Thin film assemblies of branched polyethylenimine (PEI) and poly(acrylic acid) (PAA) were deposited using the layer by layer deposition process. These unique all-polymer thin films have low oxygen permeability after a small number of bilayers. It is shown that varying exposure time to polymer solutions (i.e., dip time) significantly alters the growth rate of the thin films. The PEI/PAA system grows linearly when employing 1 second dip times, but exponentially for longer times. To optimize film thickness, films were deposited using 1 second dips for the first 4 bilayers, and then 1 minute for subsequent dips. This change in deposition time mid-growth increased the growth rate of the 1 minute exposure film, as shown in Figure 1. The thickness of an 8BL film (650 nm) prepared with 1 min dips was achieved with only 6 BL (550 nm) by changing the dip time (both films exhibit OTR below the detection limit of commercial testing equipment). This adjustment in dip time, now dubbed 'shift time', is a major breakthrough for those considering commercial application of layer-by-layer assembly due to the opportunity to deposit fewer layers in a shorter time to achieve the same thickness and performance.          

Maximizing polymer multilayer film growth and gas barrier performance by adjusting exposure time while depositing layers

247th National Meeting (2014)

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