Dissolution of Starch with Aqueous Ionic Liquid under Ambient Conditions

With increased awareness of global sustainability, there has been growing interest in the preparation of materials from natural, eco-friendly polymers (i.e., biopolymers). Nonetheless, despite their enormous application potential, biopolymers (starch, etc.) have a native semicrystalline structure with strong hydrogen bonding, and require use of solvents to improve their processability. However, the dissolution/processing of natural biopolymers such as starch often requires heating and thus significant energy input. Herein, we report an aqueous ionic liquid for fast and facile dissolution of starch, a typical semicrystalline natural polymer, under ambient conditions. The ionic liquid used is 1-ethyl-3-methylimidazolium acetate ([C₂mim][OAc]). In particular, it is revealed that 0.15:1 mol/mol [C₂mim][OAc]:water mixture disintegrates the sophisticated granule structure of native starch without apparently decreasing the molecular mass within 1 h at room temperature (i.e., 28 °C). In addition, this process did not result in any undesired derivatization. The discovery of this phenomenon could provide guidance for rationally designing “green” processes for chemical and biological engineering for the utilization of promising natural biopolymers.