Switching materials, and compositions and methods for making same
A switching material comprising one or more than one polymers and an electrolyte comprising a salt and a solvent portion comprising one or more solvents; and one or more compounds having electrochromic and photochromic properties dispersed homogeneously through the switching material; and wherein the switching material is transitionable from a light state to a dark state on exposure to UV light and from a dark state to a light state with application of an electric voltage.
1. A switching material comprising:
a. one or more than one polymers, wherein the one or more than one polymers are chemically crosslinked with a crosslinking agent comprising about 0.01 wt. % to about 1 wt. % of the switching material;
b. an electrolyte comprising;
i. a salt; and
ii. a solvent portion comprising one or more solvents;
c. one or more compounds having electrochromic and photochromic properties dispersed homogeneously through the electrolyte; and
wherein the switching material is transitionable from a light state to a dark state on exposure to UV light and from a dark state to a light state with application of an electric voltage.
2. The switching material according to claim 1 comprising, on a weight basis:
a. about 2 wt % to about 15 wt % polymer;
b. about 0.1 wt % to about 5 wt % salt;
c. about 50 wt % to about 90 wt % solvent portion;
d. about 2% to about 15 wt % of a compound having electrochromic and photochromic properties.
3. The switching material of claim 1 wherein the one or more than one polymers is a polyol or is a polyvinyl acetal, or is a polyvinyl butyral.
4. The switching material of claim 3 wherein the one or more polymers is a polyvinyl butyral having one or more of: a MW of from about 170 to about 250 k, a polyvinyl alcohol group content of from about 18% to about 21%, a polyvinyl acetate content of from about 0 to about 2.5%.
5. The switching material of claim 3 wherein the polyvinyl butyral having one or more of: a polyvinyl alcohol group content of from about 12% to about 16%, or a polyvinyl acetate content of from about 1% to about 4%.
6. The switching material of claim 1 wherein the salt comprises a TFSI or BF 4 anion.
7. The switching material of claim 1 wherein the salt comprises an organic cation.
8. The switching material of claim 1 wherein the organic cation is a tetraalkyl ammonium or a tetraalkylphosphonium cation, and wherein alkyl includes a group of from 1 to 10 carbons.
9. The switching material of claim 2 comprising about 70 wt % to about 90 wt % the solvent portion.
10. The switching material of claim 1 wherein the electrolyte has a potential range of from about −1.0V to about +1.5 V compared to an Ag/AgCl reference electrode.
11. The switching material of claim 1 wherein the solvent has one or more of the following:
a. a boiling point of about 150° C. or greater;
b. a vapour pressure of about 0.001 mmHg or less at 20° C.;
c. a Yellowness Index (YI) of about 6 or less;
d. a flash point of about 80° C. or greater; and
e. a melting point of about 40° C. or less.
12. The switching material of claim 1 wherein the solvent, in combination with a chromophore, has a change in Yellowness Index of about 6 or less after 250 hours of weathering.
13. The switching material of claim 1 wherein the solvent portion comprises one or more than one of dimethyl 2-methylglutarate, 1,2-butylene carbonate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, diethyl succinate, diethyl adipate, dimethyl adipate.
14. The switching material of claim 1 wherein the solvent portion comprises dimethyl 2-methylglutarate and 1,2-butylene carbonate.
15. The switching material of claim 1 wherein the solvent portion comprises dimethyl 2-methylglutarate and 1,2-butylene carbonate in a 5:1, 9:1 or 19:1 ratio.
16. The switching material of claim 1 wherein the crosslinking agent comprises one or more isocyanate groups.
17. The switching material of claim 1 wherein the one or more compounds having electrochromic and photochromic properties is a diarylethene.
18. A switchable film comprising:
a. a first and optionally a second substantially transparent substrate;
b. a first and a second electrode disposed on the surface of at least one of the substrates; and
c. a switching material according to claim 1 disposed between the first and the optional second substrates and in contact with the first and the second electrodes.
19. A laminated glass comprising the switchable film of claim 18 .
20. The switching material of claim 1 , wherein the crosslinking agent comprises about 0.02 wt. % to about 0.4 wt. % of the switching material.