Synthesis and photoluminescence properties of poly(1-hexyl-2-aryl acetylene)s, poly(1-phenyl-2-fluorenylacetylene), and poly(1-fluorenyl-2-fluorenlacetylene)

Abstract The metathesis polymerizations of 1-hexyl-2-arylacetylenes [ n -C 6 H 13 C CAr; Ar = phenyl ( 1a ), naphthyl ( 1b ), biphenyl ( 1c ), fluorenyl ( 1d )] were examined using NbCl 5 , TaCl 5 , and WCl 6 . When NbCl 5 / n -Bu 4 Sn was used as a catalyst in their polymerization, high-molecular-weight polymers ( 2a – 2d ) were obtained in good yield compared to TaCl 5 / n -Bu 4 Sn and WCl 6 /Ph 4 Sn. 1-Hexyl-2-[2-(9,9-dialkylfluorenyl)]acetylenes ( 1e – 1h ) also polymerized by NbCl 5 / n -Bu 4 Sn to give corresponding polymers ( 2e – 2h ) with relatively high molecular weights. Diarylacetylene polymers ( 2i and 2j ) were obtained by the metathesis polymerization using TaCl 5 / n -Bu 4 Sn. All the poly(1-hexyl-2-arylacetylene)s ( 2a – 2h ) emitted blue-colored lights, and the fluorenyl group-containing polymers exhibited strong photoluminescence. However, the fluorenyl group-containing polymers with long alkyl groups such as n -butyl and n -octyl groups at the 9-position on fluorene rings showed weak emissions because the steric hindrance of long alkyl groups prevents to form intramolecular excimers. The emission spectra of diarylacetylene polymers red-shifted, and 1-phenyl-2-[2-(9,9-dimethylfluorenyl)]acetylene ( 2i ) and 1-(2-fluorenyl)-2-[2-(9,9-dimethylfluorenyl)]acetylene ( 2j ) showed green-colored and yellow-colored emissions, respectively.