(-)-Asparagine → Aspartate asparagine

The reaction conditions and procedures of Example 9, for production of copolymers of ammonium aspartate and asparagine from polysuccinimides, were followed with the additional inclusion of crosslinker molecules along with the ammonium hydroxide. Accordingly, a sample of polysuccinimide, preferably comprised of high Mw, linear molecules (e.g. from Example 3), was slurried in water at 20 g in 100 ml water. The slurry was cooled to 2-4° C., by use of a refrigerated recirculating bath and a water-jacketed glass vessel, and precooled, concentrated ammonium hydroxide (twofold excess) was added, keeping the temperature at 2-4° C. The crosslinker, in a cooled solution of ammonium hydroxide, was added to the precooled slurry of polysuccinimide, and the reaction mixture was then stirred for 2 to 4 hours until a complete solution was formed. Water was removed at 80° C. in a forced-air oven, producing a dried product of lightly crosslinked aspartate/asparagine copolymer.