ABSTRACT The molecular mobility in 4-cyano-3-fluorophenyl 4-butylbenzoate (4CFPB), a nematic liquid crystal, was studied by differential scanning calorimetry (DSC) and thermally stimulated depolarization currents (TSDC). By TSDC a complex behavior was observed in which the main relaxation, with a wide distribution of activation energies, coalesces at high temperature with a poorly distributed mobility; this observation is in line with what was found by dielectric spectroscopy where a ‘double relaxation’ was observed. The step signal of the positional glass transition in DSC is a single and clean signal, which shows no evidence of the complexity revealed by the dielectric techniques; this signal seems to correspond to the usual main relaxation. The dynamic fragility values obtained by DSC and by TSDC indicate that 4CFPB is a moderately fragile glass former, in reasonable agreement with the values obtained by dielectric spectroscopy. Among the secondary relaxations in 4CFPB there are modes sensitive to physical aging, which makes them candidates for Johari-Goldstein’s relaxation status. It is emphasized, however, that this sensitivity to aging may not be a sufficient criterion for the attribution of this quality. Graphical abstract

中文翻译：

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玻璃态和向列液晶的玻璃转变中的相行为和慢分子动力学：4CFPB

摘要 通过差示扫描量热法 (DSC) 和热激去极化电流 (TSDC) 研究了向列液晶 4-氰基-3-氟苯基苯甲酸酯 (4CFPB) 中的分子迁移率。通过 TSDC 观察到一种复杂的行为，其中主要弛豫具有广泛的活化能分布，在高温下聚结，但迁移率分布较差；这一观察结果与介电光谱发现的结果一致，其中观察到了“双重弛豫”。DSC 中位置玻璃化转变的阶跃信号是一个单一且清晰的信号，没有证据表明介电技术揭示的复杂性；这个信号似乎对应于通常的主要放松。DSC 和 TSDC 获得的动态脆性值表明 4CFPB 是一种中等脆性的玻璃形成剂，与介电光谱法获得的值合理一致。在 4CFPB 的二次松弛中，有一些对身体老化敏感的模式，这使它们成为 Johari-Goldstein 松弛状态的候选者。然而，需要强调的是，这种对老化的敏感性可能不足以作为判断这种品质的标准。图形概要 这种对老化的敏感性可能不足以作为判断这种品质的标准。图形概要 这种对老化的敏感性可能不足以作为判断这种品质的标准。图形概要