AVS 51st International Symposium
    Surface Science Monday Sessions
       Session SS-MoP

Paper SS-MoP16
Thermal Decomposition of Generation 4-Polyamidoamine Dendrimers Films: Decomposition Catalyzed by Dendrimer-Encapsulated Pt Particles

Monday, November 15, 2004, 5:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: O. Ozturk, University of South Carolina
Authors: O. Ozturk, University of South Carolina
T.J. Black, University of South Carolina
F. Parsons, University of South Carolina
K. Pizzolato, University of South Carolina
J.S. Ratliff, University of South Carolina
C.T. Williams, University of South Carolina
D.A. Chen, University of South Carolina
Correspondent: Click to Email
The thermal decomposition of hydroxyl terminated generation-4 polyamidoamine dendrimer (G4 OH) films deposited on Au surfaces has been compared with decomposition of the same dendrimer encapsulating a ~40-atom Pt particle (Pt-G4OH). Infrared spectroscopy studies showed that when the films were heated in air to various temperatures up to 275° C, the disappearance of the amide vibrational modes occurred at lower temperature for the Pt-G4OH film. Dendrimer decomposition was also investigated by thermogravimetric analysis (TGA) in both air and argon atmospheres, and decomposition of the dendrimer films on Au surfaces was studied by temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) under ultrahigh vacuum conditions. For both G4OH and Pt-G4OH films, heating to 100° C resulted mainly in the desorption of small molecules such as H@sub 2@, H@sub 2@O, CO and CO@sub 2@. Heating the G4OH films to 200° C induced the desorption of larger dendrimer fragments around 72, 84, 98, 127, 146 and 261 amu. For the Pt-G4OH films, mass fragments above 98 amu were not observed at any temperature, but much larger intensities for H@sub 2@ desorption were detected compared to that for the G4OH film. XPS studies of the G4OH films demonstrated that nearly all of oxygen and nitrogen atoms were removed from the surface after heating to 450° C. For the Pt-G4OH dendrimer films, most of the oxygen was also removed after heating to 450° C, but there was little decrease in the intensities of the carbon and nitrogen signals. All of these results are consistent with the fact that the Pt particles inside the G4OH dendrimer catalyze thermal decomposition, allowing dendrimer decomposition to occur at lower temperatures. However, the Pt particles also catalyze bond scission within the dendrimer fragments so that greater concentrations of atomic carbon and nitrogen remain on the surface after heating the dendrimer films in vacuum.