RATE OF ADSORPTION OF DIBLOCK COPOLYMERS FROM MICELLAR SOLUTIONS ON SOLID-LIQUID INTERFACES

We present results relative to the kinetics of adsorption of the diblo ck copolymer poly(vinylpyridine)-polystyrene on silica from toluene so lution using a radiolabeled polymer. The investigations are carried ou t by controlling the rate of the polymer supply to the adsorbent to de termine the kinetic coefficient K(N(s)) as a function of the number of adsorbed copolymers N(s). The bulk concentration N is monitored by co ntrolling either the concentration of the polymer solution injected in to the reactor or the rate of injection. The variation of K(N(s)) vs N (s) is correlated to the decrease in the surface area available to the solute polymer. The first step in the adsorption is purely to fill th e surface by depositing the polymer chains on free surface areas. Over a degree of coverage close to 35%, the adsorption is mainly controlle d by limited surface accessibility and also retarded by the diffusiona l transfer through the dangling polystyrene chains. Experiments carrie d out with copolymers of different size asymmetry ratios show that the relative size of the polystyrene coil anchored at the surface control s this adsorption mechanism. As the solution is composed of unimers an d micelles whose relative concentration is a function of the total cop olymer concentration, this parameter is varied to investigate the char acteristics of the adsorption of unimers and micelles. We determined t hat the two constituents adsorb on the surface in a zigzag conformatio n.