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Pressure-Induced Polymorphism of Caprolactam: A Neutron Diffraction Study
Caprolactam, a precursor to nylon-6 has been investigated as part of our studies into the polymerization of materials at high pressure. Single-crystal X-ray and neutron powder diffraction data have been used to explore the high-pressure phase behavior of caprolactam; two new high pressure solid form...
Autores principales: | , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
MDPI
2019
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6600225/ https://www.ncbi.nlm.nih.gov/pubmed/31185609 http://dx.doi.org/10.3390/molecules24112174 |
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author | Hutchison, Ian B. Bull, Craig L. Marshall, William G. Urquhart, Andrew J. Oswald, Iain D.H. |
author_facet | Hutchison, Ian B. Bull, Craig L. Marshall, William G. Urquhart, Andrew J. Oswald, Iain D.H. |
author_sort | Hutchison, Ian B. |
collection | PubMed |
description | Caprolactam, a precursor to nylon-6 has been investigated as part of our studies into the polymerization of materials at high pressure. Single-crystal X-ray and neutron powder diffraction data have been used to explore the high-pressure phase behavior of caprolactam; two new high pressure solid forms were observed. The transition between each of the forms requires a substantial rearrangement of the molecules and we observe that the kinetic barrier to the conversion can aid retention of phases beyond their region of stability. Form II of caprolactam shows a small pressure region of stability between 0.5 GPa and 0.9 GPa with Form III being stable from 0.9 GPa to 5.4 GPa. The two high-pressure forms have a catemeric hydrogen-bonding pattern compared with the dimer interaction observed in ambient pressure Form I. The interaction between the chains has a marked effect on the directions of maximal compressibility in the structure. Neither of the high-pressure forms can be recovered to ambient pressure and there is no evidence of any polymerization occurring. |
format | Online Article Text |
id | pubmed-6600225 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2019 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-66002252019-07-16 Pressure-Induced Polymorphism of Caprolactam: A Neutron Diffraction Study Hutchison, Ian B. Bull, Craig L. Marshall, William G. Urquhart, Andrew J. Oswald, Iain D.H. Molecules Article Caprolactam, a precursor to nylon-6 has been investigated as part of our studies into the polymerization of materials at high pressure. Single-crystal X-ray and neutron powder diffraction data have been used to explore the high-pressure phase behavior of caprolactam; two new high pressure solid forms were observed. The transition between each of the forms requires a substantial rearrangement of the molecules and we observe that the kinetic barrier to the conversion can aid retention of phases beyond their region of stability. Form II of caprolactam shows a small pressure region of stability between 0.5 GPa and 0.9 GPa with Form III being stable from 0.9 GPa to 5.4 GPa. The two high-pressure forms have a catemeric hydrogen-bonding pattern compared with the dimer interaction observed in ambient pressure Form I. The interaction between the chains has a marked effect on the directions of maximal compressibility in the structure. Neither of the high-pressure forms can be recovered to ambient pressure and there is no evidence of any polymerization occurring. MDPI 2019-06-10 /pmc/articles/PMC6600225/ /pubmed/31185609 http://dx.doi.org/10.3390/molecules24112174 Text en © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Hutchison, Ian B. Bull, Craig L. Marshall, William G. Urquhart, Andrew J. Oswald, Iain D.H. Pressure-Induced Polymorphism of Caprolactam: A Neutron Diffraction Study |
title | Pressure-Induced Polymorphism of Caprolactam: A Neutron Diffraction Study |
title_full | Pressure-Induced Polymorphism of Caprolactam: A Neutron Diffraction Study |
title_fullStr | Pressure-Induced Polymorphism of Caprolactam: A Neutron Diffraction Study |
title_full_unstemmed | Pressure-Induced Polymorphism of Caprolactam: A Neutron Diffraction Study |
title_short | Pressure-Induced Polymorphism of Caprolactam: A Neutron Diffraction Study |
title_sort | pressure-induced polymorphism of caprolactam: a neutron diffraction study |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6600225/ https://www.ncbi.nlm.nih.gov/pubmed/31185609 http://dx.doi.org/10.3390/molecules24112174 |
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