NEW CATALYTIC-SYSTEMS FOR THE MANUFACTURE OF POLY(ASPARTIC ACID)

Aspartic acid (I), when heated to a temperature in excess of 180 degre es C, undergoes a solid-state condensation polymerization to afford th e useful polymeric intermediate known as poly(succinimide) (II). Treat ment of poly(succinimide) with aqueous base, such as sodium hydroxide, affords sodium poly(alpha,beta-DL-aspartate) (III) also known as ther mal poly(aspartate) (TPA). Acid catalysts, such as phosphoric acid hav e been added to the aspartic acid to afford higher-molecular-weight po ly(succinimide) than is obtained in the non-catalyzed polymerization. Recently, new sulfur-based catalysts have been disclosed for the polym erization of aspartic acid. The sulfur-containing catalysts provide a route to highly biodegradable, low-color poly(aspartate)s in the molec ular weight range of 2 000 to 20 000. A comparison of biodegradability , molecular weight, and spectral characteristics of the poly(succinimi de)s and poly(aspartate)s derived from the catalyzed and non-catalyzed polymerizations is presented.