Abstract:Defect-free one-handed contracted helical tubular ladder polymers with a π-electron-rich cylindrical helical cavity were synthesized by alkyne benzannulations of the random-coil precursor polymers containing 6,6'-linked-1,1'-spirobiindane-7,7'-diol-based chiral monomer units. The resulting tightly-twisted helical tubular ladder polymers showed remarkably high enantioseparation abilities toward a variety of chiral hydrophobic aromatics with point, axial, and planar chiralities. The random-coil precursor polymer… Show more
“…39,40 The exploration of oxepine in functional electronic materials or in polymers is extremely rare. 41 Recently, triptycene-22 and spirobiindane-based 24,26 ladder polymers with enantiopure helical ribbon/tube have been realized using the above-mentioned acid-induced electrophilic cyclization reaction as the postpolymerization annulation. This approach has broad utility in quantitative regioselective ring formation to produce ladder polymers.…”
Section: ■ Introductionmentioning
confidence: 99%
“…Among the methods of postpolymerization modification, our group first reported a highly efficient acid-induced electrophilic cyclization reaction associated with the formation of six-membered rings to realize the synthesis of graphene-like π-conjugated ladder polymer . Over decades, this facile approach has been employed by our group and others to synthesize various ladder polymers and polycyclic aromatic systems. − …”
Section: Introductionmentioning
confidence: 99%
“…Recently, triptycene- and spirobiindane-based , ladder polymers with enantiopure helical ribbon/tube have been realized using the above-mentioned acid-induced electrophilic cyclization reaction as the postpolymerization annulation. This approach has broad utility in quantitative regioselective ring formation to produce ladder polymers. − However, the vast majority of electrophilic cyclization reactions on polymers produce five- or six-membered rings (Scheme a,b). As a result, we were interested in exploring new challenges in ladder polymer synthesis by introducing seven-membered oxepine rings in the polymer backbone (Scheme c).…”
Ladder polymers with backbones of uninterrupted ring-fused units have attracted academic and industrial attention for decades because of their extended π-conjugation and intrinsic microporosity for possible potential applications in organic optoelectronics and membrane gas separations. We report herein the synthesis and characterization of a new series of oxepine-based ladder/stepladder polymers prepared by acid-promoted intramolecular aromatic electrophilic cyclization reactions on alkyne-containing poly(arylene ether) precursors. In contrast to the more common annulations that produce five-and six-membered rings, we report that a sevenmembered ring can be regioselectively and quantitatively generated postpolymerization. Model compounds with repeating units of polymers have also been synthesized, and X-ray crystallographic analysis reveals a nonplanar contorted structure that is also present in the polymers. More interestingly, the oxepine-based ladder/ step-ladder polymers appear to display a photoinduced planarization of the 8 π electron oxepine ring driven by the excited-state aromatic stabilization energy, as indicated by the large Stokes shift.
“…39,40 The exploration of oxepine in functional electronic materials or in polymers is extremely rare. 41 Recently, triptycene-22 and spirobiindane-based 24,26 ladder polymers with enantiopure helical ribbon/tube have been realized using the above-mentioned acid-induced electrophilic cyclization reaction as the postpolymerization annulation. This approach has broad utility in quantitative regioselective ring formation to produce ladder polymers.…”
Section: ■ Introductionmentioning
confidence: 99%
“…Among the methods of postpolymerization modification, our group first reported a highly efficient acid-induced electrophilic cyclization reaction associated with the formation of six-membered rings to realize the synthesis of graphene-like π-conjugated ladder polymer . Over decades, this facile approach has been employed by our group and others to synthesize various ladder polymers and polycyclic aromatic systems. − …”
Section: Introductionmentioning
confidence: 99%
“…Recently, triptycene- and spirobiindane-based , ladder polymers with enantiopure helical ribbon/tube have been realized using the above-mentioned acid-induced electrophilic cyclization reaction as the postpolymerization annulation. This approach has broad utility in quantitative regioselective ring formation to produce ladder polymers. − However, the vast majority of electrophilic cyclization reactions on polymers produce five- or six-membered rings (Scheme a,b). As a result, we were interested in exploring new challenges in ladder polymer synthesis by introducing seven-membered oxepine rings in the polymer backbone (Scheme c).…”
Ladder polymers with backbones of uninterrupted ring-fused units have attracted academic and industrial attention for decades because of their extended π-conjugation and intrinsic microporosity for possible potential applications in organic optoelectronics and membrane gas separations. We report herein the synthesis and characterization of a new series of oxepine-based ladder/stepladder polymers prepared by acid-promoted intramolecular aromatic electrophilic cyclization reactions on alkyne-containing poly(arylene ether) precursors. In contrast to the more common annulations that produce five-and six-membered rings, we report that a sevenmembered ring can be regioselectively and quantitatively generated postpolymerization. Model compounds with repeating units of polymers have also been synthesized, and X-ray crystallographic analysis reveals a nonplanar contorted structure that is also present in the polymers. More interestingly, the oxepine-based ladder/ step-ladder polymers appear to display a photoinduced planarization of the 8 π electron oxepine ring driven by the excited-state aromatic stabilization energy, as indicated by the large Stokes shift.
“…An exceptionally high charge mobility for high-performance electronics was recently observed [ 9 ]. In addition, they have the potential to reduce the energy consumption and costs of industrial chemical separations [ 10 ] and can be highly enantioselective [ 11 ]. Even polymer lasers and all-optical devices based on the principle of strong light–matter coupling are possible and under investigation [ 12 ].…”
Ladder polymers with poly(diketopyrrolopyrrole) (DPP) moieties have recently attracted enormous interest for a large variety of opto-electronic applications. Since the rigidity of the backbone increases with ladderization, a strong influence on the self-organization of thin films is expected. We study the molecular orientation of DPP-based ladder polymers in about 50 nm thin films using polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS). Exemplarily, for one polymer, the orientation in thicker films is qualitatively investigated by infrared spectroscopy in transmission. Further, this method allows us to rule out the effects of a possible azimuthal ordering, which would affect the analysis of the orientation by PM-IRRAS. For all polymers, the long axis of the polymer backbone is preferentially oriented parallel to the substrate surface, pointing to a high degree of ordering. It is suggested that the choice of the side chains might be a promising way to tune for face-on and edge-on orientations. The exemplarily performed investigation of interface properties on substrates with different work functions suggests that the choice of the side chains has a minor effect on the interfacial electronic interface structure.
Helical ladder polymers are designed by connecting planar indenofluorene chromophores by chiral triptycene linkers. The resulting hexagonal helices exhibit a substantial degree of homoconjugation across the triptycene knots, with saturation above ≈20 repeat units. The chiroptical anisotropy values gabs = Δε/ε of the lower‐energy lobes of the red‐most couplets in the circular dichroism (CD) spectra arise from the π−π* transition of the planar indenofluorene chromophores and increase almost sevenfold when going from a model dimer to the corresponding polymeric helical ladder structures. This increase represents a signature of “chiral amplification” that is observed at the molecular, single‐chain level. Here, the incorporated chiral linker units determine the chiroptical properties of the helical polymer chain, with chiral interactions arising across many achiral indenofluorene building blocks (>12). This behavior is observed for a fully covalently bound single polymer chain, in contrast to the more commonly studied supramolecular assemblies of appropriate chiral molecules.
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