Ambidextrous Chirality Transfer Capability from Cellulose Tris(phenylcarbamate) to Nonhelical Chainlike Luminophores: Achiral Solvent-Driven Helix-Helix Transition of Oligo- and Polyfluorenes Revealed by Sign Inversion of Circularly Polarized Luminescence and Circular Dichroism Spectra

作者：Guo Sibo; Kamite Hiroki; Suzuki Nozomu; Wang Laibing; Ohkubo Asuka; Fujiki Michiya

来源：Biomacromolecules, 2018, 19(2): 449-459.

DOI：10.1021/acs.biomac.7b01554

We investigated whether helicity and/or chirality of cellulose tris(phenylcarbamate) (CTPC) can transfer to noncharged, nonhelical oligo- and polyfluorenes when CTPC was employed as a solution processable homochiral platform of a D-glucose-skeletal polymer. Noticeably, CTPC revealed the solvent-driven, ambidextrous intermolecular helicity/chirality transfer capability to these fluorenes. The chiroptical inversion characteristics of circularly polarized luminescence (CPL) and the corresponding CD spectra were realized by solely choosing a proper achiral solvent and/or achiral cosolvent. When the solution of PF6 and CTPC in tetrahydrofuran (THF) was cast on a quartz substrate, the dissymmetry ratio of CPL (g(CPL)) from the polymer film showed g(CPL) = +2.1 X 10(-3) at 429 nm Conversely, when dichloromethane (DCM) was used as the solvent, the CPL sign was inverted to g(CPL) = -2.4 X 10(-3) at 429 nm. The dissymmetry ratio of Cotton CD band (g(CD)) from the THF solution was g(CD) = +3.2 X 10(-3) at 392 nm; conversely, from the DCM, the CD sign inverted to g(CD) = -0.8 X 10(-3) at 371 nm. The sign and magnitude of the g(CD) values were interpreted to a London dispersion term (delta(d)) of Hansen solubility parameter (delta) of the casting solvents rather than a dipole-dipole interaction term (delta(p)) and a hydrogen bonding interaction term (delta(h)) of the delta values and dielectric constant (epsilon). Analysis of solvent-driven changes in FTIR spectra, wide-angle X-ray diffraction profiles, and differential scanning calorimetry diagrams indicated that solvent driven on-off switching of multiple hydrogen bonds due to three urethane groups of CTPC play the key for the inversion. Intermolecular CH/pi and pi-pi interactions among phenyl rings and alkyl groups were assumed to be crucial for helicity/chirality transfer capability based on molecular mechanics and molecular dynamics simulations of PF6-CTPC hybrids. These chiroptical inversion characteristics arose from solvent-driven order-disorder transition characteristics of the CTPC helix rather than a helix-helix transition of CTPC itself.

• 出版日期2018-2