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

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.