Thermochromic composite fibres for thermal mapping in the physiological temperature range

This thesis presents original work towards the successful formation of novel thermochromic composite fibres through melt extrusion processes, and whose major application includes incorporation into wound dressings and garments, for the thermal mapping of chronic wound bed surfaces and skin surfaces, within the physiological temperature range. Specifically, this work focuses on the incorporation of thermochromic liquid crystalline (TLC) mixtures into host materials in fibre form, such that clear and reliable thermochromic behaviour is preserved, and a good colour density is maintained. TLC mixtures containing both sterol based, and non-sterol based compounds were used. The relationship between composition and thermochromic behaviour for binary and ternary TLC mixtures consisting of a selection of cholesterol derivatives is also explored in this work. Crucial to the success of the TLC containing composite fibres was the insertion of a black core material through the centre of the fibres, addressing the inherent need for TLCs to be viewed against a black or dark background for their reflected colours to be visible. Two major methods of incorporation of the TLC into a host fibre were presented using melt extrusion processes. The most successful monofilament composite fibre’s thermochromic behaviour was found to be clear, and comparable to that of unincorporated TLC mixtures. The thermochromic behaviour was found to remain stable after storage in air for at least 17 weeks, provided that the fibres were not also exposed to light. Their behaviour also remained stable upon submersion in water and saline solution, for at least 10 days. The inherent instability of TLCs to light induced degradation was unfortunately found to be preserved in these fibres, where a detrimental shift in the thermochromic behaviour of the fibres occurred with intense or long-term exposure to UV light. Methods of avoiding or slowing light induced degradation are discussed. This thesis focuses on the steps taken towards achieving the final successful fibre design, as well as its characterisation, and discussions in regards to its applicability to medical applications.