Ionic liquid: A powerful solvent for homogeneous starch–cellulose mixing and making films with tuned morphology

Corn starch and cellulose were mixed in common solvent, ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIMAc). The properties of mixtures in the liquid state (flow, viscosity, miscibility) and of films obtained via wet casting were investigated. No phase separation in mixtures was observed even at high polymer concentration studied (up to 10wt%). Mixture zero-shear rate viscosity plotted as a function of composition followed the mixing law, allowing concluding, in the first approximation, on the absence of any special interactions between the components. Hybrid films from corn starch–cellulose mixtures were obtained by coagulation in water and in ethanol. FT-IR analysis of dry films confirmed the absence of any new bonds formed between the components, and XRD showed a significant decrease of crystallinity. When coagulated in ethanol, starch was trapped in 3D cellulose network; when coagulated in water starch was partially leached out, creating pores and channels. The morphology of freeze-dried wet films showed that pore size can be tuned by altering mixture composition and varying coagulation bath. Wet film water permeability was from 10 to 60 L m−2 s−1 bar−1.