Postadsorption rearrangements of block copolymer micelles at the solid/liquid interface

The influence of postadsorption relaxation processes has been evaluated in the adsorption behavior of block copolymer micelles comprised of asymmetric poly(tert-butylstyrene-b-sodium 4-styrenesulfonate) (PtBS-NaPSS) diblock copolymers as well as star-block copolymers of similar size and composition. The adsorptions were conducted from aqueous solutions to an uncharged, hydrophobic octadecyltrichlorosilane (OTS) surface, which is highly selective for the hydrophobic PtBS block. The star-block copolymer adsorption kinetics scale linearly with concentration over the entire adsorption process and follow behavior characteristic of random sequential adsorption (RSA). At long times, the star-blocks approach a jamming limit with t(-1/2) kinetics. The micelles, in contrast, show no sign of a jamming limit and adsorb according to log(t) kinetics, signifying that the adsorbed layer is able to relax during the adsorption process. Furthermore, the rate of adsorption of the micelles scales nonlinearly with concentration at long times, indicating that the time scale of this relaxation is on the same order of magnitude as the characteristic adsorption time.