Decoupling the Impact of Entanglements and Mobility on the Failure Properties of Ultrathin Polymer Films
Decoupling the Impact of Entanglements and Mobility on the Failure Properties of Ultrathin Polymer Films
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DOI：
10.1021/acs.macromol.2c01435
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发表时间：
2022-09-27
期刊：
影响因子：
5.5
通讯作者：
Crosby, Alfred J.
中科院分区：
文献类型：
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作者：
Bay, R. Konane;Zhang, Tianren;Crosby, Alfred J.
玻璃态聚合物薄膜的机械性能随着膜厚度减小到低于平均聚合物分子尺寸而改变。这些变化已与减少链间缠结由于限制和增加分子的流动性从移动的表面层。在这里，使用实验和模拟，我们确定如何纠缠和表面迁移率分别影响玻璃状聚合物膜的失效行为，因为膜变得受限。我们利用一个定制的单轴拉伸试验机的薄膜和暗场光学显微镜表征的完整的应力-应变响应和相关的应变局部化的聚苯乙烯薄膜的不同厚度（h = 10至150 nm）的范围内的分子量Mn为61至2135 kDa。为了直接关联的分子网络中的变化，在破坏性能的变化的薄膜，我们进行非平衡态分子动力学模拟N = 250，N = 60，与h = 10至30的薄膜。从我们的研究结果，占在纠缠和流动性的变化，我们提出了一个半经验模型，捕捉在模拟和实验玻璃态聚合物薄膜的故障响应。
The mechanical properties of glassy polymer thin films change as film thickness decreases below the average polymer molecule size. These changes have been associated with a reduction in interchain entanglements due to confinement and an increase in molecular mobility from the mobile surface layer. Here, using experiments and simulations, we determine how entanglements and surface mobility each individually impact the failure behavior of a glassy polymer film as the film becomes confined. We utilize a custom-built uniaxial tensile tester for ultrathin films and dark-field optical microscopy to characterize the complete stress-strain response and the associated strain localizations for ultrathin polystyrene films of varying thicknesses (h = 10 to 150 nm) for a range of molecular weights Mn of 61 to 2135 kDa. To directly correlate the changes in the molecular network to changes in the failure properties of ultrathin films, we perform nonequilibrium molecular dynamics simulations on N = 250, N = 60, with h = 10 to 30 films. From our results, accounting for both the changes in entanglements and mobility, we propose a semiempirical model that captures the failure response in both simulated and experimental glassy polymer thin films.