Recent advances in transistor performance of polythiophenes

A review on conducting organic polymers: Concepts, applications, and potential environmental benefits

Polymer materials have long been valued for their insulating properties. But recent advancements have revealed their potential as electrically conductive materials, offering an alternative to traditional metallic conductors with the added benefit of reduced environmental impact. This review article provides a comprehensive overview of conducting organic polymers, focusing on their conceptual foundations, diverse applications, and their significant role in mitigating environmental pollution. The paper begins with an exploration of how polymeric materials have progressed from insulators to conductors, explaining the basic principles and mechanisms behind their electrical conductivity. It then provides an insight into the various applications enabled by their unique optical and electronic properties, including their use in light-emitting diodes, electrochromic displays, smart windows, fuel cells, solar cells, supercapacitors and batteries. Additionally, the review emphasizes the potential of conducting organic polymers in mitigating environmental pollution, particularly through their role in wastewater treatment and e-waste management. By examining recent advancements and promising future prospects, this article underscores the potential of conducting organic polymers to revolutionize both electronic technology and environmental sustainability.

Poly(3,4-ethylenedioxythiophene) and Poly(3-octylthiophene-2,5-diyl) Molecules as Composite Transducers in Potentiometric Sensors-Synthesis and Application

The aim of this paper is to investigate the influence of the molecules of conducting polymers on the properties of potentiometric sensors. Two conducting polymers, poly(3-octylthiophene-2,5-diyl) and poly(3,4-ethylene-1,4-dioxythiophene), were compared in the context of the design of ion-selective electrodes. This study offers a comparison of the most popular conducting polymers in the context of the design of potentiometric sensors. Firstly, the properties of both materials, such as their microstructure, electrical performance, wettability, and thermic properties, were examined. Subsequently, conducting polymers were applied as transducer layers in potassium-selective sensors. The properties of both groups of sensors were evaluated using the potentiometry method. Research has shown that the presence of poly(3-octylthiophene-2,5-diyl) (POT) in the transducer layer makes it superhydrophobic, leading to a long lifetime of sensors. On the other hand, the addition of poly(3,4-ethylene-1,4-dioxythiophene) polystyrene sulfonate (PEDOT:PSS) allows for the enhancement of electrical capacitance parameter values, which beneficially influence the stability of the potentiometric response of sensors. Both examined conducting polymers turned out to be perfect materials for transducer layers in potentiometric sensors, each being responsible for enhancing different properties of electrodes.

Lattice-guided assembly of optoelectronically active π-conjugated peptides on 1D van der Waals single crystals

The deployment of organic molecules in high-performance devices strongly relies on the formation of well-ordered domains, which is often complicated by the dynamic and sensitive nature of supramolecular interactions. Here, we engineered the assembly of water-processable, optoelectronic π-conjugated peptides into well-defined organic-inorganic heterointerfaced assemblies by leveraging the long-range anisotropic ordering of 1D van der Waals (vdW) crystals composed of subnanometer-thick transition metal sulfide chains (MS3; M = Nb, Ta) as assembly templates. We found that the monomers can readily form 1D supramolecular assemblies onto the underlying crystal surface, owing to the structural correspondence between the π-π interactions of the quaterthiophene (4T)-based peptide units (DDD-4T) and sulfur atom ordering along the NbS3 (100) surface. The heterointerfaced assemblies exhibited substantially red-shifted photoluminescence and enhanced visible-range photocurrent generation compared to solution-assembled films. Our results underscore the role of lattice matching in forming ordered supramolecular assemblies, offering an emergent approach to assembling organic building blocks endowed with improved physical properties.

Polymer-Unit Graph: Advancing Interpretability in Graph Neural Network Machine Learning for Organic Polymer Semiconductor Materials

The graph representation of complex materials plays a crucial role in the field of inorganic and organic materials investigations for developing data-centric materials science, such as those using graph neural networks (GNNs). However, the currently prevalent GNN models are primarily employed for investigating periodic crystals and organic small molecule data, yet they still encounter challenges in terms of interpretability and computational efficiency when applied to polymer monomers and organic macromolecules data. There is still a lack of graph representation of organic polymers and macromolecules specifically tailored for GNN models to explore the structural characteristics. The Polymer-unit Graph, a novel coarse-grained graph representation method introduced in study, is dedicated to expressing and analyzing polymers and macromolecules. By incorporating the Polymer-unit Graph into the GNN models and analyzing the organic semiconductor (OSC) materials database, it becomes possible to uncover intricate structure-property relationships involving branched-chain engineering, fluoridation substitution, and donor-acceptor combination effects on the elementary structure of OSC polymers. Furthermore, the Polymer-unit Graph enables visualizing the relationship between target properties and polymer units while reducing training time by an impressive 98% and minimizing molecular graph representation models. In conclusion, the Polymer-unit Graph successfully integrates the concept of Polymer-unit into the field of GNNs, enabling more accurate analysis and understanding of organic polymers and macromolecules.

Organic Transistors Based on Highly Crystalline Donor-Acceptor π-Conjugated Polymer of Pentathiophene and Diketopyrrolopyrrole

Oligomers and polymers consisting of multiple thiophenes are widely used in organic electronics such as organic transistors and sensors because of their strong electron-donating ability. In this study, a solution to the problem of the poor solubility of polythiophene systems was developed. A novel π-conjugated polymer material, PDPP-5Th, was synthesized by adding the electron acceptor unit, DPP, to the polythiophene system with a long alkyl side chain, which facilitated the solution processing of the material for the preparation of devices. Meanwhile, the presence of the multicarbonyl groups within the DPP molecule facilitated donor-acceptor interactions in the internal chain, which further improved the hole-transport properties of the polythiophene-based material. The weak forces present within the molecules that promoted structural coplanarity were analyzed using theoretical simulations. Furthermore, the grazing incidence wide-angle X-ray scanning (GIWAXS) results indicated that PDPP-5Th features high crystallinity, which is favorable for efficient carrier migration within and between polymer chains. The material showed hole transport properties as high as 0.44 cm2 V-1 s-1 in conductivity testing. Our investigations demonstrate the great potential of this polymer material in the field of optoelectronics.

Incorporation of Diketopyrrolopyrrole into Polythiophene for the Preparation of Organic Polymer Transistors

Polythiophene, as a class of potential electron donor units, is widely used in organic electronics such as transistors. In this work, a novel polymeric material, PDPPTT-FT, was prepared by incorporating the electron acceptor unit into the polythiophene system. The incorporation of the DPP molecule assists in improving the solubility of the material and provides a convenient method for the preparation of field effect transistors via subsequent solution processing. The introduction of fluorine atoms forms a good intramolecular conformational lock, and theoretical calculations show that the structure displays excellent co-planarity and regularity. Grazing incidence wide-angle X-ray (GIWAXS) results indicate that the PDPPTT-FT is highly crystalline, which facilitates carrier migration within and between polymer chains. The hole mobility of this π-conjugated material is as high as 0.30 cm2 V-1 s-1 in organic transistor measurements, demonstrating the great potential of this polymer material in the field of optoelectronics.

Polymer-Unit Fingerprint (PUFp): An Accessible Expression of Polymer Organic Semiconductors for Machine Learning

High-performance organic semiconductors (OSCs) can be designed based on the identification of functional units and their role in the material properties. Herein, we present a polymer-unit fingerprint (PUFp) generation framework, "Python-based polymer-unit-recognition script" (PURS), to identify the subunits "polymer unit" in the polymer and generate polymer-unit fingerprint (PUFp). Using 678 collected OSC data, machine learning (ML) models can be used to determine structure-mobility relationships by using PUFp as a structural input, and the classification accuracy reaches 85.2%. A polymer-unit library consisting of 445 units is constructed, and the key polymer units affecting the mobility of OSCs are identified. By investigating the combinations of polymer units with mobility performance, a scheme for designing OSCs by combining ML approaches and PUFp information is proposed. This scheme not only passively predicts OSC mobility but also actively provides structural guidance for high-mobility OSC material design. The proposed scheme demonstrates the ability to screen materials through pre-evaluation and classification ML steps and is an alternative methodology for applying ML in high-mobility OSC discovery.

Microscopic, Spectroscopic, and Electrochemical Characterization of Novel Semicrystalline Poly(3-hexylthiophene)-Based Dendritic Star Copolymer

In this study, electron-donating semicrystalline generation 1 poly(propylene thiophenoimine)-co-poly(3-hexylthiophene) star copolymer, G1PPT-co-P3HT was chemically prepared for the first time. Copolymerization was achieved with high molecular weight via facile green oxidative reaction. ¹H NMR analyses of the star copolymer demonstrated the presence of 84% regioregular (rr) head-to-tail (HT) P3HT, which accounts for the molecular ordering in some grain regions in the macromolecule’s morphology, as revealed by the high-resolution scanning electron microscopy (HRSEM) and Selected Area Electron Diffraction (SAED) images, and X-ray diffraction spectroscopy (XRD) measurements. The star copolymer also exhibited good absorption properties in the ultraviolet-visible (UV-Vis) and the near infrared (NIR) spectral regions, which give rise to an optical energy bandgap value as low as 1.43 eV. A HOMO energy level at −5.53 eV, which is below the air-oxidation threshold, was obtained by cyclic voltammetry (CV). Electrochemical impedance spectroscopy (EIS) ascertained the semiconducting properties of the macromolecule, which is characterized by a charge transfer resistance, R_ct, value of 3.57 kΩ and a Bode plot-phase angle value of 75°. The combination of the EIS properties of G1PPT-co-P3HT and its highly electron-donating capability in bulk heterojunction (BHJ) active layer containing a perylene derivative, as demonstrated by photoluminescence quenching coupled to the observed Förster Resonance charge transfer, suggests its suitability as an electron-donor material for optoelectronic and photovoltaic devices.

Molecular Tuning in Diaryl-Capped Pyrrolo[2,3-d:5,4-d']bisthiazoles: Effects of Terminal Aryl Unit and Comparison to Dithieno[3,2-b:2',3'-d]pyrrole Analogues

A series of six conjugated oligomers consisting of a central pyrrolo[2,3-d:5,4-d']bisthiazole (PBTz) end-capped with either thienyl, furyl, or phenyl groups have been prepared from N-alkyl-and N-aryl-pyrrolo[2,3-d:5,4-d']bisthiazoles via Stille and Negishi cross-coupling. The full oligomeric series was thoroughly investigated via photophysical and electrochemical studies, in parallel with density functional theory (DFT) calculations, in order to correlate the cumulative effects of both aryl end-groups and N-functionalization on the resulting optical and electronic properties. Through comparison with the analogous dithieno[3,2-b:2',3'-d]pyrrole (DTP) materials, the effect of replacing DTP with PBTz on the material HOMO energy and visible light absorption is quantified.

Probing the nature of donor-acceptor effects in conjugated materials: a joint experimental and computational study of model conjugated oligomers

A series of model oligomers consisting of combinations of a traditional strong donor unit (3,4-ethylenedioxythiophene), a traditional strong acceptor unit (benzo[c][1,2,5]thiadiazole), and the ambipolar unit thieno[3,4-b]pyrazine were synthesized via cross-coupling methods. The prepared oligomers include all six possible dimeric combinations in order to characterize the extent and nature of donor-acceptor effects commonly used in the design of conjugated materials, with particular focus on understanding how the inclusion of ambipolar units influences donor-acceptor frameworks. The full oligomeric series was thoroughly investigated via photophysical and electrochemical studies, in parallel with density functional theory (DFT) calculations, in order to correlate the nature and extent of donor-acceptor effects on both frontier orbital energies and the desired narrowing of the HOMO-LUMO energy gap. The corresponding relationships revealed should then provide a deeper understanding of donor-acceptor interactions and their application to conjugated materials.

Molecular Weight-Dependent Physical and Photovoltaic Properties of Poly(3-alkylthiophene)s with Butyl, Hexyl, and Octyl Side-Chains

A series of poly-3-alkylthiophenes (P3ATs) with butyl (P3BT), hexyl (P3HT), and octyl (P3OT) side-chains and well-defined molecular weights (MWs) were synthesized using Grignard metathesis polymerization. The MWs of P3HTs and P3OTs obtained via gel permeation chromatography agreed well with the calculated MWs ranging from approximately 10 to 70 kDa. Differential scanning calorimetry results showed that the crystalline melting temperature increased with increasing MWs and decreasing alkyl side-chain length, whereas the crystallinity of the P3ATs increased with the growth of MWs. An MW-dependent red shift was observed in the UV-Vis and photoluminiscence spectra of the P3ATs in solution, which might be a strong evidence for the extended effective conjugation occurring in polymers with longer chain lengths. The photoluminescence quantum yields of pristine films in all polymers were lower than those of the diluted solutions, whereas they were higher than those of the phenyl-C61-butyric acid methyl ester-blended films. The UV-Vis spectra of the films showed fine structures with pronounced red shifts, and the interchain interaction-induced features were weakly dependent on the MW but significantly dependent on the alkyl side-chain length. The photovoltaic device performances of the P3BT and P3HT samples significantly improved upon blending with a fullerene derivative and subsequent annealing, whereas those of P3OTs mostly degraded, particularly after annealing. The optimal power conversion efficiencies of P3BT, P3HT, and P3OT were 2.4%, 3.6%, and 1.5%, respectively, after annealing with MWs of ~11, ~39, and ~38 kDa, respectively.

Chirality in polythiophenes: A review

Chiroptical polythiophene (PTh), as one of the most important chiral conductive polymers, is an emerging and hot topic in chiral materials, which shows great application potentials in fields as diverse as chiral sensing and separation, asymmetry catalysis, chiroptoelectronics, and even chiro-spintronics. This review summarizes progress in chiral polythiophenes (PThs) in the past 10 years, including the synthesis, properties and applications. Main focus is placed on the manner in which chirality is implemented and the optical activity of the chiral PThs. We showcase examples in which the chirality of PThs is induced by side chain substituents with point, planar, and axial chirality or arises from external chiral media. Application of chiral PThs is also included. Finally, perspectives for further development are offered.

Tailored Solution-Based N-heterotriangulene Thin Films: Unravelling the Self-Assembly

The ability of a series of bridged triarylamines, so‐called N‐heterotriangulenes, to form multilayer‐type 2D‐extended films via a solution‐based processing method was examined using complementary microscopic techniques. We found that the long‐range order, crystallinity, and layer thickness decisively depend on the nature of the substituents attached to the polycyclic backbone. Owing to their flat core unit, compounds exhibiting a carbonyl unit at the bridge position provide a superior building block as compared to thioketone‐bridged derivatives. In addition, nature and length of the peripheral substituents affect the orientation of the aromatic core unit within highly crystalline films. Hence, our results stress the significance of a suitable molecular framework and provide deeper understanding of structure formation in 2D‐confined surroundings for such compounds.

Effect of doped H, Br, Cu, Kr, Ge, As and Fe on structural features and bandgap of poly C13H8OS-X: a DFT calculation

Structural features such as the shape, the lattice constant, the bond length, the total energy per cell, and the energy bandgap (Eg) of C13H8OS-X are studied by the calculating Partial Density Of States (PDOS), and DOS package of the Material Studio (MS) software. Calculations show that the bond length and the bond angle between atoms insignificant change as 1.316 Å to 1.514 Å for C-C, 1.211 Å for C-O, 1.077 Å to 1.105 Å for C-H; bond angle of round one changes from 118.883° to 121.107° for C-C-C, from 117.199° to 122.635° for H-C-C, from 119.554° to 123.147° for C-C-O and from 109.956° to 117.537° for C-C-H. When C13H8OS-X doped in the order of -Br, -Cu, -Kr, -Ge, -As, and -Fe then bond lengths, bond angles between atoms have a nearly constant value. Particularly for links C-X, there is a huge change in value, respectively 1.876, 1.909, 10.675, 2.025, 2.016, 2.014 Å; the total energy change from Etot = -121,794 eV to Etot = -202,859 eV, and the energy band gap decreases from Eg = 2.001 eV to Eg = 0.915 eV. The obtained results are useful and serve as a basis for future experimental research.

UV-to-IR Absorption of Molecularly p-Doped Polythiophenes with Alkyl and Oligoether Side Chains: Experiment and Interpretation Based on Density Functional Theory

The UV-to-IR transitions in p-doped poly(3-hexylthiophene) (P3HT) with alkyl side chains and polar polythiophene with tetraethylene glycol side chains are studied experimentally by means of the absorption spectroscopy and computationally using density functional theory (DFT) and tight-binding DFT. The evolution of electronic structure is calculated as the doping level is varied, while the roles of dopant ions, chain twisting, and π-π stacking are also considered, each of these having the effect of broadening the absorption peaks while not significantly changing their positions. The calculated spectra are found to be in good agreement with experimental spectra obtained for the polymers doped with a molybdenum dithiolene complex. As in other DFT studies of doped conjugated polymers, the electronic structure and assignment of optical transitions that emerge are qualitatively different from those obtained through earlier "traditional" approaches. In particular, the two prominent bands seen for the p-doped materials are present for both polarons and bipolarons/polaron pairs. The lowest energy of these transitions is due to excitation from the valence band to a spin-resolved orbitals located in the gap between the bands. The higher-energy band is a superposition of excitation from the valence band to a spin-resolved orbitals in the gap and an excitation between bands.

Poly-3-thienylboronic acid: a chemosensitive derivative of polythiophene

Poly-3-thiopheneboronic acid was synthesized by electrochemical polymerization from 3-thienylboronic acid dissolved in the mixture of boron trifluoride diethyl etherate and acetonitrile. Cyclic voltammetry during electropolymerization shows oxidative and reductive peaks growing in each next cycle. An investigation by scanning electron microscopy displayed the polymer layer like a highly flexible film of 110 nm thick with grains of 60–120 nm in size. Strong negative solvatochromic effect was observed. Optical spectra of poly-3-thienylboronic acid at different potentials and pH were studied. Potential cycling leads to a well reversible electrochromic effect. At pH 7.4, the increase of potential leads to the decrease in the absorption band at 480 nm and to the rise in the absorption band at 810 nm with an isosbestic point at 585 nm. Spectroelectrochemical behavior of poly-3-thienylboronic acid and polythiophene was compared. Binding of sorbitol at fixed electrode potential leads to an increase in the absorbance in the shortwave band and to the decrease in the longwave band; the effect depends on the electrode potential and pH. Perspectives of application of poly-3-thienylboronic acid as new chemosensitive material are discussed.

Conjugated and Conducting Organic Polymers: The First 150 Years

Conductive organic polymers are most commonly generated from the oxidation or reduction of conjugated polymers. Although such conjugated polymers are typically viewed as modern materials, the earliest examples of these polymers date back to the early 19th century. The modern era of conjugated polymers began with the first reports of their conductive nature in the early 1960s. However, it was advances in the 1970s that brought particular focus to these materials with the first example of conductivity values in the metallic regime, for which the 2000 Nobel Prize in Chemistry was awarded to Hideki Shirakawa, Alan MacDiarmid, and Alan Heeger. Unfortunately, the historical narrative of these polymers is currently quite muddled in the primary literature, with various inaccuracies commonly propagated. In an effort to present a more accurate account as a resource for the field, the present report will review the first 150 years of the four primary parent polymers-polyaniline, polypyrrole, polyacetylene, and polythiophene, from their early origins in 1834 to their rapid development in the mid-1980s.

SAKE: first-principles electron transport calculation code

We developed and implemented a numerical code called SAKE, which stands for (simulation code for atomistic Kohn-Sham equation). We developed it for first-principle electron transport calculations based on density-functional theory and non-equilibrium Green's function formalism. First, we present the central calculation parts of the formalism of the electronic states and transport properties for open and non-equilibrium systems. We show specific computational techniques, such as the use of a complex contour integration for charge density from the density matrix, which is compared with the calculation method of summing the residues of the Fermi-Dirac distribution, as well as the efficient achievement of the self-consistent procedures. Thereafter, for applications of the present computation code, SAKE, we present first-principle calculation results of three different systems. We first analyze electronic structures of polythiophene molecular wires, compare summation techniques for the density matrix. We show thermoelectric properties of an n-type antiferromagnetic semiconductor CuFeS2as a second application. The electrical conductance, electrical thermal conductance, and the Seebeck coefficients with carrier doping are examined, and the analytical form of the Seebeck coefficient is briefly described. For the third application, we analyze the electron transport properties of polyaniline molecular wires under structural deformations, i.e. rotations around the transport direction. The thermally averaged current-voltage characteristics are also analyzed. The results show that the current decreases as the temperature increases which are determined based on the competition between the thermal energy and the electronic energy, which increases with the rotation angle.

Synthesis and electrochemical characterization of a new benzodioxocine-fused poly(N-methylpyrrole) derivative: a joint experimental and DFT study

Synthesis of a new electropolymerizable monomer, XyPMe, regarding the reaction of diethylN-methyl-3,4-dihydroxypyrrole-2,5-dicarboxylate and 1,2-bis(bromomethyl)benzene with concomitant hydrolysis and decarboxylation reactions was accomplished.

Artificial Thiophdiyne Ultrathin Layer as an Enhanced Solid Electrolyte Interphase for the Aluminum Foil of Dual-Ion Batteries

In this study, we design a novel carbon-based material containing thiophene and acetylenic linkers as functional groups named thiophdiyne (Thi-Dy) and apply it as an ultrathin artificial protective layer for the commercially available aluminum (Al) foil of dual-ion batteries (DIBs). The Thi-Dy films can be grown easily and directly on the Al foil through a mild Glaser-Hay coupling reaction. The as-proposed thiophene and acetylenic linker functional groups in Thi-Dy layers act as energetic active sites for the effective fabrication of a stable hybrid solid electrolyte interphase (SEI) during the electrochemical process, which is revealed through the ex situ measurement. The Thi-Dy-enhanced SEI layer contributes to offer a more effective and regulated lithium intercalation and diffusion pathway and delay the pulverization and huge volume expansion of the Al-Li alloy during long cycles, which are confirmed by the improvement on the cyclic stability of DIBs. Those studies are expected to provide novel thiophene-containing functional materials and mass-produced surface modification approach for metal anode protection, which will promote the research for the next-generation rechargeable battery.

Synthesis of a one-handed helical polythiophene: a new approach using an axially chiral bithiophene with a fixed syn-conformation

An optically active polythiophene, which can fold into a one-handed helical conformation under good solvent conditions, has been developed.

We report an optically active polythiophene capable of forming a one-handed helically folded conformation without needing aggregate formation, poor solvent conditions, hydrogen-bonded ion-pair formation or guest addition. The target polythiophene (poly-T_R) with a static axial chirality in the main chain was synthesized via Stille coupling copolymerization of a glucose-linked chiral 5,5′-dibromobithiophene with 2,5-bis(stannyl)thiophene. Poly-T_R showed a characteristic circular dichroism and circularly polarized luminescence, which were completely different to those observed for an analogous polymer (poly-Ph_R) and the corresponding unimer/dimer model compounds. This chiroptical study, combined with the results of all-atom molecular dynamics simulations, revealed that poly-T_R can fold into a left-handed helical conformation under good solvent conditions. Partial conformational regulation derived from the fixed syn-conformation of the chiral bithiophene unit was considered a key factor in producing the one-handed helical polythiophene.

Poly(thieno[3,4-b]pyrazine-alt-2,1,3-benzothiadiazole)s: A New Design Paradigm in Low Band Gap Polymers

A new design paradigm for the production of low band gap polymers is reported, in which an ambipolar unit exhibiting both donor and acceptor properties is combined with a conventional acceptor. As initial examples of this approach, the synthesis of two alternating copolymers of thieno[3,4-b]pyrazine and 2,1,3-benzothiadiazole via direct arylation polymerization is reported to give soluble, processable materials with band gaps of 0.97 and 1.05 eV. Although direct arylation polymerization has been previously used to synthesize donor-acceptor materials with band gaps below 1.5 eV, this represents only the second material generated by this polymerization method with a band gap below 1.0 eV.

The Conversion of 5,5'-Bi(1,2,3-dithiazolylidenes) into Isothiazolo[5,4-d]isothiazoles

Thermolysis of 4,4'-dichloro-, 4,4'-diaryl-, and 4,4'-di(thien-2-yl)-5,5'-bi(1,2,3-dithiazol-ylidenes) affords the respective 3,6-dichloro-, 3,6-diaryl- and 3,6-di(thien-2-yl)isothiazolo[5,4-d]-isothiazoles in low to high yields. The transformation of the 4,4'-diaryl- and 4,4'-di(thien-2-yl)-5,5'-bi(1,2,3-dithiazolylidenes) occurs at lower temperatures in the presence of the thiophiles triphenylphosphine or tetraethylammonium iodide. Optimized reaction conditions and a mechanistic rationale for the thiophile-mediated ring transformation are presented.

Robust and Reversible Vapoluminescent Organometallic Copper Polymers

Emissive organometallic polymers are an important class of functional materials characterized by the combined photoluminescent features of organometallic molecules and the properties of traditional polymers. In this work, the emissive organometallic complex, [CuBr(PPh₃ )₂ (4-methylpyridine)], is successfully, mechanically ground into a random copolymer built on 4-(diphenylphosphino)styrene (DPVP) and n-butyl acrylate (BA) monomers. The resultant hybrid materials successfully inherit the emissive centers, and are significantly reinforced by the copper complexes as chemical crosslinkers in the polymeric continuum. These organometallic polymers are also proved to have excellent vapoluminescent properties, exhibiting unique responses to many organic solvent vapors, reflecting their rapid loss and recovery of photoluminescence. Mechanically robust and flexible films prepared with these organometallic Cu(I)-polymers are tested as recoverable sensors for hazardous volatile chemical compounds (VOCs) such as toluene, acetone, chloroform, and dichloromethane, and the low limits of detection (LOD) can reach as low as 1 × 10^-3 -8 × 10^-3 mg L^-1 (0.2-3.3 ppmV, parts per million-volume) for various VOCs. This work sheds lights on the design and fabrication of organometallic polymers for advanced applications.

Coordination-Driven Self-Assembly of a Molecular Knot Comprising Sixteen Crossings

Molecular knots have become highly attractive to chemists because of their prospective properties in mimicking biomolecules and machines. Only a few examples of molecular knots from the billions tabulated by mathematicians have been realized and molecular knots with more than eight crossings have not been reported to date. We report here the coordination-driven [8+8] self-assembly of a higher-generation molecular knot comprising as many as sixteen crossings. Its solid-state X-ray crystal structure and multinuclear 2D NMR findings confirmed its architecture and topology. The formation of this molecular knot appears to depend on the functionalities and geometries of donor and acceptor in terms of generating appropriate angles and strong π-π interactions supported by hydrophobic effects. This study shows coordination-driven self-assembly offers a powerful potential means of synthesizing more and more complicated molecular knots and of understanding differences between the properties of knotted and unknotted structures.

Incorporating Trialkylsilylethynyl-Substituted Head-to-Head Bithiophene Unit into Copolymers for Efficient Non-Fullerene Organic Solar Cells

Mediating the backbone coplanarity and solubility of oligothiophenes, especially the head-to-head (HH) disubstituted bithiophene, to achieve an optically and electronically advantageous building block for organic semiconductor materials is a vital yet challenging task. On the other hand, exploring polymer solar cells (PSCs) processed from nonhalogenated solvents is necessary toward their large-scale applications. In this contribution, we develop a HH-type bithiophene analogue (TIPS-T2) by strategically applying the triisopropylsilylethynyl (TIPS) scaffold as the side chain. TIPS can serve to narrow optical band gaps, lower the highest occupied molecular orbital level, reduce intrachain steric hindrance, and guarantee sufficient solubility of the involving polymers. Upon alternating with difluorobenzotriazole (FTAZ) or benzodithiophene-4,8-dione (BDD) acceptor units, two polymers named PT4Si-FTAZ and PT4Si-BDD are synthesized. Encouragingly, non-fullerene PSCs incorporating PT4Si-FTAZ yield a power conversion efficiency of 6.79% when processed from an environment-friendly solvent of trimethylbenzene because of its promoted backbone planarity, as demonstrated by density functional theory, higher hole mobility, and superior film morphology. The results indicate that TIPS-T2 is a promising building block for constructing photovoltaic polymers, and our findings offer an avenue for the ingenious use of TIPS as functional side chains.

Effect of donor to acceptor ratio on electrochemical and spectroscopic properties of oligoalkylthiophene 1,3,4-oxadiazole derivatives

A structure-property study across a series of donor-acceptor-donor structures composed of mono- and bi-(1,3,4-oxadiazole) units symmetrically substituted with alkyl functionalized bi-, ter- and quaterthiophene segments is presented. Synthetically tailoring the ratio of electron-withdrawing 1,3,4-oxadiazole to electron-releasing thiophene units and their alkyl grafting pattern permitted us to scrutinize the impact of these structural factors on the redox, absorptive and emissive properties of these push-pull molecules. Contrasting trends of redox potentials were observed, with the oxidation potential closely following the donor-to-acceptor ratio, whereas the reduction potential being tuned independently by either the number of acceptor units or the conjugation length of the donor-acceptor system. Increasing the thiophene unit contribution delivered a shift from blue to green luminescence, while the structural rigidity afforded by intramolecular non-covalent interactions between 1,3,4-oxadiazole and the thiophene moieties has been identified as the prime factor determining the emission efficiency of these molecules. All six structures investigated electro-polymerize easily, yielding electroactive and electrochromic polymers. The polymer doping process is largely influenced by the length of the oligothiophene repeating unit and the alkyl chain grafting density. Polymers with relatively short oligothiophene segments are able to support polarons and polaron-pairs, whereas those with segments longer than six thiophene units could also stabilize diamagnetic charge carries - bipolarons. Increasing the alkyl chain grafting density improved the reversibility and broadened the working potential window of the p-doping process. Stable radical anions have also been investigated, bringing detailed information about the conjugation pattern of these electron-surplus species. This study delivers interesting clues towards the conscious structural design of bespoke frontier energy level oligothiophene functional materials and their polymers by incorporating a structurally matching 1,3,4-oxadiazole unit.

Theoretical analysis of high-pressure effects on conformational equilibria

Along with temperature, pressure is the most important physical parameter determining the thermodynamic properties and reactivity of chemical systems. In this work, we discuss the effects of high pressure on conformational properties of organic molecules and propose an approach toward calculation of conformational volume changes based on molecular dynamics simulations. The results agree well with the experimental data. Furthermore, we demonstrate that pressure can be used as an instrument for fine-tuning of molecular conformations and to propel a properly constructed molecular rotor possessing a suitable combination of energy and volume profiles.

Vinylene spacer effects of benzothiadiazole–quarterthiophene based conjugated polymers on transistor mobilities

Opposite crystallinity and charge carrier mobility variation tendency with increasing vinyl ratio.

Pentafluorobenzene end-group as a versatile handle for para fluoro "click" functionalization of polythiophenes

A convenient method of introducing pentafluorobenzene (PFB) as a single end-group in polythiophene derivatives is reported via in situ quenching of the polymerization. We demonstrate that the PFB-group is a particularly useful end-group due to its ability to undergo fast nucleophilic aromatic substitutions. Using this molecular handle, we are able to quantitatively tether a variety of common nucleophiles to the polythiophene backbone. The mild conditions required for the reaction allows sensitive functional moieties, such as biotin or a cross-linkable trimethoxysilane, to be introduced as end-groups. The high yield enabled the formation of a diblock rod-coil polymer from equimolar reactants under transition metal-free conditions at room temperature. We further demonstrate that water soluble polythiophenes end-capped with PFB can be prepared via the hydrolysis of an ester precursor, and that such polymers are amenable to functionalization under aqueous conditions.

Charge transport in nanoscale vertical organic semiconductor pillar devices

We report charge transport measurements in nanoscale vertical pillar structures incorporating ultrathin layers of the organic semiconductor poly(3-hexylthiophene) (P3HT). P3HT layers with thickness down to 5 nm are gently top-contacted using wedging transfer, yielding highly reproducible, robust nanoscale junctions carrying high current densities (up to 10⁶ A/m²). Current-voltage data modeling demonstrates excellent hole injection. This work opens up the pathway towards nanoscale, ultrashort-channel organic transistors for high-frequency and high-current-density operation.

Vinylene-Linked Oligothiophene-Difluorobenzothiadiazole Copolymer for Transistor Applications

The synthesis of the novel donor-acceptor monomer 4,7-bis[(E)-2-(5-bromo-3-dodecylylthiophen-2-yl)ethenyl]-5,6-difluoro-2,1,3-benzothiadiazole (FBT-V2T2) is reported. Polymerization with 4,4'-ditetradecyl-5,5'-bistrimethylstannyl-2,2'-bithiophene afforded a highly crystalline polymer that aggregated strongly in solution. Polymer films were well ordered resulting in high performance field-effect transistors with low onset voltages, negligible hysteresis, high channel current on/off ratios, and peak hole mobilities of up to 0.5 cm² V^-1 s^-1. Notably the transistors exhibited close to ideal behavior with extracted mobilities almost independent of gate of voltage.