K P Safna Hussan, Thayyil Mohamed Shahin, Deshpande S K, T V Jinitha, K Manoj, Ngai K L
Department of Physics, University of Calicut Malappuram-673635 Kerala India
UGC-DAE Consortium for Scientific Research, Mumbai Centre, BARC Mumbai 40085 India.
RSC Adv. 2018 Jun 6;8(37):20630-20636. doi: 10.1039/c8ra01544a. eCollection 2018 Jun 5.
We studied the conductivity relaxation originating from a glass-former composed of cations and anions, and the relation to the structural α-relaxation at temperatures above and below the glass transition temperature. The material chosen was amorphous amlodipine besylate (AMB), which is also a pharmaceutical with a complex chemical structure. Measurements were made using differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and X-ray diffraction, and the characterization was assisted using density functional theory (DFT). The X-ray diffraction pattern confirms the amorphous nature of vitrified AMB. Both the ionic and dipolar aspects of the dynamics of AMB were examined using these measurements and were used to probe the nature of the secondary conductivity and dipolar relaxations and their relation to the conductivity α-relaxation and the structural α-relaxation. The coupling model predictions and quantum mechanical simulations were used side by side to reveal the properties and nature of the secondary conductivity relaxation and the secondary dipolar relaxation. Remarkably, the two secondary relaxations have the same relaxation times, and are one and the same process performing dual roles in conductivity and dipolar relaxations. This is caused by the translation-rotation coupling of the AMB molecule. Thus, AMB has both conductivity α- and β-relaxations, and application of the coupling model shows that these two relaxations are related in the same way as the structural α-relaxation and the Johari-Goldstein β-relaxation are. This important result has an impact on the fundamental understanding of the dynamics of ionic conductivity.
我们研究了由阳离子和阴离子组成的玻璃形成体产生的电导率弛豫，以及在玻璃化转变温度以上和以下温度时与结构α弛豫的关系。所选用的材料是无定形苯磺酸氨氯地平（AMB），它也是一种具有复杂化学结构的药物。使用差示扫描量热法（DSC）、宽带介电谱（BDS）和X射线衍射进行测量，并借助密度泛函理论（DFT）进行表征。X射线衍射图谱证实了玻璃化AMB的无定形性质。利用这些测量方法研究了AMB动力学的离子和偶极方面，并用于探究次级电导率和偶极弛豫的性质及其与电导率α弛豫和结构α弛豫的关系。同时使用耦合模型预测和量子力学模拟来揭示次级电导率弛豫和次级偶极弛豫的性质和特性。值得注意的是，这两种次级弛豫具有相同的弛豫时间，并且是在电导率和偶极弛豫中发挥双重作用的同一过程。这是由AMB分子的平移 - 旋转耦合引起的。因此，AMB同时具有电导率α弛豫和β弛豫，耦合模型的应用表明这两种弛豫的关系与结构α弛豫和乔哈里 - 戈尔茨坦β弛豫的关系相同。这一重要结果对离子电导率动力学的基本理解具有重要意义。
