Yu Hang, Marks Adam, Tuladhar Sachetan M, Siemons Nicholas, Anderson Iona, Bidinger Sophia, Keene Scott T, Quill Tyler J, Wu Ruiheng, Gough Olivia, Wu Guanchen, Eisner Flurin, Salleo Alberto, Rivnay Jonathan, Malliaras George G, Barnes Piers R F, McCulloch Iain, Nelson Jenny
Department of Physics and Centre for Processable Electronics, Imperial College London, SW7 2AZ, London, United Kingdom.
Department of Chemistry, University of Oxford, OX1 2JD, Oxford, United Kingdom.
Angew Chem Int Ed Engl. 2025 Feb 3;64(6):e202417897. doi: 10.1002/anie.202417897. Epub 2024 Dec 23.
Conjugated polymers (CPs) with polar side chains can conduct electronic and ionic charges simultaneously, making them promising for bioelectronics, electrocatalysis and energy storage. Recent work showed that adding alkyl spacers between CP backbones and polar side chains improved electronic charge carrier mobility, reduced swelling and enhanced stability, without compromising ion transport. However, how alkyl spacers impact polymer backbone conformation and, subsequently, electronic properties remain unclear. In this work, we design two oxy-bithiophene-based CP series, each featuring progressively extended alkyl spacer lengths and two distinct molecular weight (MW) distributions. Using operando characterisations, we evaluate the (spectro)electrochemical and swelling properties of the polymer thin films, and their performance in organic field-effect transistors and organic electrochemical transistors. Surprisingly, alkyl spacers negatively impact the hole mobility of our polymers, with higher MW amplifying this effect. Using molecular dynamics simulations, we show that it is thermodynamically favourable for adjacent non-polar alkyl spacers to aggregate in polar electrolytes, leading to backbone twisting. Further spectroscopic measurements corroborate this prediction. Our findings demonstrate the active interactions between side chain structure, MW and electrolyte/solvent polarity in influencing polymer performance, underscoring the importance of considering solvation environment effects on polymer conformation when designing new mixed conducting CPs for electrochemical applications.
带有极性侧链的共轭聚合物（CPs）能够同时传导电子和离子电荷，这使其在生物电子学、电催化和能量存储领域具有广阔前景。近期研究表明，在CP主链和极性侧链之间引入烷基间隔基可提高电子电荷载流子迁移率、减少溶胀并增强稳定性，同时不影响离子传输。然而，烷基间隔基如何影响聚合物主链构象以及随后的电子性质仍不清楚。在本工作中，我们设计了两个基于氧代联噻吩的CP系列，每个系列具有逐渐延长的烷基间隔基长度以及两种不同的分子量（MW）分布。通过原位表征，我们评估了聚合物薄膜的（光谱）电化学和溶胀性质，以及它们在有机场效应晶体管和有机电化学晶体管中的性能。令人惊讶的是，烷基间隔基对我们聚合物的空穴迁移率有负面影响，分子量越高这种影响越大。通过分子动力学模拟，我们表明相邻的非极性烷基间隔基在极性电解质中聚集在热力学上是有利的，这会导致主链扭曲。进一步的光谱测量证实了这一预测。我们的研究结果证明了侧链结构、分子量和电解质/溶剂极性之间在影响聚合物性能方面的活性相互作用，强调了在设计用于电化学应用的新型混合导电CP时考虑溶剂化环境对聚合物构象影响的重要性。
