Spin Coating for Forming Thin Composite Coatings of Montmorillonite and Poly(vinyl alcohol)

Montmorillonite (MMT) nanosheets were coassembled with poly­(vinyl alcohol) (PVA) via a spin-coating process. The resulting coating layer, consisting of a multilayered nanocomposite structure, possessed an outstanding barrier property thanks to the highly ordered structure of the MMT nanosheets creating a tortuous path for molecular diffusion. The process of alignment and stacking of MMT nanosheets on a solid substrate is controlled by an array of factors, some of which can be controlled by the coating process. To this end, the suspension concentration and spin speed were varied to determine their impact on the final film quality. The turbidity of the films was quantified using ultraviolet–visible (UV–VIS) spectroscopy. The structure of the nanocoating layers was verified via X-ray diffraction (XRD). Finally, the overall performance of the coatings was tested via oxygen transmission rate (OTR) measurements, which gives an indication of the nanosheet assembly structure. The presence of high centripetal acceleration resulted in high degrees of nanosheet alignment and a high barrier to oxygen transport. This coating technique has unique implications for thin-film vapor barrier technologies such as solar cells, dielectric materials, and biomedical devices.