Controllable synthesis of Janus-like polymer particles via oxygen-tolerant RAFT-mediated Pickering emulsion polymerization for cinnamaldehyde encapsulation and sustained release

The controlled synthesis of anisotropic polymer particles with precisely tunable morphologies remains a significant challenge in polymer science. Here, we report a straightforward and scalable strategy for the synthesis of Janus-like polymer particles via oxygen-tolerant photo-mediated reversible addition-fragmentation chain transfer (RAFT) Pickering emulsion polymerization. This method eliminates the need for prior deoxygenation, inert gas protection, or additives, offering a green and operationally simple approach to functional polymer particles. Key particle properties—including wettability, size, rigidity, and flexibility—can be precisely tuned by modulating the monomer-to-crosslinker ratio, introducing a third monomer, and varying the size of the calcium carbonate nanoparticle Pickering stabilizer. Notably, using 50-nm calcium carbonate nanoparticles enables the systematic evolution of particle morphology from spherical to fragmented, compositionally anisotropic Janus-like architectures. The resulting Janus-like polymer particles exhibit superior performance as solid emulsifiers for oil-in-water cinnamaldehyde (CA) emulsions, achieving exceptional stability and a sustained release profile (85% over 20 days, following the Weibull model). These emulsions demonstrate enhanced and sustained antibacterial activity against both E. coli and S. aureus , outperforming free CA. In a practical food preservation application, the Pickering emulsion reduces banana weight loss from 12.24% (blank control) to 8.97% and significantly delays peel browning over seven days. This work establishes a novel and green synthetic methodology for the controlled preparation of functional Janus-like polymer particles, with promising implications for polymer-based delivery systems in pharmaceutical and agricultural applications.