Combinatorial Approaches to Investigations of Thermochromic Materials
- PDF / 189,920 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 12 Downloads / 199 Views
1159-G06-10
Combinatorial Approaches to Investigations of Thermochromic Materials Hong Tang1 and Mary Anne White1 1
Department of Chemistry and Institute for Research in Materials, Dalhousie University, Halifax, Nova Scotia B3H 4J3, Canada ABSTRACT Thermochromic materials change color with temperature. Organic ternary mixtures composed of a dye, developer and solvent can reversibly change color with temperature. Although they are used in many commercial products, little is known about the detailed mechanism of thermochromism. Given the wide range of available components and compositions that could potentially show thermochromic behavior, we have embarked on combinatorial studies using inkjet printing to directly prepare thermochromic mixtures on paper. INTRODUCTION
Thermochromism is the phenomenon of change of color with temperature. There are many origins of thermochromism, such as phase changes or thermal expansion causing change in color of optical interference effects; one of the most applied thermochromic systems is organic mixtures consisting of a dye, a developer and a solvent.[1] Thermochromism can be reversible, or irreversible. One of the most exciting examples of reversible thermochromism is in the commercial product, e-BlueTM, a thermally erasable toner that allows printer paper to be erased and reused.[2] We have been studying organic thermochromic mixtures and have furthered our understanding of the molecular basis of thermochromism, especially the competition between the developer interacting with the dye (giving a colored state) and the developer acting with the solvent (giving an uncolored state).[3,4,5 ] However, we have concentrated on one dye/developer/solvent composition, and on one dye, one family of developers, and one family of solvents. The large number of possible dye/developer/solvent combinations indicates that combinatorial approaches could be useful. Although many different combinatorial approaches could be taken, we selected inkjet printing[6] to prepare thermochromic materials. The main issues were selection of a suitable printing technique, a suitable volatile solvent system, and a suitable substrate for sample deposition. In this case deposition and processing were challenging, but characterization of the resulting combinatorial libraries could be as straightforward as heating and cooling the array to look, by eye, for suitable thermochromism. EXPERIMENTAL METHODS A commercial drop-on-demand roof-shooter thermal inkjet printer Hewlett-Packard 5940 color printer was chosen due to its small orifice at the cartridge printhead (14 µm diameter) and high resolution (up to 1200 dpi). In addition, its cartridges can be easily processed. The bigger challenge was the selection of a volatile solvent to carry the dye, developer and solvent. (Note the distinction between the volatile solvent and the solvent required for the
thermochromic mixture.) The volatile solvent must show good solubility of the dye (crystal violet lactone, CVL; Aldrich, 97%), the developer (lauryl gallate; LG; Aldrich
Data Loading...
