Mapping Microstructural Dynamics up to the Nanosecond of the Conjugated Polymer P3HT in the Solid State
Mapping Microstructural Dynamics up to the Nanosecond of the Conjugated Polymer P3HT in the Solid State
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DOI：
10.1021/acs.chemmater.9b02904
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发表时间：
2019-12-10
影响因子：
8.6
通讯作者：
Nielsen, Christian B.
中科院分区：
文献类型：
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作者：
Guilbert, Anne A. Y.;Zbiri, Mohamed;Nielsen, Christian B.
我们使用不同的弹性、准弹性和非弹性中子散射技术，对区域规则（RR）和区域随机（RRa）聚（3-己基噻吩）（P3HT）的结构动力学关系进行了详细的微观研究。研究涵盖的长度尺度为几十埃，时间尺度为飞秒到纳秒。氘化被用来调制材料的相干和非相干横截面，超越了对比变化的目的，特别允许访问材料的自运动和集体动力学。中子散射测量是通过大规模经典分子动力学（MD）模拟以及分子和周期第一性原理量子化学（QC）计算进行的大量定量数值模拟来支持的。MD模拟很好地再现了主要结构特征和慢动作。此外，MD结果揭示了与pi-pi堆叠和聚合物层状堆叠相关的q值之间的集体动力学差异，其中晶体相受到的影响最大。然而，MD导致了对分子振动的有限描述。在这种情况下，第一性原理分子质量控制计算很好地描述了高能振动特征（>900 cm(-1)），而周期性质量控制可以描述中低能量振动范围（200-900 cm(-1)）。中能范围主要与分子内和分子间模式耦合有关，它包含了聚合物构象和聚合物填充的信息。我们表明，提出的基于中子的测量和多计算计算相结合的方法可以完全映射出共轭聚合物（如P3HT）的结构动力学。本研究的结果之一是验证了普遍的假设，即RRa-P3HT在宏观水平上是RRa-P3HT的非晶相的良好近似，尽管在分子水平上显示出一些差异。目前的工作有助于明确澄清后一点，这一点在很大程度上被忽视的文献。通过将中子振动结果与文献中可用的拉曼和红外数据进行比较，我们强调了用非弹性中子散射补充这种光学光谱技术的重要性。后者的优点是对离域pi-电子系统不敏感，因此可以推断出共轭长度等相关量。
We present a detailed microscopic study of the structure dynamics relationship of both regioregular (RR) and regiorandom (RRa) poly(3-hexylthiophene) (P3HT) using synergistically different elastic, quasi-elastic, and inelastic neutron scattering techniques. The length scale and the time scale covered by the study is tens of angstroms and the femtosecond to nanosecond, respectively. Deuteration is employed to modulate the coherent and incoherent cross sections of the materials, beyond a contrast variation purpose, allowing particularly access to both self-motions and collective dynamics of the materials. The neutron scattering measurements are underpinned by extensive quantitative numerical simulations using large-scale classical molecular dynamics (MD) simulations, as well as molecular and periodic first principles quantum chemical (QC) calculations. MD simulations reproduced well the main structural features and slow motions. Further, MD results shed light on differences in collective dynamics between Q-values linked with the pi-pi stacking and the lamellar stacking of the polymer, with the crystalline phase being the most impacted. However, MD led to a limited description of molecular vibrations. In this context, first principles molecular QC calculations described well the high-energy vibrational features (>900 cm(-1)), while periodic QC allowed description of the low and midenergy vibrational range (200-900 cm(-1)). The midenergy range is predominantly associated with both intramolecular and intermolecular mode coupling, which encloses information about both the polymer conformation and the polymer packing at short range. We show that the presented combined approach of neutron-based measurements and multicomputational calculations allows the full mapping out the structural dynamics of conjugated polymers such as P3HT. One of the outcomes of this study is the validation of the common assumption made that RRa-P3HT is a good approximation for the amorphous phase of RR-P3HT at the macroscopic level, although some differences are shown at the molecular level. The present work helps to clarify unambiguously the latter point which has been largely overlooked in the literature. By comparing the neutron vibrational results with available Raman and IR data in the literature, we highlight the importance to complement such optical spectroscopy techniques with inelastic neutron scattering. The latter offers the advantage of being insensitive to the delocalized pi-electron system and, thus, enables relevant quantities such as conjugation lengths to be inferred.