(649h) Influence of Charge Fraction on Transport of Penetrants through Polyelectrolyte Brushes

Polyelectrolyte brushes attached to planar surfaces have found applications as highly tunable stimuli-responsive coatings with application in separations. While the effects of charge fraction (f) on polyelectrolyte brush swelling properties have been studied extensively, the interactions with charged and uncharged penetrants have received far less attention. Here we investigate the effects of polyelectrolyte charge fraction on the dynamics of tracer penetrants in brushes using novel super-resolution single molecule microscopy techniques. Brushes are produced on silicon and fused silica surfaces using surface-initiated copper(0) controlled radical polymerization (SI-CuCRP) and fully characterized with size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. Polymers consist of 2-(dimethylamino)ethyl acrylate (DMAEA) and acrylic acid (AA), which are weakly charged, positive and negative electrolytes, respectively. Charge fraction is controlled by mixing n-butyl acrylate (nBA) monomers at different ratios, from fully charged brushes (f = 1) to neutral brushes (f = 0), enabling a full picture of charge effects on dynamics. The particle interactions with brush layers are heterogenous by nature, and due to geometrical limitations of flat surfaces, it is impossible to study them by conventional bulk rheology techniques. To overcome this challenge, we use single molecule microscopy to track motion of single tracer penetrants close to or within the brush layer, giving us insight on the dynamical modes and interactions of penetrants with a polyelectrolyte brush layer. By coupling the single particle tracking data with the fully characterized brushes, we gain an unprecedented understanding of charged brush interactions with penetrants, which is vital for designing more efficient separation processes.