Study On Morphology And Formation Mechanism Of Janus Particle And Complex Colloidal Cluster Based On PVDF Seeded Emulsion

Anisotropic poly(vinylidene fluoride)/poly(styrene-co-tert-butyl acrylate)[PVDF/P(St-co-tBA)] composite particles were prepared with PVDF as seeds and styrene(St)and tert-butyl acrylate(tBA)as comonomers via soap-free seeded emulsion polymerization using different polymerization mechanism,i.e.traditional free radical polymerization and single electron transfer living radical polymerization(SET-LRP).Morphology of composite particles synthesized by traditional free radical polymerization,chemical compositions,the size of particle and size distribution were characterized by scanning electron microscopp(SEM),fourier transform infrared spectrometer(FT-IR)and dnamic light scattering,respectively.On the other hand,The chemical composition of complex particle clusters obtained by SET-LRP,the average size of particle,microstucture of particle clusters were characterized by FT-IR,dnamic light scattering,SEM and TEM.The surface element content of PVDF/P(St-co-tBA)complex particle clusters was characterized by X-ray photoelectron spectroscopey(XPS).The results show that,for traditional free radical polymerization system,PS and PtBA copolymerized and growth at the surface of PVDF seeds,finally the core-shell shape particles were obtained.With the increase of tBA/St feed ratio and reaction temperature,no obvious change in the morphology of composite particles was observed.The composite latex after alkaline hydrolysis was tested through contact angle analysis,the result indicated the hydrophilic of composite latex improved.For SET-LRP system,in-situ formed of PVDF/P(St-co-tBA)Janus particles behaved like particle surfacants.In the in-situ Pickering emulsion polymerization,the tBA/St/PVDF feed ratio and the polymerization temperature were important for the formation of well-defined complex particle clusters.When the tBA/St/PVDF feed ratio was 0.75 g/2.5 g/0.5 g and the reaction temperature was 35 °C,relatively uniform raspberry-like complex particle clusters were obtained.The hydrophobicity of the P(St-co-tBA)domains and the affinity of PVDF to water were believed to be the driving force for the self-assembly of the in situ formed PVDF/P(St-co-tBA)Janus particles.The resultant raspberry-like CPCs with PVDF particles protruding outward may be promising for smart coatings.