Competition between dye-developer and solvent-developer interactions in a reversible thermochromic system

Multicomponent thermochromic systems contain a dye, a colour developer, and a solvent. Dye-developer interactions, including complex formation, have been examined in our previous study. In this paper, the interactions between the same developer ( lauryl gallate) and a solvent (1-octadecanol) are characterised both through phase diagram determination and from Raman spectroscopy. The role of dye-developer complex formation in the thermochromic behaviour of the ternary thermochromic system ( with the addition of crystal violet lactone dye) is addressed. We find two competing interactions for the developer: the dye-developer complex forms in the melt and in the quenched solid ( giving a coloured mixture), but a solvent-developer complex is more favorable as the solid equilibrates. The latter gives rise to concomitant decolourisation.