Study On O/w Type Pickering Emulsion And Heterophase Polymerization Stabilized By Starch-based Nanospheres

O/w type Pickering emulsion and heterophase polymerization stabilized by starch-based nanospheres was studied in this dissertation.The research content of this dissertation is mainly comprised of three parts.The details were as follows:The first part studied the interfacial activity of starch-based nanoparticles at the oil-water interface.The interfacial properties of starch-based nanospheres at the interface of n-hexane and water was investigated by monitoring the interfacial tension at different bulk concentration.A relationship between adsorption density(?)and interfacial tension(?)was proposed as a means of estimating three-phase contact angle(?)for the starch-based nanospheres at the oil-water interface.The three-phase contact angle(?)and adsorption energy(?E)increased with increasing size of particles and degree of substitution with octenyl succinic groups(OSA)in the particles.Compared with the OSA-modified starch(OSA-S)macromolecules,the particles of SNP effectively reduced the interface tension of the n-hexane-water system at relatively highly concentration and the SNP adsorption at the oil-water interface is effectively irreversible.The second part studied the Pickering emulsion and Pickering heterophase polymerization stabilized by starch-based nanospheres.Based on the experimental condition and the results,different polymerization processes were carried out to prepare varies morphology composited particles.This content is divided into three parts:1.Pickering emulsion polymerization of styrene was stabilized by starch-based nanospheres.The raspberry-like particles were fabricated after the polymerization,and the effects of the SNP content,size and pH value on the Pickering polymerization was investigated.The morphology of resultant particles transforms from bare particles to raspberry-like particles with an increase in the SNP content,meanwhile the inverse diameter of resultant particles and SNP content keep a linear relationship,meaning the polymerization was a typical Pickering polymerization.The resultant particles also be regulated by SNP size and pH value.A possible formation mechanism for the resultant particles with different morphology was proposed.2.Pickering emulsion transform to seeded emulsion during polymerization wherein starch-based nanoparticles serve as both stabilizer and seed.A facile approach for producing monodisperse core-shell starch/polystyrene composited particles was developed,the effects of the monomer content,SNP content and size,and pH value on the resultant particles were investigated.With increasing monomer content,the core size of particles remained almost unchanged,while the shell layer thickness increased almost linearly.The size of resultant particles can be regulated by adjusting the pH and SNP content and size.A possible formation mechanism for core-shell particles was explored based on the experiment results.3.Anisotropic starch/polystyrene composited particles with shape-tunable were fabrication by soap-free seeded polymerization using non-cross-linked starch-based seed.The monomer swelling process and polymerization process were investigated.After swelling process,the starch-based particles present single or multi-hole on the surface.The formation of the hole on the seed surface attributed to phase separation of monomer with seed polymer.During the subsequent polymerization,the variety morphology of composite particles,include golf-like,raspberry-like,octahedron-like and snowman-like,have been fabricated.The morphology evolution of composite particles was tailored by polymerization time,monomer feed ratio and seed type.A possible formation mechanism for the different morphology of composited particles at different monomer amount was proposed.The third part fabricated the thermo-responsive starch-based Pickering stabilizer.The core-shell particles(SNP-g-PNIPAM)with a starch-based core and thermo-responsive PNIPAM polymer brush was fabricated using surface-initiated single-electron transfer living radical polymerization and the particles can sever as Pickering stabilizer to stable Pickering emulsion.The interfacial properties of the resultant particles were studied and the effects of the grafted polymer chain length and temperature on the interfacial activity of the resultant particles also were studied.More,the emulsification/demulsification process of Pickering emulsion can be reversed and easily repeated by changing the temperature.