膜乳化法结合悬浮聚合制备均一多孔聚苯乙烯微球的过程研究
文献类型：学位论文
| 作者 | 郝冬霞 |
| 学位类别 | 博士 |
| 答辩日期 | 2009-05-30 |
| 授予单位 | 中国科学院过程工程研究所 |
| 授予地点 | 过程工程研究所 |
| 导师 | 马光辉 |
| 关键词 | 膜乳化 悬浮聚合 聚苯乙烯微球 自发形成机制 力矩平衡模型 相分离 高比表面积 反相层析 |
| 其他题名 | Process Study in Synthesis of Uniform Polystyrene Microspheres by Membrane Emulsification and Suspension Polymerization |
| 学位专业 | 生物化工 |
| 中文摘要 | 随着现代工业技术如色谱分离、固相合成、酶固定化等领域对材料微观特性的不断追求，单分散多孔聚苯乙烯类微球的应用地位日益凸显。本论文发展了以SPG （Shirasu Porous Glass）膜乳化法结合悬浮聚合法制备单分散聚苯乙烯类微球的新型工艺路线。该工艺路线的基本过程是，首先将单体、引发剂和致孔剂混合为分散相，使其在一定压力下通过SPG膜孔压入到另一与之不相溶的连续相中，形成均一单体乳液，然后对乳液进行悬浮聚合成球。论文围绕微球粒径均一性和孔结构的调控，针对以往膜乳化过程研究中乳液均一性调控无法实现模型预测以及该路线目前制备微球普遍存在孔结构单一、比表面积低（<300m2/g）等缺陷，对膜乳化过程中乳液生成及悬浮聚合中微球成孔的过程机理展开了深入研究，在此基础上制备出粒径均一、比表面积最高可达900m2/g以上的微球，所阐释的规律为膜乳化法合成路线中乳化操作条件的选择、乳液配方的设计和微球最终孔结构的设计等都提供了指导意义。 首先通过微观在线观察装置考察了膜乳化过程中不同乳化剂环境中液滴的生成行为。发现液滴自发形成是保证乳液均一生成的重要条件。在纯水和低浓度乳化剂环境中，液滴易滞留于膜孔，并簇集为多分散乳液。在高浓度的阴离子乳化剂十二烷基硫酸钠（SDS浓度>0.04%）或非离子型乳化剂聚乙烯醇（PVA>0.5%）乳化环境中，液滴表现为自发形成机制，即无连续相流动剪切下可自动从膜孔脱落，此时制备乳液粒径较为均一。液滴能否自发形成取决于乳化剂能否有效降低液滴表面所受界面张力。SDS降低界面张力的能力最强，其水溶液环境中液滴自发生成的趋势最为显著，且形成的乳液也最为均一。反之，聚乙烯醇PVA降低界面张力的能力较弱，制备乳液不如前者均一，但表现出更强的界面粘弹性，对膜乳化过程中乳液滴界面膜的修复作用和乳液的稳定性均有增强作用。结合上述均一乳液的形成机制及力矩平衡分析，确立了液滴脱离时界面张力主导的粘附力矩为液滴自发形成趋势的力学判据。建立了多因素耦合的力矩平衡模型，通过计算各影响因素对液滴达到力矩平衡时所受粘附力矩（脱离力矩）的扰动情况，来判断出液滴能否形成以自发生成机制主导的均一乳液。模型预测趋势与乳液均一性实验规律较为吻合，发现采用较低的连续相流速和跨膜压，较高的分散相粘度，降低界面张力较强的乳化剂将有利于乳液均一形成。 在制备均一单体乳液的基础上，考察了乳液在聚合过程中的孔结构调控机理。发现通过控制烷烃类非良溶剂的碳链长度，以庚烷、液体石蜡和十六烷致孔，可分别制备出多孔、多腔室及中空结构的微球；控制十六烷与助表面活性剂的复配，可以制备出超大孔结构的微球；控制良溶剂甲苯的用量，可使微球由无孔结构转变为小孔结构。采用本体聚合透光度（浊度）法描述了以上微球各种非均质结构演变的内在机理。结果表明，聚合物分子链的增长、惰性溶剂的扩散排布以及两相界面张力等作用的共同竞争促成了乳液滴内部相分离行为，以及最终聚合物微球非均质结构的差异。 在以上成球成孔规律的指导下，发展了膜乳化法结合悬浮聚合及后交联技术制备高比表面积均一聚二乙烯基苯微球的新路线。通过优化筛选致孔剂类型、用量、助表面活性剂及后交联反应条件，以庚烷和甲苯为致孔剂制备出比表面积分别为500.7、481.1m2/g、706.6 m²/g、937.5 m²/g的均一微球。将上述自制的高比表面积均一微球（PDVB）用于反相色谱层析中，与两种商品化反相介质如聚苯乙烯介质（Source30）和无定形硅胶介质（YWG C18）进行了对比，结果表明，自制均一聚二乙烯基苯微球（PDVB）填装柱具有较好的渗透性能和适宜的孔结构，能够有效克服YWG-C18粒径多分散性带来的谱带展宽效应和Source30微孔结构所造成的拖尾现象，是一种选择性高的反相色谱层析介质。 |
| 英文摘要 | With increasing requirement for microscopic materials in modern industry, porous polystyrene (PST) microspheres with uniform size presents more significant functionality in fields such as chromatographic separation, solid phase systhesis and enzyme immobilization etc. The combination of membrane emulsification and suspension polymerization is a new route to synthesize such microspheres in this century. In this route, monomer, initiator and diluent were mixed as to-be-dispersed phase, which was pressed through porous SPG (Shirasu Porous Glass) membrane and formed uniform monomer emulsion droplets in continuous phase, then the monomer droplets were further polymerized into polymer microspheres. Various polymer microspheres have been synthesized by this route. However, the controlling rules of uniformity of emulsion in membrane emulsification have not been fully understood. Besides, most of these microspheres presented limited pores structure and low surface area (<300m2/g). In this thesis, therefore, both the controlling microscopic mechanism behind uniform droplet formation in emulsification and the porous structure evolution during polymerization were further disclosed. Based on these investigations, a series of uniform polystyrene (or Polydivinylbenzene, PDVB) microspheres with high specific area were finally prepared. The main results are as follows: Firstly, by observing droplet formation process in liquid environment using microscope video system, the droplet spontaneous formation behavior were recognized as determining mechanism for emulsion size-uniformity. In pure water or the solution containing emulsifiers of low concentration, droplets tended to adhere at pore opening and cause coalescences between each other, which finally led to polydispersity of emulsion droplets. In aqueous solution with emulsifier of high concentrations, such as anionic-type of sodium dodecyl sulfate (SDS>0.04%) or nonionic-type of polyvinyl alcohol (PVA>0.5%), the droplet detached spontaneously from the membrane pore opening and finally formed uniform emulsion. SDS showed stronger ability to decrease interfacial tension and could form prepare more uniform droplet, and presented more significant tendency of spontaneous detachment. Comparatively, PVA showed stronger interfacial viscoelasticity and formed more stable emulsion. Based on above spontaneous formation mechanism and torque balance principle, a model was constructed incorporating almost all the controlling factors such as operation conditions and materials properties in membrane emulsification. The tendency of droplet spontaneous formation controlled by above factors can be predicted by calculating their disturbance on torques exerting on droplet. The experiment phenomena showed a good coincidence with model prediction. Following experiments conditions were found to facilitate the production of uniform droplets: (1) low cross-flow velocity of continuous phase; (2) low transmembrane pressure; (3) high viscosity of dispersed phase; (4) the emulsifier with great ability and rapid rate to decrease interfacial tension. The formation of porous structure was investigated during suspension polymerization of uniform droplets. It was found that by changing of diluents and co-surfactant, various porous structures could be manipulated in polydivinylbenzene microspheres. Specifically, hexadecane led to hollow structure, liquid paraffin to microvoids structure, and the combination of hexadecane and lauryl alcohol, or heptane and toluene respectively to porous structure from hundred to several nanometers. The relationship between these structures and the phase separation behaviors during polymerization were investigated by in-situ tracking photo transmittance of polymerization system. It was summarized that final heterogeneity of microspheres mainly depended on competition of three dynamics in polymerization, i.e. polymerization kinetics, interfacial energy between phases, and mass transport rate in microspheres. |
| 语种 | 中文 |
| 公开日期 | 2013-09-13 |
| 页码 | 149 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1120]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 郝冬霞. 膜乳化法结合悬浮聚合制备均一多孔聚苯乙烯微球的过程研究[D]. 过程工程研究所. 中国科学院过程工程研究所. 2009. |
入库方式： OAI收割
来源：过程工程研究所
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