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Selective Observations of Chemical Structures of Heat-treated Poly(acrylonitrile) Films at The Surface and Core Regions by Solid-state NMR

Ma, Jiayang
http://rave.ohiolink.edu/etdc/view?acc_num=akron1555600643937118

Abstract Details

2019, Master of Science, University of Akron, Polymer Science.
Atactic-Poly(acrylonitrile)(aPAN) is a precursor for carbon fibers. Chemical reactions of aPAN fibers/films during stabilization process is spatially heterogeneous due to limited oxygen diffusivity. So far, Auger Electron Spectroscopy (AES), Energy-dispersive X-ray spectroscopy (EDS), Near-edge X-ray absorption fine strucutre (NEXAFS), Synchrotoron IR imaging have been applied to investigate depth profiles of elements and functional groups of the aPAN fibers. However, these studies are not sufficient to understand the detailed chemical structures and kinetics of the chemical reactions of the stabilized aPAN fibers/films. Solid-state NMR spectroscopy is one of the powerful characterization tools for structural analysis of organic compounds at the atomic scale, however, cannot be generally applicable to structural studies as a function of depth from the surface. In this work, it is found that both 13C direct polarization magic angle spinning NMR spectra and 1H spin−lattice relaxation time in the laboratory frame (T1H) of the stabilized aPAN films highly depend on the film thickness. These differences are attributed to different chemical reaction mechanisms at the surface and inner cores due to limited oxygen diffusivity. Tunable T1H filtered 2D 13C–13C INADEQUATE NMR for the first time selectively observes either the well stabilized aPAN at the surface or poorly stabilized structures at the core region in the films. A relative fraction of the well stabilized aPAN region to the whole films is determined in terms of 13C line-shape analysis. Kinetics of chemical reactions of the stabilized aPAN film as a function of film thickness is also investigated. It is demonstrated that overall stabilization rate is significantly lowered down with increasing film thickness. This novel strategy will be useful for structural study of industrial carbon fiber precursors.
Toshikazu Miyoshi (Advisor)
Tianbo Liu (Committee Member)
54 p.
Polymer Chemistry; Polymers
atactic poly acrylonitrile; aPAN film; stabilization process; solid-state NMR; carbon fiber; size effect; kinetics

Recommended Citations

Citations

  • Ma, J. (2019). Selective Observations of Chemical Structures of Heat-treated Poly(acrylonitrile) Films at The Surface and Core Regions by Solid-state NMR [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555600643937118

    APA Style (7th edition)

  • Ma, Jiayang. Selective Observations of Chemical Structures of Heat-treated Poly(acrylonitrile) Films at The Surface and Core Regions by Solid-state NMR. 2019. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1555600643937118.

    MLA Style (8th edition)

  • Ma, Jiayang. "Selective Observations of Chemical Structures of Heat-treated Poly(acrylonitrile) Films at The Surface and Core Regions by Solid-state NMR." Master's thesis, University of Akron, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555600643937118

    Chicago Manual of Style (17th edition)

akron1555600643937118
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This open access ETD is published by University of Akron and OhioLINK.