Nucleation and growth of gas barrier aluminium oxide on surfaces of poly(ethylene terephthalate) and polypropylene: Effects of the polymer surface properties

The nucleation and initial stages of growth of aluminium oxide deposited on two different polymer surfaces [poly(ethylene terephthalate), (PET) and am orphous polypropylene, (PP)] have been studied by atomic force microscopy ( AFM). The permeation of water vapor and oxygen through the films has been m easured. The initial stages of the growth of the oxide consisted of separat ed islands on the polymer surface. Further growth of oxide depends strongly on the surface morphology and chemical nature of the polymer surface. Grow th on PET follows a layer-by-layer mechanism that maintains the native surf ace roughness of the polymer substrate. Growth on PP, however, follows an i sland mode, which leads to an increase in surface roughness. This may be du e to a lack of chemical bonding between the polymer and the arriving metal- oxygen particles. The oxide layer on PET grows more densely than on PP, pro viding superior barrier to gas permeation. (C) 2000 John Wiley & Sons, Inc.