Preparation of organically dispersible graphene nanosheet powders through a lyophilization method and their poly(lactic acid) composites

Solvent-free graphene nanosheets (GNSs), which are in the form of chemically reduced graphite oxide nanosheets, were prepared using an environmentally friendly freeze drying process. Compared with those produced through the vacuum filtration method, the lyophilized GNS powders were extremely light, loosely packed and could be readily redispersed in appropriate organic media like N,N-dimethylformamide as individual sheets with the aid of sonication. The ability of the as-lyophilized GNS powders to be redispersed in organic solvents facilitates their incorporation into polymers like poly(lactic acid) through a solution-based processing method. In the resulting composite, GNSs were uniformly dispersed in the matrix and enhanced the mechanical and thermal properties of the host polymer, suggesting the great potential of the lyophilized GNS powders in the field of polymer composites.