SIMULTANEOUS PHOTOINDUCED COLOR FORMATION AND POLYMERIZATION - THE FORMATION OF HIGHLY COLORED THIN-FILMS FROM COLORLESS PRECURSORS DUE TO FORMATION OF TRIARYLMETHANE CATIONS BY ACID GENERATING DECOMPOSITION OF IODONIUM SALTS

Highly colored thin films were prepared by irradiating transparent res ins consisting of the iodonium salt [4-[(octyloxy)phenyl]phenyl]iodoni um hexafluoroantimonate (OPPI, 1) and a dye precursor such as crystal violet lactone (CVL, 2) dissolved in an acrylate epoxide mixture. It h as been demonstrated that a mixture of CVL and OPPI is a very efficien t photoinitiator for radical polymerizations. Color formation takes pl ace via the excited state of CVL, that is oxidized by OPPI to a radica l cation, that subsequently forms the colored triarylmethane cation by hydrogen abstraction from the solvent. Formation of photoacid via the excited state of OPPI also contributes to color formation. The main a dvantage of our approach, by which films of different colors can be ma de, is that highly colored (OD > 2.0: 400-700 nm; 15 mu m thick) films can be formed at rates comparable with those of noncolored films.