Vinyl monomers bearing chromophore moieties and their polymers. XI. Synthesis and photochemical behavior of carbazole-containing methacrylic monomersand their polymers

Three carbazole-containing methacrylic monomers, 2-(N-carbazolyl)ethyl meth acrylate(CzEMA), 6-(N-carbazolyl)hexyl methacrylate(CzHMA), and 11-(N-carba zolyl)undecyl methacrylate (CzUMA), and their saturated model compounds, 2- (N-carbazolyl)ethyl isobutyrate, 6-(N-carbazolyl)hexyl isobutyrate, and 11- (hr-carbazolyl)undecyl isobutyrate, were synthesized and polymerized. UV ab sorption spectra showed that there was either negligible or no interaction between the carbon-carbon double bond of the methacrylic group and the carb azolyl chromophore moiety in the ground state for these monomers. Fluoresce nce spectra of the monomers, their model compounds, and the polymers were r ecorded in the solvents with different polarities. CzEMA exhibited the fluo rescence structural self-quenching effect (SSQE), but CzHMA and CzUMA did n ot. In addition, the SSQE of CzEMA depended strongly on the polarity of the solvents. That is, the stronger the polarity of a solvent was, the more ob vious the SSQE was. Therefore, the SSQE of CzEMA mainly was caused by the i ntramolecular charge-transfer interaction between the excited electron-dona ting carbazolyl chromophore moiety and the electron-accepting carbon-carbon double bond of the methacrylic group. This was confirmed by the fluorescen ce-decay curves and the fluorescence lifetimes of the monomers, their model compounds, and the polymers. The monomers, their model compounds, and the polymers initiated the photopolymerization of methyl methacrylate (MMA) upo n UV irradiation. CzEMA showed greater initiation ability than the other tw o monomers and their model compounds; this was ascribed to the photoinduced intramolecular charge-transfer interaction. The higher initiation efficien cy of the homopolymers compared to that of the copolymers with MMA was inte rpreted as the result of singlet energy migration of the excited carbazolyl chromophores along the polymer chains. (C) 2000 John Wiley & Sons, Inc.