Dual physically and chemically cross-linked polyelectrolyte nanohydrogels: Compositional and pH-dependent behavior studies

This study describes the composition-property relationship of a dual chemically and physically cross-linked nanohydrogel (NHG) containing a high concentration of hydrophilic pH-sensitive acrylic acid (AA). The physical and chemical cross-linking were incorporated using the aggregation of hydrophobic butyl acrylate (BA) and covalent bond of a bifunctional monomer (ethylene glycol dimethacrylate), respectively. Implementing a direct one-pot semi-batch emulsion polymerization technique in an acidic condition yielded monodispersed (PDI < 0.2) NHGs with a collapsed hydrodynamic radius of 60-100 nm. Titration studies revealed the significant effect of the chemical and physical cross-linking on the amounts of accessible carboxyl groups and their ionization behavior. These NHG dispersions displayed good colloidal stability over a wide pH and duration, the Donnan equilibrium is responsible for the observed swelling behavior of these NHGs.