Study On Synthesis Of Amphiphilic Polymer Janus Microparticles And Their Stimulative Responsibility

Amphiphilic Janus particles possessing rapidly stimulative responsibility, as a new type of solid surfactants, have significantly higher interfacial activity, stronger adsorption ability, and can effectively lower the interfacial tension to stabilize emulsion than their homogeneous counterparts. Responding to very specific changes in their environments(pH value, temperature and ionic strength), they can even induce phase inversion emulsification. In addition, the functional groups on their surfaces make them a kind of good raw materials, which can be widely applied to prepare composite materials with special performances in the methods of physical mixing and chemistry modification with organic compounds or inorganic nanoparticles. Due to intensively potential applications in the fields of food, cosmetics, controlled drug release, catalysis and coatings, developing a simple and effective strategy for preparing stimuli-responsive polymer Janus particles is of great scientific and practical importance.In this paper, based on “Particle Design”, stimuli-responsive and controllable submicron Janus particles could be simply and facilely prepared via one-step/one-pot emulsifier-free emulsion copolymerization of vinyl monomers. The influences of amounts and types of comonomers on morphology and property of colloidal particles were systematically studied. The experimental results showed that amphiphilic particles possessed good emulsifiability and stimulative responsibility. Meanwhile, their morphologies and emulsifiabilities were well controlled by simply adjusting the amounts of hydrophilic and hydrophobic monomers. New organic/inorganic composite materials could also be achieved by compositing these particles with Ag and Fe3O4 inorganic nanoparticles. Due to the emulsifier-free emulsion polymerization in water without swelling processes, crosslinking agents, any volatile organic solvents and complicated post-processes, this simple and green strategy has great conducting significance for preparation of functional and structural polymer Janus particles. The main body of this paper includes the following four parts:1. The first part introduced generally several types of synthesis methods, stimulative responsibilities and applications of polymer Janus particles, and then the study ideas were proposed.2. Choosing methacrylic acid(MAA), methyl methacrylate(MMA) and butyl acrylate(BA) as comonomers, the pH-responsive amphiphilic Janus spheres(PMAB) were first prepared via one-step emulsifier-free emulsion polymerization. The size, dispersivity, morphology and chemical structure of particles were characterized by dynamic light scattering(DLS), scanning electron microscope(SEM), transmission electron microscopy(TEM), Fourier transform infrared spectroscopy(FT-IR), whose amphiphilicity was also observed by optical microscope(OM) and static contact angle testing. The emulsifiability test showed that PMAB particles possessed good emulsifiability and pH-responsibility. As a result, the mixtures comprising amphiphilic particles stood there forming toluene-in-water(o/w) emulsions under neutral and alkaline environments, whereas the mixture formed water-in-toluene(w/o) emulsion under acidic environment, making phase inversion emulsification happen.3. Using amphiphilic PMAB particles as seeds, the double-faced polymer Janus particles could be facilely prepared by one-pot two-step emulsifier-free emulsion polymerization without masking, based on selective phase separation of hydrophobic copolymer of styrene(St) and BA. Their sizes, dispersivities, morphologies, chemical structures and amphiphilicities were characterized by DLS, SEM, TEM, FT-IR, OM and static contact angle testing. Our results showed that rough sides were well controlled by adjusting the amounts of hydrophobic comonomers, achieving the half-raspberry, half-cauliflower and multiple-bulge morphologies. The half-raspberry and half-cauliflower particles possessed good pH-responsive emulsifiabilities, making Pickering emulsions of toluene and water inverse.4. Choosing N,N-diethyl-2-acrylamid(DEAA) as thermo-responsive monomer, multi-responsive amphiphilic Janus microspheres(PMDBM) were designed and synthesized. The size, dispersivity, thermo-responsibility, component, morphology and amphiphilicity of the particles were characterized by DLS, FT-IR, SEM, TEM and OM. The results showed that PMDBM particles possessed good emulsifiability and thermo-responsibility. Pickering emulsion could be inversed by adding a small amount of salt. Besides, the amphiphilicity and emulsifiability could be also well adjusted by changing the mass ratios of MAA to DEAA.