Thionyl Chloride/Pyridine System as a Condensing Agent for the Polyesterification Reaction of N,N′-(4,4′-oxydiphthaloyl)-bis-L-leucine and Aromatic Diols

N,N′-(4,4′- Oxydiphthaloyl)-bis-L-leucine (4) was prepared as an aliphatic optically active diacid monomer from treatment of 4,4′-oxydiphthalic anhydride (1) with L-leucine (2). The direct polyesterification reaction of this diacid with several commercially available aromatic diols was performed in a system of thionyl chloride and pyridine (Py). Polycondensation was carried out by varying the initial reaction time of thionyl chloride, Py, and diacid (aging time), the reaction temperature, and the time of heating. A series of optically active poly(ester-imide)s (PEI)s were obtained in high yield and inherent viscosities under optimum conditions. All of the above polymers were fully characterized by 1HNMR, FTIR, elemental analysis and specific rotation techniques. Some structural characterization and physical properties of these optically active PEIs are reported. The resulting PEIs show good solubility and thermal stability.