PHOTOPOLYMERIZATION IN AQUEOUS-SOLUTIONS INITIATED BY THE INTERACTIONOF EXCITED PYRENE DERIVATIVES WITH ALIPHATIC-AMINES

The photolysis of pyrene derivatives in the presence of amines has bee n employed as a source of free radicals in the polymerization of 1-vin yl-2-pyrrolidinone in aqueous solution. The photoinitiation efficiency strongly depends on the amine and the sensitizer employed. With regar d to the amine, only tertiary amines are efficient cocatalysts, hydrox yethanolamines being particularly efficient. For a given amine the ini tiation efficiency is high for pyrene and its cationic derivatives, wh ile pyrenebutyric acid is a poor photoinitiator and pyrenesulfonic aci d does not initiate the polymerization. The active radicals are produc ed in the interaction between the singlet excited state and the additi ve, the photoinitiation rate being proportional to the fraction of sin glets quenched by the amine. The photoinitiation efficiency at total s inglet quenching correlates with the rate constant of the quenching pr ocess, the photobleaching rate, and the pyrene radical anion yield. Ph otobleaching yield and the lifetime of the pyrene-derived radical anio n decrease in the presence of 1-vinyl-2-pyrrolidinone. All these resul ts are compatible with an initiation mechanism involving the interacti on of the pyrene radical anion with the monomer.