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Influence of Polymer Molecular Weight on Chain Conformation at the Polystyrene/Silver Interface
Langmuir ( IF 3.7 ) Pub Date : 2021-08-11 , DOI: 10.1021/acs.langmuir.1c01211 Bianca M de Lima 1 , Patrick L Hayes 2 , Paula M Wood-Adams 1
Langmuir ( IF 3.7 ) Pub Date : 2021-08-11 , DOI: 10.1021/acs.langmuir.1c01211 Bianca M de Lima 1 , Patrick L Hayes 2 , Paula M Wood-Adams 1
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The dependence between the conformation of polystyrene (PS) and its molecular weight (Mw) in the vicinity of a metal interface was investigated by sum frequency generation (SFG) spectroscopy. Tilt angles θ ≥ 50° (the angle between the C2 axis of the pendant phenyl ring and the surface normal) were observed for all samples because of the interaction between the aromatic rings and the metal surface. Furthermore, it was found that θ decreases with increasing Mw for PS samples ranging from 20 × 103 g/mol to 400 × 103 g/mol. The intensity of the backbone SFG signal was higher for high Mw PS, compared to low Mw PS, indicating a greater number of backbone interactions with the silver substrate surface for the high Mw sample. These structural differences are driven by different entropic and enthalpic contributions to the free energy of adsorption for different polymer molecular weights. Differences in the polymer free volume and in the relative amount of chain ends with higher mobility may also influence the chain conformation. These results suggest that important interfacial properties of polymeric thin films, such as adhesion and wettability, could be tailored by modifying the polymer Mw to achieve the desired interfacial conformation.
中文翻译：
聚合物分子量对聚苯乙烯/银界面链构象的影响
通过和频生成 (SFG) 光谱研究了金属界面附近聚苯乙烯 (PS) 的构象与其分子量 (Mw) 之间的依赖性。由于芳香环和金属表面之间的相互作用，所有样品的倾角 θ ≥ 50 °（悬垂苯环的 C 2轴与表面法线之间的角度）都被观察到。此外，发现对于从 20 × 10 3 g/mol 到 400 × 10 3 的PS 样品，θ 随着 Mw 的增加而减小克/摩尔。与低 Mw PS 相比，高 Mw PS 的骨架 SFG 信号强度更高，表明高 Mw 样品与银基材表面的骨架相互作用更多。这些结构差异是由不同聚合物分子量对吸附自由能的不同熵和焓贡献驱动的。聚合物自由体积的差异和具有较高流动性的链端的相对量的差异也可能影响链的构象。这些结果表明，聚合物薄膜的重要界面特性，如粘附性和润湿性，可以通过修改聚合物 Mw 来实现所需的界面构象。
更新日期：2021-08-24
中文翻译：
聚合物分子量对聚苯乙烯/银界面链构象的影响
通过和频生成 (SFG) 光谱研究了金属界面附近聚苯乙烯 (PS) 的构象与其分子量 (Mw) 之间的依赖性。由于芳香环和金属表面之间的相互作用，所有样品的倾角 θ ≥ 50 °（悬垂苯环的 C 2轴与表面法线之间的角度）都被观察到。此外，发现对于从 20 × 10 3 g/mol 到 400 × 10 3 的PS 样品，θ 随着 Mw 的增加而减小克/摩尔。与低 Mw PS 相比，高 Mw PS 的骨架 SFG 信号强度更高，表明高 Mw 样品与银基材表面的骨架相互作用更多。这些结构差异是由不同聚合物分子量对吸附自由能的不同熵和焓贡献驱动的。聚合物自由体积的差异和具有较高流动性的链端的相对量的差异也可能影响链的构象。这些结果表明，聚合物薄膜的重要界面特性，如粘附性和润湿性，可以通过修改聚合物 Mw 来实现所需的界面构象。
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