One-step Preparation of Brush-type Polystyrene (PS)-SiO2-poly(2-hydroxyethyl methacrylate) Janus Nanoparticle to Compatibilize PS/Poly(methyl methacrylate) Blends

Compatibilization is crucial for the blending of immiscible polymers to develop high-performance composites; however, traditional compatibilization by copolymers (pre-made or in-situ generation) suffers from weak interface anchoring, and inorganic particles have gained extensive attention recently owing to their large interfacial desorption energy, while their low affinity to bulk components is a drawback. In this study, an interfacial atom transfer radical polymerization (ATRP) technique was employed to grow polystyrene (PS) and poly(2-hydroxyethyl methacrylate)(PHEMA) simultaneously on different hemispheres of Br-functionalized SiO 2 nanoparticles to stabilize a Pickering emulsion, whereby a brush-type Janus nanoparticle (SiO 2 @JNP) was developed. The polymer brushes were well-characterized, and the Janus feature was validated by transmission electron microscope (TEM) observation of the sole hemisphere grafting of SiO 2 -PS as a control sample. SiO 2 @JNP was demonstrated to be an efficient compatibilizer for a PS/poly(methyl methacrylate) (PMMA) immiscible blend, and the droplet-matrix morphology was significantly refined. The mechanical strength and toughness of the blend were synchronously enhanced at a low content SiO 2 @JNP optimized ~0.9 wt%, with the tensile strength, elongation at break and impact strength increased by 17.7%, 26.6% and 19.6%, respectively. This enhancement may be attributed to the entanglements between the grafted polymer brushes and individual components that improve the particle-bulk phase affinity and enforce interfacial adhesion.