UV/vis spectroscopic monitoring of polyelectrolyte adsorption onto monolayers of azobenzene amphiphiles

The complexation of an azobenzene-containing carboxylic acid amphiphile wit h a cationic poly(p-phenylene) polyelectrolyte at the air/water interface r esults in changes of the monolayer structure. Compared to the monolayer of the amphiphile on pure water, a more expanded liquidlike structure can be s uggested for the complex monolayer according to the increased area per amph iphilic molecule and Brewster angle microscopy. Furthermore, aggregation of the azobenzene moieties is suppressed in the complex. The differences in t he spectral properties of the pure amphiphile monolayer and the polyelectro lyte complex monolayer due to their different structural order can be emplo yed for investigation of the adsorption process: The adsorption of the poly electrolyte to an already compressed amphiphile monolayer results in struct ural rearrangements and can, therefore, be monitored in situ as a change in the monolayer UV/vis spectra.