Monitoring in Real-Time the Degrafting of Covalently Attached Fluorescent Polymer Brushes Grafted to Silica SubstratesEffects of pH and Salt.

Poly(acrylic acid) (PAA) covalently immobilized on glass substrates was made fluorescent by grafting a BODIPY derivative (PMOH) via an ester linkage. Although only nanograms/square centimeter of polymer are understood to be immobilized onto the SiO2substrate, the fluorophore-tagged polymer was readily visible to the naked eye and its fluorescence was easily detected. The characteristic BODIPY emission, centered at 550 nm, was used to follow the degrafting of PAA from the glass substrates in aqueous solution in real-time using total internal reflection fluorescence (TIRF) microscopy. The substrate−initiator bond hydrolysis and the conditions at which the PAA degrafting occurred were unequivocally confirmed in real-time by TIRF microscopy. No cleavage of the polymer occurred between pH 6.5 and 10.5 in the absence of NaCl. In contrast, polymer degrafting from the substrate occurred at pH ≥ 9.5 when 10 mM NaCl was added to the buffer solution. [ABSTRACT FROM AUTHOR]