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 sp2and sp3covalent 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 C6H6and C6D6up 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 C6D6shed light on the mechanism of polymerization of benzene. We find that C6D6-derived products recovered from P < 35 GPa actively react with moisture, forming polymers with higher sp3hydrogen contents. Significant isotopic shift (≥7 GPa) in persistence of Bragg reflections of C6D6is observed.
authors.affiliation: Department of Physics and Astronomy, University of Utah , 115S 1400E, Salt Lake City, Utah 84112, United States.
authors.forename: Weizhao
authors.identifier: http://orcid.org/0000-0001-7805-2108
authors.initials: W
authors.lastname: Cai
authors.affiliation: Department of Physics and Astronomy, University of Utah , 115S 1400E, Salt Lake City, Utah 84112, United States.
authors.forename: Mihindra
authors.initials: M
authors.lastname: Dunuwille
authors.affiliation: Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Jiangang
authors.identifier: http://orcid.org/0000-0001-9643-3617
authors.initials: J
authors.lastname: He
authors.affiliation: Department of Physics and Astronomy, University of Utah , 115S 1400E, Salt Lake City, Utah 84112, United States.
authors.forename: Trevor V
authors.initials: TV
authors.lastname: Taylor
authors.affiliation: Department of Physics and Astronomy, University of Utah , 115S 1400E, Salt Lake City, Utah 84112, United States.
authors.forename: Jasmine K
authors.initials: JK
authors.lastname: Hinton
authors.affiliation: Department of Physics and Astronomy, University of Utah , 115S 1400E, Salt Lake City, Utah 84112, United States.
authors.forename: Mary C
authors.initials: MC
authors.lastname: MacLean
authors.affiliation: Quantum Condensed Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Jamie J
authors.initials: JJ
authors.lastname: Molaison
authors.affiliation: Quantum Condensed Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Antonio M
authors.initials: AM
authors.lastname: Dos Santos
authors.affiliation: High Pressure Collaborative Access Team (HPCAT), Geophysical Laboratory, Carnegie Institute of Washington , Argonne, Illinois 60439, United States.
authors.forename: Stanislav
authors.initials: S
authors.lastname: Sinogeikin
authors.affiliation: Department of Physics and Astronomy, University of Utah , 115S 1400E, Salt Lake City, Utah 84112, United States.
authors.forename: Shanti
authors.identifier: http://orcid.org/0000-0001-5661-8801
authors.initials: S
authors.lastname: Deemyad