C_β conformer formation in poly(9,9-dioctylfluorene) single chains facilitated by endcapping with an electron deficient moiety

Using single molecule spectroscopy, we demonstrate the enhancement of C_β conformer formation in poly(9,9-dioctylfluorene) (PFO) at the single chain level by endcapping with the electron deficient moiety, triazole (TAZ) or oxadiazole (OXD). The single-chain photoemission spectra of PFO without endcapping (PFO_u) indicates that the addition of endcappers results in mixed contributions of both disordered and C_β conformations. The as-cast endcappers are found to exhibit significantly larger amounts of C_β emissions than as-cast PFO_u. A higher population of C_β conformers lead to better alignment of the chromophores in the polymer backbone, as demonstrated by the polarization modulation depth measurement. Our findings are consistent with the higher β-phase content in the thin films cast from the endcapped PFOs, which means that the intra-chain interaction mediated by EDM dominates the β-phase formation. The present study offers an important basis for a useful approach to increasing β-phase content based on endcapping PFO with TAZ or OXD without the need for further sample treatment. This journal is