Ordering pH-Responsive Polyelectrolyte-Grafted Nanoparticles in a Flow Coating Process

The effects of nanoscale interparticle interactions on deposition patterns in the flow coating process are investigated using pH-responsive poly(acrylic acid) (PAA)-grafted silica nanoparticles. Interactions between nanoparticles are effectively controlled by grafting densities, PAA brush lengths and pH, in addition to hydrogen bonding between free poly(vinylpyrrolidone) (PVP) and PAA. Consequently, various intriguing patterns of randomly distributed dots, polygonal networks, meshes, fork-like structures along with highly regulated and densely packed stripes parallel to the moving direction of substrates are fabricated. Per se, the flow coating process is shown to form regulated patterns during evaporation by controlling particle-particle interactions with inherent brush properties and external pH. In addition, we will present the rheology results of these functionalized nanoparticles to correlate their structure-viscosity relationships in solution. Hydrogen bonding capability of free poly(vinyl pyrrolidone) (PVP) chains with the grafted PAA is utilized to obtain intra- and inter-particle crosslinking systems.