Controlling Electroosmotic Flow in Microchannels with pH-Responsive Polyelectrolyte Multilayers

A polyelectrolyte multilayer coating comprising acrylic acid or imidazole units afforded precise control over the rate and direction of electroosmotic flow within fused silica capillaries. Morphological changes accompanying the pH-induced switching of surface charge were minimized by diluting the pH-responsive polyelectrolyte with permanently charged polymer. Electroosmotic stability over many runs was demonstrated

Ideal Mixing in Polyelectrolyte Complexes and Multilayers: Entropy Driven Assembly

Calorimetry and variable temperature equilibrium doping methods independently show complexation of common polyelectrolytes to be essentially entropy-driven. The complimentary techniques provide enthalpy and free energies of formation or mixing. These findings highlight the importance of polyelectrolyte complexes as ideally mixed polymer blends

Polyelectrolyte Complexes with pH-Tunable Solubility

Polyelectrolyte complexes (PECs) with pH-tunable solubility were formed from a random copolymer of diallyldimethylammonium (DADMA) and acrylic acid (AA) having a net positive charge as polycation and poly(styrenesulfonate) as polyanion. Quasi-soluble PEC nanoparticles could be produced from solutions of exceptionally high polymer concentration by manipulating pH and ionic strength. The aggregation of the PEC nanoparticles, reversible using either changes in salt concentration or pH, exhibited well-defined hysteresis. Dynamic and static light scattering as well as transmission electron microscopy showed well-defined particles produced in the quasi-soluble limit. Viscosity and titration experiments supported a core−shell model for the dispersed nanoparticles and revealed preferential ion pairing of DADMA with sulfonic acid groups over AA units