Ionically Conducting Polymers Based on Ionic Liquid-Plasticized Starch Containing Lithium Chloride
Ionic liquids (ILs) comprising 1-allyl-3-methylimidazolium chloride ([amim]Cl) with certain concentrations of lithium chloride (LiCl), have been used to prepare cast samples of ionically-conducting thermoplastic starch (TPS), with potential applications as solid biopolymer electrolytes. Atomic force microscopy (AFM) found that the diameter of residual starch granules existing in [amim]Cl and glycerol-plasticized starch films was about 10 nm. An increased concentration of LiCl tended to decrease the proportion of residual starch granules and form homogeneous TPS. LiCl also increased the interaction of [amim]Cl with plasticized starch, as detected by Fourier Transform infrared (FT-IR) spectroscopy and dynamic mechanical thermal analysis (DMTA). Thermogravimetric analysis (TGA) indicated that the supramolecular structure of starch was destroyed by [amim]Cl and LiCl. LiCl not only increased the water absorption of TPS, but also improved its electrical conductivity; the latter achieved values as high as 101.0 S cm-1 at 20 wt.% water absorption.