【作者】 李停停；

【导师】 刘华蓉；

【作者基本信息】 中国科学技术大学 ， 高分子化学与物理， 2011， 硕士

【摘要】 随着纳米技术的发展,纳米粒子在油-水界面的吸附行为及其稳定的乳液越来越受到人们的关注,但目前人们对于此类乳液的研究还不是很完善。本论文中,我们首先合成了一种新型的两亲性聚合物粒子,将其用于稳定乳液的研究;然后合成了一种AOA改性的磁性纳米粒子,并将其用于高内相乳液的研究中。具体的工作内容概括如下:1.通过反相微乳液法合成了聚(甲基丙烯酸十八酯-co-丙烯酰胺-co-丙烯酸),这种粒子内部亲水、外部疏水,通过调节油溶性单体和水溶性单体的比例,可以很方便地改善粒子的润湿性。将上述聚合物粒子用于稳定苯乙烯的正相乳液体系,聚合之后我们得到了尺寸分布较均匀的亚微米级聚苯乙烯微球。通过研究我们发现,在乳液的制备过程中,刚开始乳化时会形成Pickering乳液;但是随着时间的延长,大的液滴逐渐消失,聚合物粒子有可能被溶胀、脱落,成为种子球,即发生Pickering乳液向种子乳液的转变;这是与无机粒子稳定乳液的不同之处。2.通过共沉淀法制备磁性纳米粒子,并用12-丙烯酰氧基-9-十八烯酸(AOA)对其进行表面改性,将改性的磁性粒子用于St-DVB高内相乳液(HIPE)的制备和聚合中。由于AOA结构中含有活性双键,经AOA修饰后的磁性粒子(MPs)可以参与聚合,进一步提高了乳液稳定性和界面结合力;而且,磁性粒子的添加对聚合物多孔材料起到一定的增强作用。我们研究了MPs浓度和内水相含量对高内相乳液稳定性和多孔材料结构的影响。结果表明,当粒子浓度达到20%时,材料的杨氏模量达到最大值(69.7 MPa),压缩强度也提高到5.29 MPa。同时,材料的孔洞尺寸也随粒子浓度的增大而逐渐降低并且尺寸大小趋向均匀。然而,增加内水相含量会导致材料的机械性能下降,密度降低,孔洞尺寸增加,但是有利于多孔贯通结构的形成。3.我们还研究了室温下γ-射线辐射引发和60°C下热引发高内相乳液聚合时,表面活性剂Span 80的浓度对乳液稳定性和多孔材料结构形貌的影响。结果发现,室温下引发聚合有利于乳液的稳定,而且当表面活性剂的用量降低到1.4 wt%时,依然可以获得良好的多孔贯通的聚合物大孔材料。更多还原

【Abstract】 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.更多还原