Linear and hyperbranched polymers with high thermal stability and luminescence efficiency

New acetylene monomers, 6-{[(1-naphthylethynyl-4-phenyl)carbonyl]oxy}-1-phenyl-1-hexyne (1), 2,5-diethynylthiophene (3), and 4,4′-diethynylbiphenyl (6) were synthesized. Homopolymerization of 1 and copolycyclotrimerizations of 3 and 6 with 1-heptyne and 1-octyne have been achieved with WCl₆- and TaCl₅-Ph₄Sn catalysts, respectively, giving soluble linear disubstituted polyacetylene (2) and hyperbranched polyarylenes (5 and 8) with high molecular weights (up to 1.2 × 10⁵) in high yields (up to 98%). The structures and properties of the polymers are characterized and evaluated by IR, NMR, TGA, UV, photoluminescence (PL), and electroluminescence (EL) analyses. All the polymers possess high thermal stability and emit strong blue light upon photoexcitation. The intensity of the emitted light is greater than that of poly(1-phenyl-1-octyne), a well-known highly luminescent disubstituted polyacetylene. Little aggregation-induced red shift in the PL was observed in the thin films of the polymers. By constructing a multi-layer EL device, high EL quantum yield (0.18%) has been achieved in 2, which are the best results for substituted polyacetylenes attainable so far.