Preparation and characterization of carboxymethyl polyvinyl alcohol-graphite nanosheet composites

Carboxymethyl polyvinyl alcohol (CMPVA) was prepared by introducing carboxymethyl groups to polyvinyl alcohol (PVA) with chloroacetic acid. Graphite nanosheets (NanoG) were obtained by treating expandable graphite at a high temperature in a muffle furnace, and then sonicating it in an aqueous ethyl alcohol solution. Nanocomposites of CMPVA with NanoG were prepared by dispersing NanoG in a CMPVA aqueous solution with the aid of sonication and then casted on plastic film to remove water. Carboxymethyl groups were proved to be linked to PVA by Fourier transform infrared (FTIR) spectra and the degree of carboxymethyl substitution on the PVA was 2.77% determined by conductometric titration. Experimental results show that carboxylate anions in introduced carboxymethyl groups facilitate the dispersal of NanoG with positive charges in the CMPVA solution. The CMPVA matrix was detected by X-ray diffraction (XRD) and FTIR spectra to be less crystal, into which NanoG tend to disperse. Scanning electron microscopy was used to characterize the structure of the graphite and morphology of the composites to prove that NanoG was 40-70 nm thick. The percolation threshold of CMPVA/NanoG composites at room temperature was as low as 0.80 wt%.