Publication Details (including relevant citation information):
United States Patent 8,430,053;April 30, 2013
Color-changing emulsions for freeze indicators
Taylor; Dene H. Lentz; Carl M. & Smith; Dawn E
A color-changing emulsion for use in a freeze indicator can employ a dispersion medium, for example, an aqueous liquid, a first reactant phase and a second reactant phase, which two reactant phases can both be dispersed in the dispersion medium. The first reactant phase includes a hydrophobic liquid and a first reactant, for example, a color precursor such as a leuco dye. The second reactant phase can include a hydrophobic liquid, and includes, or can be, a second reactant, for example, a color developer such as a leuco dye developer. The first and second reactant phases can be essentially unmixed, and can be co-reactable to provide a color change. In response to a freezing temperature, the color-changing emulsion can coagulate and change color irreversibly. An intense color change can be obtained by using, for example, a suitable leuco dye precursor and developer.