Coated microcapsules
Accordingly, there are provided coated microcapsules including: a microcapsule including a polymeric shell and a liquid core material encapsulated therein; and a metallic coating surrounding said microcapsule, wherein the metallic coating comprises particles of a first metal adsorbed on said polymeric shell and a film of a second metal formed thereon; wherein said particles of the first metal are charge-stabilized nanoparticles; processes for preparing the coated microcapsules, as well as formulations related thereto are also included.
1. A coated microcapsule comprising:
a microcapsule comprising a polymeric shell and a liquid core material encapsulated therein; and
a metallic coating surrounding said microcapsule,
wherein the metallic coating comprises nanoparticles of a first metal adsorbed on said polymeric shell to form a discontinuous layer and a continuous film of a second metal overlaid thereon;
wherein said nanoparticles of the first metal are charge-stabilised nanoparticles.
2. A coated microcapsule according to claim 1 wherein said particles are adsorbed on the polymeric shell by electrostatic interaction.
3. A coated microcapsule according to claim 1 , wherein the polymeric shell comprises a surface-modifying agent on which at least some of said particles are adsorbed, wherein the surface modifying agent is a polymer or a surfactant.
4. A coated microcapsule according to claim 1 , wherein said particles are charge-stabilised by an anionic stabiliser.
5. A coated microcapsule according to claim 4 , wherein the anionic stabiliser is selected from borohydride anions and citrate ions.
6. A coated microcapsule according to claim 4 , wherein the anionic stabiliser is an anionic surfactant, wherein the anionic surfactant selected from sodium dodecyl sulfate, sodium laureth sulfate, dodecyl benzene sulfonic acid, perfluorooctanesulfonate, dioctyl sodium sulfosuccinate and sodium stearate.
7. A coated microcapsule according to claim 4 , wherein the polymeric shell comprises a cationic surface-modifying agent, wherein the cationic surface-modifying agent is a cationic surfactant or a cationic polymer.
8. A coated microcapsule according to claim 7 , wherein said cationic surface-modifying agent is a cationic surfactant selected from cetyl trimethylammonium bromide, dodecyl dimethylammonium bromide, cetyl trimethylammonium chloride, benzalkonium chloride, cetylpyridinium chloride, dioctadecyl dimethylammonium chloride and dioctadecyl dimethylammonium bromide.
9. A coated microcapsule according to claim 8 , wherein said cationic surface-modifying agent is cetyl trimethylammonium bromide.
10. A coated microcapsule according to claim 4 , wherein the polymeric shell comprises a non-ionic surface modifying agent, wherein the non-ionic surface modifying agent is a non-ionic polymer, and wherein the non-ionic polymer is selected from poly(vinyl alcohol), poly(vinyl pyrrolidone), and combination thereof.
11. A coated microcapsule according to claim 1 , wherein said particles are charge-stabilised by a cationic stabiliser.
12. A coated microcapsule according to claim 11 , wherein said cationic stabiliser is a cationic surfactant, wherein the cationic surfactant is selected from cetyl trimethylammonium bromide, tetraoctylammonium bromide, dodecyl trimethylammonium bromide, and combinations thereof.
13. A coated microcapsule according to claim 12 , wherein the polymeric shell comprises an anionic surface-modifying agent, wherein the anionic surface-modifying agent is an anionic surfactant or an anionic polymer.
14. A coated microcapsule according to claim 13 , wherein said anionic surface-modifying agent is: (i) an anionic surfactant selected from sodium dodecyl sulfate, sodium laureth sulfate, dodecyl benzene sulfonic acid, dioctyl sodium sulfosuccinate, perfluorooctanesulfonate, dioctyl sodium sulfosuccinate and sodium stearate; or (ii) an anionic polymer selected from poly(acrylic acid) and poly(methacrylic acid).
15. A coated microcapsule according to claim 11 , wherein the polymeric shell comprises a non-ionic surface modifying agent.
16. A coated microcapsule according to claim 12 , wherein the polymeric shell comprises a non-ionic surface modifying agent, wherein the non-ionic surface modifying agent s a non-ionic polymer, and wherein the non-ionic polymer is selected from poly(vinyl alcohol), poly(vinyl pyrrolidone), or combination thereof.
17. A coated microcapsule according to claim 1 , wherein:
i) the charge-stabilised nanoparticles have a particle size of less than 100 nm;
ii) the first metal is selected from palladium, platinum, silver, gold, nickel, tin and combinations thereof; and
iii) the second metal is selected from silver, gold, copper, nickel, and combinations thereof.
18. A coated microcapsule according to claim 1 , wherein:
i) the charge-stabilised nanoparticles have a particle size of less than 100 nm;
ii) (a) the first metal is platinum and the second metal is gold; (b) the first metal is gold and the second metal is silver; or (c) the first metal is gold and the second metal is copper.
19. A coated microcapsule according to claim 1 , wherein the metallic coating has a maximum thickness of 1000 nm, and a minimum thickness of 5 nm, and wherein the coated microcapsule has a particle size of from 0.5 micron to 500 microns.
20. A coated microcapsule according to claim 1 , wherein the polymeric shell comprises a polyacrylate.