AVS 47th International Symposium
    Biomaterial Interfaces Wednesday Sessions
       Session BI-WeA

Paper BI-WeA4
Film Formation of Self-assembled Monolayers of Thiol-modified Polyethylene Glycol on Gold

Wednesday, October 4, 2000, 3:00 pm, Room 202

Session: Non-fouling Surfaces
Presenter: S. Tokumitsu, Universität Heidelberg, Germany
Authors: S. Tokumitsu, Universität Heidelberg, Germany
S. Herrwerth, Universität Heidelberg, Germany
W. Eck, Universität Heidelberg, Germany
M. Himmelhaus, Universität Heidelberg, Germany
M. Grunze, Universität Heidelberg, Germany
Correspondent: Click to Email
The adsorption kinetics of self-assembled monolayer (SAM) of thiol-modified polyethylene glycol (PEG: 2000 dalton) on polycrystalline gold surface in dilute solution has been studied by using ellipsometry, infrared reflection absorption spectroscopy (IRRAS), X-ray photoemission spectroscopy (XPS) and second harmonic generation (SHG). Thickness and structure of the finally obtained layer exhibit strong dependence on the solvent. In-situ SHG monitoring of the headgroup adsorption of PEG from 50 µM DMF solution shows rapid coverage increase up to 44% within the first 10 min of immersion, followed by a slowly proceeding adsorption step. Final coverage is reached after a total immersion time of about 2 hours. On the other hand, ellipsometry reveals that film thickness drastically increases after 1-2 hours of immersion. These results indicate a restructuring of the PEG moiety from an amorphous to a crystalline-like phase at that time. The results for film thickness and structure obtained by in-situ and ex-situ experiments will be discussed in detail and finally a phenomenological model of the adsorption process will be presented.