Synthesis and characterization of polyureas derived from 4-aryl-2,6-bis(4-isocyanatophenyl)pyridines

A series of new pyridine-containing diisocyanates bearing bulky aryl groups, 4-aryl-2,6-bis(4-isocyanatophenyl)pyridines (DIC 1−3 ), was successfully synthesized by Weinstock modification of the Curtius rearrangement of the corresponding diacids, 4-aryl-2,6-bis(4-carboxyphenyl)pyridines (DA 1−3 ). These diisocyanates were fully characterized by FT-IR and NMR spectroscopy and were employed to synthesize a series of new polyureas by polycondensation with various aromatic diamines. The best synthetic approach was achieved by synthesis of a model compound via reaction of DIC 1 with aniline in N-methyl 2-pyrrolidone (NMP) and in the presence of a catalytic amount of dibuthyltin dilurate (DBTDL). The synthesized polymers were characterized by 1 H-NMR, FT-IR and elemental analysis, and physical properties, including solubility behavior, viscosity and thermal properties, were also studied. All polymers have an inherent viscosity in the range of 0.4-0.6 g/dl in DMSO at 30°C, which shows that these polymers have a high molecular weight.