Pressure-induced polymorphism of caprolactam : a neutron diffraction study
Hutchison, Ian and Bull, Craig L. and Marshall, William G. and Urquhart, Andrew J. and Oswald, Iain D.H. (2019) Pressure-induced polymorphism of caprolactam : a neutron diffraction study. Molecules, 24 (11). 2174. ISSN 1420-3049
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Abstract
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 and we have observed two new high pressure solid forms. 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 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 the 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.
Creators(s): |
Hutchison, Ian, Bull, Craig L., Marshall, William G., Urquhart, Andrew J. and Oswald, Iain D.H. ![]() | Item type: | Article |
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ID code: | 68317 |
Keywords: | high-pressure single-crystal X-ray diffraction, high-pressure neutron diffraction, phase transitions, intermolecular interactions, energy frameworks, Chemistry, Therapeutics. Pharmacology, Organic Chemistry, Pharmacology (medical) |
Subjects: | Science > Chemistry Medicine > Therapeutics. Pharmacology |
Department: | Faculty of Science > Strathclyde Institute of Pharmacy and Biomedical Sciences |
Depositing user: | Pure Administrator |
Date deposited: | 10 Jun 2019 09:06 |
Last modified: | 21 Jan 2021 10:54 |
Related URLs: | |
URI: | https://strathprints.strath.ac.uk/id/eprint/68317 |
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