Huang Xinru, Thees Michael F, Size William B, Roth Connie B
Department of Physics, Emory University, Atlanta, Georgia 30322, USA.
Department of Environmental Sciences, Emory University, Atlanta, Georgia 30322, USA.
J Chem Phys. 2020 Jun 28;152(24):244901. doi: 10.1063/5.0011380.
Numerous computer simulations have shown that local dynamics associated with the glass transition can be slower next to rough interfaces compared with smooth interfaces. Even though the impact of surface roughness has been frequently considered computationally and theoretically, almost no experimental studies exist investigating these effects. Using a hydrogen fluoride vapor treatment, we created silica substrates with an increase in roughness that left the surface chemistry unchanged. The local glass transition temperature T near silica substrates with an increase in roughness was measured using fluorescence, finding an increase in local T of 10 K with an increase in the root-mean-square roughness R from 0.5 nm to 11 nm. Characterization of the substrate roughness needed to create an experimental change in local T was found to be quite large, leaving the mechanism for this observed behavior uncertain. We discuss possible causes associated with polymer chains being more readily able to make surface contacts and adsorb to roughened interfaces.
大量计算机模拟表明，与玻璃化转变相关的局部动力学在粗糙界面附近可能比光滑界面处更慢。尽管表面粗糙度的影响已在计算和理论上被频繁考虑，但几乎没有实验研究来探究这些效应。通过氢氟酸蒸汽处理，我们制备了粗糙度增加但表面化学性质不变的二氧化硅衬底。使用荧光测量了粗糙度增加的二氧化硅衬底附近的局部玻璃化转变温度T，发现随着均方根粗糙度R从0.5纳米增加到11纳米，局部T升高了10 K。发现要在局部T上产生实验性变化所需的衬底粗糙度表征相当大，这使得这种观察到的行为的机制尚不确定。我们讨论了与聚合物链更易于与表面接触并吸附到粗糙界面相关的可能原因。
