One-Pot Double Emulsion Templated Cascade Microreactor Armored by Magnetic Responsive Anisotropic Colloid

Anisotropic Janus particles are a specialized type of particles characterized by two or more distinct physical or chemical properties on their surface. Since Dr. Pierre-Gilles de Gennes' Nobel lecture, they have garnered significant attention and have been the subject of extensive research. Notably, amphiphilic Janus particles exhibit superior adsorption energy, leading to irreversible adsorption at interfaces. These colloidal monolayers which are stabilized by Janus particles inevitably create small interstices between themselves. These gaps function as channels for material transfer across the interfacial membrane. By growing catalysts onto particles and using them to stabilize Pickering emulsions, they can achieve highly efficient interfacial catalytic reactions. Furthermore, we can fabricate the smart microreactors capable of facilitating biphasic reactions, where reactants and products exist in different phases, mediated by the transfer channels in the interfacial membrane.

Utilizing this concept, homogeneous catalytic reactions, where reactants and products coexist in the same phase, have been extensively studied due to their relative simplicity. In contrast, research on heterogeneous catalytic reactions has been limited, primarily due to challenges in solvent selection and feasibility issues. Beyond simple single interfaces, the development of coacervation-based dual catalytic reactors and double microemulsion reactors for sequential cascade reactions can overcome the limitations of conventional heterogeneous catalytic reactions. To develop these microreactors we thought that we need to establish some techniques.
1. Fabrication of colloidal immobilizer technology that can stably and evenly fix catalyst particles
2. Synthesis of interfacial catalyst particles with maximum interfacial adhesion and orientation
3. Non-uniform catalyst-based advanced interfacial catalyst technology with high reactivity and efficiency.
4. Smart refining technology that can recover 100% of products without using organic solvents

This study presents a novel one-pot cascade reaction microreactors which is templated by double emulsions. In this system, we can’t use the same particle to stabilize outer emulsion and inner emulsions. To overcome this problem, we fabricated two different particles to recycle and collect the both particles. For the magnetic controlled recyclable colloid surfactant system, iron oxide nanoplatelets (IOPLs) were synthesized by reverse precipitation of a ferrous ion. The synthesized IOPLs were easily washed by using a magnet, without the need for complex methods like centrifugation. Subsequently, the surface of IOPLs were modified to amphiphilic. For stablizing outer interface, we fabricated the amphiphilic Janus zirconium hydrogen phosphate platelet particles (ANPL) with hydrothermal synthesis. The ANPL was synthesized by Surface-induced atomic transfer radical polymerization. The polymerization were started from the both sides of macroinitiator, which has bromine site on the final. We chose poly(N-isopropylacrylamide) (pNIPAAm) in the hydrophilic plane to make temperature-responsive particles. Over the LSCT, pNIPAAm changes to hydrophobic and it makes particle not to amphpihlic, resulting break out of the outer emulsions. Finally, metal particles were grown onto the surface of ANPL. We can extract the inner droplet with magnet aiming to develop novel double emulsion templated microreactor system after the whole reaction. This advanced colloidal interfacial catalysis technology is unprecedented in existing research. If its comprehensive applicability across various catalyst types is verified, it has the potential to introduce a new catalytic paradigm in the green chemistry industry.