Although considerable progress has been made to optimize the optoelectronic properties of conjugated polymers (CPs), the rational design of CPs with tailored physical properties for end-use applications remains a significant challenge. Specifically, experimental characterization of conjugated polymer backbone conformations remains underexplored due to limited techniques that are capable of distinguishing the backbone and side-chain structures at nanoscopic resolution. Thus, relating the electronically functional backbone conformation to the material’s macroscopic optoelectronic property is an ongoing challenge. Here, small-angle neutron scattering techniques (SANS) with contrast-variation (CV) experiments are employed on poly(3-alkylthiophenes) (P3ATs) with both deuterated and protonated side chains in a mixture of protonated and deuterated solvents to decouple the backbone and side-chain scattering signals. We obtained the form factor of P3ATs’ backbone, side chains, and cross-scattering term by deconvoluting their respective scattering signals. Poly(3-decylthiophene) shows a persistence length of 1.05 ± 0.1 nm for the conjugated polymer backbone and 2.10 ± 0.2 nm for the entire chain. The strong scattering signal from long and flexible alkyl side chains leads to a seemingly more rigid conjugated polymer, which is further revealed by coarse-grained molecular dynamics (CG-MD) simulations. This work offers a methodology to decouple the scattering contribution from the CPs’ backbone and side chains, thus elucidating the inherent conformation of the electronically active conjugated backbone, which provides guidance for the rational design of next-generation polymeric semiconductors.

中文翻译：

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通过选择性氘化和中子散射将聚（3-烷基噻吩）的骨架和侧链构象解耦。

尽管在优化共轭聚合物（CP）的光电性能方面已经取得了很大的进步，但是具有针对最终用途应用量身定制的物理性能的CP的合理设计仍然是一个巨大的挑战。具体而言，由于能够在纳米分辨率下区分主链和侧链结构的有限技术，共轭聚合物主链构象的实验表征仍未得到充分研究。因此，将电子功能主链构象与材料的宏观光电性能相关是一个持续的挑战。这里，小角度中子散射技术（SANS）和对比变化（CV）实验用于具有氘代和质子化侧链的聚（3-烷基噻吩）（P3AT），在质子化和氘化溶剂的混合物中使骨架和侧面解偶联-链散射信号。通过反卷积它们各自的散射信号，我们获得了P3ATs骨架，侧链和交叉散射项的形状因子。聚（3-癸基噻吩）对于共轭聚合物主链的持久性长度为1.05±0.1 nm，对于整个链而言则为2.10±0.2 nm。来自长而柔软的烷基侧链的强散射信号导致看似更刚性的共轭聚合物，这通过粗粒分子动力学（CG-MD）模拟得以进一步揭示。