COMPETITION BETWEEN MICELLIZATION AND ADSORPTION OF DIBLOCK COPOLYMERS IN A COLLOIDAL SYSTEM

Significant adsorption of polystyrene-poly(ethylene oxide) (PS-PEO) di block copolymers onto PS latex particles in an aqueous dispersion is a ccomplished through suppression of micelle formation by adding tetrahy drofuran (THF) as a cosolvent. We add THF, a good solvent for the mice lle core, to weaken the micelle and allow free chains for adsorption t o the colloidal particles. Choosing a PS colloidal particle as the ads orption substrate (thus the adsorbed PS block can fully wet the subsur face), we eliminate the complications which arise from micelle formati on on the colloidal surface. Since the PS particles swell in the mixed solvent, the adsorbed PS block may penetrate into the swollen latex c ore, which is favored for entropic reasons. A subsequent water quench of the system to a low THF solution shrinks the PS particle to its ori ginal size while retaining most of the adsorbed polymers. The adsorbed chains cannot be removed by adding surfactants or raising temperature to 90 degrees C, indicating that the adsorbed layer is tightly attach ed to the surface due to kinetic hinderance of the chains in a confine d environment. Neutron scattering experiments is being carried out to settle whether the PS penetrates the PS particle. (C) 1995 John Wiley & Sons, Inc.