Stable pH responsive layer-by-layer assemblies of partially hydrolysed poly(2-ethyl-2-oxazoline) and poly(acrylic...

Polyoxazolines have received increasing attention as low-fouling materials with good stability and ease of functional group incorporation. We investigated layer-by-layer (LbL) assembly of poly(2-ethyl-2-oxazoline) (PEOX) with poly(acrylic acid) (PAA) to incorporate PEOX into thin conformal coatings with controllable thicknesses ranging from the nano- to micron range. Partial hydrolysis of PEOX (to form PEOX-I) was used to introduce secondary amine groups that enable post-assembly multilayer stabilization by heat-induced crosslinking. While as-assembled multilayers dissolve in aqueous solutions at pH 5 and above, thermally crosslinked multilayers were stable against film loss and instead exhibit pH responsive swelling. The anti-fouling properties of crosslinked coatings were assessed by evaluating the resistance of PEOX-I containing multilayers to fouling by proteins, cells and bacteria. Our study of multilayers with thicknesses ranging from ∼12nm to ∼1.5μm revealed thickness dependence of surface fouling resistance to BSA. Crosslinked multilayers of ∼220nm were found to be highly effective in suppressing surface adsorption of bovine serum albumin (BSA), while thinner or thicker layers were increasingly susceptible to BSA adsorption. We further found that coatings of ∼220nm and above were all highly effective at preventing surface attachment of fibroblasts, gram-positive (S. aureus) and gram-negative (E. coli) bacteria.