This work revealed that the interactions between starch, the ionic liquid 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]), and water might contribute to the phase transition (gelatinization, dissolution, or both) of native starch at reduced temperature. Using mixtures of water and [Emim][OAc] at certain ratios (7.2/1 and 10.8/1 mol/mol), both the gelatinization and dissolution of the starch occur competitively, but also in a synergistic manner. At lower [Emim][OAc] concentration (water/[Emim][OAc] molar ratio≥25.0/1), mainly gelatinization occurs which is slightly impeded by the strong interaction between water and [Emim][OAc]; while at higher [Emim][OAc] concentration (water/[Emim][OAc] molar ratio≤2.8/1), the dissolution of starch is the major form of phase transition, possibly restricted by the difficulty of [Emim][OAc] to interact with starch.

The catastrophic impact of petroleum based plastics on our environment has resulted in the development of a new class of biodegradable polymers. Starch is an attractive raw material for biodegradable plastic applications due to its low cost, sustainability and its availability in large quantities. Besides, it can be transformed into thermoplastic material using conventional plastic processing techniques. Despite its attractive potential as a source of biopolymer materials, the use of starch-based plastic products has been restricted to niche markets that do not require high performance applications due to poor mechanical properties and moisture sensitivity of the materials. Starch cannot be thermally processed without water but thermoplastic starch materials developed from water are brittle due to retrogradation. Much research has been devoted to the use of plasticizers other than water. Non-volatile plasticizers such as glycerol, glycol, sorbitol, urea and ammonium derived amines have mainly been used in the plasticization of starch, but due to their high water sensitivity, recent researches have diverted to novel plasticizers, particularly the ionic liquids. Possible explanation for this behaviour is suggested.iv