Graphene sulphonic acid/chitosan nano biocomposites with tunable mechanical and conductivity properties

Nanocomposites of chitosan are produced using graphene sulphonic acid (SG) at five different compositions and are designated as SG0.5, SG0.75, SG1, SG3 and SG5; the numbers indicate weight percent of SG. The TEM & AFM micrographs indicate that the SG sheets are in exfoliated state. The thermal stability and the storage modulus of the composites increase with increasing SG concentration showing a maximum increase (202%) for SG5 sample. The stresses at break and Young’s modulus have increased with increasing SG content. SG5 shows the highest increase of both tensile strength and Young’s modulus of 290 ± 7% and 200 ± 7%, respectively. Analysis of the Young’s modulus data suggests that SG sheets are randomly distributed and at ≥1 wt% concentration they are unidirectionally oriented parallel to the film. The system exhibits percolation threshold of 0.49 wt% SG and it attains maximum conductivity of 0.13 S m−1 at 1.6 wt% SG.