Role of Intrinsic Factors of Polyimides in Glass Transition Temperature: An Atomistic Investigation
Role of Intrinsic Factors of Polyimides in Glass Transition Temperature: An Atomistic Investigation
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聚酰亚胺的内在因素在玻璃化转变温度中的作用：原子研究
DOI：
10.1021/acs.jpcb.9b06585
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发表时间：
2019-10-10
影响因子：
3.3
通讯作者：
Lu, Qinghua
中科院分区：
文献类型：
--
作者：
Ma, Xiaoru;Zheng, Feng;Lu, Qinghua
聚酰亚胺（PI）由于其优异的耐热性、化学稳定性和机械性能而在有源矩阵有机发光二极管显示器领域中具有很高的需求。然而，其应用的最关键的关键是进一步提高其玻璃化转变温度（Tg），这直接影响到PI薄膜上薄膜晶体管的加工温度。因此，研究影响PI的Tg的因素具有重要意义。为了实现这一目标，PI衍生自均苯四甲酸二酐和三组异构咪唑基二胺进行了研究。该研究通过计算方法阐明与PI分子结构相关的内在因素对其T-g的影响，并构建这些PI的结构-T-g关系。对于每个模型系统，全原子分子动力学模拟被用来识别和区分链刚性，分数自由体积（FFV），内聚能密度，氢键相互作用，和电荷转移复杂的相互作用对T-g的影响。结果表明，无论聚合物主链结构如何，聚合物的物理性质，即链刚性，都对T-g有直接的影响。由于氢键作用的存在，FFV的增加和T-g的降低之间没有建立线性相关性，但保持了这种趋势。此外，氢键的形成被发现有一个间接的关系与T-g。也就是说，链内氢键的增加将导致链刚性的降低，从而降低T-g值。
Polyimides (PIs) are in high demand in the field of active matrix organic light-emitting diode displays because of their excellent heat resistance, chemical stability, and mechanical properties. However, the most critical key to their application is to further enhance their glass transition temperature (T-g), which directly affects the processing temperature of thin-film transistors on the PI films. Therefore, it is of great importance to study the factors that have an influence on the T-g of PIs. To accomplish this goal, PIs derived from pyromellitic acid dianhydride and three sets of isomeric imidazole-based diamines were investigated. The investigation, by computational methods, was to clarify the effect of intrinsic factors associated with the molecular structure of the PIs on their T-g and to construct a structure-T-g relationship for these PIs. For each model system, all-atom molecular dynamics simulations were used to identify and distinguish the effects of chain rigidity, fractional free volume (FFV), cohesive energy density, hydrogen-bonding interactions, and charge-transfer complex interactions on T-g. The results showed that the physical property, chain rigidity, has a direct impact on T-g regardless of the polymer backbone structure. A linear correlation between the increase of FFV and the decrease of T-g was not established due to the existence of hydrogen-bonding interactions, but the tendency was maintained. Furthermore, the formation of hydrogen bonds was found to have an indirect relationship with T-g. That is, the increase of intrachain hydrogen bonds would lead to a decrease in chain rigidity and consequently reduce the T-g value.