Tenopala-Carmona Francisco, Fronk Stephanie, Bazan Guillermo C, Samuel Ifor D W, Penedo J Carlos
Organic Semiconductor Centre, Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, UK.
Department of Materials and Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
Sci Adv. 2018 Feb 16;4(2):eaao5786. doi: 10.1126/sciadv.aao5786. eCollection 2018 Feb.
Conjugated polymers (CPs) are an important class of organic semiconductors that combine novel optoelectronic properties with simple processing from organic solvents. It is important to study CP conformation in solution to understand the physics of these materials and because it affects the properties of solution-processed films. Single-molecule techniques are unique in their ability to extract information on a chain-to-chain basis; however, in the context of CPs, technical challenges have limited their general application to host matrices or semiliquid environments that constrain the conformational dynamics of the polymer. We introduce a conceptually different methodology that enables measurements in organic solvents using the single-end anchoring of polymer chains to avoid diffusion while preserving polymer flexibility. We explore the effect of organic solvents and show that, in addition to chain-to-chain conformational heterogeneity, collapsed and extended polymer segments can coexist within the same chain. The technique enables real-time solvent-exchange measurements, which show that anchored CP chains respond to sudden changes in solvent conditions on a subsecond time scale. Our results give an unprecedented glimpse into the mechanism of solvent-induced reorganization of CPs and can be expected to lead to a new range of techniques to investigate and conformationally manipulate CPs.
共轭聚合物（CPs）是一类重要的有机半导体，它将新颖的光电特性与可从有机溶剂中进行简单加工的特性结合在一起。研究溶液中CP的构象对于理解这些材料的物理性质很重要，因为它会影响溶液加工薄膜的性能。单分子技术在逐链提取信息方面具有独特能力；然而，在CPs的背景下，技术挑战限制了它们在限制聚合物构象动力学的主体基质或半液体环境中的普遍应用。我们引入了一种概念上不同的方法，该方法能够在有机溶剂中使用聚合物链的单端锚定进行测量，以避免扩散同时保持聚合物的柔韧性。我们探究了有机溶剂的影响，并表明，除了链间构象异质性外，折叠和伸展的聚合物链段可以在同一链中共存。该技术能够进行实时溶剂交换测量，结果表明锚定的CP链在亚秒时间尺度上对溶剂条件的突然变化做出响应。我们的结果让人们前所未有的深入了解了溶剂诱导CPs重组的机制，并且有望带来一系列用于研究和构象操纵CPs的新技术。
