Direct Arylation Polymerization Research Articles

Soft and Stretchable Thienopyrroledione‐Based Polymers via Direct Arylation

Abstractπ‐conjugated polymers (CPs) that are concurrently soft and stretchable are needed for deformable electronics. Molecular‐level modification of indacenodithiophene (IDT) copolymers, a class of CPs that exhibit high hole mobilities (hole), is an approach that can help realize intrinsically soft and stretchable CPs. Numerous examples of design strategies to adjust the stretchability of CPs exist, but imparting softness is comparatively less studied. In this study, a systematic molecular weight (MW) series is constructed on a promising candidate for soft CPs, poly(indacenodithiophene‐co‐thienopyrroledione) (p(IDTC16‐TPDC8)), by optimizing direct arylation polymerization conditions in hopes of improving stretchability and μhole without significantly impacting softness. We found p(IDTC16‐TPDC8) at a degree of polymerization of 32 shows high stretchability (crack onset strain, CoS > 100%) without significantly impacting softness (elastic modulus, E = 32 MPa), which to the best of our knowledge outperforms previously reported stretchable and soft CPs. To further study how molecular‐level modifications impact polymer properties, a MW series of a new extended donor unit polymer, poly(indacenodithienothiophene‐co‐thienopyrroledione) (p(IDTTC16‐TPDC8)), was synthesized. The IDTTC16 copolymers did not result in a greater average μhole when comparing between p(IDTTC16‐TPDC8) and p(IDTC16‐TPDC8) despite their higher crystallinity observed by GIWAXS. While these findings warrant further investigation, this study points toward unique charge transport properties of IDT‐based polymers.

Electrochromic conjugated polymers: The relationship of gradient band gap and electrochromic performance

In the pursuit of high-performance electrochromic materials, in this paper, six donor-acceptor type with different gradient band gaps electrochromic conjugated polymers, named PBTz-T, PBTz-TT, PBTz-DT, PTBTO8-T, PTBTO8-TT, and PTBTO8-DT, were synthesized via direct (hetero) arylation polymerization, employing two benzothiadiazole derivatives with varying electron-accepting capabilities and three thiophene derivatives with different electron-donating capacities. The structures, optical, electrochemical, and electrochromic properties of the six polymers were investigated. As the number of fused thiophene increases, enhancing the electron-donating ability, a growth trend of electrochemical stability is observed for all polymers. Meanwhile, enhance electron-accepting capabilities of acceptors (from benzotriazole to benzothiadiazole) significantly lower the electronic band gap and improve electrochemical stability. PBTz-DT boasts a bleaching time of 0.3 s, outperforming most reported electrochromic polymers. PBTz-T, at 530 nm, exhibits exceptionally high coloration efficiency, reaching 916 cm2 C⁻1, and demonstrates higher electron utilization and lower energy consumption, making it an excellent candidate for high-performance electrochromic devices. This work compared studies the relationship of gradient band gaps of electrochromic conjugated polymers and their electrochemical and electrochromic performance, offers new insights into enhancing the electrochemical stability and synthesizing high coloration efficiency electrochromic materials.

Dimension-matching crystallized linear conjugated polymer/graphitic carbon nitride heterojunctions for boosting visible/near-infrared light photocatalytic hydrogen production

Linear conjugated polymer photocatalysts remain suffer from insufficient near-infrared light absorption and poor photogenerated-carriers separation efficiency caused by twisted backbone, limiting their further application for photocatalytic water splitting to produce hydrogen energy. Herein, we first synthesized crystallized 2D poly(thiophene-co-nitrothiophene) (PN) with narrow band gap through direct (hetero) arylation polymerization (DHAP) method, then constructed dimension-matching PN/graphitic carbon nitride (CN) heterojunctions (PN/CN) with 2D/2D structure for visible/near-infrared light photocatalytic hydrogen production. The resulting 2D/2D heterojunctions exhibit excellent visible/near-infrared light absorption and photocatalytic activates. The ratio-optimized 15PN/CN shows boosting hydrogen production activity up to 11.73 mmol/hg−1 under visible/near-infrared light (λ > 420 nm) irradiation, which is ∼ 30-time and ∼ 46.9-time improvement than that of PN and CN separately. Notably, the apparent quantum yield (AQY) of 15PN/CN is calculated to be 2.35 % at 700 nm and 0.62 % at 800 nm. It is proved that the π − π interaction of dimension-matching heterojunctions between PN and CN facilitates electrons transfer from LUMO of PN to LUMO of CN. This study provides another new train of thought for reasonably developing dimension-matching polymer heterojunctions by manipulating crystallinity and band structure of linear conjugated polymers for efficient visible/near-infrared light photocatalytic hydrogen production.

Construction of diverse adaptive camouflage nets based on soluble yellow-to-green switching electrochromic materials

The potential application of electrochromic (EC) materials and devices as adaptive camouflage in diverse environments requires further investigation. In this study, we aimed to enhance the camouflage effect of electrochromic devices (ECDs) by developing innovative EC camouflage nets. Three soluble EC materials (FTP, FEP and FBP) were synthesized by incorporating phenothiazine and ProDOT with different donors through direct(hetero) arylation polymerization. Due to the fine-tuning of the energy gap, the three materials exhibit yellow, yellowish-brown and reddish-brown colors in their neutral states, respectively. Particularly, FTP and FEP can switch between different yellow-to-green with superior EC performance. Furthermore, FTP-PEDOT and FEP-PEDOT ECDs were constructed. Notably, the FEP-PEDOT ECD demonstrated enhanced EC performance, characterized by a more noticeable yellow-to-green switch, faster switching times and improved cycle stability. To meet the adaptability for multi-environmental camouflage and wearable applications, we created diverse camouflage patterns using the mask-spray technique and developed three types (“stripe”/ “cross stripe”/ “block”) camouflage net ECDs. This study offers a comprehensive approach for developing adaptive camouflage nets tailored to diverse real combat settings.

Highly Transmissive, Processable, Highly Conducting and Stable Polythiophene Derivatives via Direct (Hetero)arylation Polymerization.

The development of modern optoelectronic devices increases the need for lightweight and flexible transparent conductors. It is thus essential to develop new eco-friendly materials that can be easily processed for the fabrication of such devices. For this purpose, the synthesis of self-doped, highly conducting, transmissive, and water-processable polythiophene derivatives was performed via the direct heteroarylation polymerization method and a protection/deprotection strategy. Stable conductivities up to 1000 S cm-1 have been obtained. Champion materials (P1 and P7) were scaled and processed via the roll-to-roll compatible slot-die coating method to demonstrate their large area applicability. The best coated films exhibited optical transmittance greater than 79% at 550 nm with sheet resistances of 116 Ω □-1. These values are comparable to indium-tin oxide on plastic and thus present a viable alternative to metal oxide-based electrodes.

Design and synthesis of donor-acceptor electrochromic polymers with remarkable near-infrared modulation

Developing electrochromic polymers (ECPs) for application in smart windows is highly desirable in the electrochromic field. However, most ECPs present weak solar irradiance regulation due to the inverse visible and NIR modulation. Herein, three donor-acceptor polymers containing 4,7-bis(4-hexylthiophen-2-yl)benzo[c][1,2,5]thiadiazole (HT-TZ) units are synthesized via direct arylation polymerization (DArP) method, and two copolymers with similar structure are prepared by electrochemical copolymerization for comparison. The copolymers synthesized by the DArP method present weak visible and high NIR modulation with an average visible (380 nm–780 nm) contrast below 15 % and NIR (750 nm–1400 nm) contrast above 60 %, inducing a high solar heat gain coefficient (SHGC) difference above 0.2 between the neutral and oxidized states, which is much higher than the reported high-performance ECPs. Additionally, these synthesized copolymers also present good electrochromic properties such as good stability and normal coloration efficiency, confirming their broad application potential in smart windows.

Understanding Degradation Dynamics of Azomethine-containing Conjugated Polymers.

Understanding the influence of chemical environments on the degradation properties of conjugated polymers is an important task for the continued development of sustainable materials with potential utility in biomedical and optoelectronic applications. Azomethine-containing polymers were synthesized via palladium-catalyzed direct arylation polymerization (DArP) and used to study fundamental degradation trends upon exposure to acid. Shifts in the UV-vis absorbance spectra and the appearance/disappearance of aldehyde and imine diagnostic peaks within the 1H NMR spectra indicate that the polymers will degrade in the presence of acid. After degradation, the aldehyde starting material was recovered in high yields and was shown to maintain structural integrity when compared with commercial starting materials. Solution-degradation studies found that rates of degradation vary from 5 h to 90 s depending on the choice of solvent or acid used for hydrolysis. Additionally, the polymer was shown to degrade in the presence of perfluoroalkyl substances (PFASs), which makes them potentially useful as PFAS-sensitive sensors. Ultimately, this research provides strategies to control the degradation kinetics of azomethine-containing polymers through the manipulation of environmental factors and guides the continued development of azomethine-based materials.

Degradable π-Conjugated Polymers.

The integration of next-generation electronics into society is rapidly reshaping our daily interactions and lifestyles, revolutionizing communication and engagement with the world. Future electronics promise stimuli-responsive features and enhanced biocompatibility, such as skin-like health monitors and sensors embedded in food packaging, transforming healthcare and reducing food waste. Imparting degradability may reduce the adverse environmental impact of next-generation electronics and lead to opportunities for environmental and health monitoring. While advancements have been made in producing degradable materials for encapsulants, substrates, and dielectrics, the availability of degradable conducting and semiconducting materials remains restricted. π-Conjugated polymers are promising candidates for the development of degradable conductors or semiconductors due to the ability to tune their stimuli-responsiveness, biocompatibility, and mechanical durability. This perspective highlights three design considerations: the selection of π-conjugated monomers, synthetic coupling strategies, and degradation of π-conjugated polymers, for generating π-conjugated materials for degradable electronics. We describe the current challenges with monomeric design and present options to circumvent these issues by highlighting biobased π-conjugated compounds with known degradation pathways and stable monomers that allow for chemically recyclable polymers. Next, we present coupling strategies that are compatible for the synthesis of degradable π-conjugated polymers, including direct arylation polymerization and enzymatic polymerization. Lastly, we discuss various modes of depolymerization and characterization techniques to enhance our comprehension of potential degradation byproducts formed during polymer cleavage. Our perspective considers these three design parameters in parallel rather than independently while having a targeted application in mind to accelerate the discovery of next-generation high-performance π-conjugated polymers for degradable organic electronics.

Universal Design and Efficient Synthesis for High Ambipolar Mobility Emissive Conjugated Polymers.

High ambipolar mobility emissive conjugated polymers (HAME-CPs) are perfect candidates for organic optoelectronic devices, such as polymer light emitting transistors. However, due to intrinsic trade-off relationship between high ambipolar mobility and strong solid-state luminescence, the development of HAME-CPs suffers from high structural and synthetic complexity. Herein, a universal design principle and simple synthetic approach for HAME-CPs are developed. A series of simple non-fused polymers composed of charge transfer units, π bridges and emissive units are synthesized via a two-step microwave assisted C-H arylation and direct arylation polymerization protocol with high total yields up to 61 %. The synthetic protocol is verified valid among 7 monomers and 8 polymers. Most importantly, all 8 conjugated polymers have strong solid-state emission with high photoluminescence quantum yields up to 24 %. Furthermore, 4 polymers exhibit high ambipolar field effect mobility up to 10-2 cm2 V-1 s-1, and can be used in multifunctional optoelectronic devices. This work opens a new avenue for developing HAME-CPs by efficient synthesis and rational design.

Universal Design and Efficient Synthesis for High Ambipolar Mobility Emissive Conjugated Polymers

AbstractHigh ambipolar mobility emissive conjugated polymers (HAME‐CPs) are perfect candidates for organic optoelectronic devices, such as polymer light emitting transistors. However, due to intrinsic trade‐off relationship between high ambipolar mobility and strong solid‐state luminescence, the development of HAME‐CPs suffers from high structural and synthetic complexity. Herein, a universal design principle and simple synthetic approach for HAME‐CPs are developed. A series of simple non‐fused polymers composed of charge transfer units, π bridges and emissive units are synthesized via a two‐step microwave assisted C−H arylation and direct arylation polymerization protocol with high total yields up to 61 %. The synthetic protocol is verified valid among 7 monomers and 8 polymers. Most importantly, all 8 conjugated polymers have strong solid‐state emission with high photoluminescence quantum yields up to 24 %. Furthermore, 4 polymers exhibit high ambipolar field effect mobility up to 10−2 cm2 V−1 s−1, and can be used in multifunctional optoelectronic devices. This work opens a new avenue for developing HAME‐CPs by efficient synthesis and rational design.

Aza[5]helicene‐Derived Semiconducting Polymers for Improved Performance in Perovskite Solar Cells: Exploring Energetic and Morphological Influences

AbstractThe strategic design of solution‐processable semiconducting polymers possessing both matched energy levels and elevated glass transition temperatures is of urgent importance in the progression of thermally robust n‐i‐p perovskite solar cells with efficiencies exceeding 25 %. In this work, we employed direct arylation polymerization to achieve the high‐yield synthesis of three aza[5]helicene‐derived copolymers with distinct HOMO energy levels and exceptional glass transition temperatures. Upon integration of these semiconducting polymers into formamidinium lead triiodide‐based perovskite solar cells, marked disparities in photovoltaic parameters manifest, primarily stemming from variations in the electrical conductivity and film morphology of the hole transport layers. The p‐A5HP‐E‐POZOD‐E copolymer, featuring a main chain comprising alternating repeats of aza[5]helicene, ethylenedioxythiophene, phenoxazine, and ethylenedioxythiophene, attains an initial average efficiency of 25.5 %, markedly surpassing reference materials such as spiro‐OMeTAD (23.0 %), PTAA (17.0 %), and P3HT (11.6 %). Notably, p‐A5HP‐E‐POZOD‐E exhibits a high cohesive energy density, resulting in enhanced Young's modulus and diminished external species diffusion coefficients, thereby conferring perovskite solar cells with exceptional 85 °C tolerance and operational stability.

Aza[5]helicene-Derived Semiconducting Polymers for Improved Performance in Perovskite Solar Cells: Exploring Energetic and Morphological Influences.

The strategic design of solution-processable semiconducting polymers possessing both matched energy levels and elevated glass transition temperatures is of urgent importance in the progression of thermally robust n-i-p perovskite solar cells with efficiencies exceeding 25 %. In this work, we employed direct arylation polymerization to achieve the high-yield synthesis of three aza[5]helicene-derived copolymers with distinct HOMO energy levels and exceptional glass transition temperatures. Upon integration of these semiconducting polymers into formamidinium lead triiodide-based perovskite solar cells, marked disparities in photovoltaic parameters manifest, primarily stemming from variations in the electrical conductivity and film morphology of the hole transport layers. The p-A5HP-E-POZOD-E copolymer, featuring a main chain comprising alternating repeats of aza[5]helicene, ethylenedioxythiophene, phenoxazine, and ethylenedioxythiophene, attains an initial average efficiency of 25.5 %, markedly surpassing reference materials such as spiro-OMeTAD (23.0 %), PTAA (17.0 %), and P3HT (11.6 %). Notably, p-A5HP-E-POZOD-E exhibits a high cohesive energy density, resulting in enhanced Young's modulus and diminished external species diffusion coefficients, thereby conferring perovskite solar cells with exceptional 85 °C tolerance and operational stability.

A soluble electron conjugated polymer for fast electrochromism and exceptional metal ion detection

The design of soluble electrochromic materials with fast responsivity for use in flexible displays and electronic papers remains a challenge. Most of the materials explored properties such as excellent contrast and rich color variation, while fast responsivity is also one of the key properties, which together push electrochromic materials into everyday life. Here we report a soluble electron conjugated polymer PDT-BTz, i.e., poly[3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine-alt-(2-(heptan-3-yl)benzo[d]thiazole], which was designed to be highly redox active polymeric backbone for electrochromism and constructed to engineer with chelating sites for metal ion detection, via direct (hetero)arylation polymerization of 3, 4-propenyldioxythiophene with benzothiazole derivative. The resultant PDT-BTz exhibited a pair of distinct redox peaks in the range of 0.41–––1.20 V, corresponding to a clear color change in the visible region between yellow and light green as revealed by cyclic voltammetry. PDT-BTz is easily casted into thin film and is highly responsive to visible light to achieve a very short response time of only 0.21 s, which is much far superior to other polymers reported so far. Remarkably, this electrochromic PDT-BTz is highly luminescent and enables to selectively detect iron Fe (III) and Ru (III) ions, via built-in C–S and C = N chelating units, with exceptional rate constants and detection limits. Together with the high thermal stability, the electron polymer opens a way to a novel class of soluble conjugated polymer that can merge dual functions of electrochromism with ion detection capability into one material.

Water/Alcohol‐Processable Low‐Cost Dihydropyrazine‐Based Polymers for Highly Sensitive, Stable and Flexible Temperature Sensors

AbstractFlexible temperature sensors based on π–conjugated polymers are well‐suited for diverse applications, including food packaging and human health monitoring. Herein, novel dihydropyrazine (DHP)‐based polymers designed for the development of flexible temperature sensors are introduced. The DHP‐based polymers are synthesized via direct arylation polymerization, eliminating toxic byproducts. Polymers with carboxylate potassium salt side chains, which exhibit high solubility in green solvents like water and alcohol are obtained via post‐polymerization hydrolysis of carboxylate ester chains. Furthermore, a post‐deposition treatment converts the carboxylate potassium salt side chains into carboxylic acid side chains, resulting in highly solvent‐resistant polymers. Notably, these DHP‐based polymers exhibit moderate electrical conductivity in the range of ≈10−4 to 10−1 S cm−1 without the need for additional dopants. Resistor‐type temperature sensors based on the self‐doped DHP‐based polymers, processed with ethylene glycol (EG) on flexible polyethylene terephthalate (PET) substrates via blade coating, demonstrate an impressive temperature coefficient of resistance (TCR) of up to −1.5% °C−1 (20–60 °C) and outstanding long‐term stability under ambient conditions. This work presents a well‐founded design of π–conjugated polymers that simultaneously fulfill performance, stability, processability, and cost criteria, paving the way for practical applications of flexible and printable temperature sensors.

Development of Synthetically Accessible Glycolated Polythiophenes for High‐Performance Organic Electrochemical Transistors

AbstractFour glycolated polythiophene‐based organic mixed ionic‐electronic conductors (OMIECs), PE2gTT, PE2gT, PT2gTT, and PT2gT are prepared by atom‐efficient direct arylation polymerization, avoiding the need for toxic organometallic precursors. PE2gT, PT2gTT, and PT2gT are operable in p‐type accumulation mode organic electrochemical transistors (OECTs), with PT2gT displaying the best device performance with a µC* product figure‐of‐merit of 290 F cm−1 V−1 s−1. A record volumetric capacitance among p‐type glycolated polythiophene OMIECs of 313 F cm−3 is observed for PE2gT, ascribed to the high proportionality of polar components in its materials design. The good OECT performance of PE2gT with µC* = 84.2 F cm−1 V−1 s−1, comparable with state‐of‐the‐art poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) devices, coupled with its synthetic accessibility and favorable accumulation mode operation makes PE2gT an ideal glycolated alternative to PEDOT:PSS in bioelectronics. PE2gT with the least negative threshold voltage also displays the best OECT operational cycling stability, linked to better resistance of its oxidized state against parasitic redox side reactions . Shelf life stability of OECTs stored (without bias) is observed to be better for materials with a more negative threshold voltage and higher average molecular weight (PT2gT), that are less susceptible to ambient auto‐oxidation and film delamination.

Tuning “ligandless” direct arylation polymerization toward less-branching EDOT polymers

Direct arylation polymerization conditions can be classified into phosphine-assisted and “ligandless” conditions.

High-mobility organic mixed conductors with a low synthetic complexity index via direct arylation polymerization

The synthesis of conjugated copolymers with glycolated thieno[3,2-b]thiophene units by direct arylation polymerization, their synthetic complexity in the context of literature compounds, and their performance in organic electrochemical transistors is described.

Room Temperature Synthesis of a Well-Defined Conjugated Polymer Using Direct Arylation Polymerization (DArP).

While a major improvement to the sustainability of conjugated polymer synthesis, traditional direct arylation polymerization (DArP) still requires high temperatures (typically >100 °C), necessitating a significant energy input requirement. Performing DArP at reduced or ambient temperatures would represent an improvement to the sustainability of the reaction. Here we describe the first report of a well-defined conjugated polymer synthesized by DArP at room temperature. Previous efforts toward room temperature DArP relied on the use of a near-stoichiometric silver reagent, an expensive coinage metal, which makes the reaction less cost-effective and sustainable. Here, room temperature polymerizations of 3,4-ethylenedioxythiophene (EDOT) and 9,9-dioctyl-2,7-diiodofluorene were optimized and provided molar mass (Mn) up to 11 kg/mol PEDOTF, and performing the reaction at the standard ambient temperature of 25 °C provided Mn up to 15 kg/mol. Model studies using other C-H monomers of varying electron density copolymerized with 9,9-dioctyl-2,7-diiodofluorene provided insight into the scope of the room temperature polymerization, suggesting that performing room temperature DArP is highly dependent on the electron richness of the C-H monomer.

The syntheses of fluorescein-based conjugated microporous polymers by direct arylation polymerization and fluorescence sensing Fe3+ in aqueous solutions

Determination of ferri ions in environment and human bodies is very important for environmental protection and disease diagnosis. Recently, conjugated microporous polymers (CMPs) used for fluorescence sensing metal ions have attracted much attention, but this technique is done in organic solvents. In this study, the two new fluorescein-based CMPs named FLEDOT and FLBTh were synthesized by “greener method”, direct arylation polymerization, with tetraiodofluorescein sodium salt (TIFS) and 3,4-ethylenedioxy thiophene or 2,2′-bithiophene. Pleasely, the prepared fluorescein-based CMPs can fluorescently sense for Fe3+ in water with high sensitivity and selectivity. The quenching constants (KSV) of FLEDOT and FLBTh are 1.51 × 104 and 1.09 × 104 L mol−1, and the limits of detection (LODs) as low as 1.99 × 10−10 and 2.75 × 10−10 mol L−1, which are comparable to the sensitivity found in organic solvents' dispersions such as N,N-dimethylformamide (DMF)′ dispersions. UV–Vis absorption spectra show that the fluorescence quenching mechanisms of Fe3+ are absorption competition quenching process and energy transfer process.

Electrochromic conjugated polymers containing benzotriazole and thiophene performing sub-second response time and 916 cm2 C−1 superb coloration efficiency

In pursuit of high-performance electrochromic conjugated polymers (ECPs), three benzotriazole-thiophene ECPs employing benzotriazole as acceptor and different thiophene repeating units as donors, namely, PBTz-T, PBTz-BT, and PBTz-TT, were synthesized via direct (hetero)arylation polymerization (DHAP). Meanwhile, following the above ECPs model, we investigated the effect of corresponding conjugated chain length of monomers on their optical, electrochemical and electrochromic properties. The results showed that along with the increase of the numbers of thiophene in the repeating unit of ECPs, the electronic and optical band gaps decreased, the UV–Vis absorption and fluorescence spectra showed significant bathochromic shift, and the electrochemical cycle stability gradually improved. PBTz-T exhibited giant coloration efficiency (916 cm2 C−1 at 530 nm), which is one of the best results in the visible region. And higher coloration efficiency means less energy consumption, which holds great potential for various applications, including electrochromic back covers of smartphones. PBTz-BT displayed the highest transmittance (28% at 550 nm), and BTz-TT illustrated the fastest switching time (0.6 s/0.5 s for doping/dedoping process). Flexible electrochromic device (ECD) fabricated employed PBTz-T as functional layer gradually changed from red (reduction) to dark green (oxidation), and maintained good cycling stability.