Institut für Festkörperphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany.
J Chem Phys. 2013 Mar 21;138(11):114501. doi: 10.1063/1.4793762.
We investigate the reorientational dynamics of supercooled m-toluidine contained in a matrix of nanoporous Vycor with depolarized dynamic light scattering. Under equilibrium conditions a clear sample is obtained and the dynamics of m-toluidine molecules from inside the nanopores can be accessed via light scattering. However, when supercooling the imbibed liquid at conventional cooling rates, strong non-equilibrium effects occur due to the mismatch of expansion coefficients and the sample gets turbid several tens of Kelvin above the bulk glass transition. Only at cooling rates as low as 0.02 K/min this can be avoided and the dynamics of m-toluidine in confinement can be followed even below the bulk glass transition temperature. In confinement a pronounced acceleration of the reorientational dynamics is observed and the characteristic correlation times follow an Arrhenius law close to T(g). However it seems likely that part of the observed differences to bulk behavior is due to density effects, which are reduced but cannot be fully avoided at low cooling rates.
我们使用去偏振动态光散射研究了填充在纳米多孔 Vycor 基质中的间甲苯胺的重取向动力学。在平衡条件下，可以获得清晰的样品，并且可以通过光散射来研究纳米孔内间甲苯胺分子的动力学。然而，当以常规冷却速率对吸收的液体进行过冷时，由于膨胀系数不匹配，会产生强烈的非平衡效应，并且在比本体玻璃化转变温度高几十开尔文的温度下，样品会变得混浊。只有在冷却速率低至 0.02 K/min 的情况下，才能避免这种情况，并可以在低于本体玻璃化转变温度的情况下跟踪间甲苯胺在受限环境中的动力学。在受限环境中，观察到重取向动力学明显加速，特征相关时间遵循接近 T(g)的 Arrhenius 定律。然而，观察到的与本体行为的部分差异似乎归因于密度效应，尽管在低冷却速率下这些效应会降低，但仍无法完全避免。
