Microfluidic interface boosted synthesis of covalent organic polymer capsule
Yun Zhao, Min Zhang, Xin Wen, Zhonghua Xiang
Abstract
Microcapsules have been widely used in drug carriers, nano/microreactors, artificial organelles for their empty space and functional shell. Microcapsules synthesized from spherical liquid-liquid interface show ultrathin shell and large cavities. However, spherical liquid-liquid interfaces generated by stirring or sonicating are difficult in controlling the droplet size and preventing their coalescence, which results in inhomogeneous capsules. Here, we demonstrate a microfluidic interfacial synthetic method to produce microcapsules using the hot covalent organic polymers (COPs) coupled with Schiff-base reaction. A very high throughput of uniform and individual microdroplets about ~1400 min−1 was generated under high flow rate for COP capsules fabrication. Acidic catalyst promoted amine and aldehyde condensation that reacted less than 1 s assured the polymerization occurred at the liquid-liquid interface regardless of the diffusion intensification in microfluidic system. COP capsules with shell thickness around 50 nm were flexible enough to response to slight interior capillary force and exterior filtration force to form origami structure and sealed flat membrane, respectively. Each of the interfacial synthesized capsule expressed large capacity by encapsulating 1.41 × 10−2 μg SiO2 nanoparticles as theoretically calculated. Thus, these properties make the COP capsules promising in, but not limited to, fast drug delivery and microreactors.