Perfluorophenyl methacrylate (pp-PFM) was plasma-polymerized using low duty cycle conditions to yield a surface rich in active ester groups. The reactivity of this surface towards different primary amines was investigated using infrared reflection absorption spectroscopy (IRRAS) and micromechanical cantilever (MC) sensors. While IRRAS provided information on the chemistry, the MC sensors technique gave insights into volume changes induced by the reactions of the polymer film. We found that the volume change upon reaction was different for each of the amines studied and correlated this to the ability of the amines to diffuse into the polymer matrix. The changes observed can be related to reactions occurring either at the liquid-solid interface or to reactions occurring within the matrix of the polymer and appear to be related to the chemical structure of the amines.