Das Rajsekhar, Bhowmik Bhanu Prasad, Puthirath Anand B, Narayanan Tharangattu N, Karmakar Smarajit
Department of Chemistry, University of Texas at Austin, Austin, TX 78712, USA.
TIFR Center for Interdisciplinary Science, Tata Institute of Fundamental Research, Hyderabad 500046, India.
PNAS Nexus. 2023 Aug 25;2(9):pgad277. doi: 10.1093/pnasnexus/pgad277. eCollection 2023 Sep.
Enormous enhancement in the viscosity of a liquid near its glass transition is a hallmark of glass transition. Within a class of theoretical frameworks, it is connected to growing many-body static correlations near the transition, often called "amorphous ordering." At the same time, some theories do not invoke the existence of such a static length scale in the problem. Thus, proving the existence and possible estimation of the static length scales of amorphous order in different glass-forming liquids is very important to validate or falsify the predictions of these theories and unravel the true physics of glass formation. Experiments on molecular glass-forming liquids become pivotal in this scenario as the viscosity grows several folds (), and simulations or colloidal glass experiments fail to access these required long-time scales. Here we design an experiment to extract the static length scales in molecular liquids using dilute amounts of another large molecule as a pinning site. Results from dielectric relaxation experiments on supercooled Glycerol with different pinning concentrations of Sorbitol and Glucose, as well as the simulations on a few model glass-forming liquids with pinning sites, indicate the versatility of the proposed method, opening possible new avenues to study the physics of glass transition in other molecular liquids.
液体在其玻璃化转变温度附近时，其黏度会大幅增加，这是玻璃化转变的一个标志。在一类理论框架中，它与转变附近不断增长的多体静态关联有关，这种关联通常被称为“非晶有序”。与此同时，一些理论并未假定该问题中存在这样一个静态长度尺度。因此，证明不同玻璃形成液体中非晶序静态长度尺度的存在并对其进行可能的估计，对于验证或证伪这些理论的预测以及揭示玻璃形成的真正物理机制非常重要。在这种情况下，对分子玻璃形成液体的实验变得至关重要，因为黏度会增长几倍（），而模拟或胶体玻璃实验无法达到这些所需的长时间尺度。在这里，我们设计了一个实验，通过使用少量另一种大分子作为钉扎位点来提取分子液体中的静态长度尺度。对具有不同山梨醇和葡萄糖钉扎浓度的过冷甘油进行介电弛豫实验的结果，以及对一些具有钉扎位点的模型玻璃形成液体的模拟结果，表明了所提出方法的通用性，为研究其他分子液体中的玻璃化转变物理机制开辟了可能的新途径。
