Surface nucleation-induced fluoropolymer Janus nanoparticles via emulsifier-free batch-seeded emulsion polymerization

Nonspherical poly(vinylidene fluoride)/polystyrene (PVDF/PS) composite latex particles were prepared via a facile emulsifier-free batch-seeded emulsion polymerization. It was found that the styrene (St)/PVDF feed ratio was a determining factor for the formation of well-defined Janus particles. Transmission electron microscopy study revealed that the immiscibility between PVDF and St-swollen PS (PS/St) was the driving force for the dewetting and nucleation of PS/St bulges on the PVDF particle surface. When the St/PVDF feed ratio was high, easy fusion of multiple PS/St bulges into one single bulge on the PVDF particle resulted in well-defined PVDF/PS Janus particles. When the St/PVDF feed ratio was low, it was difficult for multiple bulges to fuse together to form PVDF/PS Janus particles.