The relation between colour and structural changes in thermochromic systems comprising crystal violet lactone, bisphenol A, and tetradecanol

Abstract

The aim of the paper was to find a direct connection between dynamic colour changes, phase changes and chemical interactions in model three-component leuco dye based thermochromic systems. The model systems, containing crystal violet lactone as a colour former, bisphenol A as a developer and 1tetradecanol as a co-solvent, were analysed by DSC and FTIR spectroscopy and the results were related to the characteristics of the dynamic colour change. The ternary thermochromic systems were also compared with binary mixtures of the co-solvent with the developer and colour former, respectively. The temperatures characterizing the dynamic colour change at decolouration limits were directly related to the solid-liquid transition on heating and liquid-solid transition on cooling, regardless the concentration of bisphenol A. In ternary thermochromic systems, an indistinctive phase transition at the temperatures below the solid-solid (crystal-rotator) transition was observed. The straight connection between the phase transitions and temperatures characterizing the dynamic colour change at colouration limits was not proved. The colour contrast of thermochromic systems was found to be directly related to the ratio of integrated intensity of lactone ring opened (solid) and lactone ring closed (liquid) carbonyl vibration characterized by infrared spectroscopy.

Preparation of poly(methyl methacrylate‐co‐ethylene glycol dimethacrylate‐co‐glycidyl methacrylate) walled thermochromic microcapsules and their application to cotton fabrics

“…The peak at 835 cm −1 in the spectra of microcapsules was out‐of‐plane C─H shaking deformation in the aromatic ring of BFA. Besides, C─O stretching peak at 1064 cm −1 and double peaks at 730 cm −1 and 720 cm −1 belonged to the TD . These were important findings, which proved the presence of the TS components in the microcapsule structure.…”

“…Besides, C─O stretching peak at 1064 cm −1 and double peaks at 730 cm −1 and 720 cm −1 belonged to the TD. 32 These were important findings, which proved the presence of the TS components in the microcapsule structure. Additionally, the peaks at 933 cm −1 in the spectra of microcapsules were characteristic absorption peaks of epoxy ring of the glycidyl methacrylate monomer.…”

Combined colorimetric and thermal analyses of reversible thermochromic composites using crystal violet lactone as a colour former

“…At present, more thorough interpretation was not possible due to the lack of precision in colorimetric measurement of dynamic colour change when compared to information available from DSC measurement. This issue is also discussed in [19], where the investigation of thermochromic systems comprising CVL, BPA, and TD is extended by IR analysis, including corresponding binary systems.…”

Raspberry‐Shaped Thermochromic Energy Storage Nanocapsule with Tunable Sunlight Absorption Based on Color Change for Temperature Regulation

“…It consists of color former, color developer and hydrophobic, nonvolatile organic solvents, which possesses an excellent reversibility . The thermochromic transition takes place around the melting point of the solvents . When the temperature reaches the melting point, the solvent undergoes a phase transition from solid to liquid with heat storage.…”