thermo- and photo-switchable nanocapsules containing leuco-dye mixture and spiropyran

In this study, leuco-dye with spirolactone structure and hydroxyl-functionalized spiropyran (spoh) were synthesized and coencapsulated with bisphenol a and tetradecanol (tdh), or dodecanol (ddh) into a crosslinked polymethyl methacrylate substrate through miniemulsion polymerization. the generated nanocapsules containing tdh (tpl@t) and ddh (tpl@d) had spherical and smooth morphology with an average particle size of 109–120 nm. the coated tpl@d and tpl@t nanocapsules on cellulose substrate displayed thermo-switchable color shifts between deep red and colorless. in addition, upon uv irradiation at 365 nm, the coated nanocapsules on cellulose showed color change from colorless to purple. reversible thermo- and photo-switching of the prepaed nanocapsules over 10 cycles of uv-vis and heating-cooling cycles demonstrated their effectiveness for use in anti-counterfeiting systems.