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Reorientational dynamics of trimethoxyboroxine: A molecular glass former studied by dielectric spectroscopy and 11B nuclear magnetic resonance.
The Journal of Chemical Physics ( IF 3.1 ) Pub Date : 2020-01-21 , DOI: 10.1063/1.5129769
Lars Hoffmann 1 , Joachim Beerwerth 1 , Dominik Greim 2 , Jürgen Senker 2 , Christian Sternemann 3 , Wolf Hiller 4 , Roland Böhmer 1
Affiliation  

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.

中文翻译:

三甲氧基环硼氧烷的重排动力学:一种分子玻璃前体,通过介电谱和11B核磁共振研究。

在这项工作中,三甲氧基环硼氧烷(TMB)被鉴定为小分子玻璃形成剂。在TMB的粘性液体和玻璃态下,使用各种技术来探索TMB的静态和动态特性。已发现,平均而言,缩合的TMB分子的结构偏离三重对称性,因此TMB的电偶极矩不为零,从而使宽带电介质光谱学可适用。该方法揭示了表征玻璃中超过TMB的TMB的超级Arrhenius动力学,该现象发生在约204K。为扩展可研究分子动力学的温度范围,还分别在旋转和静止状态下进行了11B核磁共振实验样本:利用动态二阶移位,自旋松弛时间,线形效果,
更新日期:2020-01-22
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