Temperature Effect on the Molecular Weight and the Optical Purity of Anhydropolyaspartic Acid Prepared by Thermal Polycondensation

Anhydroyplyaspartic acid (APAA) was prepared by the thermal polycondensation of l-aspartic acid in the solid state at 160-220 °C for 5 h. The effect of temperature on molecular weight and optical purity of APAA was investigated. The molecular weight increases rapidly in the temperature range 180–200 °C, the yield of APAA also increasing rapidly. The optical purity deecreases rapidly with rise in temperature from 160–180 °C.