Alternately conjugated polymers have important application prospects in the field of organic optoelectronics due to their advantages of easy modification of chemical structures, solution preparation, and adjustable energy bands and spectra. At present, its preparation methods are mainly cross-coupling polymerization methods such as thermally activated Stille, Suzuki and direct arylation. However, such thermally activated synthesis methods have problems such as poor synthesis reproducibility and structural defects, which greatly limit the performance and application of conjugated polymer materials. In recent years, the team of Professor Huang Hui from the University of Chinese Academy of Sciences has reported a series of novel cross-coupling synthesis methods (Nat. Commun., 2022, 13, 144. Angew. Chem. Inter. Ed., 2019, 58, 5044.), in Important progress has been made in the green and efficient synthesis of organic/polymer semiconductor materials. In this work, the team used the efficient catalytic system of Buchwald precatalyst P(t-Bu)3 Pd G3 to realize the traditional Stille polymerization reaction at room temperature for the first time. The experimental results show that this method is not only widely applicable, but more importantly, it can completely suppress the generation of homopolymeric structural defects and improve the quality and reproducibility of the copolymer.
Figure 1: Comparison of traditional thermally activated Stille polymerization with room temperature Stille polymerization
Based on the optimal catalytic reaction conditions, the authors conducted extensive studies on nucleophilic and electrophilic substrates, and successfully synthesized 12 conjugated polymers with high molecular weight (11.3 kDa-77.8 kDa), high yield and low dispersion. , indicating that the method has good generality.
Figure 2: Twelve conjugated polymers synthesized using room temperature Stille polymerization methodology
Further research found that efficient room temperature coupling can not only improve the yield of cross-coupling, but also significantly inhibit the self-coupling of electrophiles or nucleophiles. Therefore, structural analysis of the polymer (P1a) obtained by the room temperature method compared with the materials obtained by the traditional high temperature method (P1b and P1c) shows that P1a is completely free of structural defects, while P1b and P1c contain homopolymers of nucleophilic or electrophilic monomers Structural defects. The theoretical study of the absorption spectrum shows that the existence of homopolymeric structural defects can lead to the shift of the absorption spectrum, which is also highly consistent with the experimental results.
Figure 3: Defect Study
The authors used the above three materials to study the density of defect states and organic field effect transistors (OFETs) respectively, and found that the materials synthesized at room temperature showed lower density of defect states and higher hole mobility, which were better than those of traditional thermal Activation of the prepared material further supports the superiority of this method.
Figure 4: OFET device fabrication and comparison
Therefore, the Huang Hui/Shi Qinqin team adopted a simple and efficient catalyst strategy to develop a universal room-temperature catalytic polymerization method. The cross-polymer prepared by this method has no homopolymeric structural defects, so it has higher device performance. The development of this method not only provides a new method for the preparation of high-performance conjugated polymer materials, but also lays a foundation for the study of the structure-activity relationship of conjugated polymer materials, and provides a new research idea for the development of organic electronics.
This work was published in Angew. Chem. Int. Ed. At the same time, the paper was selected as VIP (Very Important Paper), and it is reported that less than 5% of the papers can receive such a positive evaluation. The first author of the article is Ma Bowei, a doctoral student at the University of Chinese Academy of Sciences, and the corresponding authors are Associate Professor Shi Qinqin and Professor Huang Hui. This work was supported by the National Natural Science Foundation of China, the Key R&D Program of the Ministry of Science and Technology, the Frontier Key Fund of the Chinese Academy of Sciences and the Pilot Fund.
Defect-Free Alternating Conjugated Polymers Enabled by Room-Temperature Stille Polymerization
Bowei Ma, Qinqin Shi, Xiaoying Ma, Yawen Li, Hao Chen, Kaikai Wen, Ruihua Zhao, Fengjiao Zhang, Yuze Lin, Zhixiang Wang, Hui Huang
Angewandte Chemie International Edition