*2.2.1. Biopolymeric films*

The biopolymeric films consisted of a mixture of chitosan and cellulose, prepared by means of the solution casting technique. To prepare the chitosan solution, a fixed concentration of the polymer (1.5 v%) was dissolved in an acetic acid aqueous solution and mechanically stirred. Furthermore, the cellulose solution was made by adding the polymer into a 4-Methylmorpholine N-oxide (NMMO) solvent, followed by mechanical stirring at 65°C to enhance the polymer solubility. A fixed concentration of cellulose, i.e., 0.5 v%, was used for the preparation of the composites. A higher concentration of cellulose would have raised the water content, which could have been detrimental for the resulting electrical, mechanical, and thermal properties.

After the stock solutions of chitosan and cellulose were prepared separately, we readied smaller stock solutions with different volume percentages of chitosan and cellulose: 85 v%Ch-15 v%Cel and 75 v%Ch-25 v%Cel. After mixing the components, we mechanically stirred the solutions, poured them into petri dishes, and let them dry in an oven at 40°C. Afterwards, we removed the films from the petri dishes using a basic solution and dried them in an oven once again [7].
