Thermochromic materials undergo temperature-dependent colour changes. Although there are several origins of thermochromism, two distinct types of thermochromism are common in thermochromic mixtures. Melt-lightened thermochromism occurs when the colour density of a mixture decreases with increasing temperature, and is usually associated with colour loss upon mixture melting. Melt-darkened thermochromism occurs when the colour density of a mixture increases with increasing temperature, and is usually associated conversion from a decoloured solid state to a coloured melt. Three-component thermochromic systems generally consist of a leuco dye (minor component), a phenolic colour developer (intermediate component), and a high melting-point organic solvent (dominant component). In these systems, the colouring behaviour is controlled by competing binary interactions, with the dye:developer interaction responsible for colour formation and the developer:solvent interaction responsible for colour erasure. In the present study, three-component mixtures composed of CVL (dye), long-chain alkyl gallates (phenolic developer), and long-chain alkyl alcohols (long-chain solvent) were examined. The thermochromic behaviour (i.e., melt-lightened vs. melt-darkened thermochromism) of these mixtures was examined as a function of the matching of the alkyl chain length of the gallate developer and alcohol solvent. When the alkyl chain lengths were well matched, the developer:solvent interaction dominated in the solid state and melt-darkened thermochromism was observed. When the alkyl chain lengths were poorly matched, the dye:developer interaction dominated in the solid state, and melt-lightened thermochromism was observed. The colour density of the molten state was determined by the developer:dye molar ratio, with high molar ratios yielding coloured melts and low molar ratios yielding decoloured melts. Additional studies employing chemically dissimilar developers and solvents (e.g., bisphenol A with 1-hexadecanol) yielded mixtures that displayed optimal melt-lightened thermochromism. The high solid-state colour density due to weak developer:solvent interactions provides further evidence that competing binary interactions are responsible for the colouring behaviour observed for three-component thermochromic systems. Ternary thermochromic phase diagrams were used to define compositional regions of optimal thermochromic behaviour (i.e., high colour contrast), providing a useful experimental tool for the rapid identification of ideal sample compositions. Additionally, an examination of the properties of thermally erasable ink-jet printer inks was carried out during the present study. / An assessment of the thermochromic behaviour of three-component chemical systems comprising a colour-changing leuco dye, an electron-accepting phenolic developer, and a long-chain alkyl alcohol solid solvent.

A dynamic mathematical model was developed to simulate the response of polyacrylamide gel (PAG) dosimeters to a single spherical radioactive brachytherapy seed. Simulations were conducted for a high dose-rate (HDR) seed using 192Ir and a low dose-rate (LDR) seed using 125I. The model is able to predict the amount of polymer formed, the crosslink density, and the volume fraction of aqueous phase as a function of radial distance and time. Results show that PAG dosimeters can provide accurate HDR brachytherapy dosimetry at distances larger than 4 mm from the centre of the seed but will give poor results for LDR due to monomer diffusion. Experiments were conducted to evaluate the potential for using pentacosa-10,12-diynoic acid (PCDA) as the reporter molecule in micelle gel dosimeters for optical computed tomography (CT) readout. Several gels containing PCDA that was solubilized using sodium dodecyl sulfate (SDS) responded to radiation by changing from colourless to blue. Unfortunately, all phantoms that showed colour changes were turbid, making them unsuitable for optical CT scanning. Several techniques were used to produce transparent gels containing PCDA but none of these gels responded noticeably to radiation. Only turbid gels with precipitated PCDA responded, indicating that the colour change was due to oligomerization within PCDA crystals and that PCDA molecules solubilized in micelles did not undergo oligomerization. As a result, PCDA is not suitable for use in radiochromic micelle gel dosimeters. A new recipe for a radiochromic leuco crystal violet (LCV) micelle gel dosimeters with enhanced dose sensitivity was developed for optical CT readout. The recipe contains LCV, trichloro acetic acid (TCAA), Cetyl Trimethyl Ammonium Bromide (CTAB), 2,2,2-Trichloroethanol (TCE), and gelatin. Experiments were conducted to improve understanding about interactions between the different components of LCV micelle gel, highlighting the importance of pH on dose sensitivity and transparency. Results also showed the effectiveness of chlorinated compounds in improving dose sensitivity. Statistical techniques were used to build empirical models that were used to optimize the gel recipe. Additional testing in larger phantoms will be required to assess the effectiveness of the proposed gel for clinical dosimetry. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2014-03-27 11:11:47.655

With the technological progress of materials science, the palette of colours with which to print on textiles has expanded beyond those with previously known properties and expressions to a new generation, with more advanced functionality and expressive properties. This new range of colours is characterised by their ability when printed on textiles to change colour in relation to external factors and internal programmes; for example, leuco dye-based thermochromic inks generally change colour in response to temperature fluctuations. This research explores the design properties and potentials of leuco dye-based thermochromic inks printed on textiles, with regard to creating a wider range of colour-changing effects for textile applications. The significance of this for textile design is related to the development of a methodology for designing dynamic surface patterns. The research was conducted by creating a series of design experiments using leuco dye-based thermochromic inks, which resulted in different recipes and methods, along with a pedagogical tool. The results highlighted the diverse colour-changing properties of leuco dye-based thermochromic inks, which have the potential to create more complex patterns on textiles. The outcome of this research proposes a foundation for textile designers with which to approach new ways of thinking and designing.

Identification of viable vat dye candidates of a trichromatic series (compatible red, yellow and blue colorants) plus an orange based on the developed single-stage acid leuco vat dyeing process for unmodified polypropylene (PP) flat woven fabrics has been achieved with adequate fastness properties to washing, crocking and dry-cleaning: C. I. Vats Orange 1, Yellow 2 and Red 1 have been certified, whereas Vat Blue 6 is a marginal candidate. Vat Blue 1 has been demonstrated to be a viable colorant for dyeing of PP fiber as a single colorant. Molecular dynamics simulation and solubility parameter (SP) approaches have been utilized to screen the potential vat dye candidates for generic PP coloration. Experimental K/S results have exhibited good correlation with the predicted mixing energy of acid leuco vat dyes-PP fiber and the calculated dyes' SP's. The low SP/mixing energy acid leuco vat dyes (e.g., C. I. Vat Red 1) have shown better color-yield/fastness properties than the high SP/mixing energy vat dyes (e.g., C. I. Vat Brown 1), exhibiting that increasing difference of SP between the vat dye and the PP fiber, coupled with a higher mixing energy of dye-PP blend, resulted in decreased interactions between the two. For example, C.I. Vat Brown 1 with its high SP and calculated mixing energy with PP gave least color yield than the certified vat dyes, all with lower SP's and mixing energies. Cross-section micrographs of the dyed fibers revealed the absence of "ring-dyeing". Experimentally determined kinetic parameters such as affinity of dyeing and heat of dyeing quantified the presence of interaction between acid leuco vat dyes and PP fiber. Tensile test and X-ray crystallinity results have confirmed that dyeing process did not alter the tensile strength and modulus of the dyed PP textiles significantly. PP Fabrics dyed with simulated continuous dyeing processes (pad-steam and pad-dry heat) demonstrated good color yields and levelness with adequate fastness to crocking, washing and dry cleaning.

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