SIMULTANEOUS PHOTOINDUCED COLOR FORMATION AND PHOTOINITIATED POLYMERIZATION

Crystal violet lactone (CVL, 1, )phenyl]-6-(dimethylamino)-1(3H)-isobe nzofuranone) and other lactone dye precursors 2-5 form colored triphen ylmethyl cations when irradiated with UV light in the presence or abse nce of [4-(octyloxy)phenyl]phenyliodonium hexafluoroantimonate (OPPI). In selected monomers in the presence of iodonium salt, color formatio n and polymerization occur simultaneously. The excited singlet state l ifetimes of 1-5 estimated from quantum yields for the disappearance of CVL in the presence of OPPI are similar to those observed for fluores cence quenching and occur mainly by electron transfer. On the basis of the transient absorption spectral it can be concluded that triarylmet hane cations are generated from the lactone precursors in the presence of OPPI in acetonitrile with a pseudo first order rate constant of 10 (4) s(-1). Color formation in the absence of OPPI is suggested to occu r from the excited singlet states of the lactone via a biradical forme d by photoinduced beta-bond cleavage.