ABSTRACT
In an effort to reduce deposition time and number of layers needed to achieve high gas barrier, multilayer films were deposited using 1 s exposures for the first four bilayers (BLs) and 1 min for subsequent dips. Thin-film assemblies of polyethylenimine (PEI) and poly(acrylic acid) (PAA) were deposited onto poly(ethylene terephthalate) [PET] using the layer-by-layer deposition process. Varying the exposure time of PET to polyelectrolyte solutions (i.e., dip time) significantly alters the growth rate of the multilayer thin films. The PEI/PAA system grows linearly with 1 s dip times and exponentially with longer times. Eight bilayers (650 nm) were required to achieve an undetectable oxygen transmission rate (<0.005 cm3/(m2·day)) using 1 min deposition steps, but this barrier was obtained with only 6 BLs (552 nm) using 1s deposition of the initial layers, reducing total deposition time by 73%. This "shift-time" concept makes layer-by-layer assembly much faster and more commercially feasible.
