Efficient Preparation of Core–Shell Particles via Photopolymerization for Toughening Photocurable Resins

Core–shell particles have been widely used in improving the toughness of resin, but a convenient and efficient large-scale preparation method for core–shell particles is lacking currently. In this work, an efficient and simple method has been developed to fabricate core–shell particles by combining photopolymerization and phase separation inside the emulsion droplet. In this strategy, two photocurable prepolymers with different hydrophilicity were dissolved in a cosolvent and dispersed in an aqueous solution to form an emulsion. Upon the removal of the cosolvent, phase separation occurred inside the emulsion droplet. The hydrophilic prepolymer migrated toward the oil–water interface and converted to a shell under UV irradiation, while the hydrophobic prepolymer migrated to the interior of the emulsion droplet and converted to a core. In addition, the core–shell ratio and size of the particle could be easily adjusted, which provided an idea for the efficient and large-scale preparation of the core–shell particle. The influence of the structure and contents of the core–shell particles on the toughening effect was investigated. Under the optimal parameters (the core–shell ratio of 1:1, the size of 1 μm, and the concentration of 7.5 wt %), the toughness, impact strength, flexural strength, and fracture toughness (KIC) of the composites were enhanced by 52, 8.4, 30.8, and 288.4% compared to the pure resin system, respectively. Furthermore, the Tg value and the viscosity of the resin system were not greatly influenced after the addition of core–shell particles, i.e., an outstanding toughening effect was achieved without sacrificing its thermal property and processability.