High pressure as a tool for polymorph screening in small organic molecules

  • Ian Hutchison

Student thesis: Doctoral Thesis

Abstract

Application of high pressure is a well-known tool used to induce. Presented in this thesis are the studies of three small organic molecules under high pressure,investigating the importance of particle size, the choice of pressure-transmitting medium (PTM) and the solvent from which the material is recrystallised on the high-pressure behaviour of the material.Chapters 3 describes the characterisation of a metastable polymorph of glycolide,formed at high pressure and recovered to ambient conditions. Chapter 4 describes a neutron diffraction study of glycolide under high pressure, characterising the behaviour of each of the two known forms as well as seeking to characterise a third polymorph which had been observed during earlier work.Chapter 5 presents a neutron diffraction study of acrylamide under high pressure inthree different pressure-transmitting media – a 1:1 (v/v) mixture of pentane and isopentane,a 4:1 (v/v) mixture of methanol and ethanol, and iso-propyl alcohol (IPA).A different high pressure phase was identified in each of the three media, with the crystal structures of those in the pentanes and methanol/ethanol environments being fully solved.Chapter 6 describes a study of caprolactam under high pressure, through a combination of single crystal X-ray diffraction and powder neutron diffraction. In this study, it was observed that a caprolactam sample recrystallised from ethylacetate underwent a polymorph transition to one high pressure phase, while a sample recrystallised from alcohol (either ethanol or 1-butanol) underwent a polymorph transition to a different high pressure form despite the fact that both samples were in the same polymorphic form at the beginning of the experiment.The high pressure form observed from the sample recrystallised from ethanol (or 1-butanol) was fully structurally solved.Recent progress made by the group beyond the scope of this PhD have permitted unit cell parameters to be fitted to the neutron diffraction data, although associated discussion of this form is limited due to time constraints.
Date of Award1 Oct 2015
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council)
SupervisorIain Oswald (Supervisor) & (Supervisor)

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