Light-triggered “on–off” switching of fluorescence based on a naphthopyran-containing compound polymer micelle

We report a compound polymer micelle with light-triggered “on–off” switching of fluorescence based on the self-assembly of two block copolymers. First, the naphthalimide fluorophore is incorporated into poly(styrene-stat-naphthalimide)-b-poly(N-isopropyl acrylamide) [P(St-stat-MANI)-b-PNIPAM]. Second, the naphthopyran unit is engineered in poly(styrene-stat-naphthopyran)-b-poly(N-isopropyl acrylamide) [P(St-stat-NP)-b-PNIPAM] to manipulate the fluorescence when self-assembled into compound micelles with fluorophore-containing P(St-stat-MANI)-b-PNIPAM. The fluorescence of naphthalimide (MANI) can be modulated between “on” and “off” states by the photochromic reaction of naphthopyran (NP) upon UV irradiation and thermal fading reaction. Furthermore, Nile red (NR) was encapsulated in the micelle and showed a controlled release behavior by light. Our strategy may be extended for designing a range of multifunctional smart fluorescent materials such as chemical sensors.