Structure-induced switching of interpolymer adhesion at a solid-polymer melt interface
Structure-induced switching of interpolymer adhesion at a solid-polymer melt interface
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DOI：
10.1039/c7sm02279d
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发表时间：
2018-02-21
期刊：
影响因子：
3.4
通讯作者：
Sumpter, Bobby G.
中科院分区：
文献类型：
--
作者：
Jiang, Naisheng;Sen, Mani;Sumpter, Bobby G.
在这里，我们报告了物理吸附(即通过物理吸附)到固体上的均聚物链的界面结构和粘附性之间的联系。以聚氧乙烷(PEO)为模型，通过公认的Guiselin方法，在硅衬底上创建了两种不同的吸附聚合物链构象：一种是平铺在固体上并密集堆积的“扁平链”，另一种是“松散吸附的聚合物链”，它形成了连接固体表面附近空位并覆盖平坦链的桥梁。利用自制的粘附性测试装置研究了两种不同吸附链的粘附性。对平坦链或疏松吸附链上厚厚的PEO覆盖层进行了粘附性测试。结果表明，扁平链即使与化学上相同的自由聚合物在顶部也不表现出任何粘附性，而松散吸附的链表现出粘附性。中子反射率实验证实，界面粘附性的差异不是由于自由聚合物-吸附聚合物界面的界面溴化所致。相反，粗粒分子动力学模拟结果表明，疏松吸附的链的尾部起到了连接分子的作用，桥接了自由链和基片表面，改善了界面粘附性，这些发现不仅揭示了界面处的结构-性质关系，而且为通过精确控制界面聚合物纳米结构来开发粘/防粘技术提供了一种新的途径。
Here we report a link between the interfacial structure and adhesive property of homopolymer chains physically adsorbed (i.e., via physisorption) onto solids. Polyethylene oxide (PEO) was used as a model and two different chain conformations of the adsorbed polymer were created on silicon substrates via the well-established Guiselin's approach: "flattened chains'' which lie flat on the solid and are densely packed, and "loosely adsorbed polymer chains'' which form bridges jointing up nearby empty sites on the solid surface and cover the flattened chains. We investigated the adhesion properties of the two different adsorbed chains using a custom-built adhesion testing device. Bilayers of a thick PEO overlayer on top of the flattened chains or loosely adsorbed chains were subjected to the adhesion test. The results revealed that the flattened chains do not show any adhesion even with the chemically identical free polymer on top, while the loosely adsorbed chains exhibit adhesion. Neutron reflectivity experiments corroborated that the difference in the interfacial adhesion is not attributed to the interfacial brodening at the free polymer-adsorbed polymer interface. Instead, coarse-grained molecular dynamics simulation results suggest that the tail parts of the loosely adsorbed chains act as "connector molecules'', bridging the free chains and substrate surface and improving the interfacial adhesion. These findings not only shed light on the structure-property relationship at the interface, but also provide a novel approach for developing sticking/anti-sticking technologies through precise control of the interfacial polymer nanostructures.