Thermal Analysis of Aspartic Acid and Its Polymers

Aspartic acid is one of the proteinaceous acidic amino acids, has two carboxyl groups per molecule. Together, these two different carboxyl groups play an important role in thermal reactions. When aspartic acid is heated at elevated temperatures (up to 400 degrees C), it polymerizes to form polyaspartic acid. This reaction does not proceed on heating glutamic acid, which is another acidic amino acid. Present research used both thermal analysis and infrared measurements to examine the heating behaviour of aspartic acid over a given time period. The measurements reveal some aspects of the thermal reaction mechanism. During the heating reactions, amide bonds gradually form and then imide bond formation follows. This work may be useful for clarifying the mechanism of thermal polycondensation of aspartic acid and the structural features of the products.