Chiral Π-conjugated Polymers Research Articles

Near-unity angular anisotropy of circularly polarized luminescence from microspheres of monodispersed chiral conjugated polymers.

A microsphere, assembled from a chiral π-conjugated polymer with narrow polydispersity, features a well-organized twisted-bipolar structure and exhibits highly biased circularly polarized luminescence (CPL). The CPL emitted toward the equatorial direction is 61-fold greater than that emitted along the zenith direction, which is the highest anisotropy among existing microscopic CPL emitters.

Chiral Diketopyrrolopyrrole-Based Conjugated Polymers with Intramolecular Rotation-Isomeric Conformation Asymmetry for Near-Infrared Circularly Polarized Light-Sensing Organic Phototransistors.

Recent advances in chiral nanomaterials interacting with circularly polarized (CP) light open new expectations for optoelectronics in various research fields such as quantum- and biology-related technology. To fully utilize the great potential of chiral optoelectronic devices, the development of chiral optoelectronic devices that function in the near-infrared (NIR) region is required. Herein, we demonstrate a NIR-absorbing, chiroptical, low-band-gap polymer semiconductor for high-performance NIR CP light phototransistors. A newly synthesized diketopyrrolopyrrole-based donor-acceptor-type chiral π-conjugated polymer with an asymmetric alkyl side chain exhibits strong chiroptical activity in a wavelength range of 700-1000 nm. We found that the attachment of an enantiomerically pure stereogenic alkyl substituent to the π-conjugated chromophore backbone led to strong chiroptical activity through symmetry breaking of the π-conjugation of the backbone in a molecular rotational motion while maintaining the coplanar backbone conformation for efficient charge transport. The NIR CP light-sensing phototransistors based on a chiral π-conjugated polymer photoactive single channel layer exhibit a high photoresponsivity of 26 A W-1 under NIR CP light irradiation at 920 nm, leading to excellent NIR CP light distinguishability. This study will provide a rationale and strategy for designing chiral π-conjugated polymers for high-performance NIR chiral optoelectronics.

Consequences of Chirality in Directing the Pathway of Cholesteric Helix Inversion of π-Conjugated Polymers by Light.

Control over main-chain motion of chiral π-conjugated polymers can lead to unexpected new functionalities.Here, it is shown that by combining photoswitchable azobenzene units in conjugation with chiral fluorene comonomers and appropriate plasticizers, the polymer organization and chiroptical properties of these alternating copolymers steered by light and its state of polarization can be dynamically controlled. The configuration of the stereogenic centers in the side chains of the fluorene units determines the handedness of the cholesteric organization in thermally annealed films, indicating cooperative behavior. The polymer alignment and helicity of the supramolecular arrangement can be switched by irradiating with linearly and circularly polarized light, respectively.Intriguingly, when switching the handedness of thermally induced cholesteric organizations by illuminating with circularly polarized light that is opposite to the handedness of the cholesteric phases, a nematic-like intermediate state is observed during helix interconversion. By the sequence of irradiation with left and right circularly polarized light followed by thermal annealing, an asymmetric motion, reminiscent of that seen in molecular motors is observed. These findings suggest that functional conjugated polymers can exhibit emergent properties at mesoscopic scale.

Helical Spin Polymer with Magneto-Electro-Optical Activity

A chiral π-conjugated polymer bearing a stable radical side group was synthesized by electrochemical polymerization in a cholesteric liquid crystal. The polymer thus obtained shows paramagnetism as...

Helical Folding of π-Conjugated Polymers Bearing Glucose-Linked Biphenyl Units in the Main Chain: Application to Circularly Polarized Luminescence Materials

Abstract We have synthesized a series of chiral π-conjugated polymers bearing glucose-linked biphenyl units in the main chain through copolymerizations of a key diethynyl compound (GLB-1), containing the structural element of naturally-occurring ellagitannin, with various diiodoaryls. The circular dichroism and circularly polarized luminescence properties of the obtained polymers were investigated in solution and the solid state. Based on a comparative study using the corresponding unimer model compounds, poly-3 and poly-4 bearing (oligo)thiophene-type comonomer units are considered to be able to fold into an excess one-handed helical conformation in solution and the solid state under an appropriate exterior environment. In contrast, analogous polymers bearing p- and m-phenylene residues as comonomer units did not form regular higher-ordered structures. We also observed that poly-3 and poly-4 efficiently emitted left-handed circularly polarized light with a corresponding fluorescence region arising from their helical chirality, and possessed dissymmetry factors of approximately 1.0 × 10−2 for the film state.

Synthesis and chiroptical properties of a π-conjugated polymer containing glucose-linked biphenyl units in the main chain capable of folding into a helical conformation

Naturally occurring ellagitannins provide us with inspiration for the development of a chiral π-conjugated polymer bearing glucose-linked biphenyl units in the main chain.

Luminescent and Axially Chiral π-Conjugated Polymers Linked by Carboranes in the Main Chain

Sonogashira−Hagihara polycondensations of two bis(4-iodophenyl)carborane compounds with axially chiral diyne monomers having binaphthyl unit were carried out to obtain the corresponding chiral π-conjugated polymers having o- or m-carborane segment in the main chain. The polymer structures and their optical properties were characterized by 1H, 13C, and 11B NMR, FT-IR, UV−vis absorption, photoluminescence, and circular dichroism spectroscopies. Photoluminescence study revealed that the polymer having m-carborane exhibited intense blue emission in solution state, whereas polymers having o-carborane exhibited aggregation-induced emission (AIE). All polymers showed strong CD signals, indicating the construction of highly ordered conformation.

Magneto-optically active polythiophene derivatives bearing a stable radical group from achiral monomers by polycondensation in cholesteric liquid crystal

Chiral π-conjugated polymers bearing a stable radical group are successfully prepared by chiral inductive asymmetric polymerization using a cholesteric liquid crystal medium. The polymers thus synthesized form “structural chirality”, with the structure of the polymer being analogous to that of the one-handed helical form of the cholesteric liquid crystal. Chirality and magnetic properties of the present polymers were elucidated.

Single Molecular Imaging of a micro-Brownian Motion and a Bond Scission of a Supramolecular Chiral π-Conjugated Polymer as a Molecular Bearing Driven by Thermal Fluctuations

Abstract The micro-Brownian motion of a single polymer chain was directly measured by high-speed (rapid-scan) AFM on a mica substrate under an aqueous solution at room temperature. The diffusion constant was 1.3×10−14 m2/s, which is a basic property of a molecular bearing at a solid–liquid interface. The molecule was a micrometer-long supramolecular chain in which π-conjugated polyrotaxane was coupled by a π–π interaction. Bond scission of this supramolecular chain was directly observed, and the dynamic folding behavior of a single polymer chain was also imaged.

Synthesis and properties of chiral π-conjugated polymer

The polymerization of 2-propynyl-tetra-O-β-glucopyranoside, an acetylene derivative having optically active moieties, was performed by such transition metal catalysts as PdCl 2, (NBD)PdCl 2, [Rh(NBD)Cl] 2, PtCl 2, WCl 6, and MoCl 5. The polymerization proceeded well to give a moderate yield of polymer, regardless of the bulky substituents. The spectroscopic data for the poly(2-propynyl-tetra-O-ß-glucopyranoside) indicated that the polymer has a conjugated polymer backbone system bearing the corresponding chiral substituents. The electrical conductivity of the iodine-doped polymer were in the range of 7.4 × 10 −4–2.0 × 10 −3 S/cm. The poly(2-propynyl-tetra-O-ß-glucopyranoside) prepared by [Rh(NBD)Cl] 2 showed more intense CD signal at around 350 nm than those of the same polymers prepared by other transition metal catalysts. The polymer thin films exhibited reversible electrochemical behaviors between the doping and undoping peaks.

New chiral pi-conjugated polymers based on a (1R,2R)-diiminocyclohexane chiral unit with weak interchain pi stacking.

New chiral pi-conjugated polymers consisting of alternating conjugated segments and (1R,2R)-diiminocyclohexane units with C2 symmetry were prepared by a palladium-catalyzed coupling reaction, they exhibited very high specific optical rotations ([alpha] up to -3000 degrees) and strong Cotton effects ([theta] 10(6) deg cm2 mol-1).