Conjugated polymers show superior performance in optoelectronic devices, energy conversion, biosensors, and biomedical applications, etc. The critical properties of conjugated polymers in functional devices, such as light absorption/emission, charge transport, and mechanical properties, are determined by not only the molecular structure but also the solid-state morphology and microstructure. Developing functional materials and devices based on conjugated polymers requires an in-depth understanding of the structure−function relationship among molecular structure, morphology, microstructure, and charge transport mechanism.However, such morphology and microstructure from molecules to solid states are challenging to understand due to the complexity of chemical structures, chain conformation, molecular interactions, chain packing, crystallinity etc(as shown in Fig. 1). Therefore, it is a significant challenge to reveal the relationship among molecular structures to the complex microstructure and finally to device functions.
Fig.1Schematic diagram of the solid-state morphology, microstructures, corresponding spatial scale, and characterization methods.
Aiming to understand the complex multi-level assembly structures of conjugated polymers, this review focuses on the formation, behavior, and evolution of solution-state aggregation of conjugated polymers, which can influence and even determine the solid-state morphology and microstructure, ultimately clarifying the relationship between the microstructure and the properties of conjugated polymers (as shown in Fig. 2). The critical role of solution-state aggregation is highlighted from a theoretical understanding of molecular interactions between polymer chains (conjugated backbones and/or flexible side chains) and solvent molecules. This reviewdiscusses the concept of solution-state aggregation and its application in controlling the solid-state microstructures and morphology. The controllable molecular interactions in polymer solution systems make it possible to tune the solution-state aggregation, further assembly, and crystallization behavior during the film-formation process. Therefore, a complete multi-level structure−function relationship of conjugated polymers can be described from between molecular structures, solution-state aggregation, and solid-state microstructures to charge transport properties (as shown in Fig. 3).
Fig.2The key role of solution-state aggregation of conjugated polymers towards controlling the solid-state morphology and microstructures.
Fig.3The key role of solution-state aggregation in designing and developing conjugated polymers.
Ze-fan Yao, aPh.D. student at the College of Chemistry and Molecular Engineering, Peking University, is the first author of this paper. Prof. Jian Pei from the College of Chemistry and Molecular Engineering, Peking University is the corresponding author. This work is supported by the Beijing National Laboratory for Molecular Sciences,National Key R&D Program of China, National Natural Science Foundation of China, and Beijing Outstanding Young Scientist Program.
Original link for the paper:https://www.sciencedirect.com/science/article/pii/S0079670022001241
