Influence of polymeric counter-ions on the Langmuir- and LB-film stability of amphiphilic 1,3,4-oxadiazoles

The effect of the polyelectrolyte complexation of an amphiphilic diphenyl-1,3,4-oxadiazole with a carboxylic head group is studied experimentally as a function of the polyelectrolyte concentration and of the subphase pH. The surface pressure–area isotherms, surface potential kinetics and Brewster angle microscopy images are used in order to gain insight into the influence of the polyelectrolyte complexation on the structural evolution of the Langmuir film, as well as its time stability. After polyelectroyte complexation, a reproducible Langmuir–Blodgett (LB-) deposition of well ordered Y-type films proved to be possible. The structure of these films was investigated by means of X-ray specular reflectivity (XSR) and scanning force microscopy (SFM) measurements. The influence of the polyelectrolyte concentration and of the subphase pH on structure and stability of the oxadiazole Langmuir films is studied.