Microwave-promoted synthesis of new optically active poly(ester-imide)s derived from N,N′-(pyromellitoyl)-bis-L-leucine diacid chloride and aromatic diols

Pyromellitic dianhydride (benzene-1,2,4,5-tetracarboxylic dianhydride) (1) was reacted with L-leucine (2) in a mixture of acetic acid and pyridine (3:2) and the resulting imide-acid [N,N'-(pyromellitoyl)-bis-L-leucine diacid] (4) was obtained in quantitative yield. The compound (4) was converted to the N,N'-(pyromellitoyl)-bis-L-leucine diacid chloride (5) by reaction with thionyl chloride. A new facile and rapid polycondensation reaction of this diacid chloride (5) with several aromatic diols such as phenol phthalein (6a), bisphenol-A (6b), 4,4'-hydroquinone (6c), 1,8-dihydroxyanthraquinone (6d), 1,5-dihydroxy naphthalene (6e), 4,4-dihydroxy biphenyl (6f), and 2,4-dihydroxyacetophenone (6g) 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 10 min, producing a series of optically active poly(ester-imide)s (PEIs) with good yield and moderate inherent viscosity of 0.10-0.27 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 PEIs are reported. (C) 2003 Elsevier Ltd. All rights reserved.