Electric field induced switching of poly(ethylene glycol) terminated self-assembled monolayers: a parallel molecular dynamics simulation.

Effects of electric field on the structure of poly(ethylene glycol) (PEG) terminated alkanethiol self-assembled monolayer (SAM) on gold have been studied using parallel molecular dynamics method. An applied electric field triggers a conformational transition from all-trans to a mostly gauche conformation. The polarity of the electric field has a significant effect on the surface structure of PEG leading to a profound effect on the hydrophilicity of the surface. The electric field applied antiparallel to the surface normal causes a reversible transition to an ordered state in which the oxygen atoms are exposed. On the other hand, an electric field applied in a direction parallel to the surface normal introduces considerable disorder in the system and the oxygen atoms are buried inside. The parallel field affects the overall tilt structure of SAMs more adversely than the antiparallel field.