Synthesis and properties of thermoplastic starch laurates

Abstract Maize starch was allowed to react homogeneously in N,N-dimethylacetamide (DMAc)/LiCl with lauric acid activated with 4-toluenesulfonyl chloride, N,N′-dicyclohexylcarbodiimide/4-(1-pyrrolidinyl)pyridine, 1,1′-carbonyldiimidazole, and N,N-dimethylformamide (DMF) combined with oxalyl chloride. Characterization of the products by means of 13C NMR spectroscopy revealed different substitution patterns depending on the activation agent. The activation of lauric acid with DMF in combination with oxalyl chloride gave starch laurates of highest degree of substitution (DS), yield and reaction efficiency. The melting temperatures and the solubility of the thermoplastic starch laurates were found to depend on the DS, the substitution pattern, and on the molar mass of the starch esters.