The thermomechanical properties of conjugated polymers (CPs) play a crucial role in device morphological, mechanical, and thermal stability and influence device processing parameters. However, the thermal transition behavior of CPs can be difficult to characterize, particularly as the molecular complexity increases. Here, we introduce a characterization technique that is an effective and sensitive approach to observing and defining thermal transitions in CPs. Our approach combines strain alignment with in situ polarized ultraviolet–visible absorption spectroscopy, which we name AFIPS. By monitoring changes in the absorption spectra and dichroism, we demonstrate the ability to effectively identify and characterize thermal transitions undetected using calorimetry. We use this in situ characterization method along with dynamic mechanical analysis (DMA) to probe the thermal transitions of various CPs, including F8T2, P3HT, PCDTBT, PTB7-Th, PM6, and PBnDT-FTAZ. We show that the measurement has a unique response to glass transitions (T_g), cold crystallization (T_cc), liquid crystal transitions, and melting. In this investigation, we uncover signatures of a T_g in PTB7-Th and a T_cc in PCDTBT. Using the AFIPS technique complements other thermomechanical measurements, such as DMA, while being simple and effective to implement, providing a valuable tool for polymer thin film characterization.

中文翻译：

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通过取向薄膜的原位光学表征来辨别共轭聚合物的热转变行为


共轭聚合物 （CP） 的热机械性能在器件形态、机械和热稳定性方面起着至关重要的作用，并影响器件的加工参数。然而，CP 的热转变行为可能难以表征，特别是随着分子复杂性的增加。在这里，我们介绍了一种表征技术，这是一种有效且灵敏的方法，用于观察和定义 CP 中的热转变。我们的方法将应变对准与原位偏振紫外-可见光吸收光谱相结合，我们将其命名为 AFIPS。通过监测吸收光谱和二向色性的变化，我们证明了有效识别和表征使用量热法未检测到的热转变的能力。我们使用这种原位表征方法以及动态力学分析 （DMA） 来探测各种 CP 的热转变，包括 F8T2、P3HT、PCDTBT、PTB7-Th、PM6 和 PBnDT-FTAZ。我们表明，该测量对玻璃化转变 （T_g）、冷结晶 （T_cc）、液晶转变和熔化具有独特的响应。在这项研究中，我们发现了 PTB7-Th 中 T_g 和 PCDTBT 中 T_cc 的特征。使用 AFIPS 技术可以补充其他热机械测量，例如 DMA，同时实施简单有效，为聚合物薄膜表征提供了有价值的工具。