Reduced graphene oxide as water, carbon dioxide and oxygen barrier in plasticized poly(vinyl chloride) films

RGO films prepared by chemical reduction of graphene oxide (GO) with hydroiodic acid [1] were sandwiched as a barrier layer in 400 µm thick plasticized PVC films (RGO-PVC) being the main constituent in ion-selective membranes used in potentiometric solid-contact ion-selective electrodes (SCISE). [2-4] We report here that the 10 µm thick RGO barrier efficiently impedes the diffusion of liquid water, CO2 and O2 through plasticized PVC.

FTIR-ATR and oxygen transmission rate (OTR) measurements reveal that the embedded RGO barrier completely blocks the CO2 diffusion, while it fully blocks the water diffusion for 16 h and reduces the OTR in average by 85% [2]. These are all causing potential instability and irreproducibility of the SCISEs forming the main obstacle for their commercialization. The FTIR-ATR technique measures water and CO2 on the backside of the polymer film (Fig. 1) by observing changes occurring in the vibrational intensity of the OH stretching bands of water at ca. 3000-3700 cm-1 [5] and CO2 at ca. 2335/2365 cm-1. The FTIR-ATR spectroscopy has been previously used to determine the water uptake in polymers (e.g. PMMA, PET and PVC) [4], but also for studying the detrimental water layer formation in SCISEs [3-5,7,8].

The µm-thick RGO films used here are easier to handle and incorporate in host polymers, and they form more robust barriers than mono-, few- and multilayer graphene commonly applied as barriers for liquids and gases. Moreover, we show that the FTIR-ATR spectroscopy is a very sensitive and simple technique for studying low levels of water diffusing through RGO and RGO-PVC compared to gravimetric techniques. We have also measured the electrical conductivity and water contact angles of the RGO films and characterized them with Raman spectroscopy, XRD, XPS and SEM.

References
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