Functionalized 4-(dialkylamino)-4 '-nitrostilbenes as reactive fluorescentprobes for monitoring the photoinitiated polymerization of MMA

A series of reactive (2, 4) and nonreactive (3, 5) fluorescent probes based on 4-(dimethylamino)-4'-nitrostilbene (1) have been synthesized. Substitut ion of a methyl on the dimethylamino group results in blue shifts in emissi on and increases in Phi(f), and corresponding reactive and nonreactive prob es are indistinguishable. Emission spectra of 1-5 were recorded during the photoinitiated polymerization of methyl methacrylate (MMA). For nonreactive probes, only minor changes in emission are observed during the first 40% o f the reaction, while at conversions between 50 and 90% lambda(max) is prop ortional to the conversion. For reactive probes shifts of lambda(max) durin g the early stages of the process are observed, enabling them to monitor th e full polymerization process. It was proven that the shift in emission dur ing the first stage of the reaction is due to covalent attachment of the re active probes to the PMMA backbone.