【作者】 田云霞；

【导师】 王新；

【作者基本信息】 青岛科技大学 ， 高分子化学与物理， 2009， 硕士

【摘要】 聚四氟乙烯(PTFE)多孔膜在化工分离领域有广泛应用,其表面的亲水化是相关领域的研究热点之一。国内外研究人员围绕PTFE膜的表面改性进行了大量研究,如等离子体处理、化学溅涂等,但是改性后膜材料的接触角都随时间有一定程度的回升。鉴于此,我们采用了新的方法,即采用分散聚合原位沉积成膜的方法在等离子体预处理的PTFE膜上引入刚性聚合物聚苯胺(PANI)或苯胺共聚物进行亲水改性,期望刚性亲水大分子不易运动的特征能够保持亲水改性效果的持久性。本文以聚乙烯吡咯烷酮(PVP)为空间稳定剂,过硫酸铵(APS)为氧化剂,盐酸(HCl)水溶液为反应介质,苯胺(An)或者An与第二单体5-氨基邻苯二甲酸(AIA)为反应单体,在溶液中发生氧化聚合反应的同时完成在基体PTFE膜表面的原位成膜,制备了PANI/PTFE和An/AIA共聚物/PTFE复合膜。通过扫描电镜、体式显微镜、X射线光电子光谱、红外光谱、拉曼光谱、接触角等测试,研究了复合膜的表观形貌、膜的结构、生长历程及其亲水改性效果。试验结果表明,在An的分散聚合体系中实现PANI在PTFE膜表面的原位成膜,并获得了表面光滑致密的PANI/PTFE复合膜。初步探讨该膜的形成机理为基体通过物理吸附诱导期生成的An阳离子自由基,形成聚合中心,PANI链从这些初级成核中心增长,然后再经过链增长和链结构调整得到有序薄膜。拉曼光谱和红外光谱证实复合膜中的PANI为掺杂态。通过对PANI/PTFE复合膜进行掺杂,制备了可做盐水分离的复合膜,能在保持较高的盐分截留率的情况下有效提高蒸馏通量。接触角测试表明,PANI在PTFE膜表面的沉积可以较好的对其进行亲水改性,并且PANI作为刚性亲水大分子,其分子链不易运动的特征保证了亲水改性的持久性。研究了PANI在等离子体预处理的PTFE膜表面的沉积过程。实验结果表明,聚合历程大致分为诱导期、聚合生长期、饱和终止期。适当的等离子体处理缩短了诱导期,加速了苯胺的聚合速率,使峰值温度提高,这是由于等离子处理使PTFE膜的表面纤维结构和化学成分发生变化的结果,但单纯的等离子体处理对PTFE亲水改性不明显。拉曼光谱和接触角测试表明,An/AIA共聚物与PANI有类似的化学结构;An/AIA共聚物在PTFE薄膜表面的沉积使其接触角发生巨大变化,亲水性有了很好的改善。相比而言,An/AIA共聚物优于PANI的亲水改性效果,这与加入的第二单体AIA的结构有关。研究了PANI在等离子体预处理PTFE基体上的生长过程,结果表明:PANI在基体表面的成膜过程呈三个阶段:含An的结构单元(包括An盐酸盐、阳离子自由基、低聚体)在PTFE基体表面吸附成核阶段(吸附作用包括物理吸附和等离子体处理后过氧自由基活性点的吸附);膜快速成长阶段;成长达到饱和阶段。吸附生长起始于反应的诱导期,贯穿反应全过程,对膜表面质量的影响较大。更多还原

【Abstract】 Polytetrafluoroethylene(PTFE) porous membranes have been widely used in chemical separation industry, and its hydrophilic modification has been one of the focuses of the relevant researches. Some researchers have done a large number of studies, such as plasma treatment and coating. However, the contact angle of membrane will return in some degree after the treatments. So in this paper, we used a new method: air plasma-pretreated PTFE membranes were subjected to further surface modification by polyaniline and aniline copolymer, with the expect that the hydrophilic characteristics would last longer because of their rigid molecular chains.The experiment used PVP as steric stabilizer, APS as the oxidizer, HCl as reaction medium, annilie or aniline(An) and 5-aminoisophthalic acid(AIA) as the monomer. Polyaniline(PANI) or An/AIA copolymer was in-situ deposited onto the surface of PTFE membranes during dispersion polymerization of An with PTFE membranes dipped in. The membrane morphology, chemical structure, the growth and hydrophilic modification of PANI were characterized by SEM, Micrographs, XRD, FTIR, Raman spectrum and Contact angle measurement.The results indicated that PANI/PTFE composite membranes were prepared successfully using in-situ dispersion polymerization. It was proposed that the growth mechanism of PANI membrane occurred through the quick absorption of An monomer cation radicals on the PTFE surfaces by physical absorption to form polymerization centers, and then the chain grew to PANI membrane. Raman spectrum and FTIR indicated that PANI of composite membrane was doped. And the composite membrane was used as distillation with higher blocking of salt and higher flux. The Contact angle measurement showed that there was a good change on hydrophilic modification of PTFE membrane by in-situ deposited PANI.The polymerization process of PANI on PTFE pretreated by plasma was studied. The results indicated that polymerization included induction period, growth and saturation period. Plasma processing could shorten induction period, enhance polymerization rate and increase the apex temperature in that plasma treatment could modify structure and chemical component of PTFE membrane. But the hydrophilic modification was not obvious by single plasma treatment.SEM and Contact angle measurement showed that the chemistry structure of An/AIA copolymer was similar with PANI. There was a good change on hydrophilic modification of PTFE membrane by depositing An/AIA copolymer, with comparison, the modification effect of An/AIA copolymer on PTFE micro-porous membrane was superior to PANI’s because of the structure of AIA.The process of growth of PANI on PTFE pretreated by plasma was studied. The results indicated it contained three periods: adsorption nucleation(including physical absorption and peroxy radicals absorption), growth and growth saturation. The growth started at induction period, ran through the whole process with an important effect on the quality of membrane.更多还原