Measurement of contact angles has been performed using aqueous solutio
ns of different pH in order to study the contribution of Bronsted acid
-base interactions to hydrophilicity. Besides paraffin (PF), air and N
H3 plasma treated PF samples have been analyzed. While the contact ang
les measured on the non treated polymer do not depend on the pH of the
test fluids, they vary for the plasma treated PF samples. These varia
tions are interpreted in terms of acid-base interactions with the func
tional groups resulting from the plasma treatment. The surface of the
PF treated in air appears essentially acid while the NH3 plasma leads
to a surface where both basic and acid groups are found. XPS analyses
provide a deeper insight into the chemical nature of these functional
groups.