Gas Barrier Film with a Compositional Gradient Interface Prepared by Plasma Modification of an Organic/Inorganic Hybrid Sol-Gel Coat

A high-performance gas barrier film has been prepared using a simple oxygen plasma treatment of an organic/inorganic hybrid sol-gel coat on a poly(ether sulfone) substrate. The gas barrier layer formed from the plasma treatment was an inorganic silicon oxide (SiOx) having a compositional gradient interface with the sol-gel coat, where the chemical compositions changed gradually from inorganic to organic structure at the interface. The minimum attained oxygen transmission rate (OTR) of the gas barrier layer was 0.2 cm(3)/(m(2) day), which is superior or comparable to that of the gas barrier layer prepared by plasma-enhanced chemical vapor deposition (PECVD) or sputtering. Low-temperature oxygen plasma combustion of alkyl groups existing in the sol-gel coat is considered to be the major reaction for the formation of the SiOx gas barrier layer, where oxygenated carbon compounds and hydrogen were the main volatile components as verified by the analysis of optical emission spectroscopy. Plasma treatment time necessary to attain a high-performance SiOx gas barrier layer decreased with increasing R F plasma power. In a dynamic bending test, the gas barrier film preserved the initial gas barrier properties without any formation of film cracks or delamination. The compositional gradient at the interface between the gas barrier and the sol-gel coat is considered to provide a stress-relieving effect at the interface.