Tuning Optical and Electroluminescent Properties of Poly(thiophene)s via Post-Functionalization

摘要

Electrophilic substitution of P3HT was conducted using N-bromosuccinimide (NBS), N-chlorosuccinimide (NCS), and fuming nitric acid under mild conditions to afford quantitatively brominated, chlorinated, and nitro-substituted polymers, Br-PHT, Cl-PHT, and NO_2-PHT, respectively. Br-PHT was further transformed to various aryl, vinyl, and alkylnyl-substituted poly(thiophene)s via Suzuki, Stille, and Heck coupling reactions. The optical properties of polymers could be tuned by the steric and electronic effects of incorporated substituents. Polymers possessing ortho-alkylphenyl or 2-(3-alkyl)thienyl groups exhibit significantly enhanced fluorescence yield (Φ_(fl)) in the solid state (～22%), which is one order of magnitude greater than that of P3HT (1.6%). Electroluminescence study of o-tolyl substituted polymers (50 - 100% of substitution) revealed that the EL efficiency of these polymers was much enhanced (internal Φ_(fl), 0.7 - 1.8%), compared with P3HT.