Polymer modifiers have been used to improve the performances of asphalt binders in pavement engineering. The modifying effect of polymers on asphalt is largely dependent on the morphological characteristics of polymer-modified asphalt. The morphologies of polymer-modified asphalt are composed of a polymer-rich phase, a asphaltene-rich phase, and the interphase between the two phases. Interfacial interactions importantly contribute to the morphology but are commonly overlooked. In this study, carbon nanotubes (CNTs) were selected to improve the interfacial interactions of polymer-modified asphalt. Fluorescence microscopy (FM), scanning electron microscopy (SEM), micro-Raman spectroscopy (MRS), and molecular dynamics (MD) simulation were used to capture the characteristics of the interphase and polymer-rich phase. CNTs-polymer-modified asphalt involves stronger intermolecular forces than those in asphalt-modified by only styrene–butadiene–styrene (SBS) or CNTs. This discrepancy highlights the intensified interfacial interaction in the former material. Raman peak and MD findings reveal that the C═C of CNTs interacted with the alkanes and aromatic hydrocarbons of asphalt. SBS were entwined or surrounded with CNTs through the π–π conjugation of the benzene rings of the two components. Consequently, a synergistic effect enhanced the intermolecular force between SBS and CNTs in the interphase. SEM results indicated that CNTs were enriched in the interphase, enhancing mechanical anchorage between the polymer and asphalt. As a result, CNTs increased the roughness of the interphase and produced a prominent cage construction of polymer-rich phase. Moreover, the observed pullout behaviors of CNTs alleviated interfacial failure. FM images displayed that CNTs enhanced the swelling degree of the polymer-rich phase. This effect was realized because CNTs served as a tunnel for transporting saturates, aromatics, and small resin molecules, as shown by molecular dynamics MD analysis. This work revealed the importance of the interfacial interactions on the micromorphologies of polymer-modified asphalt.

中文翻译：

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高分子和碳纳米管改性的沥青微观形态的分子动力学模拟和实验：增强的界面相互作用的作用

聚合物改性剂已用于改善路面工程中沥青粘合剂的性能。聚合物对沥青的改性效果在很大程度上取决于聚合物改性沥青的形态特征。聚合物改性沥青的形态由富含聚合物的相，富含沥青质的相以及两相之间的中间相组成。界面相互作用对形态起重要作用，但通常被忽略。在这项研究中，选择碳纳米管（CNTs）来改善聚合物改性沥青的界面相互作用。荧光显微镜（FM），扫描电子显微镜（SEM），显微拉曼光谱（MRS）和分子动力学（MD）模拟用于捕获相间和富聚合物相的特征。碳纳米管聚合物改性的沥青比仅用苯乙烯-丁二烯-苯乙烯（SBS）或碳纳米管改性的沥青具有更大的分子间力。这种差异突显了前一种材料中的界面相互作用加剧。拉曼峰和MD结果表明，CNT的C═C与沥青的烷烃和芳烃相互作用。SBS通过两个组件的苯环的π-π共轭缠绕或被CNT包围。因此，协同作用增强了相间SBS和CNT之间的分子间作用力。扫描电镜结果表明，碳纳米管在相间富集，增强了聚合物与沥青之间的机械锚固作用。结果，CNT增加了中间相的粗糙度并产生了富含聚合物的相的显着的笼状构造。而且，观察到的碳纳米管的拔出行为减轻了界面破坏。FM图像显示CNT增强了富含聚合物的相的溶胀度。之所以能实现这种效果，是因为CNT充当了传输饱和物，芳族化合物和小的树脂分子的通道，如分子动力学MD分析所示。这项工作揭示了界面相互作用对聚合物改性沥青微观形貌的重要性。