Sulfonate-functionalized polyacrylonitrile-based nanoparticles; synthesis, and conversion to pH-sensitive nanogels

The present paper reports the synthesis of polyacrylonitrile (PAN)-based nanoparticles through soap-free emulsion polymerization (SFEP). Employing different types of co-solvent, as well as ionic commoners, synthesis of pure PAN nanoparticles was unsuccessful. However, when vinyl acetate,or methyl (meth) acrylate was introduced (conc. > 10 mol%), crystallization of PAN was decreased and consequently stable nanoparticles in the size range of 80–250 nm were achieved. Such a co-polymerization not only produced clean and functionalized nanoparticles but also allowed addition of a cross-linker without sacrificing colloidal stability. As a model, the cross-linked poly(acrylonitrile-co-vinyl acetate) nanoparticles were hydrolyzed in alkaline media, which yielded poly(acrylic acid-co-vinyl alcohol) nanogels. The swelling measurement exhibited that the prepared nanogels have a pH-sensitive behavior.