Abstract
Although self-assembled monolayers of oligo(ethylene glycol)-terminated alkanethiols (OEG-SAM) is widely known as a model system of bioinert surfaces, the underlying mechanism has not been clear. In this work, the interactions between the OEG-SAMs in water were explored with an atomic force microscope (AFM). We found that repulsion operates between the OEG-SAMs even at high ion concentrations and that the decay length of the repulsion is too large to be interpreted with the conventional DLVO theory. Disappearance of the repulsion in mixture of ethanol and water strongly indicates that the repulsion is attributed to the force induced by a water layer in vicinity of the OEG-SAM. In this review, we discuss the interfacial behavior of water molecules near the OEG-SAM with combining our findings and recent reports from other research groups.
