Preparation and characterization of polystyrene–poly(p-acetoxystyrene) and polystyrene–poly(p-vinylphenol) composite latex particles

Polystyrene-core poly(p-vinylphenol)-shell (PS–PVPh) latexes were prepared by the hydrolysis of polystyrene-core poly(p-acetoxystyrene)-shell (PS–PAS) latexes. Polymerization conditions required for uniform core/shell structures were identified. The latexes were made by surfactant-free aqueous emulsion polymerization which gave stable latexes and uniform particle size distributions. It was necessary to use divinylbenzene in the second stage of PS–PAS polymerization to prevent dissolution and removal of poly(p-vinylphenol) during hydrolysis. Infrared spectroscopy, dynamic light scattering, electron microscopy, potentiometric and conductometric titration, disc centrifugation and electrophoresis were used to elucidate the structure of the shell layer. After hydrolysis, the PVPh shell contained approximately 59% water for 20% divinylbenzene crosslinker and 76% water for 1% crosslinker. Cleaned core-shell particles bore sufficient negative charge to render the particles electrostatically stable over a wide pH range. Phenolic groups in the particle shell region dissociated in the pH range 10 to above 11.5.