Weak polyacid brushes: Preparation by LB deposition and optically detectedtitrations

We present a new technique for preparing and characterizing brushes consist ing of weak acidic monomers. The brushes consist of polystyrene-polyacrylic acid block copolymers. The block copolymers are deposited from the air/wat er interface on a hydrophobically modified Si wafer via the Langmuir-Blodge tt technique. The titration of such brushes at low ionic strength is measur ed with reflectometry. It is shown that the titration curve of the grafted PAA is shifted toward higher pH with increasing grafting density, as predic ted by theoretical models for weak acidic brushes.