Plasticizing Effect of Choline Chloride/urea Eutectic-based Ionic Liquid on Physicochemical Properties of Agarose Films

Agarose films were formed with the addition of 30 to 70 wt% choline chloride/urea eutectic-based ionic liquid (ChCl/Urea). The ChCl/Urea was prepared through complexation at a 1:2 mole ratio. The films were prepared by dissolving ChCl/Urea in distilled water followed by dispersion of the agarose at 95 °C. The solution was gelled at room temperature, and the formed gel was dried in an oven overnight at 70 °C. Mechanical testing indicated that the agarose film containing 60 wt% ChCl/Urea had higher tensile extension and tensile strain at break compared to the pristine agarose film. The addition of ChCl/Urea also reduced the glass transition temperature (Tg) of agarose films. Crosssection SEM images of the agarose films showed that surface roughness disappeared with the incorporation of ChCl/Urea. FTIR spectra confirmed the presence of intermolecular hydrogen bonding between agarose and ChCl/Urea. XRD patterns demonstrated that an amorphous phase was obtained when ChCl/Urea was added. Agarose films containing more ChCl/Urea exhibited higher transparency, as measured by a UV-Vis spectrometer. In summary, the physicochemical properties of agarose films were evidently affected by the incorporation of the ChCl/Urea as a plasticizing agent.