Biobased Polyimides Derived From Adenine Diamine With High Thermal Stability and Flame Retardancy

ABSTRACT This study addresses the dual imperatives of sustainability and flame‐retardant safety in high‐performance polymers by utilizing nucleobases—specifically adenine—as renewable biobased monomers for the synthesis of a new series of polyimides. Among the synthesized polyimides, the one derived from the polymerization of the adenine‐derived diamine (ADA) with 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA), referred to as ADA‐6FDA, exhibits outstanding performance, with a glass transition temperature ( T g ) exceeding 356°C, a low coefficient of thermal expansion ( CTE ) of 25.2 ppm K −1 , and a remarkable limiting oxygen index ( LOI ) of 52%. These results indicate that the adenine structure imparts thermomechanical properties comparable to or superior to those of petroleum‐based polyimides. At the same time, the high nitrogen content provides an intrinsic flame‐retardant pathway through the release of inert gas and the formation of char. This heterocyclic contribution to high flame retardancy is also evidenced by a series of reference polyimides comprising aromatic or isosorbide‐based diamines. This work establishes a sustainable class of polyimides that combines high performance with enhanced safety, offering an eco‐friendly alternative for advanced electronic and aerospace applications.