Molecular Dynamics Simulations of Surface and Interfacial Tension of Graft Polymer Melts
Molecular Dynamics Simulations of Surface and Interfacial Tension of Graft Polymer Melts
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DOI：
10.1021/acs.langmuir.8b02876
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发表时间：
2018-10-30
期刊：
影响因子：
3.9
通讯作者：
Dobrynin, Andrey, V
中科院分区：
文献类型：
--
作者：
Jacobs, Michael;Liang, Heyi;Dobrynin, Andrey, V
了解聚合物熔体的表面性质对于设计新的聚合物涂料、粘合剂和复合材料至关重要。在这里，我们研究的接枝和线性聚合物熔体的表面和界面张力的分子结构的影响，通过分子动力学模拟。特别是，我们阐明了侧链的聚合度n（SC）和它们的接枝密度1/n（g）对接枝聚合物/真空界面的表面张力γ（G）和接枝和线性聚合物熔体之间的界面的界面张力γ（GL）的影响。对于接枝聚合物/真空界面的情况，我们的模拟证实了表面张力是主链末端分数f（be）和侧链末端分数f（se）的线性函数，γ（G）= γ（infinity）- gamma（be）f（be）- Delta gamma f（se），其中γ（无穷大）是具有无穷大分子量和γ（be）的接枝聚合物体系的表面张力和Δ γ分别是来自主链末端的表面张力贡献以及来自侧链末端和接枝点的贡献之间的差。表面张力的这种依赖性突出了与接枝点和界面处的端部的重新分布相关联的表面张力校正的熵起源。然而，接枝和线性聚合物熔体之间的界面的界面张力不显示任何显着的依赖性的接枝聚合物的分子结构，从而指出的主导地位的接枝贡献的界面张力。
Understanding the surface properties of polymer melts is crucial for designing new polymeric coatings, adhesives, and composites. Here, we study the effect of molecular architecture on surface and interfacial tension of melts of graft and linear polymers by molecular dynamics simulations. In particular, we elucidate the effect of the degree of polymerization of the side chains n(sc) and their grafting density 1/n(g) on the surface tension of the graft polymer/vacuum interface, gamma(G), and the interfacial tension of the interface between graft and linear polymer melts, gamma(GL). For the case of the graft polymer/vacuum interface, our simulations confirm that the surface tension is a linear function of the fraction of the backbone ends f(be) and side chain ends f(se), gamma(G) = gamma(infinity) - gamma(be)f(be) - Delta gamma f(se), where gamma(infinity) is the surface tension of the system of graft polymers with infinite molecular weight and gamma(be) and Delta gamma are surface tension contributions from backbone ends and difference between contributions coming from the side chain ends and grafting points, respectively. This dependence of the surface tension highlights the entropic origin of the surface tension corrections associated with the redistribution of the grafting points and ends at the interface. However, the interfacial tension of the interface between graft and linear polymer melts does not show any significant dependence on the molecular structure of the graft polymers, thus pointing out the dominance of enthalpic contribution to the interfacial tension.