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Title: Deuterium isotope effects in polymerization of benzene under pressure

Abstract

The enormous versatility in the properties of carbon materials depends on the content of the sp2 and sp3 covalent bonds. Under compression, if intermolecular distances cross a critical threshold, then unsaturated hydrocarbons gradually transform to saturated carbon polymers. However, the mechanism of polymerization, even for benzene, the simplest aromatic hydrocarbon, is still not understood. We used high-pressure synchrotron X-ray, neutron diffraction, and micro-Raman spectroscopy together with density functional calculations to investigate the isotope effects in benzene isotopologues C6H6 and C6D6 up to 46.0 GPa. Raman spectra of polymeric products recovered from comparable pressures show the progression of polymerization exhibiting a pronounced kinetic isotope effect. Kinetically retarded reactions in C6D6 shed light on the mechanism of polymerization of benzene. Lastly, we find that C6D6-derived products recovered from P < 35 GPa actively react with moisture, forming polymers with higher sp3 hydrogen contents. Significant isotopic shift (≥7 GPa) in persistence of Bragg reflections of C6D6 is observed.

Authors:
ORCiD logo [1];  [1]; ORCiD logo [2];  [1];  [1];  [1];  [3];  [3];  [4]; ORCiD logo [1]
  1. Univ. of Utah, Salt Lake City, UT (United States)
  2. Northwestern Univ., Evanston, IL (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Carnegie Institute of Washington, Argonne, IL (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source
Sponsoring Org.:
USDOE
OSTI Identifier:
1366413
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry Letters
Additional Journal Information:
Journal Volume: 8; Journal Issue: 8; Journal ID: ISSN 1948-7185
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Cai, Weizhao, Dunuwille, Mihindra, He, Jiangang, Taylor, Trevor V., Hinton, Jasmine K., MacLean, Mary C., Molaison, Jamie J., dos Santos, Antonio M., Sinogeikin, Stanislav, and Deemyad, Shanti. Deuterium isotope effects in polymerization of benzene under pressure. United States: N. p., 2017. Web. doi:10.1021/acs.jpclett.7b00536.
Cai, Weizhao, Dunuwille, Mihindra, He, Jiangang, Taylor, Trevor V., Hinton, Jasmine K., MacLean, Mary C., Molaison, Jamie J., dos Santos, Antonio M., Sinogeikin, Stanislav, & Deemyad, Shanti. Deuterium isotope effects in polymerization of benzene under pressure. United States. doi:10.1021/acs.jpclett.7b00536.
Cai, Weizhao, Dunuwille, Mihindra, He, Jiangang, Taylor, Trevor V., Hinton, Jasmine K., MacLean, Mary C., Molaison, Jamie J., dos Santos, Antonio M., Sinogeikin, Stanislav, and Deemyad, Shanti. Mon . "Deuterium isotope effects in polymerization of benzene under pressure". United States. doi:10.1021/acs.jpclett.7b00536. https://www.osti.gov/servlets/purl/1366413.
@article{osti_1366413,
title = {Deuterium isotope effects in polymerization of benzene under pressure},
author = {Cai, Weizhao and Dunuwille, Mihindra and He, Jiangang and Taylor, Trevor V. and Hinton, Jasmine K. and MacLean, Mary C. and Molaison, Jamie J. and dos Santos, Antonio M. and Sinogeikin, Stanislav and Deemyad, Shanti},
abstractNote = {The enormous versatility in the properties of carbon materials depends on the content of the sp2 and sp3 covalent bonds. Under compression, if intermolecular distances cross a critical threshold, then unsaturated hydrocarbons gradually transform to saturated carbon polymers. However, the mechanism of polymerization, even for benzene, the simplest aromatic hydrocarbon, is still not understood. We used high-pressure synchrotron X-ray, neutron diffraction, and micro-Raman spectroscopy together with density functional calculations to investigate the isotope effects in benzene isotopologues C6H6 and C6D6 up to 46.0 GPa. Raman spectra of polymeric products recovered from comparable pressures show the progression of polymerization exhibiting a pronounced kinetic isotope effect. Kinetically retarded reactions in C6D6 shed light on the mechanism of polymerization of benzene. Lastly, we find that C6D6-derived products recovered from P < 35 GPa actively react with moisture, forming polymers with higher sp3 hydrogen contents. Significant isotopic shift (≥7 GPa) in persistence of Bragg reflections of C6D6 is observed.},
doi = {10.1021/acs.jpclett.7b00536},
journal = {Journal of Physical Chemistry Letters},
number = 8,
volume = 8,
place = {United States},
year = {2017},
month = {4}
}

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