Focusing on a one-pot heterogeneous process, we synthesized a promising mixed cellulose ester, cardanol-bonded cellulose thermoplastic, with bonding a short side chain (acetyl) and a long one (a derivative of cardanol). In the heterogeneous process, reaction solvents are important factors in the reactivity of long and short side chain moieties on cellulose. Investigating various kinds of solvents, we found that the solvents' affinity for cellulose was an important parameter for the reactivity of long side chain moiety, and the polarity of solvents affected the reaction ratio of long and short chain moieties. Especially, when the middle-basic type of the solvent such as N,N-dimethylformamide or N-methyl-pyrrolidone was used, the obtained thermoplastics had adequate degree of substitutions of long and short chain moieties, and sufficient mechanical properties (50 MPa of bending strength, and 1.4 GPa of bending modulus) to use in durable products such as electric devices in addition to general products. (C) 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license.