{"title":"剪切流中纠缠短链支链环熔体的界面聚合物流变学","authors":"Tae Yong Ha, Seung Heum Jeong and Chunggi Baig*, ","doi":"10.1021/acs.macromol.4c00607","DOIUrl":null,"url":null,"abstract":"<p >We present a detailed analysis of the rheological behavior of entangled short-chain-branched (SCB) ring polymers at interfaces via direct comparison with the corresponding pure (unbranched) ring polymers using atomistic nonequilibrium molecular dynamics simulations of confined polyethylene melt systems under shear flow. To elucidate the general structural and dynamical characteristics of interfacial polymer chains, we analyze various physical properties of the chains in the bulk and interfacial regions separately within the confined systems, such as the chain radius of gyration and its distribution, the average streaming velocity profile, and the degree of interfacial slip, with respect to the applied flow strength. The pure ring polymer melt has a highly extended and aligned chain structure along the flow (<i>x</i>-)direction at the interface, even under weak flow fields, indicative of the strong wall effects via the attractive polymer–wall interactions. In contrast, the interfacial SCB ring chains generally form a compact structure like that of the corresponding bulk chains in the weak flow regime, representing a significant role of the short branches to effectively diminish the wall effect. In conjunction with these structural characteristics, the entangled SCB ring polymer melt displays a markedly smaller degree of interfacial slip than the corresponding pure ring analogue in the weak-to-intermediate flow regimes. Furthermore, while both the pure ring and the SCB ring polymer melt systems reveal similar fundamental molecular mechanisms at the interface with respect to the flow strength (i.e., <i>z</i>-to-<i>x</i> rotation, loop wagging, loop migration, and loop tumbling mechanisms), the SCB ring polymer melt displays relatively weaker loop migration and loop wagging dynamics with highly curvy backbone structures in the intermediate flow regime. In the strong flow regime, both the pure ring and SCB ring systems exhibit the loop tumbling mechanism together with intensive collisions between the interfacial chains and the wall. However, the interfacial SCB ring chains execute substantial loop migration dynamics even at high flow fields, which facilitates interfacial slip.</p>","PeriodicalId":51,"journal":{"name":"Macromolecules","volume":null,"pages":null},"PeriodicalIF":5.1000,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Interfacial Polymer Rheology of Entangled Short-Chain Branched Ring Melts in Shear Flow\",\"authors\":\"Tae Yong Ha, Seung Heum Jeong and Chunggi Baig*, \",\"doi\":\"10.1021/acs.macromol.4c00607\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p >We present a detailed analysis of the rheological behavior of entangled short-chain-branched (SCB) ring polymers at interfaces via direct comparison with the corresponding pure (unbranched) ring polymers using atomistic nonequilibrium molecular dynamics simulations of confined polyethylene melt systems under shear flow. To elucidate the general structural and dynamical characteristics of interfacial polymer chains, we analyze various physical properties of the chains in the bulk and interfacial regions separately within the confined systems, such as the chain radius of gyration and its distribution, the average streaming velocity profile, and the degree of interfacial slip, with respect to the applied flow strength. The pure ring polymer melt has a highly extended and aligned chain structure along the flow (<i>x</i>-)direction at the interface, even under weak flow fields, indicative of the strong wall effects via the attractive polymer–wall interactions. In contrast, the interfacial SCB ring chains generally form a compact structure like that of the corresponding bulk chains in the weak flow regime, representing a significant role of the short branches to effectively diminish the wall effect. In conjunction with these structural characteristics, the entangled SCB ring polymer melt displays a markedly smaller degree of interfacial slip than the corresponding pure ring analogue in the weak-to-intermediate flow regimes. Furthermore, while both the pure ring and the SCB ring polymer melt systems reveal similar fundamental molecular mechanisms at the interface with respect to the flow strength (i.e., <i>z</i>-to-<i>x</i> rotation, loop wagging, loop migration, and loop tumbling mechanisms), the SCB ring polymer melt displays relatively weaker loop migration and loop wagging dynamics with highly curvy backbone structures in the intermediate flow regime. In the strong flow regime, both the pure ring and SCB ring systems exhibit the loop tumbling mechanism together with intensive collisions between the interfacial chains and the wall. 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引用次数: 0
摘要
我们利用原子非平衡分子动力学模拟了剪切流下的密闭聚乙烯熔体体系,通过与相应的纯环聚合物(未支化)的直接比较,详细分析了缠结短链支化环聚合物在界面处的流变行为。为了阐明界面聚合物链的一般结构和动力学特征,我们分别分析了密闭体系中块状区和界面区聚合物链的各种物理性质,如链的回转半径及其分布、平均流速曲线以及界面滑移程度与所施加的流动强度的关系。即使在弱流场条件下,纯环聚合物熔体在界面上沿流动(x-)方向也具有高度延伸和排列整齐的链结构,这表明通过聚合物与壁的吸引力相互作用产生了强烈的壁效应。与此相反,界面 SCB 环链在弱流动条件下通常会形成与相应体链一样的紧凑结构,这表明短枝在有效减弱壁效应方面发挥了重要作用。结合这些结构特征,缠结 SCB 环聚合物熔体在弱到中间流动体系中的界面滑移程度明显小于相应的纯环类似物。此外,虽然纯环和 SCB 环聚合物熔体系统在界面上显示出与流动强度类似的基本分子机制(即 z 到 x 旋转、环摆动、环迁移和环翻滚机制),但 SCB 环聚合物熔体在中间流动体系中显示出相对较弱的环迁移和环摆动动态,并具有高度弯曲的骨架结构。在强流动体系中,纯环和 SCB 环体系都表现出翻滚机制,同时界面链与壁之间会发生激烈碰撞。然而,即使在高流动场下,界面 SCB 环链也会执行大量的环迁移动力学,从而促进界面滑移。
Interfacial Polymer Rheology of Entangled Short-Chain Branched Ring Melts in Shear Flow
We present a detailed analysis of the rheological behavior of entangled short-chain-branched (SCB) ring polymers at interfaces via direct comparison with the corresponding pure (unbranched) ring polymers using atomistic nonequilibrium molecular dynamics simulations of confined polyethylene melt systems under shear flow. To elucidate the general structural and dynamical characteristics of interfacial polymer chains, we analyze various physical properties of the chains in the bulk and interfacial regions separately within the confined systems, such as the chain radius of gyration and its distribution, the average streaming velocity profile, and the degree of interfacial slip, with respect to the applied flow strength. The pure ring polymer melt has a highly extended and aligned chain structure along the flow (x-)direction at the interface, even under weak flow fields, indicative of the strong wall effects via the attractive polymer–wall interactions. In contrast, the interfacial SCB ring chains generally form a compact structure like that of the corresponding bulk chains in the weak flow regime, representing a significant role of the short branches to effectively diminish the wall effect. In conjunction with these structural characteristics, the entangled SCB ring polymer melt displays a markedly smaller degree of interfacial slip than the corresponding pure ring analogue in the weak-to-intermediate flow regimes. Furthermore, while both the pure ring and the SCB ring polymer melt systems reveal similar fundamental molecular mechanisms at the interface with respect to the flow strength (i.e., z-to-x rotation, loop wagging, loop migration, and loop tumbling mechanisms), the SCB ring polymer melt displays relatively weaker loop migration and loop wagging dynamics with highly curvy backbone structures in the intermediate flow regime. In the strong flow regime, both the pure ring and SCB ring systems exhibit the loop tumbling mechanism together with intensive collisions between the interfacial chains and the wall. However, the interfacial SCB ring chains execute substantial loop migration dynamics even at high flow fields, which facilitates interfacial slip.
期刊介绍:
Macromolecules publishes original, fundamental, and impactful research on all aspects of polymer science. Topics of interest include synthesis (e.g., controlled polymerizations, polymerization catalysis, post polymerization modification, new monomer structures and polymer architectures, and polymerization mechanisms/kinetics analysis); phase behavior, thermodynamics, dynamic, and ordering/disordering phenomena (e.g., self-assembly, gelation, crystallization, solution/melt/solid-state characteristics); structure and properties (e.g., mechanical and rheological properties, surface/interfacial characteristics, electronic and transport properties); new state of the art characterization (e.g., spectroscopy, scattering, microscopy, rheology), simulation (e.g., Monte Carlo, molecular dynamics, multi-scale/coarse-grained modeling), and theoretical methods. Renewable/sustainable polymers, polymer networks, responsive polymers, electro-, magneto- and opto-active macromolecules, inorganic polymers, charge-transporting polymers (ion-containing, semiconducting, and conducting), nanostructured polymers, and polymer composites are also of interest. Typical papers published in Macromolecules showcase important and innovative concepts, experimental methods/observations, and theoretical/computational approaches that demonstrate a fundamental advance in the understanding of polymers.