Microwave-assisted synthesis and characterization of optically active poly (ester-imide)s incorporating l-alanine

Abstract

Pyromellitic dianhydride (1) was reacted with L-alanine (2) to result [N,N′-(pyromellitoyl)-bis-l-alanine diacid] (3). This compound (3) was converted to N,N′-(pyromellitoyl)-bis-l-alanine diacyl chloride (4) by reaction with thionyl chloride. The microwave-assisted polycondensation of this diacyl chloride (4) with polyethyleneglycol-diol (PEG-200) and/or three synthetic aromatic diols furnish a series of new PEIs and Co-PEIs in a laboratory microwave oven (Milestone). The resulting polymers and copolymers have inherent viscosities in the range of 0.31–0.53 dl g⁻¹. These polymers are optically active, thermally stable and soluble in polar aprotic solvents such as DMF, DMSO, NMP, DMAc, and sulfuric acid. All of the above polymers were fully characterized by IR spectroscopy, ¹H NMR spectroscopy, elemental analyses, specific rotation and thermal analyses. Some structural characterizations and physical properties of these optically active PEIs and Co-PEIs have been reported.