Ionic Liquids (ILs) have been used for polycondensation processes, especially for polyimide synthesis. The influence of various reaction parameters including IL's cations and anions nature, monomer structure and concentration, reaction temperature, upon polyimide molecular weight (ηinh) was investigated. The possibility of process activation by the application of IL's small additives in one step polyimide synthesis in common organic solvents was demonstrated. The peculiarities of C–H⋯Br contacts in solid state were carried out using single crystal X-ray diffraction data. Various high molecular weight polyimides including commercial and sulfonated ones have been obtained in quantitative yields with inherent viscosities ranging from 0.10 to 2.17 dl g−1.