Detection and characterisation of secondary relaxations in solids using thermally stimulated current spectroscopy

Thermally stimulated current (TSC) spectroscopy has been used, in these reported investigations, as an innovative experimental technique for the detection and characterisation of secondary relaxation phenomena in the crystalline state for a number of low-molecular weight organic materials (LOMs), namely α-alanine, β-alanine, a co-crystal system (salicylic acid and benzamide) and the drug paracetamol (form I). The aim of the research was to significantly improve the contemporary understanding of secondary relaxation phenomena in crystalline LOMs; an area of science that is of significant inter-disciplinary interest throughout academia and industry. In all the materials examined, secondary relaxations were detected and characterised by TSC; in order to achieve the foregoing different experimental methodologies (e.g. thermal windowing) and data processing techniques (e.g. relaxation map analysis) were employed. Of significant prevalence throughout is the phenomenon of compensation behaviour; in both the thermodynamic (i.e. enthalpy and entropy compensation) and in the kinetic (i.e. pre-exponent and activation energy (of the Arrhenius equation)) sense. Derived compensation points were linked to real physical processes; identifying a relationship between secondary relaxations and primary transitions. It is proposed, herein, that secondary relaxations have a pre-requisite relationship with primary transitions. Secondary relaxations are preparatory motions, essential for primary transitions to occur. In addition, throughout this thesis, additional information on topics such as co-crystal synthesis, chirality, degradation, the nature of secondary/primary relaxations, the nature of primary transitions and physical properties of LOMs, are examined in relation to the LOMs under investigation. TSC has proven to be an effective, and perhaps unique, instrumental technique for the detection and characterisation of secondary relaxations in LOMs.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Greenwich

Year dc:date.issued

2013

Author dc:creator

• Cherry, Anthony John

Advisors dc:contributor.advisor

• Antonijevic, Milan
• Chowdhry, Babur

• QC Physics

Language dc:language

en