Continuous Two-Step Synthesis of PS@HMEM Core–Shell Nanoparticles via Emulsion Polymerization in Microreactors

Spherical polyelectrolyte brushes (SPBs) are widely applied in protein controllable adsorption, nanocatalysis, and surface modification, while the polystyrene (PS) nanoparticles covered with well-distributed photoinitiator 2-[p-(2-hydroxy-2-methylpropiopenone)]-ethylene glycol methacrylate (HMEM) shells (PS@HMEM) are of critical importance to synthesize SPBs by photoemulsion polymerization. In this paper, a two-step continuous flow strategy consisting of emulsion polymerization of PS nanoparticles and a coating of HMEM was rationally designed for the construction of PS@HMEM core–shell nanoparticles in a microreactor. The structure of PS@HMEM core–shell nanoparticles was characterized by Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and transmission electron microscope (TEM). The electron paramagnetic resonance (EPR) technique was employed to estimate the grafted amount of HMEM, and it was verified that feeding through a single or two streams had a significant advantage for the optimization of the “starved condition.” This work provided a new strategy for synthesizing PS@HMEM core–shell polymer nanoparticles and showed great potential for the construction of other functional nanoparticles.