Adsorption of polymeric micelles and vesicles on a surface investigated by quartz crystal microbalance

Polystyrene-b-poly(N-isopropylacrylamide) (PS-b-PNIPAM) diblock copolymers either with or without thiol end groups, depending on the relative length of the two blocks, form micelles or vesicles in water. The adsorption of such micelles or vesicles on a gold surface from aqueous solution was investigated in situ at 20 degrees C by use of a quartz crystal microbalance with dissipation monitoring (QCM-D). The changes in frequency (Deltaf) and dissipation (DeltaD) revealed that the micelles and vesicles without thiol groups were intact with some deformation when they were deposited on the surface. On the other hand, the micelles and vesicles with thiol groups at the end of PNIPAM blocks would transform into trilayers due to the strong interaction between thiols and gold surface.