Decomposition of poly(amidoamine) (PAMAM) dendrimers under O2 plasma conditions

Results of FTIR and XPS measurements of bulk and γ-Al2O3-supported fourth generation hydroxyl-terminated (G4OH) poly(amidoamine) (PAMAM) dendrimers during O2 plasma treatment at room temperature indicate that such treatment can effectively decompose the structure of the dendrimer. No new functionalities appear in the dendrimer structure during such treatment, but instead fragmentation of this structure is taking place. The dendrimer backbone likely disintegrates into small molecules (i.e., NOx, CO, CO2) which in the case of the supported dendrimers interact with the γ-Al2O3 support and form surface nitrate and carboxy species. Subsequent treatment in H2 at 300 °C leads to the complete removal of the nitrogen-containing species from the surface of γ-Al2O3. However, carbon-containing species still remain on the surface in relatively small amounts. Finally, XRD measurements further show that the crystallinity of the support is not affected substantially by the O2 plasma treatment.