Microwave-assisted synthesis of poly(aspartic acid)

The reactions of poly(aspartic acid) syntheses were carried out in the microwave reactor. The cyclic form obtained, i.e. polysuccinimide [PSI, formula(IV) in Scheme A] was then subjected to alkaline hydrolysis in the presence of NaOH to reach finally the linear form, sodium salt of poly(aspartic acid) (PAspNa) [formula (V) in Scheme A presents its anion]. D,L-aspartic acid being a monomer [formula (III)] was dispersed in propylene carbonate and polimerized without the catalyst at temp. 160―230 °C for 41 min. The polymer obtained was precipitated with non-solvent, filtered and washed first with the same non-solvent and then with distilled water, and dried at room temperature. The effects of weight ratio monomer:solvent and the type of non-solvent on the reaction yield and molecular weight and polydispersity of the product were investigated changing the parameters mentioned.