Thermomechanical properties of conjugated polymers (CPs) are greatly influenced by both their microstructures and backbone dynamics. In the present work, to investigate the effect of the side-chain branch position on the backbone's mobility and molecular packing structure, four poly (3-alkylthiophene-2,5-diyl) derivatives (P3ATs) with different side chains, either branched or linear, were synthesized by a quasi-living Kumada catalyst transfer polymerization (KCTP) method. The side-chain branch position greatly influences the glass transition temperature (T_g) of the backbone of P3ATs as well as the melting temperature (T_m), as measured by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) respectively. Placing the branching point closer to the conjugated backbone leads to increased backbone T_g and T_m. Also, according to grazing incidence wide-angle X-ray scattering (GIWAXS) results, branching closer to the backbone causes tighter packing in the side-chain direction. The tighter packing along the side-chain direction coresponds with the higher T_m, which decreases the free volume of the polymer system and subsequently increases the T_g at the same time. This work provides the first in-depth understanding of branch point influences on the thermal properties of poly(3-alkylthiophenes). It would provide guidance to the future development of side-chain engineering on next-generation CPs with desirable thermomechnical properties for stretchable and wearable electronics.

中文翻译：

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侧链支链位置对聚（3-烷基噻吩）的热性能的影响†

共轭聚合物（CP）的热力学性能受其微观结构和主链动力学的影响很大。在当前的工作中，为了研究侧链支链位置对主链迁移率和分子堆积结构的影响，研究了具有不同侧链的四个聚（3-烷基噻吩-2,5-二基）衍生物（P3ATs），它们是支链或支链的。通过准活的熊田催化剂转移聚合法（KCTP）合成线型化合物。侧链支链位置极大地影响了P3ATs骨架的玻璃化转变温度（T _g）以及熔融温度（T _m）），分别通过动态力学分析（DMA）和差示扫描量热法（DSC）进行测量。将分支点放置在更靠近共轭骨架的位置会导致骨架T _g和T _m的增加。而且，根据掠入射的广角X射线散射（GIWAXS）结果，靠近主链的分支导致在侧链方向上的堆积更紧密。沿着侧链方向更紧密的堆积会伴随着较高的T _m，这会降低聚合物体系的自由体积，并随后增加T _g同时。这项工作提供了第一个深入了解分支点对聚（3-烷基噻吩）的热性能的影响。它将为具有可伸缩和可穿戴电子产品所需的热机械性能的下一代CP的侧链工程的未来发展提供指导。