KINETICS OF COMPETITIVE ADSORPTION OF POLYSTYRENE CHAINS AT A POROUS SILICA SURFACE

Kinetic studies of individual adsorption of homodisperse polystyrenes (PS), polydisperse PS, and binary mixtures of homodisperse PS at a porous silica surface were performed as a function of polymer concentration under theta solvent conditions. When a PS chain is easily penetrated into the pores in the silica surfaces, the time to attain an equilibrium state was less than 10 h, whereas for the larger PS that is forced to penetrate into the pores with much deformation, an adsorption equilibrium time of 35 h was attained. For adsorption of the binary mixture of the homodisperse PS at higher initial concentration the small PS was preferentially adsorbed over the large PS at the early adsorption stage and with an increase in adsorption time the large PS adsorbed more than the small PS, and finally an equilibrium adsorption was attained within 35 h. Adsorption of the polydisperse PS was monitored by GPC chromatograms of PS in the supernatant for before and after adsorption. The adsorption rate at the early adsorption stage was faster than the binary mixture due to the continuous molecular weight distribution and the middle portions in the polydisperse PS were finally adsorbed more.