Synthesis of Polyimides, Polyamides, and Poly(Amide-Imides) in the “Green” Solvent N-Butyl-2-Pyrrolidone (TamiSolve NxG): Features, Optimization, and Versatility

Owing to their outstanding thermal and mechanical properties, polyimides (PIs), polyamides (PAs), and poly(amide-imides) (PAIs) are essential for developing and manufacturing modern high-tech products, including electroactive ones. Despite their large-scale production for diverse applications, the synthesis of these polymers traditionally relies on highly toxic solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone (NMP), and <i>m</i>-cresol. This work investigates the possibility of replacing these hazardous solvents with a more sustainable and "green" alternative, N-butyl-2-pyrrolidone (NBP). We have thoroughly studied and analyzed the synthesis of various PIs, PAs, and PAIs via one- and two-step polycondensation of tetracarboxylic acid dianhydrides with diamines, low-temperature polycondensation of terephthaloyl chloride with diamines, and low-temperature polycondensation of tetracarboxylic acid dianhydrides and terephthaloyl chloride with diamines, respectively. Our results demonstrate that substituting NBP for NMP presents distinct characteristics and outcomes for each process. By optimizing the reaction conditions, we were able to obtain high-molecular-weight products (M_n = 37-346 kDa; M_w = 133-537 kDa) for all polymer classes studied. Thus, this work establishes NBP as a suitable and promising solvent for synthesizing PIs, PAs, and PAIs with diverse chemical structures and tunable molecular weight characteristics.