Abstract
Dispersion of graphene and related materials in water is needed to enable sustainable processing of these 2D materials. In this work, we demonstrate the capability of branched polyethylenimine (BPEI) and polyacrylic acid (PAA) to stabilize reduced graphite oxide (rGO) dispersions in water. Atomic force microscopy colloidal probe measurements were carried out to investigate the interaction mechanisms between rGO and the polyelectrolytes (PEs). Our results show that for positive PEs, the interaction appears electrostatic, originating from the weak negative charge of graphene in water. For negative PEs, however, van der Waals forces may result in the formation of a PE shell on rGO. The PE-stabilized rGO dispersions were then used for the preparation of coatings to enhance gas barrier properties of polyethylene terephthalate films using the layer-by-layer self-assembly. Ten bilayers of rGOBPEI/rGOPAA resulted in coatings with excellent barrier properties as demonstrated by oxygen transmission rates below detection limits [<0.005 cm3/(m2 day atm)]. The observed excellent performance is ascribed to both the high density of the deposited coating and its efficient stratification. These results can enable the design of highly efficient gas barrier solutions for demanding applications, including oxygen-sensitive pharmaceutical products or flexible electronic devices.
Highlights
In the last 20 years, graphene and graphene-related materials (GRMs) have attracted a lot of attention from both the scientific and industrial communities, due to their fascinating properties such as excellent electrical and thermal conductivity,[1] coupled with outstanding mechanical properties.[2]
The reduced graphite oxide (rGO) nanoplate concentration was evaluated by TGA, following the procedure described in the Characterization section (Figure 1c)
The stability of neat components was first evaluated showing that rGO nanoplates have a negligible weight loss in the considered range of temperatures, while polyacrylic acid (PAA) and branched polyethylenimine (BPEI) decompose leaving final residues of 13 and
Summary
In the last 20 years, graphene and graphene-related materials (GRMs) have attracted a lot of attention from both the scientific and industrial communities, due to their fascinating properties such as excellent electrical and thermal conductivity,[1] coupled with outstanding mechanical properties.[2]. Protonation of the other PEs in the layer, as previously described.[70] As this process continues, with each deposition step, more BPEI and PAA are adsorbed, resulting in a nonlinear growth of film thickness as a function of deposited layers.[71,72] While both BPEI/PAA and rGOBPEI/rGOPAA display a superlinear growth regime, differences in FT-IR signal growth (Figure 3b) suggest that BPEI/PAA assembly grows thicker than rGOBPEI/rGOPAA at comparable layer numbers This can be ascribed to the presence of rGO partially limiting the diffusion and interpenetration of polymer chains through the assembly, as previously reported in the literature for “exponentially” growing LbL encompassing inorganic sheets.[73]. The inclusion of rGO in the multilayers improves the barrier efficiency of the rGOBPEI/rGOPAA-deposited coatings, yielding a permeability 5 times lower than that of BPEI/PAA coatings under 50% RH conditions (Table S3) Comparing this result with other LbL assemblies (Figure 5d and Table S3), it is clear that the permeability of coatings prepared in this work is well below the previously reported permeability of 10−20 BL coatings of other PE/nanoplate assemblies. A comparison with other high oxygen and water vapor barrier technologies points out that the developed (rGOBPEI/ rGOPAA)[10] coating is capable of competing with some of the best packaging solutions currently applied in practice such as EVOH films, metalized polymer laminates, and SiOx coatings (Table S5).[83]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
