Graphene oxide and base-washed graphene oxide as reinforcements in PMMA nanocomposites

摘要

Graphene oxide (GO) prepared using the Hummers' method is known to be composed of functionalized graphene sheets decorated by strongly-bound oxidative debris that can be removed by a simple base wash. The use of as-made GO and base-washed GO as reinforcing fillers in poly(methyl methacrylate) (PMMA) nanocomposites has been compared through dynamic mechanical thermal analysis and tensile testing. Nanocomposites with loadings from 0.5 to 10 wt.% were produced by melt mixing using a twin screw extruder. Large shifts in the values of T_g for the nanocomposites with respect to PMMA suggest the presence of interactions between the GO and polymer. Thermogravimetric analysis also revealed a significant increase in the decomposition temperatures upon the addition of the GO. Optimal loadings of 1 wt.% were found for both fillers, up to which substantial mechanical reinforcement was observed. Comparison with previous nanotube systems, suggests that there was a good dispersion of both fillers below 1 wt.%, with aggregation and a deterioration of the mechanical properties occurring at higher loadings. Stressinduced shifts of the Raman D band in the GO revealed the existence of stress-transfer from the PMMA matrix to the fillers during deformation. Overall the as-made GO gave nanocomposites with better properties than those reinforced with based-washed material. Hence, it appears that the presence of the oxidative debris in GO, which acts as a compatibilising surfactant, is beneficial in producing nanocomposites with both a good dispersion and a strong interface between GO and a polymer matrix.