Giuntoli Andrea, Puosi Francesco, Leporini Dino, Starr Francis W, Douglas Jack F
Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersbug, Maryland 20899, USA.
Department of Physics, Wesleyan University, Middletown, Connecticut 06459, USA.
Sci Adv. 2020 Apr 24;6(17):eaaz0777. doi: 10.1126/sciadv.aaz0777. eCollection 2020 Apr.
We examine the influence of steady shear on structural relaxation in a simulated coarse-grained unentangled polymer melt over a wide range of temperature and shear rates. Shear is found to progressively suppress the α-relaxation process observed in the intermediate scattering function, leading ultimately to a purely inertially dominated β-relaxation at high shear rates, a trend similar to increasing temperature. On the basis of a scaling argument emphasizing dynamic heterogeneity in cooled liquids and its alteration under material deformation, we deduce and validate a parameter-free scaling relation for both the structural relaxation time τ from the intermediate scattering function and the "stretching exponent" β quantifying the extent of dynamic heterogeneity over the entire range of temperatures and shear rates that we can simulate.
我们研究了在广泛的温度和剪切速率范围内，稳态剪切对模拟的粗粒非缠结聚合物熔体中结构弛豫的影响。发现剪切会逐渐抑制在中间散射函数中观察到的α弛豫过程，最终在高剪切速率下导致完全由惯性主导的β弛豫，这一趋势类似于温度升高。基于强调冷却液体中动态不均匀性及其在材料变形下变化的标度论证，我们推导并验证了一个无参数标度关系，该关系适用于从中间散射函数得到的结构弛豫时间τ以及量化我们能够模拟的整个温度和剪切速率范围内动态不均匀程度的“拉伸指数”β。
