Graduate School of Materials Science, Nara Institute of Science and Technology , 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
Department of Chemistry, College of Science, Rikkyo University , 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan.
Biomacromolecules. 2018 Feb 12;19(2):449-459. doi: 10.1021/acs.biomac.7b01554. Epub 2018 Jan 8.
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) from the polymer film showed g = +2.1 × 10 at 429 nm. Conversely, when dichloromethane (DCM) was used as the solvent, the CPL sign was inverted to g = -2.4 × 10 at 429 nm. The dissymmetry ratio of Cotton CD band (g) from the THF solution was g = +3.2 × 10 at 392 nm; conversely, from the DCM, the CD sign inverted to g = -0.8 × 10 at 371 nm. The sign and magnitude of the g values were interpreted to a London dispersion term (δ) of Hansen solubility parameter (δ) of the casting solvents rather than a dipole-dipole interaction term (δ) and a hydrogen bonding interaction term (δ) of the δ values and dielectric constant (ε). 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/π and π-π 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.
我们研究了当 CTPC 被用作 D-葡萄糖骨架聚合物的溶液处理手性平台时，其螺旋和/或手性是否可以转移到不带电荷、非螺旋的低聚和多芴上。值得注意的是，CTPC 显示出对这些芴的溶剂驱动的、左右逢源的分子间螺旋/手性转移能力。圆偏振发光（CPL）和相应的 CD 光谱的手性反转特征仅通过选择合适的非手性溶剂和/或非手性共溶剂即可实现。当 PF6 和 CTPC 在四氢呋喃（THF）中的溶液浇铸在石英基板上时，聚合物膜的 CPL（g）的不对称比显示 g = +2.1 × 10 在 429nm 处。相反，当使用二氯甲烷（DCM）作为溶剂时，CPL 符号反转至 g = -2.4 × 10 在 429nm 处。来自 THF 溶液的 Cotton CD 带（g）的不对称比为 g = +3.2 × 10 在 392nm 处；相反，来自 DCM 的 CD 符号反转至 g = -0.8 × 10 在 371nm 处。g 值的符号和大小解释为铸膜溶剂的 Hansen 溶解度参数（δ）的伦敦色散项（δ），而不是δ值的偶极-偶极相互作用项（δ）和氢键相互作用项（δ）和介电常数（ε）。对溶剂驱动的傅里叶变换红外光谱、广角 X 射线衍射谱和差示扫描量热法图的分析表明，由于 CTPC 的三个氨酯基团，溶剂驱动的多个氢键的开-关切换在反转中起关键作用。基于 PF6-CTPC 杂化物的分子力学和分子动力学模拟，假设芳基环和烷基之间的分子间 CH/π 和 π-π 相互作用对于螺旋/手性转移能力至关重要。这些手性反转特征源于 CTPC 螺旋的溶剂驱动的有序-无序转变特征，而不是 CTPC 本身的螺旋-螺旋转变。
