Dissolution Behavior of Maize Starch in Aqueous IonicLiquids: Effect of Anionic Structure and Water/Ionic Liquid Ratio

摘要

The effect of the anionic structure of ionic liquids (ILs) and water/IL ratio on the dissolution behavior of maize starch at room temperature (22–23 °C) was investigated. The ILs used were 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), 1-ethyl-3-methylimidazolium formate ([C2mim][HCOO]), and 1-ethyl-3-methylimidazolium acetate ([C2mim][CH3COO]). The structural analysis indicated that the long- and short-range molecular order in the starch after treatment with water/[C2mim][Cl] and water/[C2mim][HCOO] mixtures decreased with the decreasing water/IL ratio from 10:1 to 2:1 and was completely disrupted at the 2:1 ratio. However, the ordered structure of starch was disrupted completely in the water/[C2mim][CH3COO] ratio of 5:1. The disruption extent of starch structures followed the order: [C2mim][CH3COO] > [C2mim][HCOO] > [C2mim][Cl] at water/IL ratios of 10:1 and 5:1, but the opposite was observed at lower water/IL ratio (2:1). Our results clearly showed that both the nature of the anion and water/IL ratio affected the dissolution behavior of maize starch. The hydrogen bonding capacityof IL anions and viscosity of water/IL mixtures were proposed to playthe key roles in the structural disruption of starch. These findingswould be of great importance for rationally designing “greenand sustainable” processes for the utilization of promisingnatural biopolymers.