Web Release Date: July 18,
NMR Studies of the Thermal Degradation of a Perfluoropolyether on
the Surfaces of 
-Alumina and Kaolinite
and
Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802
Received February 14, 2007
In Final Form: June 4, 2007
Abstract:
Solid-state nuclear magnetic resonance (NMR) methods are used to follow the thermal degradation of Krytox 1506,
a common perfluoropolyether, following adsorption onto the surfaces of -Al2O3 and a model clay (kaolinite). The
alumina studies are complemented with thermogravimetric analysis (TGA) to follow the degradation process
macroscopically. Molecular-level details are revealed through 19F magic-angle spinning (MAS), 27Al MAS, and
19F 
27Al cross-polarization MAS (CPMAS) NMR. The CPMAS results show the time-dependent formation of
probable VIAl(O6 - nFn) (n = 1, 2, 3) species in which the fluorine atoms are selectively associated with octahedrally
coordinated aluminum atoms. For the alumina system, the changes in peak shapes of the CP spectra over time suggest
the early formation of catalytically active degradation products, which in turn lead to the formation of additional
perfluoropolyether degradation products. Similar to the alumina system, the kaolinite system also displays new resonances
in both the 27Al MAS and 19F 27Al CPMAS spectra after thermal treatment at 300 
C for up to 20 h but reveals
a more distinct species at -15.5 ppm that forms at the expense of an initial species (3 ppm), which is in greater
abundance at shorter heating times.
Download the full text: PDF | HTML
