Starch films plasticized by imidazolium-based ionic liquids: effect of mono- and dicationic structures and different anions

Recently, imidazole-based ionic liquids have been widely used as starch plasticizers. These salts are very effective in transforming starch, a widely available and inexpensive biopolymer, into biodegradable films with good mechanical properties and ionic conductivity. These films could have interesting applications in flexible electronics and solid polymer electrolytes. Since a wide variety of cation–anion combinations can be used, it is useful to evaluate the impact of different anion and cation structures on the properties of plasticized starch to select the most suitable ionic liquid for each specific application. In this work, starch films plasticized with imidazolium-based ionic liquids were prepared by the solution casting method. 1-Ethyl-3-methyl imidazolium was chosen as a cation and the effect of different anions such as [SO4Et]−, [N(CN)2]−, [OAc]−, and [Cl]− on the film properties was investigated. In addition, a dicationic structure, consisting of two closely bonded imidazolium rings, was also considered. The characteristics of the corresponding starch-based films were analyzed and compared with those of films prepared with monocationic ionic liquids.