Synthesis and chiroptical properties of chiral binaphthyl-containing polyfluorene derivatives

Abstract

New chiral binaphthyl-containing polyfluorene (PF) derivatives, PFOH, PFMOM, and PFP, bearing different binaphthyl units ((S)-2,2′-bis(methoxymethoxy)-1,1′-binaphthyl for PFMOM, (S)-1,1′-binaphthyl-2,2′-diol for PFOH, and (S)-2,2′-bis(diphenylphosphinyl)-1,1′-binaphthyl for PFP) in the backbone have been designed and synthesized through Pd-catalyzed Suzuki polycondensation. Their properties have been investigated in detail by 1H NMR, 13C NMR, TGA, DSC, UV–vis, photoluminescence (in solutions, in thin films before and after annealing), and circular dichroism (CD) spectroscopic methods compared with poly(9,9-dihexylfluorene-2,7-diyl) (PF). The resulting copolymers possessed excellent solubility in organic solvents and emitted strong blue light. The phosphine oxide-containing copolymers PFP and PFMOM exhibited higher quantum yields and better thermal spectral stability in comparison with PF. All the copolymers exhibited obviously the linearly polarized photoluminescent properties both in solutions and in solid states. High emission polarization ratios (RPL) of PFP were observed with no obvious decrease upon thermal annealing. In addition, investigation of the CD spectroscopic properties of these copolymers in THF solutions indicated that the chirality of the binaphthyls could be transferred to the whole PF backbone. All these results demonstrated that introduction of the chiral binaphthyls, particularly BINAPO, into the backbone could effectively improve the performances of the copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011