐bonded (open) form is active for self‐assembly. The effective concentration of PBI (C n =3) should be decreased under the equilibrium concentration. Throughout this paper, we have investigated whether microflow fields could influence the supramolecular polymerization processes of PBIs. It was found that the mole fraction of aggregated dye (α agg ) drastically increased in the microflow field compared to the conventional vial process. Especially for PBI (C n =3), effective self‐assemblies were achieved even at lower concentrations. Under the same conditions, self‐assembly did not occur in a vial. Furthermore, aggregation rates also accelerated in microflow. These results were reasonably responsible for reducing the activation energy required for nucleation. In other words, the microflow field raised the local concentration of activated PBI (C n =3) toward nucleation. Throughout this paper, we have highlighted the importance of laminar flow from the viewpoint of a non‐equilibrium field. Firstly, it causes uniform molecular diffusion that would be essential for effective supramolecular polymerization (nucleation and elongation). In addition, laminar flow itself – a microscaled non‐equilibrium phenomenon – allowed preliminary supramolecular polymers to form a hierarchical assembly. These processes occurred along the microflow channel very rapidly.