Institute for Molecular Engineering, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA.
Soft Matter. 2016 Jul 6;12(27):5898-904. doi: 10.1039/c6sm00810k.
Glasses produced via physical vapor deposition can display greater kinetic stability and lower enthalpy than glasses prepared by liquid cooling. While the reduced enthalpy has often been used as a measure of the stability, it is not obvious whether dynamic measures of stability provide the same view. Here, we study dynamics in vapor-deposited and liquid-cooled glass films using molecular simulations of a bead-spring polymer model as well as a Lennard-Jones binary mixture in two and three dimensions. We confirm that the dynamics in vapor-deposited glasses is indeed slower than in ordinary glasses. We further show that the inherent structure energy is a good reporter of local dynamics, and that aged systems and glasses prepared by cooling at progressively slower rates exhibit the same behavior as vapor-deposited materials when they both have the same inherent structure energy. These findings suggest that the stability inferred from measurements of the energy is also manifested in dynamic observables, and they strengthen the view that vapor deposition processes provide an effective strategy for creation of stable glasses.
通过物理气相沉积生产的眼镜比通过液体冷却制备的眼镜具有更高的动力学稳定性和更低的焓。虽然降低的焓通常被用作稳定性的度量,但动态稳定性度量是否提供相同的观点并不明显。在这里,我们使用珠子弹簧聚合物模型以及二维和三维的 Lennard-Jones 二元混合物的分子模拟来研究气相沉积和液体冷却的玻璃膜中的动力学。我们证实气相沉积玻璃中的动力学确实比普通玻璃慢。我们进一步表明,固有结构能量是局部动力学的良好报告者,并且老化系统和以逐渐较慢的速率冷却制备的玻璃在具有相同固有结构能量时,表现出与气相沉积材料相同的行为。这些发现表明,从能量测量推断出的稳定性也在动态观测中表现出来,并且它们加强了这样一种观点,即气相沉积过程为创建稳定的玻璃提供了有效的策略。