Reorientational dynamics of trimethoxyboroxine: A molecular glass former studied by dielectric spectroscopy and 11B nuclear magnetic resonance.
Reorientational dynamics of trimethoxyboroxine: A molecular glass former studied by dielectric spectroscopy and 11B nuclear magnetic resonance.
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DOI：
10.1063/1.5129769
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发表时间：
2020-01
期刊：
影响因子：
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通讯作者：
Lars Hoffmann;Joachim Beerwerth;Dominik Greim;J. Senker;C. Sternemann;W. Hiller;R. Böhmer
中科院分区：
文献类型：
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作者：
Lars Hoffmann;Joachim Beerwerth;Dominik Greim;J. Senker;C. Sternemann;W. Hiller;R. Böhmer
在这项工作中，三甲氧基硼氧烷（TMB）被确定为一种小分子玻璃形成剂。在其粘性液体以及玻璃态，静态和动态性能的TMB的探索使用各种技术。据发现，平均而言，凝聚的TMB分子的结构偏离三重对称，使TMB的电偶极矩是非零的，从而呈现宽带介电谱适用。该方法揭示了TMB在其玻璃化转变（发生在约204 K）以上的超Arrhenius动力学特征。为了扩大可以研究分子动力学的温度范围，还对旋转和静止样品进行了11B核磁共振实验：利用动态二阶位移、自旋弛豫时间、线形效应以及受激回波和二维交换光谱，获得了有关该玻璃形成剂动力学的连贯图像。
In this work, trimethoxyboroxine (TMB) is identified as a small-molecule glass former. In its viscous liquid as well as glassy states, static and dynamic properties of TMB are explored using various techniques. It is found that, on average, the structure of the condensed TMB molecules deviates from threefold symmetry so that TMB's electric dipole moment is nonzero, thus rendering broadband dielectric spectroscopy applicable. This method reveals the super-Arrhenius dynamics that characterizes TMB above its glass transition, which occurs at about 204 K. To extend the temperature range in which the molecular dynamics can be studied, 11B nuclear magnetic resonance experiments are additionally carried out on rotating and stationary samples: Exploiting dynamic second-order shifts, spin-relaxation times, line shape effects, as well as stimulated-echo and two-dimensional exchange spectroscopy, a coherent picture regarding the dynamics of this glass former is gained.