The invention provides novel
polyimide. Copolymerized aliphatic
polyimide is synthesized through a salt
monomer method. The preparation method comprises the following specific steps: 1) respectively dissolving cyclobutanetetracarboxylic acid (CBTA), NH2 (CH2) mNH2 (m = 2, 3, 4... 20) and NH2 (CH2) nNH2 (n = 2, 3, 4... 20) in an
organic solvent, and stirring to obtain a solution; or respectively dissolving
cyclobutane tetracarboxylic acid (CBTA),
cyclopentane tetracarboxylic acid (CPTA) or
cyclohexane tetracarboxylic acid (CHTA) or bicyclo [2.2. 2] oct-7-ene-2, 3, 5, 6-tetracarboxylic acid (BC-CHTA) or pyromellitic tetracarboxylic acid (PMTA) and NH2 (CH2) nNH2 (n = 2, 3, 4... 20) in an
organic solvent, and stirring to obtain a solution; 2) mixing the obtained different solutions, and separating out
ion pairs to obtain corresponding crystals; and 3) carrying out thermal
polymerization on the salt
monomer to obtain the copolymerized aliphatic
polyimide. The novel transparent polyimide is prepared through the green, environment-friendly, simple and efficient synthesis method, and the application prospect is wide.