  Successful ways of fully exploiting the excellent structural and
multifunctional performance of graphene and related materials are of great
scientific and technological interest. New opportunities are provided by the
fabrication of a novel class of nanocomposites with a nanolaminate
architecture. In this work, by using the iterative lift-off/float-on process
combined with wet depositions, we incorporated cm-size graphene monolayers
produced via Chemical Vapour Deposition into a poly (methyl methacrylate)
(PMMA) matrix with a controlled, alternate-layered structure. The produced
nanolaminate shows a significant improvement in mechanical properties, with
enhanced stiffness, strength and toughness, with the addition of only 0.06 vol%
of graphene. Furthermore, oxygen and carbon dioxide permeability measurements
performed at different relative humidity levels, reveal that the addition of
graphene leads to significant reduction of permeability, compared to neat PMMA.
Overall, we demonstrate that the produced graphene-PMMA nanolaminate surpasses,
in terms of gas barrier properties, the traditional discontinuous
graphene-particle composites with a similar filler content. Moreover, we found
that the gas permeability through the nanocomposites departs from a monotonic
decrease as a function of relative humidity, which is instead evident in the
case of the pure PMMA nanolaminate. This work suggests the possible use of
Chemical Vapour Deposition graphene-polymer nanolaminates as a flexible gas
barrier, thus enlarging the spectrum of applications for this novel material.
