Synthesis of High Tg and Low CTE Polyimides From Acridinone Diamines With Various Linearity

ABSTRACT Polyimide (PI) films with ultra‐high glass transition temperature (T g ) and low coefficient of linear thermal expansion (CTE) have great potential in flexible, foldable advanced optoelectronic materials. In order to make PI films better suited for flexible electronic devices, this research tried to introduce acridone groups into the diamine backbone and successfully designed and synthesized two isomeric diamine monomers: 2,7‐diaminoacridin‐9‐ketones (3a) and 2,6‐diaminoacridin‐9‐ketones (3b). Due to the presence of linear rigid acridone groups and strong intermolecular hydrogen bonds, the prepared novel aromatic PI films (3a‐BPDA and 3b‐BPDA) through a two‐step method had excellent high‐temperature resistance ( T d5% = 565.15°C and 551.04°C; T g = 469.05°C and 442.58°C) and low linear thermal expansion coefficients (CTE = 24.50 and 17.19 ppm K −1 ). In addition, this study further elucidated the influence of the acridone group and the varying linearity of diamine monomers on tight‐chain fillers, revealing the successful incorporation mechanism of these components into polyimide polymer chains, providing a new insight for exploring the application of the acridone group in polyimide systems and developing higher‐performance polyimide film materials.