NMR Studies of the Thermal Degradation of a Perfluoropolyether on the Surfaces of -Alumina and Kaolinite
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- 作者：Kerri A. Denkenberger ; Ruth A. Bowers ; A. Daniel Jones ; Karl T. Mueller
- 刊名：Langmuir
- 出版年：2007
- 出版时间：August 14, 2007
- 年：2007
- 卷：23
- 期：17
- 页码：8855 - 8860
- 全文大小：106K
- 年卷期：v.23,no.17(August 14, 2007)
- ISSN：1520-5827
文摘
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). Thealumina studies are complemented with thermogravimetric analysis (TGA) to follow the degradation processmacroscopically. Molecular-level details are revealed through 19F magic-angle spinning (MAS), 27Al MAS, and19F 
tities/rarr.gif"> 27Al cross-polarization MAS (CPMAS) NMR. The CPMAS results show the time-dependent formation ofprobable VIAl(O6 - nFn) (n = 1, 2, 3) species in which the fluorine atoms are selectively associated with octahedrallycoordinated aluminum atoms. For the alumina system, the changes in peak shapes of the CP spectra over time suggestthe early formation of catalytically active degradation products, which in turn lead to the formation of additionalperfluoropolyether degradation products. Similar to the alumina system, the kaolinite system also displays new resonancesin both the 27Al MAS and 19F tities/rarr.gif"> 27Al CPMAS spectra after thermal treatment at 300 tities/deg.gif">C for up to 20 h but revealsa more distinct species at -15.5 ppm that forms at the expense of an initial species (3 ppm), which is in greaterabundance at shorter heating times.
-Al2O3 and a model clay (kaolinite). Thealumina studies are complemented with thermogravimetric analysis (TGA) to follow the degradation processmacroscopically. Molecular-level details are revealed through 19F magic-angle spinning (MAS), 27Al MAS, and19F tities/rarr.gif"> 27Al cross-polarization MAS (CPMAS) NMR. The CPMAS results show the time-dependent formation ofprobable VIAl(O6 - nFn) (n = 1, 2, 3) species in which the fluorine atoms are selectively associated with octahedrallycoordinated aluminum atoms. For the alumina system, the changes in peak shapes of the CP spectra over time suggestthe early formation of catalytically active degradation products, which in turn lead to the formation of additionalperfluoropolyether degradation products. Similar to the alumina system, the kaolinite system also displays new resonancesin both the 27Al MAS and 19F tities/rarr.gif"> 27Al CPMAS spectra after thermal treatment at 300 tities/deg.gif">C for up to 20 h but revealsa more distinct species at -15.5 ppm that forms at the expense of an initial species (3 ppm), which is in greaterabundance at shorter heating times.