Dynamics of Preaggregation and Film Formation of Donor–Acceptor π-Conjugated Polymers

It is important to understand the film formation mechanism of π-conjugated polymers to realize their high-performance electronic devices. In this study, the dynamics of the preaggregate, which affects the conformation and alignment of a typical donor–acceptor (D-A) π-conjugated polymer during film formation, was investigated by two approaches based on a small-angle X-ray scattering (SAXS) method. SAXS analysis of a highly concentrated solution, assuming the state before becoming the solid-state thin film, provided insight into the aggregation phenomena of the D-A π-conjugated polymer during the film formation process. In solution, the small rod-like structure of the polymer seems to form a large preaggregate, the shape of which almost coincided with that of the aggregate in the solid-state thin film. Besides, in situ grading incident SAXS (in situ GISAXS) analysis in the actual film formation process from the solution state revealed a microstructural change of the aggregate over time.