Molecular mobility, phase transitions and phase transformations in crystalline ortho- and meta-carboranes
Molecular mobility, phase transitions and phase transformations in crystalline ortho- and meta-carboranes
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晶体邻碳硼烷和间碳硼烷的分子迁移率、相变和相变
DOI：
10.1016/j.jpcs.2004.11.001
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发表时间：
2005
影响因子：
4
通讯作者：
J. Ramos
中科院分区：
文献类型：
--
作者：
H. Diogo;N. T. Correia;J. Ramos
采用热激去极化电流（TSDC）技术研究了碳硼烷高度对称极性异构体晶型中的慢分子迁移率。作为高分子对称性的结果，其产生具有高度球形度的分子形状，预期具有相对快的再取向流动性的塑性结晶相。TSDC的结果表明，有一个取向的玻璃转化在第三阶段的邻碳硼烷，但不是在间碳硼烷，加强的结论的量热研究表明，第三阶段的m-碳硼烷是一个取向有序相。此外，TSDC在邻碳硼烷的相II中检测到缓慢的分子迁移率，在一定程度上低于II→I转变温度。间碳硼烷的第II相的迁移率太快，无法用TSDC探测。有人建议，这两种异构体的动力学行为的差异可能是由于它们的不同极性。
The thermally stimulated depolarisation currents (TSDC) technique was used to study the slow molecular mobility in the crystalline forms of highly symmetric polar isomers of carborane. As a consequence of the high molecular symmetry, that originates a molecular shape with a high degree of globularity, plastic crystalline phases with relatively fast reorientational mobility are expected. The TSDC results showed that there is an orientational glass transformation in phase III of ortho-carborane but not in meta-carborane, reinforcing the conclusions of the calorimetric study that suggests that phase III of m-carborane is an orientationally ordered phase. Furthermore, a slow molecular mobility is detected by TSDC in phase II of o-carborane, some degrees below the II→I transition temperature. The mobility in phase II of m-carborane is too fast to be probed by TSDC. It is suggested that the difference in the dynamic behaviour of the two isomers probably arises from their different polarity.