Microwave‐assisted synthesis of polyaspartic acid and its effect on calcium carbonate precipitate

Without organic solvent or catalyst, polyaspartic acid (PASP) was synthesized from maleic anhydride (MA) and ammonia (AN) under microwave irradiation. The influences of the molar ratio of maleic anhydride to ammonia and the microwave output power and irradiation time on product yield were investigated. Also, the function of microwave in the process was simply addressed. The results showed that when the molar ratio of MA/AN was 1.2, the output power was 900 W, the irradiation time was 3.5 min, and the product yield was highest and its inhibition performance on calcium carbonate was as good as the polymer synthesized by conventional pyrocondensation polymerization. The main function of microwave was its heat effect. Characterization of the product was carried out by IR, ¹HNMR, and ¹³CNMR spectra and the results showed that the product was PASP. The microwave‐assisted synthesis process of PASP has many advantages, including quicker reaction rate, high purity, lower cost, and little pollution. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:358–364, 2007