Surface energy modification of graphene oxide film by silanization co-functionalized with fluorine to maximize the moisture barrier property

There is a driving necessity for moisture barrier to be flexible as organic-based optoelectronics such as organic photovoltaic devices and organic light emitting diode display devices are opting towards flexible configuration. Most as-reported researches have been focused on increasing the diffusion path of water molecule by adding filler materials in the polymer matrix to improve the water barrier property. However, the surface energy of the barrier film is also an important factor to determine the water barrier property as it controls the degree of water molecule adsorption on the barrier film surface. Herein, surface energy of the graphene oxide (GO) film was varied from 56.7 mN m−1 to 26.3 mN m−1 by combination of removing hydrophilic functional groups by fluorine-silanization and thermal reduction. Altering the surface energy successfully reduced the water permeability value of the bare GO film from 1.86 × 10−2 g mm m−2 day−1 to 6.31 × 10−3 g mm m−2 day−1 which corresponds to improvement of about 70%. Furthermore, the surface energy and the water permeability value showed the linear correlation indicating that required water permeability value can be easily manipulated by controlling the surface energy of the GO film.