| Summary: | Nanocomposite films of polybutylene succinate (PBS)/graphene nanoplatelets (GnP) with a GnP content ranging from 0 to 1.35 wt.% were prepared by melt processing. The morphology of both the neat PBS and PBS/GnP nanocomposites were investigated and revealed no significant impact of GnP on the crystalline microstructure. Moisture sorption at 10 °C, 25 °C, and 40 °C were analyzed and modeled using the Guggenheim, Andersen, and De Boer (GAB) equation and Zimm-Lundberg theory, allowing for a phenomenological analysis at the molecular scale. An understanding of the transport sorption properties was proposed by the determination of the molar heat of sorption (Δ<i>H<sub>s</sub></i>), and the activation energy of the diffusion (<i>E<sub>d</sub></i>) of water in the matrix since both solubility and diffusion are thermo-activable properties. Both Δ<i>H<sub>s</sub></i> and <i>E<sub>d</sub></i> showed a good correlation with the water clustering theory at high water activity. Water and dioxygen permeabilities ( and ) were determined as a function of temperature and water activity. and decreased with the addition of a small amount of GnP, regardless of the studied temperature. Moreover, the evolution of as a function of water activity was driven by the solubility process, whereas at a given water activity, was driven by the diffusion process. Activation energies of the permeability (<i>E<sub>p</sub></i>) of water and dioxygen showed a dependency on the nature of the permeant molecule. Finally, from the Δ<i>H<sub>s</sub></i>, <i>E<sub>d</sub></i>, and <i>E<sub>p</sub></i> obtained values, the reduction in water permeability with the addition of a low content of GnP was attributed mainly to a tortuosity effect without diffusive interfaces rather than a significant change in the transport property mechanism.
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