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

Abstract

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.