Naphthalimide‐functionalized pH ‐responsive amphiphilic block copolymer nanoparticles

Abstract An amphiphilic block copolymer, poly(ethylene glycol)‐ b ‐poly( N ‐vinyl carbazole), functionalized with a 1,8‐naphthalimide fluorescent signaling moiety containing a pH‐responsive piperazinyl recognition unit (PEG‐ b ‐PVK‐ co ‐PNA), was synthesized via reversible addition‐fragmentation chain transfer polymerization. The block copolymer demonstrates a low molar mass dispersity and spontaneously self‐assembles into uniform nanoparticles in aqueous media, serving as a fluorescent sensor for detecting hydrogen ion. The emission from the PVK block is effectively quenched, whereas the 1,8‐naphthalimide moiety exhibits a pronounced fluorescence enhancement at 505 nm due to Förster resonance energy transfer between the PVK donor and the 1,8‐naphthalimide acceptor in the copolymer nanoparticles. The photoluminescence intensity at 505 nm displays a linear correlation with decreasing pH values in the range 3.0–6.5 for the copolymer nanoparticles in acidic medium, highlighting the block copolymer's potential for quantitative pH sensing in acidic environments. © 2025 Society of Chemical Industry.