Blue electroluminescence of substituted polyacetylenes

We report blue emission from a series of alkyl and phenyl disubstituted polyacetylenes, i.e., poly(1-phenyl-1-alkynes) (PPhAs), with alkyne being n-propyne, n-butyne, and n-octyne. Blue electroluminescence from PPhAs is observed by employing a cell with an ITO (indium-tin oxide) coated glass substrate/PPhA/Mg/Al structure. The color of luminescence is changed from blue-green to pure blue and the luminescence intensity is enhanced when the length of alkyl side chain increases, while neither an alkyl nor a phenyl monosubstituted polyacetylene shows an intense luminescence. The electroluminescence efficiency of PPhAs is not efficiently improved by doping with a common electron-transporting material 2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD).