Automated Supramolecular Polymerization in a Microflow: A Versatile Platform for Multistep Supramolecular Reactions

This work reports a basic microflow system capable of performing multistep supramolecular polymerization. In this system, injection of the monomer, directional supramolecular copolymerization, removal of the unreacted monomer, and purification of the product supramolecular diblock copolymers are realized along a three-stream flow. When injecting a supramolecular polymer into the central stream of the three-stream flow, the supramolecular polymerization always occurs in the central flow, with the two lateral flows serving as supply and removal lines for the monomer. Employing two kinds of perylene bisimide derivatives as monomers, we confirmed that the reaction occurred selectively at the forward-facing terminus of the supramolecular polymer, along with recovery of the unreacted monomer, ultimately leading to a high-purity supramolecular diblock copolymer. Diblock copolymers are basic units for preparing multicomponent supramolecular block copolymers. Thus, connecting the present system in series would, in principle, result in a "microplant" capable of producing supramolecular polymers having desired inner complexity.

Geometrical pH mapping of Microfluids by principal-component-analysis-based xyz-spectrum conversion method

The absorption spectra of bromothymol blue (BTB) solution introduced in microfluidic devices were reproduced by principal component analysis (PCA)-based xyz-spectrum conversion methods for geometric mapping of the pH values of fluids. We fabricated PDMS-made microfluidic devices with a channel depth of 1 mm to overcome the lower detection limits of transmittance image acquisition. Aqueous solutions of pH indicators under various pH conditions were hydrodynamically introduced into the channel, and RGB values of the region of interest (ROI) were obtained via image analysis. The xyz values were then converted into absorption spectral data of the pH indicator using the PCA-based spectral reproduction previously proposed by the authors. The high reproducibility of the spectra was confirmed to be comparable to that of the conventional method using a spectrophotometer. We applied the present method to elucidate the pH gradient at an aqueous biphasic interface in the microfluidic channels generated by contacting multiple laminar flows of two or three buffered solutions. We confirmed that the pH gradient ranged from approximately 70 to 140 μm, which is consistent with the results reported using other approaches. The results demonstrate the applicability of the present method to the fluctuation field in micro/nanospaces to acquire spectrophotometric information in the order of milliseconds without monochromating equipment.

Microfluidics for the rapid and controlled preparation of organic nanotubes of bent-core based dendrimers

Recently, bent-core molecules have emerged as excellent building blocks for the obtaining of nanostructures in solvents. Herein, we report the use of a coaxial microfluidic system as a promising tool to control the self-assembly of non-conventional bent-core amphiphiles. Moreover, a TEM study to comprehend the hierarchical self-assembly process in solution was carried out. The proposed tool provides both a cost-effective platform to save hard-to-synthesise reagents and a rapid method to screen a plethora of different parameters, i.e., THF/water ratio, residence time, concentration of the amphiphile, temperature and pH. The experiments allowed to test for the first time the suitability of microfluidics for the self-assembly of bent-core molecules, as well as the study of a range of conditions to control the assembly of different nanostructures in a rapid and controlled manner. Additionally, organic nanostructures were combined with gold nanoparticles to prepare nanocomposites with enhanced properties. Both organic and hybrid nanostructures were also obtained in the solid state. These results may inspire scientists working on supramolecular chemistry and bent-core molecules expanding the scope of microfluidic systems for the self-assembly of other low-molecular-weight compounds.