All-conjugated rod-rod block copolymers (BCPs) have gained immense interest over the past few years because they combine fascinating self-assembly properties of BCPs with the optical and electronic properties of conjugated polymers. Based on it, an all-conjugated rod-rod BCPs, poly(3-hexylselenophene)-b-poly[3-(6-hydroxyl)hexylthiophene] (P3HS-bP3HHT) with hydroxyl groups as side substitution groups was synthesized via the Grignard metathesis (GRIM) method. The introduction of side hydroxyl groups was designed to endow different polarity between P3HS and P3HHT blocks and enrich the solution structures of P3HS-b-P3HHT. During thermal annealing, the cross-linking of hydroxyl groups was also utilized to improve the thermal stability of poly(3-hexylthiophene) (P3HT)-based organic field-effect transistors (OFETs) when blended with a certain amount of P3HS-b-P3HHT. On one hand, the use of mixed solvents provided an effective way to control the self-assembly behavior of P3HS-b-P3HHT. Depending on the mixed solvent ratio (i.e., chloroform/pyridine or methanol/pyridine), the rod-rod interaction of the copolymer chains was controlled, yielding a series of nanostructures such as nanoribbons, nanofibers, and nanospheres. Detailed morphologies and the corresponding photophysical behavior of different nanostructures were characterized by transmission electron microscope and UV-vis absorption spectra. The conformations of the P3HS and P3HHT chains in the solutions influenced their photophysical properties greatly. On the other hand, based on the thermal cross-linkable properties of hydroxyl groups, a certain amount of P3HS-b-P3HHT was mixed with P3HT homopolymer to fabricate P3HS-b-P3HHT/P3HT OFETs. For control samples, the charge carrier mobility of pure P3HT-based OFETs was improved with the increased annealed temperatures up to 170 °C, then decreased significantly when the temperature further increased to 200 °C. While overall, the charge carrier mobilities of P3HS-b-P3HHT/P3HT OFETs were lower than those of pure P3HT-based OFETs, they were improved with the increased temperature to 200 °C. It was found the P3HS-b-P3HHT(10%)/P3HT OFETs exhibited the charge carrier mobility of 0.040 cm•V•s after annealing at 200 °C for 1 h, which was higher than P3HT OFETs (0.025 cm•V•s) under the same experimental condition. It was due to the cross-linking of hydroxyl groups in P3HS-b-P3HHT retain the crystallization structures of P3HT, thus improved the thermal stability of OFETs. Overall, this work demonstrates a new polythiophene-polyselenophene BCP with controlled nanostructures by solvent blending and promising application in OFETs to improve their thermal stability.

中文翻译：

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全共轭聚噻吩-聚硒吩二嵌段共聚物的合成与性能

全共轭棒-棒嵌段共聚物（BCPs）在过去几年中引起了极大的兴趣，因为它们结合了 BCPs 迷人的自组装特性和共轭聚合物的光学和电子特性。在此基础上，通过格氏法合成了以羟基为侧取代基的全共轭棒-棒BCPs，聚（3-己基硒吩）-b-聚[3-（6-羟基）己基噻吩]（P3HS-bP3HHT）复分解（GRIM）方法。侧羟基的引入旨在赋予 P3HS 和 P3HHT 嵌段之间不同的极性，并丰富 P3HS-b-P3HHT 的溶液结构。在热退火过程中，当与一定量的 P3HS-b-P3HHT 混合时，羟基的交联也被用来提高基于聚（3-己基噻吩）（P3HT）的有机场效应晶体管（OFET）的热稳定性。一方面，混合溶剂的使用提供了一种控制 P3HS-b-P3HHT 自组装行为的有效方法。根据混合溶剂比例（即氯仿/吡啶或甲醇/吡啶），控制共聚物链的棒-棒相互作用，产生一系列纳米结构，如纳米带、纳米纤维和纳米球。通过透射电子显微镜和紫外可见吸收光谱表征了不同纳米结构的详细形态和相应的光物理行为。溶液中 P3HS 和 P3HHT 链的构象极大地影响了它们的光物理性质。另一方面，基于羟基的热交联特性，将一定量的 P3HS-b-P3HHT 与 P3HT 均聚物混合制备 P3HS-b-P3HHT/P3HT OFET。对于对照样品，纯 P3HT 基 OFET 的电荷载流子迁移率随着退火温度升高至 170 °C 得到改善，然后当温度进一步升高至 200 °C 时显着降低。虽然总体而言，P3HS-b-P3HHT/P3HT OFET 的电荷载流子迁移率低于纯 P3HT 基 OFET 的电荷载流子迁移率，但随着温度升高至 200 °C，它们得到了改善。发现 P3HS-b-P3HHT(10%)/P3HT OFETs 在 200 °C 退火 1 h 后表现出 0.040 cm•V•s 的电荷载流子迁移率，在相同的实验条件下，它高于 P3HT OFET (0.025 cm•V•s)。这是由于P3HS-b-P3HHT中羟基的交联保留了P3HT的结晶结构，从而提高了OFET的热稳定性。总的来说，这项工作展示了一种新的聚噻吩 - 聚硒吩 BCP，通过溶剂混合具有可控的纳米结构，并有望在 OFET 中应用以提高其热稳定性。