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PE films grafted with poly(methyl acrylate) and labeled with pyrene groups were obtained by irradiation with γ-rays in the presence of acryloyl chloride and further reacting them with 1-pyrenebutanol or 1-pyrenemethylamine. Characterization of the polymer films benefited from the dual use of the pyrene probe as an indicator of, first, polymer chain dynamics by monitoring pyrene excimer formation by fluorescence and, second, polymer morphology by staining the pyrene-rich domains of the films with RuO(4) for scanning electron microscopy (SEM). The grafted polymers labeled with 1-pyrenemethylamine showed much stronger absorbance than those labeled with 1-pyrenebutanol despite having similar pyrene contents. The fluorescence spectra of the grafted polymers labeled with 1-pyrenebutanol exhibited monomer emission, whereas those labeled with 1-pyrenemethylamine exhibited exclusively excimer emission. These dramatic differences could be accounted for by noting that labeling of the grafted poly(acryloyl chloride) with 1-pyrenemethylamine results in cross-linking of the polymer matrix, with an associated enhancement of the concentration of pyrene in the cross-linked domains, which was confirmed by SEM. Formation of discrete domains in the polymer film can induce multiple scattering at the domain boundaries which lengthens the path of light in the film and increases absorption of the light by the tightly packed pyrene-rich domains. Implementation of this effect for fabrication of plastic color filters should generate more efficient filters which should find numerous practical applications.

Dithiafulvene oligomers (3) were prepared by cycloaddition polymerization of aldothioketenes with their alkynethiol tautomers derived from 1,4-diethynylbenzene (2) with the addition of 1-ethynyl-4-methylbenzene (1) as a monofunctionalized compound. Different feed ratios of 2/1 were used to control the molecular weights of 3. The structures of 3 were confirmed by IR and 1 H NMR spectroscopies in comparison with those of 2-(4-tolylidene)-4-tolyl-1,3-dithiol (4) as a model compound, which was obtained by the treatment of lithium 2-tolylethynethiolate with water in Et 2 O. The numberaverage degree of polymerization (DP) and the number-average molecular weight were measured by gel permeation chromatographic and 1 H NMR analysis. DP increased with an increasing feed ratio of 2/1. The ultraviolet-visible spectra of 3 in diluted acetonitrile showed that the absorption maxima of 3 increased with an increasing DP of 3. These redshifts are ascribed to an effective expansion of the -conjugation system in 3. The oligomers exhibited a maximum conjugation length of seven repeating units. The redox properties of 3 were examined by cyclic voltammetry. The oxidation halfpeak potentials (E p/2 ) of 3 were slightly cathodically shifted with increasing DP.