Polymerization of fluorene-based monomers modified with thiavinylidene structure at 9-position and their optical properties

Abstract

Two iodo-functionalized fluorene-based monomers having a thiavinylidene moiety at 9-position [2,7-diiodo-9-( n-hexylthiavinylidene)fluorene and 2,7-diiodo-9-((2-(2-methoxyethoxy)ethyl)thiavinylidene)fluorene] were synthesized. Suzuki coupling reactions with thienylboronic acids bearing a n-hexyl chain were subsequently conducted to obtain two thiophene-functionalized monomers [2,7-bis(4-hexylthienyl)-9-( n-hexylthiavinylidene)fluorene and 2,7-bis(3-hexylthienyl)-9-( n-hexylthiavinylidene)fluorene]. The dehalogenative polycondensation using Ni(cod) 2/cod/bpy system and the oxidation coupling polymerization using FeCl 3 gave three homopolymers ( HP1, HP2, and HP3). The polymerization under Suzuki coupling condition gave three copolymers ( CP1, CP2, and CP3). The number-averaged molecular weights ranged from 2500 to 23,000. The optical properties of polymer were dependent upon the character of arylene unit. Namely, HP1 solely consisting of a 9-( n-hexylthiavinylidene)fluorene segment demonstrated the short absorption maximum wavelength but the large red-shift (13 nm) from the solution state to film state. CP3 having a hydrophilic side chain showed the larger red-shift (13 nm) as compared with CP2 bearing the similar backbone and a hydrophobic side chain.