Abstract: Thermoplastic starch-based materials formed as a reactive extrusion product from one or more starches, one or more plasticizers, and micro or nano particles or fibers, with such particles or fibers being added before gelatinization of the starch. A diacid or acid anhydride may also be included. Such components are added and then gelatinized together, before blending of a resulting starch-based polymeric material with any other polymer (e.g., polyester biopolymers, polyolefins, or the like). Addition of such nano or micro particles during synthesis of the thermoplastic starch advantageously results in a far more homogenous distribution of such particles or fibers throughout the starch-based material matrix than occurs where addition of similar particles or fibers is attempted after formation of the thermoplastic starch, e.g., when mixing with a partner resin material. Addition of a diacid during synthesis can reduce molecular weight and viscosity, further aiding in achieving substantially uniform distribution.