Ultra thin films of pp-PFM offer highly reactive ester groups throughout the structure of the film that allow for subsequent reactions with amino-group containing reagents. The reactivity of this surface towards simple primary amines was studied in DI-H2O and in PBS using IRRAS and XPS. Plasma-polymerised PFM films are typically characterised by a high roughness. Immersion in aqueous media leads to a smoothening of the surface as was observed using SEM and scanning force microscopy. Chemical reactivity towards primary (1°), secondary (2°) and tertiary (3°) amines was investigated using IRRAS in combination with MC sensors. While IRRAS provided information on the chemistry occurring at the surface, the MC sensors technique gave insights into the surface stress induced by the changes in the chemistry of the polymer film upon reaction. These changes in surface stress were related to reactions occurring either at the liquid-solid interface or within the matrix of the polymer. The reactivity of the pp-PFM towards amines seems to be influenced not only by the chemical structure of the amines but also by their size, which influences the diffusion into the polymer film.