5. Synthesis of polyimides from "AB" monomers

The one-pot high-temperature catalytic polycyclocondensation in molten BA was successfully used to obtain homo- and co-PEIs from 4-(3-aminophenoxy)-phthalic acid (3-APPA) which has a structure of latent "AB" monomer [29]. In solid state, 3- APPA exists in a zwitterionic form. In molten BA at 140°C, it transfers to the "open" form which is able to dehydrate to give monomer with amino and anhydride groups. It is able for auto-polycondensation with moderate rate. Homo-PEI prepared from 3- APPA in molten BA is high molecular weight amorphous thermoplastic PEI with a glass temperature of 210–220°C soluble in chloroform and DMSO. The yield and degree of imidization are close to 100%. In contrast, homo-PEI prepared at the same conditions from isomeric 4-(4-aminophenoxy) phthalic acid (4-APPA) is insoluble and intractable till 400°C. Properties of copolyimides 3-APPA/4-APPA depend on composition. When the 3-APPA/4-APPA ratio in staring monomer mixture is 30:70 or less, the polymer is amorphous and soluble in organic solvents. At 3-APPA/4- APPA ratios of 40:60 or higher, CPIs lose solubility and tractability.

Synthesis of Polyimides in the Melt of Benzoic Acid DOI: http://dx.doi.org/10.5772/intechopen.87032
