  Due to its exceptionally outstanding electrical, mechanical and thermal
properties, graphene is being explored for a wide array of applications and has
attracted enormous academic and industrial interest. Graphene and its
derivatives have also been considered as promising nanoscale fillers in gas
barrier application of polymer nanocomposites (PNCs). In this review, recent
research and development of the utilization of graphene and its derivatives in
the fabrication of nanocomposites with different polymer matrices for barrier
application are explored. Most synthesis methods of graphene-based PNCs are
covered, including solution and melt mixing, in situ polymerization and
layer-by-layer process. Graphene layers in polymer matrix are able to produce a
tortuous path which works as a barrier structure for gases. A high tortuosity
leads to higher barrier properties and lower permeability of PNCs. The
influence of the intrinsic properties of these fillers (graphene and its
derivatives) and their state of dispersion in polymer matrix on the gas barrier
properties of graphene/PNCs are discussed. Analytical modeling aspects of
barrier performance of graphene/PNCs are also reviewed in detail. We also
discuss and address some of the work on mixed matrix membranes for gas
separation.
