Study Of Particles-stabilized Emulsion And High Internal Phase Emulsion

With the development of nanotechnology, the adsorption behavior of nano-particles in the oil - water interface and the stability of the emulsion attract more and more attention, but the study of such emulsions is not very systemic. In this thesis, we first synthesized a new kind of amphipathic polymer particles, and used them to stablilize emulsion; then synthesized magnetite nanoparticles surface-modified with AOA for the study of high internal phase emulsion (HIPE). The specific contents of the work are summarized as follows:1. Poly(stearyl methacrylate-co-acrylamide-co-acrylic acid) [P(SMA-co-AM-co- AA)] was synthesized through inverse microemulsion polymerization which owns the hydrophilic interior core and hydrophobic surface. By changing the ratio of oil-soluble monomers to water-soluble monomers, it is easy to control the wettability of nanoparticles. The P(SMA-co-AM-co-AA) nanoparticles were used to stabilize styrene- water emulsion, and submicron-sized polystyrene (PS) microspheres with a relatively narrow particle size distribution were obtained after polymerization. We found that Pickering emulsion was first formed after emulsification, but the big droplets disappeared grasually with the passage of time, and the polymer nanoparticles might be swollen, dropped off and became seeds, namely Pickering emulsion would change into seeded emulsion afterwards,which is different from the emulsions stabilized by inorganic particles.2. Magnetite nanoparticles (MPs) modified with 12-acryloxy-9-octadecenoic acid (AOA) were synthesized by the coprecipitation method, and St-DVB HIPEs were prepared solely stabilized by MPs. Due to the existence of an active double bond in the structure of AOA, AOA-modified magnetite nanoparticles would take part in the polymerization, improving on their binding to the interface and the stability of HIPE. Moreover, MPs play an important role in the reinforcement for macroporous polymer foams. We studied the effects of MPs concentration and internal phase weight fraction on the stability of HIPE and the structure of macroporous materials. It is found that when the concentration of MPs was 20 wt% based on oil phase, the Young's modulus reached to the maximum value (69.7 MPa) and the compression strength was improved to 5.29 MPa. Meanwhile, the void sizes and size distributions decreased with increasing the content of MPs until up to 20 wt%. However, increasing the internal phase fraction would lead to the decrease of mechanical properties and foam density and the increase of voids size, but it is favorable for the formation of macroporous interconnected structure.3. We also studied the effect of the surfactant Span 80 concentration on the stability of HIPE and the structure of macroporous materials when the polymerization is initiated byγ-ray at room temperature or by chemical initiator at 60°C. The results showed that it is beneficial to the stability of HIPE when polymerized at room temperature, and even if the Span 80 concentration is as low as 1.4 wt% we can still obtain macroporous interconnected polymer materials.