A rapid microwave-induced synthesis of polyamides–containing amino acid moieties

Abstract

5-(2-(9,10-Dihydro-9,10-ethanoanthracene-11,12-dicarboximido)propanoylamino)isophthalic acid as a novel aromatic dicarboxylic acid monomer was prepared in four steps. In the first step, cis-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid anhydride was reacted with l-alanine in acetic acid solution and the resulting imide acid was obtained in high yield. In the second step, treatment of this imide acid with excess thionyl chloride gave acid chloride in good yield. In the last step, this acid chloride was reacted with 5-aminoisophthalic acid to provide novel bulky chiral aromatic dicarboxylic acid. The direct polycondensation reactions of this diacid with several aromatic diamines were carried out under microwave irradiation. In order to compare this technique with classical heating, the polymerization reactions were also performed under solution polycondensation conditions. The polymerization reactions occurred rapidly under microwave conditions and produced a series of novel optically active polyamides (PAs)–containing pendent 9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido)propanoylamino group, with good yields and moderate inherent viscosities of 0.27–0.47 dL g−1. The resulting new PAs showed good solubility and are readily soluble in organic solvents. PAs were thermally stable, with 10% weight loss recorded at 411°C and 450°C under nitrogen atmosphere and char yields at 800°C higher than 44% and glass transition temperature above 163°C.