Facile synthesis of new optically active poly (amide-imide) s derived from N,N'-(pyromellitoyl)-bis-L-leucine diacid chloride and aromatic diamines under microwave irradiation

Abstract

Pyromellitic dianhydride (benzene-1,2,4,5-tetracarboxylic dianhydride) () was reacted with l-leucine () in a mixture of acetic acid and pyridine (3:2) and the resulting imide-acid [N,N^′-(pyromellitoyl)-bis-l-leucine diacid] () was obtained in high yield. The compound () was converted to the N,N^′-(pyromellitoyl)-bis-l-leucine diacid chloride () by reaction with thionyl chloride. A new facile and rapid polycondensation reaction of this diacid chloride () with several aromatic diamines such as 4,4^′-diaminodiphenylsulfone (4,4^′-sulfonyldianiline) (), 4,4^′-diaminodiphenyl methane (), p-phenylenediamine (), m-phenylenediamine (), 2,4-diaminotoluene () and benzidine () was developed by using a domestic microwave oven in the presence of a small amount of a polar organic medium such as o-cresol. The polymerization reactions proceeded rapidly and are completed within 12 min, producing a series of optically active poly(amide–imide)s with good yield and moderate inherent viscosity of 0.28–0.46 dl/g. All of the above polymers were fully characterized by IR, elemental analyses and specific rotation. Some structural characterization and physical properties of these optically active poly(amide–imide)s are reported