Engineering rose bengal-decorated core-shell latex by RAFT dispersion PISA for photosensitized singlet oxygen generation

Spherical photoactive polymer colloids grafted with Rose Bengal (RB) photosensitizer (PSens) were synthesized by dispersion polymerization-induced self-assembly (PISA) in alcoholic media to promote singlet oxygen production ( 1 O 2 ) from a supported PSens. RB-based methacrylate monomer (EMARB) was synthesized before its copolymerization with oligo(ethylene glycol) methyl ether methacrylate (OEGMA) by reversible addition-fragmentation chain transfer (RAFT) to produce a macromolecular chain transfer agent (macroCTA). The macroCTAs with various EMARB fractions were subsequently used for RAFT PISA of benzyl methacrylate (BzMA) in ethanol. Size-exclusion chromatography (SEC) confirmed efficient EMARB copolymerization, control of molar masses, and high blocking efficiency, despite some unexpected elution of RB-based polymer chains in tetrahydrofuran. Systematically varying the degree of polymerization (DP) of the PBzMA core-forming block enabled us to obtain a series of RB-functionalized particles of spherical morphology with tunable mean diameters (60 to ∼ 260 nm), for solids content ranging from 9 to 21 wt-%. The singlet oxygen quantum yield of the heterogenized RB (ϕ Δ = 0.48 to 0.64 ± 0.10), in a close range with that of free RB in ethanol (ϕ Δ = 0.80 ± 0.10), revealed particularly high photoactivity of the shell-functionalized photosensitized latex particles synthesized by RAFT PISA. This value was independent of both EMARB monomer loading (1.1 to 3.4 µmol.g −1 ) and particle diameter. By monitoring photobleaching yield, we demonstrated that covalent immobilization of RB within the core–shell particles significantly improved photostability without compromising 1 O 2 generation efficiency.