Glassy carbons from poly(furfuryl alcohol) copolymers: structural studies by high-resolution solid-state NMR techniques

Journal Article · Thu Aug 25 04:00:00 EDT 1988 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100328a037· OSTI ID:6254849

Eckert, H; Levendis, Y A; Flagan, R C

The chemical structure of glass carbon particles produced from poly(furfuryl alcohol) copolymers is studied by /sup 13/C cross-polarization/magic-angle spinning (CP-MAS) NMR and high-speed /sup 1/H MAS NMR. In agreement with earlier proposals, /sup 13/C NMR spectra confirm the buildup of a highly unsaturated system at the expense of furan rings and aliphatic carbon atoms, and upon heating to 800 K this conversion is essentially complete. Successive carbonization by air oxidation or pyrolysis at temperatures up to 1600 K is reflected in a gradual decrease of the /sup 13/C chemical shift from ca. 130 to 115 ppm versus tetramethylsilane. /sup 1/H MAS NMR is used to detect and quantitate the amount of residual C-bonded hydrogen species at various stages of the carbonization process. In addition, these spectra show intense, narrow resonances due to sorbed H/sub 2/O molecules, which resonate over a wide range of chemical shifts (between 2.5 and /minus/8 ppm versus tetramethylsilane). In analogy with effects observed by Tabony and co-workers for molecules adsorbed above the basal plane of graphite, the upfield shifts observed for water sorbed in the glassy carbons of the present study are attributed to the large susceptibility anisotropy of submicroscopically ordered, turbostratic, or partially graphitized regions of the samples. The extent of this ordering is inversely correlated with the absolute content of residual C-bonded hydrogen species and depends mainly on the temperature of pyrolysis, whereas the oxygen content of the heating atmosphere and the composition of the initial polymeric material appear to be of secondary importance. The results suggest that sorbed H/sub 2/O molecules can function as sensitive NMR chemical shift probes for the initial stages of crystallization processes in glassy carbons.

• Research Organization: Univ. of California, Santa Barbara (USA)
• DOE Contract Number: FG22-84PC70775
• OSTI ID: 6254849
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 92:17; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400800 -- Combustion
Pyrolysis
& High-Temperature Chemistry
ALCOHOLS
CARBON 13
CARBON ISOTOPES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
COHERENT SCATTERING
COPOLYMERS
DATA
DECOMPOSITION
DIFFRACTION
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
GLASS
GRAVIMETRIC ANALYSIS
HIGH TEMPERATURE
HYDROXY COMPOUNDS
INFORMATION
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC POLYMERS
POLYMERS
POWDERS
PYROLYSIS
QUANTITATIVE CHEMICAL ANALYSIS
RESONANCE
SCATTERING
SPECTRA
STABLE ISOTOPES
STRUCTURAL CHEMICAL ANALYSIS
THERMAL ANALYSIS
THERMAL GRAVIMETRIC ANALYSIS
THERMOCHEMICAL PROCESSES
VERY HIGH TEMPERATURE
X-RAY DIFFRACTION