Understanding the complex crystallization process of semiconducting polymers is key for the advance of organic electronic technologies as the optoelectronic properties of these materials are intimately connected to their solid-state microstructure. These polymers often have semirigid backbones and flexible side chains, which results in a strong tendency to organize/order in the liquid state. Therefore, crystallization of these materials frequently occurs from liquid states that exhibit─at least partial─molecular order. However, the impact of the preexisting molecular order on the crystallization process of semiconducting polymers─ indeed, of any polymer─remained hitherto unknown. This study uses fast scanning calorimetry (FSC) to probe the crystallization kinetics of poly(9,9-di-n-octylfluorenyl-2,7-diyl (PFO) from both an isotropic disordered melt state (ISO state) and a liquid-crystalline ordered state (NEM state). Our results demonstrate that the preexisting molecular order has a profound impact on the crystallization of PFO. More specifically, it favors the formation of effective crystal nucleation centers, speeding up the crystallization kinetics at the early stages of phase transformation. However, samples crystallized from the NEM state require longer times to reach full crystallization (during the secondary crystallization stage) compared to those crystallized from the ISO state, likely suggesting that the preexisting molecular order slows down the advance in the latest stages of the crystallization, that is, those governed by molecular diffusion. The fitting of the data with the Avrami model reveals different crystallization mechanisms, which ultimately result in a distinct semicrystalline morphology and photoluminescence properties. Therefore, this work highlights the importance of understanding the interrelationships between processing, structure, and properties of polymer semiconductors and opens the door for performing fundamental investigations via newly developed FSC methodologies of such materials that otherwise are not possible with conventional techniques.

中文翻译：

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揭示预先存在的分子顺序对半导体半晶聚 (9,9-二正辛基芴基-2,7-二基 (PFO)) 结晶的影响

了解半导体聚合物复杂的结晶过程是有机电子技术进步的关键，因为这些材料的光电特性与其固态微观结构密切相关。这些聚合物通常具有半刚性主链和柔性侧链，这导致在液态下具有很强的组织/有序倾向。因此，这些材料的结晶经常发生在呈现出——至少是部分——分子有序的液态。然而，先前存在的分子顺序对半导体聚合物——事实上，任何聚合物——结晶过程的影响迄今仍然未知。本研究使用快速扫描量热法 (FSC) 来探测聚 (9,9-di- n ) 的结晶动力学-octylfluorenyl-2,7-diyl (PFO) 来自各向同性无序熔体状态（ISO 状态）和液晶有序状态（NEM 状态）。我们的结果表明，预先存在的分子顺序对 PFO 的结晶具有深远的影响。更具体地说，它有利于形成有效的晶体成核中心，加速相变早期的结晶动力学。然而，与从ISO 状态结晶的样品相比，从NEM 状态结晶的样品需要更长的时间才能达到完全结晶（在二次结晶阶段），可能表明先前存在的分子顺序减慢了结晶最新阶段的进展，即那些受分子扩散控制的阶段。数据与 Avrami 模型的拟合揭示了不同的结晶机制，最终导致不同的半晶形态和光致发光特性。因此，这项工作强调了理解聚合物半导体的加工、结构和性能之间相互关系的重要性，并为通过新开发的 FSC 方法对此类材料进行基础研究打开了大门，否则传统技术是不可能的。