氟化端基标记法研究聚甲基丙烯酸甲酯薄膜分子链扩散行为

发布时间：2018-06-29 07:26

本文选题：氟化端基 + 聚甲基丙烯酸甲酯　；参考：《浙江理工大学》2015年硕士论文

【摘要】：随着纳米材料的快速发展,纳米尺度的聚合物薄膜在光电材料、超薄涂层以及分离膜等领域的应用越来越广泛。聚合物薄膜分子链的扩散行为影响材料的界面粘附性以及黏弹性等诸多性能,对聚合物薄膜材料的实际使用有至关重要的作用。研究聚合物薄膜分子链扩散行为,不仅可对聚合物纳米材料性能调控提供理论指导,而且对于澄清空间受限聚合物分子动力学的微观机制具有重要理论意义。近年来,随着本课题组对含氟聚合物研究的深入,发现氟化端基标记法可以作为聚合物分子链运动行为的研究手段。本论文利用氟化基团标记聚甲基丙烯酸甲酯分子链,构建了下层为氟化端基标记PMMA(Mn=4kg/mol),上层为未标记PMMA(Mn=60~570kg/mol)的双层膜。利用接触角、X射线光电子能谱(XPS)等手段监测不同温度下氟化端基标记PMMA分子在上层薄膜内的迁移时间,研究了PMMA薄膜的分子扩散行为。探讨了上层PMMA薄膜厚度、分子量以及温度对标记PMMA分子扩散行为的影响。结果发现:(1)标记PMMA扩散至上层膜表面所需要时间t*与上层膜厚度h关系符合菲克扩散方程。通过两者的关系(t*~h)可求得PMMA分子链的扩散系数D。扩散系数与文献报道值基本一致,说明氟化端基标记法是研究聚合物扩散行为的有效方法。(2)标记PMMA分子链扩散系数依赖于上层膜厚度。当上层PMMA薄膜的厚度小于某一临界值hup*时,标记PMMA分子链的扩散系数随上层薄膜厚度的降低而降低;当薄膜厚度减小到另一临界厚度hlow*时,扩散系数又趋于恒定。PMMA分子链缠结分子量随薄膜厚度的变化而变化可能是引起扩散系数随上层膜厚度改变而改变的主要原因。当上层膜厚度小于上临界厚度hup*时,薄膜的缠结分子量Me随薄膜厚度降低而减小,导致PMMA分子链扩散系数D降低;当上层膜厚度降低到下临界厚度hlow*时,薄膜的缠结分子量Me不再随着薄膜厚度的变化而变化,因而PMMA分子链的扩散系数D又趋于恒定。(3)当上层膜厚度大于上临界厚度hup*时,扩散系数D与上层膜分子量的关系为D~M-0.8;当上层膜厚度小于下临界厚度hlow*时,扩散系数D与上层膜分子量的关系为D~M-0.4;当上层膜厚度在hup*与hlow*之间时,扩散系数D与上层膜分子量的关系为D~M-0.47(上层膜厚度为40nm)。随着上层膜厚度的减小,扩散系数的厚度依赖性逐渐减弱。此外,发现下临界厚度hlow*基本不随上层膜PMMA分子量的改变而改变。上临界厚度hup*随着上层膜分子量的增加而逐渐减小。hup*与上层PMMA分子链回转半径(Rg)呈现-0.62次方标度关系:hup*~Rg-0.62。
[Abstract]:With the rapid development of nanomaterials, nano-scale polymer films are widely used in the fields of optoelectronic materials, ultrathin coatings and separation films. The diffusion behavior of molecular chains in polymer films affects the interfacial adhesion and viscoelasticity of polymer films and plays an important role in the practical use of polymer films. The study of molecular chain diffusion behavior of polymer films can not only provide theoretical guidance for the performance regulation of polymer nanomaterials, but also be of great theoretical significance in clarifying the micro mechanism of molecular dynamics of spatially confined polymers. In recent years, with the further study of fluorinated polymers, we found that fluorinated end group labeling can be used as a means to study the molecular chain movement of polymers. In this paper, the fluorinated groups were used to label the molecular chain of polymethyl methacrylate (PMMA), and a bilayer membrane with a fluorinated end group labeled PMMA (MNO 4 kg / mol) and an unlabeled PMMA (MN 60570 kg / mol) was constructed. The molecular diffusion behavior of PMMA films was studied by means of X-ray photoelectron spectroscopy (XPS) and X-ray photoelectron spectroscopy (XPS), which were used to monitor the migration time of fluorinated end-group labeled PMMA molecules in the upper layer of films at different temperatures. The effects of the thickness, molecular weight and temperature of the upper PMMA film on the diffusion behavior of the labeled PMMA were investigated. The results are as follows: (1) the relationship between the time t * and the thickness h of the PMMA diffusion film accords with the Fick diffusion equation. The diffusion coefficient D of PMMA molecular chain can be obtained by the relationship between them. The diffusion coefficient is basically consistent with the reported values, which indicates that the fluorinated end group labeling method is an effective method for studying the diffusion behavior of polymers. (2) the molecular chain diffusion coefficient of labeled PMMA depends on the film thickness. When the thickness of the upper PMMA film is less than a critical value, the diffusion coefficient of the labeled PMMA molecular chain decreases with the decrease of the thickness of the upper film, and when the thickness of the film decreases to another critical thickness, the diffusion coefficient of the molecular chain decreases. The change of molecular entanglement molecular weight of PMMA molecular chain with film thickness may be the main reason for the change of diffusion coefficient with the change of film thickness. When the upper layer thickness is less than the upper critical thickness, the tangle molecular weight of the film decreases with the decrease of the film thickness, which leads to the decrease of the diffusion coefficient D of PMMA molecular chain, and when the upper layer thickness decreases to the lower critical thickness, the molecular chain diffusion coefficient D decreases. The entangled molecular weight of the film no longer varies with the thickness of the film, so the diffusion coefficient D of the PMMA molecular chain tends to be constant. (3) when the thickness of the upper layer is larger than that of the upper critical thickness, The relationship between the diffusion coefficient D and the molecular weight of the upper layer is DUM-0.8.The relationship between the diffusion coefficient D and the molecular weight of the upper layer is DfM 0.4 when the thickness of the upper layer is less than the lower critical thickness of the film, and when the thickness of the upper layer is between hup* and hlow*, the relationship between the diffusion coefficient D and the molecular weight of the upper layer is DUM-0.4. The relationship between the diffusion coefficient D and the molecular weight of the film is DfM 0.47 (the thickness of the film is 40nm). The thickness dependence of diffusion coefficient decreases with the decrease of the film thickness. In addition, it is found that the lower critical thickness of hlow* basically does not change with the molecular weight of PMMA. The supercritical thickness hup* decreases gradually with the increase of the molecular weight of the upper layer and the radius of gyration (R g) of the upper PMMA molecular chain presents a scale of -0.62 to the power of -0.62.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ317;TB383.2

【参考文献】