Ionic liquid induces flexibility and thermoplasticity in cellulose film.

It is still challenging to melt-process cellulose. In this paper, we proposed a method for the formation of thermally processable flexible cellulose films via gelation from its solution in ionic liquid (1-butyl-3-methylimidazolium chloride; BMIMCl). Cotton, as a source of cellulose, was dissolved (5 wt%) in BMIMCl and subsequently placed in different amounts of water. The obtained ion gels were dried at 60 °C for 24 h; during drying process, water was removed while BMIMCl was retained. It was found that the amount of retained BMIMCl had a critical role in determining the mechanical properties of the films. It was suspected that the processing conditions altered the degree of crystallinity of cellulose in the films as evidenced by X-ray diffraction measurement. The ionic liquid, i.e., BMIMCl induced the plasticity into the films, so that thermal processability to different shapes became possible.