Synthesis of thermoplastic starch mixed esters catalyzed by the in situ generation of imidazolium salts

The concept of using a starch mixed ester to avoid brittleness in starch esters is promising. This paper will present new economical synthesis methods as well as the resulting mechanical properties of different starch mixed esters after thermoplastic processing. The use of imidazole derivatives as precursors to imidazolium salts, also known as ionic liquids, is shown to catalyze the esterification of starch. This simple synthesis pathway allows varying the mechanical properties in starch mixed esters using the substitution pattern. Not only the mechanical properties are unique in comparison of established starch-based materials, but also the water uptake in the resulting material is lower. It can be assumed that the properties of standard plastics are closely matched by these starch mixed esters. 13C NMR spectroscopy, dynamic vapor sorption measurement and tensile tests are applied to examine the noted issues.