It is well known that macromolecular structure, including composition, topology and sequence, significantly determines the properties of conjugated polymers/oligomers. To accurately understand the structure-induced properties, discrete oligomers/polymers with molecularly defined structures are the ideal model because they provide distinct nonstatistical results. Herein, a series of discrete conjugated fluorene-azo oligomers with different positions of the azobenzene units along the main chain (i.e., sequence) are efficiently prepared based on CuAAC “click” chemistry via a stepwise chain-growth strategy. Position-dependent behavior has an evident impact on the properties of oligomers, such as thermal properties, optical properties and photoresponsive behavior in both solution and thin film states. In addition, the fluorene-azo oligomers show less photodegradation of 9,9-dioctyl-fluorene in the solid-state than oligofluorene during UV light irradiation; however, position-dependent photodegradation is found in solution. Optimized configurations and UV–vis absorption spectra of fluorene-azo oligomers are calculated by density functional theory. Experimental results and theoretical analysis indicate that the location of azobenzene can play a dominant role in determining the properties of fluorene-azo oligomers resulting from sequence-mandated conformational changes. Undoubtedly, this work can provide deeper insight into the structure–property relationships based on precisely sequence-defined polymer structures.

中文翻译：

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用于研究偶氮苯位置相关物理特性和光响应行为的离散共轭芴-偶氮低聚物的合成

众所周知，大分子结构，包括组成、拓扑和序列，显着决定了共轭聚合物/低聚物的性质。为了准确理解结构诱导特性，具有分子定义结构的离散低聚物/聚合物是理想的模型，因为它们提供了不同的非统计结果。在此，基于CuAAC“点击”化学通过逐步链增长策略有效地制备了一系列具有沿主链（即，序列）的偶氮苯单元的不同位置的离散的共轭芴-偶氮低聚物。位置相关行为对低聚物的性质有明显的影响，例如在溶液和薄膜状态下的热性质、光学性质和光响应行为。此外，在紫外光照射期间，芴-偶氮低聚物对固态9,9-二辛基-芴的光降解比低聚芴少；然而，在溶液中发现了位置相关的光降解。通过密度泛函理论计算出芴-偶氮低聚物的优化配置和紫外-可见吸收光谱。实验结果和理论分析表明，偶氮苯的位置可以在确定由序列强制构象变化引起的芴-偶氮低聚物的性质方面起主导作用。毫无疑问，这项工作可以更深入地了解基于精确序列定义的聚合物结构的结构-性能关系。在溶液中发现了位置相关的光降解。通过密度泛函理论计算出芴-偶氮低聚物的优化配置和紫外-可见吸收光谱。实验结果和理论分析表明，偶氮苯的位置可以在确定由序列强制构象变化引起的芴-偶氮低聚物的性质方面起主导作用。毫无疑问，这项工作可以更深入地了解基于精确序列定义的聚合物结构的结构-性能关系。在溶液中发现了位置相关的光降解。通过密度泛函理论计算出芴-偶氮低聚物的优化配置和紫外-可见吸收光谱。实验结果和理论分析表明，偶氮苯的位置可以在确定由序列强制构象变化引起的芴-偶氮低聚物的性质方面起主导作用。毫无疑问，这项工作可以更深入地了解基于精确序列定义的聚合物结构的结构-性能关系。实验结果和理论分析表明，偶氮苯的位置可以在确定由序列强制构象变化引起的芴-偶氮低聚物的性质方面起主导作用。毫无疑问，这项工作可以更深入地了解基于精确序列定义的聚合物结构的结构-性能关系。实验结果和理论分析表明，偶氮苯的位置可以在确定由序列强制构象变化引起的芴-偶氮低聚物的性质方面起主导作用。毫无疑问，这项工作可以更深入地了解基于精确序列定义的聚合物结构的结构-性能关系。