Influence of Side-Chain Chemistry on Structure and Ionic Conduction Characteristics of Polythiophene Derivatives: A Computational and Experimental Study
Influence of Side-Chain Chemistry on Structure and Ionic Conduction Characteristics of Polythiophene Derivatives: A Computational and Experimental Study
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DOI：
10.1021/acs.chemmater.8b05257
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发表时间：
2019-02-26
影响因子：
8.6
通讯作者：
Patel, Shrayesh N.
中科院分区：
文献类型：
--
作者：
Dong, Ban Xuan;Nowak, Christian;Patel, Shrayesh N.
虽然人们已经付出了大量的努力来理解共轭聚合物中的电子输运，但对它们与聚合物化学、加工和形态学有关的离子导电特性知之甚少。本工作提出了一种结合计算和实验研究的形态和离子传输的薄膜共混物的聚噻吩衍生物轴承低聚乙二醇侧链和锂双（三氟甲磺酰基）-酰亚胺（LiTFSI）。使用分子动力学（MD）模拟，我们表明，在非晶相，聚噻吩衍生物P3 MEET轴承低聚乙二醇侧链与氧直接连接到噻吩环具有较低的锂离子电导率相比，其类似物P3 MEEMT，具有甲基间隔之间的氧和噻吩环。P3 MEET和P3 MEEMT薄膜与LiTFSI共混后的结构表征表明，添加LiTFSI扩展了聚合物微晶的侧链域，同时降低了总结晶度。此外，发现LiTFSI在低浓度下渗透非晶和结晶状态，但优选地在高LiTFSI浓度下驻留在非晶域中。在P3 MEET和P3 MEEMT-LiTFSI薄膜中通过电化学阻抗谱测量的离子传输被发现主要发生在非晶域中，并且P3 MEEMT-LiTFSI中的离子电导率总是高于P3 MEET-LiTFSI样品，与MD模拟的预测一致。我们的工作为预测和研究高分子化学对共轭高分子离子电导率的影响提供了一个平台。
Although extensive efforts have been devoted to understanding electronic transport in conjugated polymers, little is known about their ionic conduction characteristics in relation to polymer chemistry, processing, and morphology. This work presents a combined computational and experimental study on morphology and ion transport in thin-film blends of polythiophene derivatives bearing oligoethylene glycol side-chains and lithium bis(trifluoromethanesulfonyl)-imide (LiTFSI). Using molecular dynamics (MD) simulation, we show that in the amorphous phase, the polythiophene derivative P3MEET bearing oligoethylene glycol side-chains with oxygen directly attached to the thiophene rings possesses lower Li+ ionic conductivity compared to its analog P3MEEMT that has a methyl spacer between the oxygen and the thiophene rings. Structural characterization of P3MEET and P3MEEMT thin film upon blending with LiTFSI indicates that adding LiTFSI expands the side-chain domains of the polymer crystallites and reduces the total degree of crystallinity at the same time. Moreover, LiTFSI is found to infiltrate both the amorphous and crystalline regimes at low concentrations but preferably resides in the amorphous domain at high LiTFSI concentrations. Ionic transport measured by electrochemical impedance spectroscopy in both P3MEET- and P3MEEMT-LiTFSI thin films is found to occur predominately in the amorphous domain, and ionic conductivity in P3MEEMT-LiTFSI is always higher than in P3MEET-LiTFSI samples, consistent with predictions from MD simulations. Our work provides a platform to predict and study the influence of polymer chemistry on the ionic conductivity of conjugated polymers.