- NATURE PUBLISHING GROUP
Yamamoto coupling polymerizations of 2,3-diiodo-N-cyclohexylmaleimide (DICHMI) with dihalide carbazole derivatives (DXRCz) (3,6-dibromo-N-methylcarbazole (3,6-DBrMCz), 3,6-diiodo-N-hexylcarbazole (3,6-DIHCz) and 2,7-dibromo-N-hexylcarbazole (2,7-DBrHCz)) were performed using a nickel complex. The number-average molecular weights (M-n) of poly(N-cyclohexylmaleimide-co-N-substituted carbazole)s (poly(CHMI-co-RCz)) were in the range of 600-7300, as determined by gel permeation chromatography analyses. The fluorescence emissions of the poly(CHMI-co-RCz) solution showed two emission maxima in the 417-426 and 581-595 nm regions. The fluorescence peaks of co-oligomers at long wavelengths (581-595 nm) were attributable to the conjugated neighboring CHMI-RCz units of polymer main chains. The intensities of fluorescence emissions were significantly affected by the polarity of organic solvents such as tetrahydrofuran and N,N-dimethylformamide. The solvatochromic fluorescence phenomenon may be attributable to the twisting of CHMI-RCz bonds in an excited state in polar solvents.
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