聚合物薄膜表面活性层厚度与其分子量关系研究

发布时间：2018-01-04 09:28

本文关键词：聚合物薄膜表面活性层厚度与其分子量关系研究　出处：《浙江理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：聚合物表面分子动力学是高分子物理领域的重要理论科学问题之一。表面高分子链具有与本体不同的聚集态结构及分子运动能力,其重要特征之一在于其具有深度依赖性。随着距离表面深度的增加,相应深度高分子链的分子运动行为也随之发生变化。近年来,聚合物表面分子运动能力的深度依赖性成为了表面动力学领域的研究热点之一。由于研究手段的缺乏,聚合物表面玻璃化转变行为的分子量依赖性的文献报道相对较少,而且不同方法得到的研究结果不能很好地统一。弄清表面玻璃化转变温度、表面效应的影响深度与聚合物链尺寸(分子量)的关系,对于进一步澄清聚合物表面分子动力学的微观物理机制具有重要意义。为了解决聚合物表面玻璃化转变深度分布及其分子量依赖性的问题,本文采用含氟基团标记结合不同表面深度敏感度的表面表征手段研究了不同分子量的聚甲基丙烯酸甲酯与聚苯乙烯表面分子玻璃化转变行为及其分子量依赖性。并关联了表面Tg的分子量依赖性与其薄膜玻璃化转变行为的关系,所得结论如下:(1)聚合物表面分子运动能力呈现出深度依赖性。根据分子运动能力与深度的关系可以将聚合物膜划分为三层。第一层为直接与空气接触厚度很薄的表面层(surface layer),该层其分子运动能力很强,Tg不随深度的改变而变化。第二层为梯度层(gradient region),该区域内的局部Tg随深度增加而上升,将表面的高活性传递至本体。第三层为本体层。(2)PMMA与PS薄膜表面活性层厚度与表面层Tg均依赖于聚合物链尺寸(分子量)。表面层厚度与高分子链回转半径大约呈0.45的倍数关系:Hsurface=0.45 R这是由于聚合物/空气界面的存在,表面高分子链采取椭球状的构象而造成的;表面Tg与链回转半径的关系为:Tg PMMA=2.1 Rg+57.6,Tg PS=1.57 Rg+59.4,说明随着聚合物分子量增大,表面高分子链运动能力减弱。表面高分子链的“滑移运动”机制可以对这一现象进行定性解释。本实验结果也直接证实了de gennes提出的“滑移运动”理论模型的合理性。(3)利用water casting的方法在二氧化硅基底上构筑一层PMMA强吸附层,然后以其为基底制备不同厚度的无界面效应的PMMA薄膜,使用成像椭圆偏振仪对薄膜进行Tg的测定,结果发现薄膜Tg存在分子量依赖性。且薄膜厚度越小,薄膜Tg受分子量的影响越大。将之前通过不同分析深度的CA、SFG及XPS测得的表面Tg值与椭圆偏振仪测得的薄膜Tg值进行叠加,发现二者吻合度良好。这是由于当薄膜厚度较小时,表面层所占体积分数较大,聚合物表面分子运动能力的分子量依赖性导致薄膜整体Tg依赖于分子量;随着薄膜厚度的上升,表面层在薄膜中所占体积分数降低,薄膜Tg受分子量的依赖性减弱,最终达到本体Tg值。
[Abstract]:The surface of the polymer molecular dynamics theory is one of the most important scientific problems in polymer physics. The surface of polymer chains with different ontology aggregation structure and molecular mobility, one of its important features is that it has a depth dependence. With the increase of depth from the surface, the corresponding depth of molecular motion behavior of polymer chains has changed in recent years. The molecular mobility of polymer surface, depth dependence has become a hot topic in the field of surface dynamics. Due to the lack of methods, the molecular weight of polymer on the surface of the glass transition behavior of the dependence of the literature is relatively small, and the results obtained by different methods is not well unified. Clarify the surface of the glass transition temperature, influence the depth and size of the surface effect of polymer chains (molecular weight) of the relationship, to further clarify the polymer surface points The micro physical mechanism has important significance. In order to solve the transformation of subdynamics depth distribution of polymer surface glass and its molecular weight dependence of the problem, this paper uses fluorinated groups of PMMA and polystyrene labeled molecule on the surface of glass transition behavior and different molecular weight dependence with different surface depth sensitive surface characterization methods. And the relationship between the molecular weight dependence of the surface of Tg films with glass transition behavior, the conclusions are as follows: (1) the polymer surface molecular movement ability showing depth dependence. According to the relationship between the molecular movement ability and the depth of the polymer film can be divided into three layers. The first layer is in direct contact with the air is very thin the surface layer (surface layer), the layer of the molecular motion ability is very strong, Tg does not change with depth change. The second layer is gradient Layer (gradient region), local Tg in the region increased with increasing depth, high active surface transfer to the body. The third layer is the ontology layer. (2) surface activity of PMMA and PS thin film thickness and surface layer of Tg are dependent on the size of the polymer chain (molecular weight). The thickness of the surface layer and the polymer the chain is about 0.45 times the radius of gyration relationship: Hsurface=0.45 R this is due to the presence of the polymer / air interface, the surface of polymer chain conformation to ellipsoidal caused; relationship between surface Tg and the radius of gyration chain is: Tg PMMA=2.1 Rg+57.6, Tg PS=1.57 Rg+ 59.4, with the molecular weight of the polymer increases, weaken the surface of polymer chain exercise capacity. Surface of polymer chain "slip" mechanism of this phenomenon is explained. The experimental results also confirmed that de Gennes's "slip" theory model. The rationality of the use of W (3) Ater casting PMMA is a layer of strong adsorption layer on the silica substrate, and the interface effect of PMMA thin film substrates with different thickness, determination of Tg on film using imaging ellipsometry, results showed that the molecular weight dependence of Tg thin film. And the film thickness is small and the effect of film Tg the molecular weight of the larger. Through different depth analysis of CA SFG and XPS before the measurement of surface Tg values of Tg films with ellipsometry measured values were superimposed, it is found that the two good agreement. This is because when the film thickness is small, the surface layer of volume fraction of large molecular weight. The polymer surface molecular mobility dependence leads to the whole film Tg depends on the molecular weight; with the rise of film thickness, surface layer volume fraction decreased, dependent on the molecular weight of Tg films decreased, and eventually reach the body Tg value.

【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】：TB383.2;TQ317

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