Subtle Molecular Changes Largely Modulate Chiral Helical Assemblies of Achiral Conjugated Polymers by Tuning Solution-State Aggregation,ACS Central Science

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Subtle Molecular Changes Largely Modulate Chiral Helical Assemblies of Achiral Conjugated Polymers by Tuning Solution-State Aggregation
ACS Central Science ( IF 12.7 ) Pub Date : 2023-11-13 , DOI: 10.1021/acscentsci.3c00775
Kyung Sun Park ₁ , Xuyi Luo ₂ , Justin J Kwok ₃ , Azzaya Khasbaatar ₁ , Jianguo Mei ₂ , Ying Diao _{1,

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Affiliation

Understanding the solution-state aggregate structure and the consequent hierarchical assembly of conjugated polymers is crucial for controlling multiscale morphologies during solid thin-film deposition and the resultant electronic properties. However, it remains challenging to comprehend detailed solution aggregate structures of conjugated polymers, let alone their chiral assembly due to the complex aggregation behavior. Herein, we present solution-state aggregate structures and their impact on hierarchical chiral helical assembly using an achiral diketopyrrolopyrrole-quaterthiophene (DPP-T4) copolymer and its two close structural analogues wherein the bithiophene is functionalized with methyl groups (DPP-T2M2) or fluorine atoms (DPP-T2F2). Combining in-depth small-angle X-ray scattering analysis with various microscopic solution imaging techniques, we find distinct aggregate in each DPP solution: (i) semicrystalline 1D fiber aggregates of DPP-T2F2 with a strongly bound internal structure, (ii) semicrystalline 1D fiber aggregates of DPP-T2M2 with a weakly bound internal structure, and (iii) highly crystalline 2D sheet aggregates of DPP-T4. These nanoscopic aggregates develop into lyotropic chiral helical liquid crystal (LC) mesophases at high solution concentrations. Intriguingly, the dimensionality of solution aggregates largely modulates hierarchical chiral helical pitches across nanoscopic to micrometer scales, with the more rigid 2D sheet aggregate of DPP-T4 creating much larger pitch length than the more flexible 1D fiber aggregates. Combining relatively small helical pitch with long-range order, the striped twist-bent mesophase of DPP-T2F2 composed of highly ordered, more rigid 1D fiber aggregate exhibits an anisotropic dissymmetry factor (g-factor) as high as 0.09. This study can be a prominent addition to our knowledge on a solution-state hierarchical assembly of conjugated polymers and, in particular, chiral helical assembly of achiral organic semiconductors that can catalyze an emerging field of chiral (opto)electronics.

中文翻译：

细微的分子变化通过调节溶液状态聚集来很大程度上调节非手性共轭聚合物的手性螺旋组装

了解溶液态聚集结构以及随后的共轭聚合物的分层组装对于控制固体薄膜沉积过程中的多尺度形貌以及由此产生的电子特性至关重要。然而，理解共轭聚合物的详细溶液聚集结构仍然具有挑战性，更不用说由于复杂的聚集行为而导致它们的手性组装。在此，我们使用非手性二酮吡咯并吡咯-四噻吩（DPP-T4）共聚物及其两种紧密结构的类似物（其中联噻吩被甲基（DPP-T2M2）或氟官能化）展示了溶液态聚集结构及其对分级手性螺旋组装的影响原子（DPP-T2F2）。将深入的小角 X 射线散射分析与各种显微溶液成像技术相结合，我们在每个 DPP 溶液中发现了不同的聚集体：(i) 具有强结合内部结构的 DPP-T2F2 半结晶一维纤维聚集体，(ii) 半结晶具有弱结合内部结构的 DPP-T2M2 的一维纤维聚集体，以及 (iii) DPP-T4 的高度结晶的二维片状聚集体。这些纳米级聚集体在高溶液浓度下发展成溶致手性螺旋液晶（LC）中间相。有趣的是，溶液聚集体的维度在很大程度上调节了纳米级到微米尺度的分层手性螺旋螺距，更刚性的 DPP-T4 2D 片状聚集体比更灵活的 1D 纤维聚集体产生更大的螺距长度。将相对较小的螺距与长程有序相结合，由高度有序、刚性更强的一维纤维聚集体组成的 DPP-T2F2 条纹扭曲弯曲中间相表现出高达 0 的各向异性不对称因子（g 因子）。09. 这项研究可以是对我们关于共轭聚合物的溶液态分级组装的知识的重要补充，特别是非手性有机半导体的手性螺旋组装，可以催化手性（光）电子学的新兴领域。

更新日期：2023-11-13

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