Rams-Baron Marzena, Błażytko Alfred, Casalini Riccardo, Paluch Marian
August Chełkowski Institute of Physics, University of Silesia, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland.
Chemistry Division, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, District of Columbia 20375, USA.
J Chem Phys. 2024 Aug 14;161(6). doi: 10.1063/5.0217660.
Sizable glass formers feature numerous unique properties and potential applications, but many questions regarding their glass transition dynamics have not been resolved yet. Here, we have analyzed structural relaxation times measured as a function of temperature and pressure in combination with the equation of state obtained from pressure-volume-temperature measurements. Despite evidence from previous dielectric studies indicating a remarkable sensitivity of supercooled dynamics to compression, and contrary to intuition, our results demonstrated the proof for the almost equivalent importance of thermal energy and free volume fluctuations in controlling reorientation dynamics of sizable molecules. The found scaling exponent γ = 3.0 and Ev/Ep ratio of 0.6 were typical for glass-forming materials with relaxation dynamics determined by both effects with a minor advantage of thermal fluctuations involvement. It shows that the high values of key parameters characterizing the sensitivity of the glass transition dynamics to pressure changes, i.e., activation volume ΔV and dTg/dP, are not a valid premise for a remarkable contribution of volume to glass transition dynamics.
大型玻璃形成体具有许多独特的性质和潜在应用，但关于它们的玻璃化转变动力学仍有许多问题尚未解决。在这里，我们结合从压力-体积-温度测量中获得的状态方程，分析了作为温度和压力函数测量的结构弛豫时间。尽管先前的介电研究表明过冷动力学对压缩具有显著的敏感性，且与直觉相反，但我们的结果证明了热能和自由体积涨落在控制大型分子的重取向动力学方面几乎具有同等重要性。发现的标度指数γ = 3.0和Ev/Ep比为0.6对于由两种效应决定弛豫动力学且热涨落参与占较小优势的玻璃形成材料来说是典型的。这表明表征玻璃化转变动力学对压力变化敏感性的关键参数的高值，即活化体积ΔV和dTg/dP，并不是体积对玻璃化转变动力学有显著贡献的有效前提。
