Chain structure and β conformation of poly(9,9-dioctylfluorene) (PFO) with different molecular weights delivering from the solution to the film in a drop-casting process

ranging from 25 100 Da to 117 000 Da were obtained by the precipitation fractionation method. In dilute THF solution, the molecular chains were in α conformation without aggregates. In films, as the molecular weight increased, the content of β conformation and ordered structure increased first and then decreased. By studying the solvent evaporation process, for the first time, we propose a possible mechanism for the transformation process of chain structure and β conformation from the solution to the film, which involves three stages. This study reveals the transformation process of the chain structure and β conformation of PFO from the solution to the film and its relationship with the molecular weight, which provides theoretical and practical versions for in-depth understanding and control of the formation of the ordered structure in high-efficiency films.