Signature of collective elastic glass physics in surface-induced long-range tails in dynamical gradients
Signature of collective elastic glass physics in surface-induced long-range tails in dynamical gradients
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DOI：
10.1038/s41567-023-01995-8
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发表时间：
2023-03-23
期刊：
影响因子：
19.6
通讯作者：
Simmons, David S.
中科院分区：
文献类型：
--
作者：
Ghanekarade, Asieh;Phan, Anh D.;Simmons, David S.
大系统分子动力学模拟的玻璃形成聚合物膜揭示了空间上的长程尾巴的界面驱动的梯度的玻璃化转变温度，暗示了一个组合的本地笼和远程集体弹性起源的松弛和玻璃化的玻璃形成liquid.Understanding的基本性质的动力学相关性，认为驱动体玻璃化转变是一个长期存在的问题。在这里，我们表明，界面附近的玻璃化转变温度和结构弛豫时间的空间梯度的形式确实提供了在散装玻璃形成液体的性质的松弛签名。我们报告的结果，长时间，大系统的分子动力学模拟厚玻璃形成聚合物薄膜与一个蒸汽界面，支持动态中性基板。我们发现，在玻璃化转变温度和对数的结构弛豫时间成核在蒸汽界面的梯度表现出两个不同的制度：一个中等范围，大幅度的指数梯度，其次是一个远程缓慢衰减的尾巴，可以描述的逆幂律。这种行为不同意多个提出的玻璃态动力学理论，但预测的“弹性集体非线性朗之万方程”理论作为两个耦合机制的结果：一个中等范围的界面成核梯度的表面改性的局部笼约束，和界面截断的远程集体弹性场。这些研究结果支持一个耦合的空间本地-非本地机制的激活玻璃弛豫和动力学玻璃化在各向同性体和对称性破缺膜。
Large-system molecular dynamics simulations of films of glass-forming polymers reveal spatially long-range tails of interface-driven gradients of the glass transition temperature, suggestive of a combined local caging and long-range collective elasticity origin of relaxation and vitrification in glass-forming liquids.Understanding the underlying nature of dynamical correlations believed to drive the bulk glass transition is a long-standing problem. Here we show that the form of spatial gradients of the glass transition temperature and structural relaxation time near an interface indeed provide signatures of the nature of relaxation in bulk glass-forming liquids. We report the results of long-time, large-system molecular dynamics simulations of thick glass-forming polymer films with one vapour interface, supported on a dynamically neutral substrate. We find that gradients in the glass transition temperature and logarithm of the structural relaxation time nucleated at a vapour interface exhibit two distinct regimes: a medium-ranged, large-amplitude exponential gradient, followed by a long-range slowly decaying tail that can be described by an inverse power law. This behaviour disagrees with multiple proposed theories of glassy dynamics but is predicted by the 'elastically collective nonlinear Langevin equation' theory as a consequence of two coupled mechanisms: a medium-ranged interface-nucleated gradient of surface-modified local caging constraints, and an interfacial truncation of a long-ranged collective elastic field. These findings support a coupled spatially local-nonlocal mechanism of activated glassy relaxation and kinetic vitrification in both the isotropic bulk and in broken-symmetry films.