Anti-yellowing for thermochromic systems
Ligand exchange thermochromic systems comprising a. a transition metal ion, iodide; and at least one material capable of minimizing or eliminating yellow color formation in the system, wherein at 25° C. the color coordinate b* value of the system is less than 30.
1. A ligand exchange thermochromic system comprising:
a. a transition metal ion;
b. iodide;
c. a derivative of 1,4-hydroquinone material capable of minimizing or eliminating yellow color formation due to iodine or tri-iodide formation or interaction of the thermochromic system with air, or via a photochemical reaction caused by exposure to sunlight and/or simulated sunlight, wherein at 25° C. the color coordinate b* value of the system is less than 30; and
d. a polymer.
2. The ligand exchange thermochromic system of claim 1 , wherein the transition metal ion is selected from the group consisting of ions of nickel, ions of cobalt and combinations thereof.
3. The ligand exchange thermochromic system of claim 1 , wherein the system comprising:
a. a transition metal ion;
b. iodide;
c. a derivative of 1,4-hydroquinone capable of minimizing or eliminating yellow color formation due to iodine or tri-iodide formation, wherein at 25° C. the color coordinate b* value of the system is less than 30; and
d. a polymer.
4. The ligand exchange thermochromic system of claim 3 , wherein the derivatives of 1,4-hydroquinone are selected from the group consisting of 2,5-di-tert-butyl-1,4-hydroquinone, 2,5-bis(1,1,3,3-tetramethylbutyl)-1,4-hydroquinone, 2,5-bis(1,1-dimethylethyl)-1,4-hydroquinone, 2,3,5-trimethyl-1,4-hydroquinone, 2,3,5,6-tetramethyl-1,4-hydroquinone, 1,4-hydroquinone-bis(2-hydroxyethylether), 3,5-di-tert-butyl-4-hydroxyanisole and combinations thereof.
5. The ligand exchange thermochromic system of claim 1 , wherein the system comprising:
a. a transition metal ion;
b. iodide;
c. a derivative of 1,4-hydroquinone capable of minimizing or eliminating yellow color formation due to the interaction of the thermochromic system with air, wherein at 25° C. the color coordinate b* value of the system is less than 30; and
d. a polymer.
6. The ligand exchange thermochromic system of claim 5 , wherein the derivatives of 1,4-hydroquinone are selected from the group consisting of 2,5-di-tert-butyl-1,4-hydroquinone, 2,5-bis(1,1,3,3-tetramethylbutyl)-1,4-hydroquinone, 2,5-bis(1,1-dimethylethyl)-1,4-hydroquinone, 2,3,5-trimethyl-1,4-hydroquinone, 2,3,5,6-tetramethyl-1,4-hydroquinone, 1,4-hydroquinone-bis(2-hydroxyethylether), 3,5-di-tert-butyl-4-hydroxyanisole and combinations thereof.
7. The ligand exchange thermochromic system of claim 1 , wherein the system in a film comprising:
a. a transition metal ion;
b. iodide;
c. a derivative of 1.4-hydroquinone capable of minimizing or eliminating yellow color formation in the film wherein at 25° C. the color coordinate b* value of the film is less than 30; and
d. a polymer.
8. The ligand exchange thermochromic system in a film of claim 7 , wherein the derivatives of 1,4-hydroquinone are selected from the group consisting of 2,5-di-tert-butyl-1,4-hydroquinone, 2,5-bis(1,1,3,3-tetramethylbutyl)-1,4-hydroquinone, 2,5-bis(1,1-dimethylethyl)-1,4-hydroquinone, 2,3,5-trimethyl-1,4-hydroquinone, 2,3,5,6-tetramethyl-1,4-hydroquinone, 1,4-hydroquinone-bis(2-hydroxyethylether), 3,5-di-tert-butyl-4-hydroxyanisole and combinations thereof.
9. A ligand exchange thermochromic system comprising:
a. a transition metal ion;
b. iodide; and
c. one or more than one material of structure I:
wherein R 1 and R 4 are independently selected from the group consisting of hydrogen, substituted and unsubstituted alkyl, branched alkyl, aryl and aralkyl; wherein R 2 , R 3 , R 5 and R 6 are independently selected from the group consisting of hydrogen, alkyl, branched alkyl, aryl, aralkyl, OR 7 and NR 8 R 9 , and wherein R 7 , R 8 and R 9 are independently selected from the group consisting of hydrogen, alkyl and branched alkyl or optionally R 2 and R 3 and/or R 5 and R 6 form a fused ring.
10. The ligand exchange thermochromic system of claim 9 , wherein the carbon containing radicals of R 1 to R 9 contain from 1-20 carbon atoms.
11. The ligand exchange thermochromic system of claim 9 , wherein the material of structure I is selected from the group consisting of 2,5-di-tert-butyl-1,4-hydroquinone, 2,5-bis(1,1,3,3-tetramethylbutyl)-1,4-hydroquinone, 2,5-bis(1,1-dimethylethyl)-1,4-hydroquinone, 2,3,5-trimethyl-1,4-hydroquinone, 2,3,5,6-tetramethyl-1,4-hydroquinone, 1,4-hydroquinone-bis(2-hydroxyethylether), 3,5-di-tert-butyl-4-hydroxyanisole and combinations thereof.
12. The ligand exchange thermochromic system of claim 9 , wherein the material of structure I is present in the thermochromic system at 0.1-5.0 weight percent by weight of the system.
13. The ligand exchange thermochromic system of claim 9 , wherein at 25° C. the color coordinate b* value of the thermochromic system is below 30.
14. The ligand exchange thermochromic system of claim 9 , wherein the system comprising:
a. a transition metal ion;
b. iodide; and
c. a derivative of 1,4-hydroquinone capable of minimizing or eliminating yellow color formation via a photochemical reaction caused by exposure to sunlight and/or simulated sunlight selected from the group consisting of derivatives of 1,4-hydroquinone according to structure I.
15. The ligand exchange thermochromic system of claim 14 , wherein the derivatives of 1,4-hydroquinone are selected from the group consisting of 2,5-di-tert-butyl-1,4-hydroquinone, 2,5-bis(1,1,3,3-tetramethylbutyl)-1,4-hydroquinone, 2,5-bis(1,1-dimethylethyl)-1,4-hydroquinone, 2,3,5-trimethyl-1,4-hydroquinone, 2,3,5,6-tetramethyl-1,4-hydroquinone, 1,4-hydroquinone-bis(2-hydroxyethylether), 3,5-di-tert-butyl-4-hydroxyanisole and combinations thereof.