(578f) Super Gas Barrier of All-Polymer Layer-by-Layer Assemblies

Super Gas Barrier of All-Polymer
Layer-by-Layer Assemblies

Layer-by-layer
assembly of cationic branched polyethylenimine
(PEI) and
anionic poly (acrylic acid) (PAA) was investigated with regard to pH of each
polymer solution during deposition. Thickness and surface roughness can be
altered dramatically due to the pH-responsive morphology of PEI and PAA (from
90 nm to 4.74 mm for 30-bilayer films). Crosslinking these films
with glutaraldehyde (GA) creates an inhibition of polymer interdiffusion,
causing exponential film growth to be reset.  The oxygen permeability was
improved by increasing the number of PEI/PAA bilayers. P_O2 of an
8-bilayer, glutaraldehyde-crosslinked PEI/PAA film (305 nm thick) is below
3.2×10^-21 cm³·cm/cm²·s·Pa, which is believed
to be the lowest permeability of an all-polymer system ever reported. Tremendous
PEI/PAA interfaces result in a scrambled egg structure with a high gas barrier,
so this relatively simple recipe may be of use for a variety of applications,
including polymeric membranes, flexible electronics, and food packaging.