Diisocyanate route as a convenient method for the preparation of novel optically active poly(amide–imide)s based on N-trimellitylimido-S-valine

A new class of optically active poly(amide–imide)s based on an α-amino acid was synthesized via direct polycondensation reaction of different diisocyanates with a chiral diacid monomer. The step-growth polymerization reactions of N-trimellitylimido-S-valine (TISV) (1) with 4,4′-methylene-bis(4-phenylisocyanate) (MDI) (2) was performed under microwave irradiation, as well as solution polymerization under graduate heating and reflux conditions. The optimized polymerization conditions for each method were performed with tolylene-2,4-diisocyanate (TDI) (3), hexamethylene diisocyanate (HDI) (4), and isophorone diisocyanate (IPDI) (5) to produce optically active poly(amide–imide)s via diisocyanate route. The resulting polymers have inherent viscosities in the range of 0.02–1.10 dL/g. Decomposition temperatures for 5% weight loss (T5) occurred above 300 °C (by TGA) in nitrogen atmospheres. These polymers are optically active, thermally stable and soluble in amide-type solvents. Some structural characterization and physical properties of this new optically active poly(amide–imide)s are reported.