Adsorption energies of single charged polymers

We peel off cationic and anionic polyelectrolytes from different substrates (cationic, hydrophobic and metallic) with the atomic force microscope (AFM). By varying the salt concentration, the measured plateau forces can be separated into electrostatic and non-electrostatic contributions to the adsorption energy. Surprisingly, i) the non-electrostatic contribution dominates even for highly charged substrates, and ii) hydrophobic substrates act like negatively charged surfaces. In the theoretical modeling the surface-induced charge regulation of the polymers has to be included.