Next Article in Journal
Catechins Controlled Bioavailability of Benzo[a]pyrene (B[α]P) from the Gastrointestinal Tract to the Brain towards Reducing Brain Toxicity Using the In Vitro Bio-Mimic System Coupled with Sequential Co-Cultures
Next Article in Special Issue
Effect of H2O on the Pressure-Induced Amorphization of Hydrated AlPO4-17
Previous Article in Journal
Synthesis and Cytostatic Effect of 3’-deoxy-3’-C-Sulfanylmethyl Nucleoside Derivatives with d-xylo Configuration
Previous Article in Special Issue
The Effect of Pressure on Halogen Bonding in 4-Iodobenzonitrile
Open AccessArticle

Pressure-Induced Polymorphism of Caprolactam: A Neutron Diffraction Study

1
Strathclyde Institute of Pharmacy & Biomedical Sciences (SIPBS), University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK
2
ISIS Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, UK
3
Department of Health Technology, Technical University of Denmark, Produktionstorvet, 2800 Kgs. Lyngby, Denmark
*
Author to whom correspondence should be addressed.
Deceased on 5 November 2015.
Academic Editors: Ines Collings, Andrew B. Cairns and Miklos Kertesz
Molecules 2019, 24(11), 2174; https://doi.org/10.3390/molecules24112174
Received: 3 May 2019 / Revised: 31 May 2019 / Accepted: 1 June 2019 / Published: 10 June 2019
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. View Full-Text
Keywords: high-pressure single-crystal X-ray diffraction; high-pressure neutron diffraction; phase transitions; intermolecular interactions; energy frameworks high-pressure single-crystal X-ray diffraction; high-pressure neutron diffraction; phase transitions; intermolecular interactions; energy frameworks
Show Figures

Graphical abstract

MDPI and ACS Style

Hutchison, I.B.; Bull, C.L.; Marshall, W.G.; Urquhart, A.J.; Oswald, I.D. Pressure-Induced Polymorphism of Caprolactam: A Neutron Diffraction Study. Molecules 2019, 24, 2174.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Back to TopTop