Synthesis of poly(succinimide) by bulk polycondensation ofL-aspartic acid with an acid catalyst

The bulk polycondensation of L-aspartic acid (ASP) with an acid catalyst under batch and continuous conditions was established as a preparative method for producing poly(succinimide) (PSI). Although sulfuric acid, p-toluenesulfonic acid, and methanesulfonic acid were effective at producing PSI in a high conversion of ASP, o-phosphoric acid was the most suitable catalyst for yielding PSI with a high weight-average molecular weight (Mw) in a quantitative conversion; that is, the Mw value was 24,000. For the continuous process using a twin-screw extruder at 3.0 kg · h−1 of the ASP feed rate, the conversion was greater than 99%, and the Mw value was 23,000 for the polycondensation with 10 wt % o-phosphoric acid at 260°C. Sodium polyaspartate (PASP-Na) originating from the acid-catalyzed polycondensation exhibited high biodegradability and calcium-ion-chelating ability. The total organic carbon value was 86 ∼ 88%, and 100 g of PASP-Na chelated with 5.5 ∼ 5.6 g of calcium ion, which was similar to the value for PASP-Na from the acid-catalyzed polycondensation with a mixed solvent © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 117–122, 2000