Mechanisms of drying of graphene/poly (amide imide) solutions for films with enhanced gas barrier and mechanical as investigated by real time measurement system

• Application of graphene oxide containing soluble polyamide-imide for barrier film applications is reported.
• Graphene oxide reinforced solution cast films exhibit flexibility particularly at high nanoparticle concentrations.
• Increase in graphene-oxide content resulted in reduction on hygroscopicity of DMAc caused by hydrophobic polyamide-imide matrix.
• He permeability of dried hybrid films decreased over 40% even at very small graphene-oxide concentrations.

The drying behavior of polyamide-imide (PAI)/graphene-oxide nanosheets (GO) in dimethylacetamide (DMAc) with and associated anisotropy development were determined using a real-time measurement system that tracks weight loss, thickness, in and out of plane birefringence. Initially optically isotropic cast films develop out of plane optical anisotropy at a critical solvent concentration. For PAI/DMAc solution the decrease of initial casting thickness lead to earlier onset of out of plane birefringence development caused primarily by increased depletion rate of solvent. Addition of GO content resulted in increased evaporation rate caused by reduction of hygroscopicity of DMAc in the presence of GO as shown by contact angle measurements. Planar orientation of nanosheets resulted in excellent helium-barrier properties even at very small GO concentrations.

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