Three low band gap (below 1.6 eV) copolymers based on 2,5-bis(3-octylthiophen-2-yl)thieno[3,2-b]thiophene) donor unit and isoindigo acceptor units were designed and successfully synthesized by the direct arylation polycondensation method. The backbones of the copolymers were chosen to be similar while the alkyl side chain substituted on the isoindigo units were systematically tailored as 2-hexyldecyl in P1, 2-octyldecyl in P2 and 2-decyltetradecyl in P3. The thermal stabilities of the copolymers was found to be highly dependent on the lengths of alkyl side chains. The long alkyl side chains in P3 were found to be detrimental to its stability. P2 was found to have a higher thermal stability was found in due to the optimized side chains that reduced steric repulsion between the side chains in the donor and acceptor units. The thermogravimetric analysis also revealed that the backbone decomposition of P2 is at higher temperature than P3 and P1. The results confirmed the importance of alkyl side chain optimization for the stability of copolymers

设计并成功合成了三种基于 2,5-双（3-辛基噻吩-2-基）噻吩并[3,2- b ]噻吩）供体单元和异靛蓝受体单元的低带隙（低于 1.6 eV）共聚物。芳基化缩聚法。共聚物的主链被选择为相似，而在isoindigo单元取代烷基侧链如2-己基癸在进行了系统的定制P1，2-辛基在P2和2-癸基十四烷基P3。发现共聚物的热稳定性高度依赖于烷基侧链的长度。发现P3中的长烷基侧链对其稳定性有害。P2由于优化的侧链减少了供体和受体单元中侧链之间的空间排斥，因此发现具有更高的热稳定性。热重分析还表明，P2的骨架分解温度高于P3和P1。结果证实了烷基侧链优化对共聚物稳定性的重要性