Aqueous dispersions of cross-linked poly-N-vinylcaprolactam stabilized with hydrophobically modified polyacrylamide: synthesis, colloidal stability, and thermosensitive properties

Temperature-responsive nanoparticles of cross-linked poly-N-vinylcaprolactam (microgels), stabilized by high molecular weight emulsifier-monohelic hydrophobically modified polyacrylamide-have been synthesized in oil-in-water emulsion. Nanodispersions of spherical particles of about 100 nm in size rather narrowly distributed as defined by dynamic light scattering and TEM and AFM microscopy were stable in time. Electrokinetic potential, which depended on pH, revealed negative charges on nanoparticle surface arisen from hydrolysis of amide groups of polymer-stabilizer. Due to electrosterical stabilization caused by the adsorption of weakly charged polymeric stabilizer, the prepared dispersions exhibited higher stability against an action of electrolytes as compared with sols stabilized with low molecular weight surfactants. The prepared microgels exhibited high stability at high temperatures.