Stress-Structure Correlation in PS-PMMA Mixed Polymer Brushes
Stress-Structure Correlation in PS-PMMA Mixed Polymer Brushes
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DOI：
10.1021/ma2025286
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发表时间：
2012-04-10
期刊：
影响因子：
5.5
通讯作者：
Gutmann, Jochen S.
中科院分区：
文献类型：
--
作者：
Ochsmann, Jannis W.;Lenz, Sebastian;Gutmann, Jochen S.
在外界刺激下改变表面性质（如形态和表面能）的能力使可切换聚合物表面成为一个有前途的研究领域。由两种不同的均聚物共价附着在表面组成的混合聚合物刷是一种表面性质可以切换的系统。本文研究了选择性溶剂对薄聚（甲基丙烯酸甲酯）聚苯乙烯混合聚合物刷膜结构变化与表面应力之间的关系。通过测量作用在薄膜内部的力，我们能够对观察到的结构变化有更深入的了解。为了深入了解薄膜的形态，通过扫描探针显微镜、x射线反射率和掠射小角x射线散射（GISAXS）对其结构进行了分析。在暴露于醋酸（PMMA的一种选择性溶剂）时，薄膜显示出一个酒窝状结构。这与被PMMA链覆盖的聚苯乙烯的塌缩结构域有关。弯曲实验的结果是拉伸应力，指向作用在聚合物薄膜内部的吸引力。暴露于二氯甲烷（两种聚合物的良好溶剂）后，弯曲实验显示拉伸应力降低但仍然很高，表明微畴仍然存在。实验结果使我们能够进一步解释在这类混合聚合物刷系统中通常发现的域记忆效应。
The ability to alter surface properties such as morphology and surface energy upon external stimuli makes switchable polymer surfaces a promising field of research. Mixed polymer brushes consisting of two different homopolymers covalently attached to a surface are one system in which surface properties can be switched. In this work the correlation between the change in structure and the resulting surface stress in thin poly(methyl methacrylate) polystyrene mixed polymer brush film upon exposure to selective solvents is investigated. By measuring the forces acting inside the film, we are able to achieve a deeper understanding of the observed structural changes. To obtain a thorough understanding of the film's morphology, the structure is analyzed by scanning probe microscopy, X-ray reflectivity, and grazing incidence small-angle X-ray scattering (GISAXS). Upon exposure to acetic acid, a selective solvent for PMMA, the film showed a dimple-like structure. This is linked to collapsed domains of polystyrene covered by PMMA chains. Bending experiments resulted in tensile stress, pointing to attractive forces acting inside the polymer film. After exposure to dichloromethane, a good solvent for both polymers, bending experiments revealed a decreased but still high tensile stress, indicating that the microdomains are still present. The results of the experiments enable us to further explain the domain memory effect typically found in these kinds of mixed polymer brush systems.