†Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
‡Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States.
J Am Chem Soc. 2015 May 20;137(19):6254-62. doi: 10.1021/jacs.5b00493. Epub 2015 May 7.
With the abundant variety and increasing chemical complexity of conjugated polymers proliferating the field of organic semiconductors, it has become increasingly important to correlate the polymer molecular structure with its mesoscale conformational and morphological attributes. For instance, it is unknown which combinations of chemical moieties and periodicities predictably produce mesoscale ordering. Interestingly, not all ordered morphologies result in efficient devices. In this work we have parametrized accurate classical force-fields and used these to compute the conformational and aggregation characteristics of single strands of common conjugated polymers. Molecular dynamics trajectories are shown to reproduce experimentally observed polymeric ordering, concluding that efficient organic photovoltaic devices span a range of polymer conformational classes, and suggesting that the solution-phase morphologies have far-reaching effects. Encouragingly, these simulations indicate that despite the wide-range of conformational classes present in successful devices, local molecular ordering, and not long-range crystallinity, appears to be the necessary requirement for efficient devices. Finally, we examine what makes a "good" solvent for conjugated polymers, concluding that dispersive π-electron solvent-polymer interactions, and not the electrostatic potential of the backbone interacting with the solvent, are what primarily determine a polymer's solubility in a particular solvent, and consequently its morphological characteristics.
随着共轭聚合物在有机半导体领域的种类繁多且化学复杂性不断增加，将聚合物分子结构与其介观构象和形态属性相关联变得越来越重要。例如，尚不清楚哪些化学部分和周期性组合可预测地产生介观有序性。有趣的是，并非所有有序形态都能产生高效器件。在这项工作中，我们参数化了精确的经典力场，并使用这些力场来计算常见共轭聚合物单链的构象和聚集特性。分子动力学轨迹表明可以重现实验观察到的聚合物有序性，这得出结论，高效的有机光伏器件跨越了一系列聚合物构象类别，并表明溶液相形态具有深远的影响。令人鼓舞的是，这些模拟表明，尽管成功器件中存在广泛的构象类别，但局部分子有序性，而不是远程结晶度，似乎是高效器件的必要要求。最后，我们研究了是什么使共轭聚合物成为“良好”的溶剂，得出的结论是，分散的π-电子溶剂-聚合物相互作用，而不是聚合物主链与溶剂的静电势，主要决定了聚合物在特定溶剂中的溶解度，进而决定了其形态特征。
