【作者】 云洋；

【导师】 励杭泉；

【作者基本信息】 北京化工大学 ， 高分子化学与物理， 2001， 硕士

【摘要】 这个课题的主要目的是通过超浓乳液聚合的方法制备具有疏水核／亲水壳的双亲性胶体粒子。核的主要组成成分是聚苯乙烯(PS)，壳的主要组成成分是聚丙烯酰胺(PAM)。 这种核壳粒子的主要特点是核壳聚合物间没有共聚物过渡层，仅仅是嵌套在一起，从而最大限度地保持了二者的特性及粒子的双亲性。更重要的是，通过控制条件，可以获得网孔形态的壳层(图2)。壳层孔的存在使得粒子具有双亲性：亲水性的壳层使得这种粒子对水有亲和力；壳层孔的存在使得疏水性的核能够与外界接触，从而使粒子对有机溶剂也有亲和力。这种双亲性体现在粒子具有相应的吸水率和吸油率。 在本实验中，双亲性核壳粒子的制备是分开的两步。首先，用超浓乳液聚合的方法，制备出疏水性聚苯乙烯核：将苯乙烯、二乙苯、过氧化羟基异丙苯(CHPO)、乙苯、偶氮二异丁腈(AIBN)混合均匀作为分散相，水作为连续相，十二烷基硫酸钠(SDS)为乳化剂，配成超浓乳液，加热聚合，使苯乙烯转化率达到100％，得到乙苯溶胀的聚苯乙烯胶体粒子(图1)。然后，在聚苯乙烯胶体粒子表面包覆聚丙烯酰胺壳：取一定量的聚苯乙烯胶体粒子作为分散相，丙烯酰胺(AM)、N，N’—亚甲基双丙烯酰胺(DAM)、硫酸亚铁(FS)的水溶液作为连续相。核粒子表面层的CHPO首先与FS反应，产生自由基，引发AM聚合。生成的聚丙烯酰胺在交联和缠结的共同作用下，粘附在核的表面形成壳层(图2、3)。 研究发现，丙烯酰胺聚合的温度、反应时间、引发剂的用量、丙烯酰胺的用量及其交联剂DAM的用量对壳层的形态都有着显著的影响。北京化工大学硕士学位论文 这种双亲性核壳粒子的亲油性是壳层的网孔形态决定的。壳层孔的存在使得疏水性聚苯乙烯核可以与外界接触。同时，有机溶剂(例如柴油)也可以通过孔进入粒子内部，从而使粒子具有一定的吸油率。由于壳层是由亲水性的聚丙烯酞胺构成的，粒子对水也有亲和力。显然，壳层越厚，吸水率越高，吸油率越低。所以，粒子的吸水吸油率既可以表征粒子的双亲性，也可以印证壳层的形态。其次，扫描电镜、红外、溶礼悬浮测试也是有效的定量表征手段。 这种双亲粒子可被广泛应用于药物缓释及催化剂载体等领域。譬如药物传递与释放:我们知道，细胞膜是疏水性的，细胞核是亲水性的，兼具疏水性和亲水性的载体粒子可以顺利地通过细胞膜，进入细胞内部释放出药物分子。 超浓乳液聚合是九十年代发展起来的新技术，现己广泛应用于制备互穿聚合物网络、自增容合金、分离膜。但对于超浓乳液聚合的机理，迄今为止，没有进行过系统的研究。在总结前人研究的基础上，论文的第五部分对户dBN引发的苯乙烯超浓乳液聚合的机理做一些初步的探讨，得出了一些经验性的规律。关键词:超浓乳液，胶体粒子，核壳，双亲性更多还原

【Abstract】 Amphiphilic particles can be prepared by jointing hydrophilic polymer chains and hydrophobic chains. The jointing methods include blocking, grafting, and random copolymerization. The amphiphilic particles prepared by these methods contain hydrophilic and hydrophobic chains combined by chemical bonds. The jointing portions, however, are neither hydrophilic nor hydrophobic. Thus, the amphiphilicity of the particles is reduced. In order to overcome this shortcoming, a novel and simple method to prepare amphiphilic colloidal particles with hydrophobic core/hydrophilic shell is proposed.In the first step, the individual polystyrene (PS) colloidal particles (Fig. 1) were obtained by using a concentrated emulsion as precursor. Divinyl benzene (DVB) was employed as a crosslinker, and AIBN, an initiator. Sodium dodecyl sulfate (SDS) was used as the emulsifier and water as the continuous phase.Subsequently, amphiphilic monomer, acrylamide (AM) was introduced into the polymerized concentrated emulsion with N, N -methylenebisacrylamide (DMA) as its crosslinker, water as a diluent and Ferrous Sulfate (FS) a reductant initiator. FS and Cumene Hydroperoxide (CHPO), which was introduced into the PS core particles during the first step, formed an ox-reduction initiator system. CHPO diffused into the surface of the PS core, reacted with the FS in the continuous phase, and released free radicals. Under the proper conditions, polyacrylamide shells could encapsulate PS cores, and the shells possessed a porous (Fig.2) or wrinkle structure (Fig.3).A notable feature of the work is that no copolymer jointing portions exist. The hydrophobic cores were just encapsulated by hydrophilic shells.The porous shell (Fig.2) ensured the hydrophobic cores accessible to the outside media. As a result, such particles could be dispersed in both water and organic solvents. That is to say, they were compatible with both polar and nonpolar solvents.Scanning electron microscope (SEM) photographs confirmed the shell structure. The amphiphilicity of the particles was characterized by their water and diesel oil absorbabilities.It was found that polymerization recipes and reaction conditions, such as the amount of ox-reduction initiator, diluent, hydrophilic monomer, DAM and the temperature of polymerization could adjust the structure and thickness of the hydrophilic shells.The stability of the concentrated emulsions was studied. Other monomer, such as methyl methacrylate, was also employed.Such amphiphilic colloidal particles can be used widely in drug delivery and catalytic processes.更多还原