【作者】 王建莉；

【导师】 励杭泉；

【作者基本信息】 北京化工大学 ， 材料学， 2009， 博士

【摘要】 浓乳液模板法(Concentrated emulsion templating)制备多孔材料是将浓乳液的连续相作为聚合相,在一定温度下进行聚合反应,聚合结束后经洗涤干燥即可得到多孔结构的聚合物材料。与其它制备多孔材料的方法相比,浓乳液模板法具有可精确控制孔及通道直径的大小和分布的优点。本文用浓乳液聚合模板法制备了一系列具有多孔结构的聚合物材料。主要工作如下:1.用浓乳液聚合的方法合成了聚丙烯酰胺泡孔材料。其中以丙烯酰胺为单体,过二硫酸钾为引发剂,水为溶剂,十六烷基三甲基溴化铵为乳化剂,环己烷为分散剂,聚乙二醇为交联剂。得到的泡孔材料具有相互连通的多孔结构;讨论了乳化剂用量,分散相体积分数的变化对泡孔结构和材料密度的影响;研究了交联剂用量对材料吸水性的影响;且通过对比发现浓乳液法制得的聚丙烯酰胺泡孔材料比本体法制得的有较高的吸水性;2.用两步法合成了亲水/亲油多孔材料。其中用浓乳液聚合首先合成聚苯乙烯多孔基体,然后通过浸泡将丙烯酰胺填充到孔中并聚合,制得复合材料。采用压汞测孔法表征了其孔隙率和孔径,发现孔隙率随浓乳液分散相体积分数的增加而增大,孔径变化不大;改变丙烯酰胺溶液浓度时则对自由孔隙有明显影响,浓度越高孔隙越小。对复合材料进行吸水性和饱和水蒸气渗透测试,观察到丙烯酰胺浓度越低,材料吸水率越高,在饱和水蒸气中闭孔需要的时间越长;反之,当丙烯酰胺浓度越高,吸水率越低,越容易闭孔;3.研究了双酚A环氧树脂反相浓乳液体系的稳定性。发现有乳化剂存在的同时,在分散相中加入二氧化硅胶体粒子能大大改善浓乳液的稳定性,增强浓乳液体系中界面膜的强度,有效抑制液滴聚并;同时,环氧树脂的预固化能适当调节连续相的黏度,也能促使乳液稳定;乳化剂用量的增加能使体系的界面强度提高,抑制液滴间的聚并,有利于浓乳液稳定,而分散相体积分数的提高则不利于乳液稳定;4.用浓乳液模板法制备出了双酚A环氧树脂多孔材料。系统研究了二氧化硅胶粒浓度,连续相预固化程度,乳化剂用量,固化剂用量以及分散相体积分数等诸多因素的变化对多孔材料孔径和分布的影响。发现当预固化时间低于5min时连续相黏度较低,体系界面强度降低导致孔结构有所变型,当预固化高于60min不利于液滴的分散,孔径分布均匀性降低;当乳液浓度超过82%时,分散的液滴聚并的趋势增加,孔径分布均匀性变差,当乳液浓度为86%时,有大孔出现;5.系统的研究了对氨基苯酚三缩水甘油基环氧树脂浓乳液的稳定性。发现此液系统在HLB值为8.6时稳定性较高,HLB值较小或较大时,均不能得到足够稳定的浓乳液,因而不能得到理想的多孔结构;并且在HLB值为8.6的情况下研究了三种乳化剂(聚乙二醇型非离子乳化剂NPE-4、多元醇型非离子乳化剂Span 20和由Span 80和Tween 80组成的复合乳化剂)对浓乳液稳定性的影响。并通过对三种情况下多孔材料孔壁结构的观察和体系中分子之间相互关系对浓乳液体系界面模型进行分析模拟,合理的解释了浓乳液的稳定机理;6.用浓乳液模板法制备出了对氨基苯酚三缩水甘油基环氧树脂多孔材料。研究了二氧化硅胶粒胶粒浓度,乳化剂用量,连续相预固化时间,固化剂用量,分散相体积分数等因素对多孔形态的影响。发现连续相预固化时间,固化剂用量和分散相体积分数对多孔结构影响较大。当预固化时间低于15min时,乳液稳定性差,不能得到多孔材料;当预固化时间高于75min时,体系黏度过高,不利于浓乳液形成过程中液滴的分散,也得不到分布均匀的多孔材料;只有当预固化时间为60min时得到多孔材料的孔径最小。此外,还发现当连续相浓度大于76%时,得到的多孔材料相邻的孔之间形成相互连接的通道,并通过对材料孔隙率的测量发现材料为半开孔结构。更多还原

【Abstract】 Preparation of porous materials via concentrated emulsion templating method is to polymerize the continuous phase at certain temperature, and then the porous monolith can be obtained when the polymerization completed after cleaning. Comparatively, concentrated emulsion templating method is convenient and inexpensive, more importantly; the pore size and distribution are controllable. In this dissertation, a series of polymer materials with porous structure were prepared. Many factors influenced the stability of the concentrated emulsion and the the morphology of porous monolith were investigated.1. The porous polyacrylamide (PAM) was polymerizated by the template of concentration emulsion, in which cyclohexane is the dispersed phase, acrylamide and poly (ethy glycol) is the continous phase. The density and porosity of PAM can be adjusted by the changing of the content of emulsifier, and the dispersed phase volume fraction. The water absorption of different porosity was studied. The results show that the water absorption of porous PAM is larger than bulk PAM, and increases with the porosity of porous PAM.2. A porous hydrophilic/hydrophobic composite was prepared by concentrated emulsion polymerization, which composed of a porous hudrophobic polystyrene matrix with its cells and intercellular pores partially filled with hydrophilic PAM. The permeation of ther resulted composites was controllable according to the environment humidity. In condition of low humidity, the materials kept open-celled and exhibited a high permeation, whereas at high humidity, the filled PAM was swolled by aqueous vapor and blocked the intercellular pore, the materials became nonpermeated.3. Inverse concentrated emulsions were prepared using aqueous colloidal silica suspension as the hydrophilic dispersed phase and a solution of diglycidyl ether of bisphenol -A (DGEBA), its curing agent polyamide resin, low molecular weight 650, surfactant nonyl phenol polyoxyethylene ether in 4-methyl-2-pentanon as the continuous phase. Without colloidal silica in the aqueous phase and the pre-curing of the continuous phase, the stability of the concentrated emulsion was poor. The colloidal silica tended to accumulated on the surface of the dispersed droplets forming an encapsulation, which strengthened the steric repulsion in the system and thus improved the stability. Pre-curing of the continuous phase provided an increased initial viscosity and enhanced the stability. Lower volume fraction of the dispersed phase can help to maintain stability of the concentrated emulsions.4. A DGEBA porous monolith was prepared via concentrated emulsion templating. The introduction of colloidal silica into the hydrophilic phase strengthened the steric repulsion at the interface and ensured the stability of the concentrated emulsion. A proper pre-curing of the precursors in the continuous phase viscosity, a larger amount of the curing agent accelerated the curing rate. All above factors effectively retarded the rate of phase separation and realized the formation of a porous structure.5. The uniform porous monoliths of glycidyl amino epoxy resin (GAE) were prepared via concentrated emulsion template method. It was found the nonionic surfactant, HLB=8.6, in the aid of colloidal silica were well suited to stabilize such concentrated emulsions. The effect of HLB values of non-ionic emulsifier was taken into account, and the correlation of oil phase, surfactant and colloidal silica was investigated. In addition, a model was built to interpret the stabilization mechanism of concentrated emulsion stabilized by the non-ionic emulsifier in the aid of colloidal silica.6. It was found that a proper pre-cure of the precursors and proper curing agent amount in the continuous phase viscosity can accelerated the curing rate and increased the stability of concentrated emulsion. It was also found when the emulsion concentration was higher than 0.76, the obtained porous monolith possessed high porous with a complex network of channels and interconnected pores.更多还原