Siemons Nicholas, Pearce Drew, Cendra Camila, Yu Hang, Tuladhar Sachetan M, Hallani Rawad K, Sheelamanthula Rajendar, LeCroy Garrett S, Siemons Lucas, White Andrew J P, McCulloch Iain, Salleo Alberto, Frost Jarvist M, Giovannitti Alexander, Nelson Jenny
Department of Physics, Imperial College, London, Exhibition Rd, South Kensington, London, SW7 2AZ, UK.
Department of Materials Science and Engineering, Stanford University, 450 Serra Mall, Stanford, CA, 94305, USA.
Adv Mater. 2022 Sep;34(39):e2204258. doi: 10.1002/adma.202204258. Epub 2022 Aug 28.
Exchanging hydrophobic alkyl-based side chains to hydrophilic glycol-based side chains is a widely adopted method for improving mixed-transport device performance, despite the impact on solid-state packing and polymer-electrolyte interactions being poorly understood. Presented here is a molecular dynamics (MD) force field for modeling alkoxylated and glycolated polythiophenes. The force field is validated against known packing motifs for their monomer crystals. MD simulations, coupled with X-ray diffraction (XRD), show that alkoxylated polythiophenes will pack with a "tilted stack" and straight interdigitating side chains, whilst their glycolated counterpart will pack with a "deflected stack" and an s-bend side-chain configuration. MD simulations reveal water penetration pathways into the alkoxylated and glycolated crystals-through the π-stack and through the lamellar stack respectively. Finally, the two distinct ways triethylene glycol polymers can bind to cations are revealed, showing the formation of a metastable single bound state, or an energetically deep double bound state, both with a strong side-chain length dependence. The minimum energy pathways for the formation of the chelates are identified, showing the physical process through which cations can bind to one or two side chains of a glycolated polythiophene, with consequences for ion transport in bithiophene semiconductors.
将基于疏水性烷基的侧链交换为基于亲水性二醇的侧链，是一种广泛采用的提高混合传输器件性能的方法，尽管对固态堆积和聚合物 - 电解质相互作用的影响了解甚少。本文提出了一种用于模拟烷氧基化和二醇化聚噻吩的分子动力学（MD）力场。该力场针对其单体晶体的已知堆积模式进行了验证。MD模拟与X射线衍射（XRD）相结合表明，烷氧基化聚噻吩将以“倾斜堆积”和直的叉指状侧链堆积，而其二醇化对应物将以“偏转堆积”和S形弯曲侧链构型堆积。MD模拟揭示了水进入烷氧基化和二醇化晶体的渗透途径，分别是通过π堆积和层状堆积。最后，揭示了三甘醇聚合物与阳离子结合的两种不同方式，显示出形成亚稳单键态或能量上较深的双键态，两者都具有很强的侧链长度依赖性。确定了螯合物形成的最低能量途径，显示了阳离子与二醇化聚噻吩的一个或两个侧链结合的物理过程，这对双噻吩半导体中的离子传输有影响。
