Diblockcopolymers of polystyrene and poly(oxyethylene) were adsorbed at the toluene/water interface. The short water soluble poly(ethylene oxide) block anchors the polymer at the interface, whereas the long nonadsorbing Polystyrene block remains in toluene in good solvent conditions. The adsorption layer adopts a brushlike conformation, and the system serves as a model for end-adsorbed polymers. A film balance especially designed for liquid-liquid interfaces allows a compression of the adsorption layer via a movable barrier and allows the control of the anchor density of the polymer. The balance was optimized for optical reflection measurements and enables the simultaneous determination of the surface tension. Ellipsometric measurements reveal that the density of the adsorption layer does not change with compression. However, the thickness of the layer depends linearly on the anchor density. This finding is in reasonable agreement with the prediction of the sca領(lǐng) laws. 組合式多功能橢偏儀