Microwave Step-Growth Polymerization of 5-(4-methyl-2-phthalimidylpentanoylamino)-isophthalic acid with Different Diisocyanates.
The utilization of microwave energy in polymer synthesis is a fast growing field of research leading to a more rapid and cleaner polymerization process. In order to synthesize novel optically active monomer 5-(4-methyl-2-phthalimidylpentanoylamino)isophthalic acid (6), the reaction of phthalic anhydride with l-leucine was carried out in an acetic acid solution and 4-methyl-2-phthalimidylpentanoic acid as an imide acid was obtained in good yield. Then, it was converted to 4-methyl-2-phthalimidylpentanoyl chloride by treatment with thionyl chloride. This acid chloride was reacted with 5-aminoisophthalic acid and the novel bulky aromatic amide-imide chiral monomer 6 was obtained in high yield and was characterized with spectroscopy techniques as well as specific rotation and elemental analysis. Polycondensation of monomer 6 with different diisocyanates such as 4,4′-methylenebis(phenyl isocyanate), toluene-2,4-diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate was performed by two different methods: microwave irradiation and classical heating polymerization techniques in the presence of various catalysts and without a catalyst. The microwave polymerization technique provides a new way for the production of polymers at high rates. The resulting novel optically active polyamides have inherent viscosities in the range of 0.25–0.63 dl/g. They show good thermal stability and are soluble in amide-type solvents. The obtained polyamides were characterized by FT-IR, 1H-NMR spectroscopy, elemental analyses, specific rotation, and thermal analyses methods. Copyright © 2008 John Wiley & Sons, Ltd.