Synthesis and photoluminescence properties of heterocycle-containing poly(disubstituted acetylene)s

The metathesis polymerizations of disubstituted acetylenes containing heterocycles such as thiophene, furan, benzo[b]thiophene, and benzothiazole were examined using NbCl5, TaCl5, and WCl6. Thiophene-containing monomers polymerized to afford relatively high-molecular-weight polymers in moderate yields. Benzo[b]thiophene-containing monomers also polymerized to give polymers with relatively high molecular weights. On the other hand, furan- and benzothiazole-containing monomers exhibited low metathesis polymerizability, and the polymerizations did not provide high-molecular-weight polymers. Poly(1-hexyl-2-arylacetylene)s having heterocycles [poly(1a) and poly(3a), Scheme 1] emitted blue-colored lights, and the emission maxima were around 480 nm. Heterocycle-containing poly(1-phenyl-2-arylacetylene) [poly(1b)] and poly(1-fluorenyl-2-arylacetylene) [poly(3d)] showed green-colored and yellow-colored emissions, and the emission maxima were 520 and 540 nm, respectively. The emission wavelengths of poly(disubstituted acetylene)s having heterocycles were almost the same as those of the corresponding poly(disubstituted acetylene)s without heterocycles. However, heterocycle-containing polymers showed high fluorescence quantum yields compared to the corresponding polymers without heterocycles. Diarylacetylene polymers showed emission red-shifts between the solution and cast film, while the emission maximum of poly(1-hexyl-2-phenylacetylene) [poly(1a)] in the cast film was almost the same as that in the solution. Benzo[b]thiophene-containing poly(1-(4-trimethylsilylphenyl)-2-phenylacetylene) [poly(3b)] and poly(1-(9,9-dimethyl-2-fluorenyl)-2-phenylacetylene) [poly(3d)] afforded the free-standing membranes because of their high molecular weights. The oxygen permeability coefficient (PO2) of poly(3b) was as large as 1400 barrers. Poly(3d) showed higher gas permeability, and its PO2 was 5300 barrers.