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Ziwei Hu, [Takeshi Yasuda](https://orcid.org/0000-0003-4652-9105), Takaki Kanbara, [Junpei Kuwabara](https://orcid.org/0000-0002-9032-5655)

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[Synthesis of Conjugated Polymers with Controlled Terminal Structures by Direct Arylation Polycondensation and Correlation Between Terminal Structures and Emission Properties](https://mdr.nims.go.jp/datasets/22835d68-9b9d-40e1-a412-a4e02f013538)

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Synthesis of Conjugated Polymers with Controlled Terminal Structures by Direct Arylation Polycondensation and Correlation Between Terminal Structures and Emission PropertiesRESEARCH ARTICLEwww.mcp-journal.deSynthesis of Conjugated Polymers with Controlled TerminalStructures by Direct Arylation Polycondensation andCorrelation Between Terminal Structures and EmissionPropertiesZiwei Hu, Takeshi Yasuda, Takaki Kanbara,* and Junpei Kuwabara*Conjugated polymers are promising semiconducting materials forapplications in organic electronic devices such as organic light-emittingdiodes (OLEDs). Recent advances in direct arylation polycondensation haveenabled the synthesis of defect-free polymers in the main chain; however,terminal groups have not been fully investigated. This research focuses on thesynthesis of polymers with controlled terminal groups and the evaluation oftheir effects on photophysical and OLED properties. Investigation of themonomer feed ratio and terminal treatment methods allows the synthesis ofthree polymers with different terminal groups. The terminal groups affect thephotoluminescence quantum yield in the thin-film state and the externalquantum efficiency in OLEDs. These findings indicate that a small percentageof terminal groups in the polymer material has a significant impact on thedevice properties.1. IntroductionWith the development of semiconducting polymers, the proper-ties of organic electronic devices have improved significantly.[1–8]Z. Hu, T. Kanbara, J. KuwabaraInstitute of Pure and Applied SciencesUniversity of Tsukuba1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, JapanE-mail: kanbara@ims.tsukuba.ac.jp; kuwabara@ims.tsukuba.ac.jpT. YasudaResearchCenter forMacromolecules andBiomaterialsNational Institute forMaterials Science (NIMS)1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, JapanJ. KuwabaraTsukubaResearchCenter for EnergyMaterials Science (TREMS)Institute of Pure andAppliedSciencesUniversity of Tsukuba1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, JapanThe ORCID identification number(s) for the author(s) of this articlecan be found under https://doi.org/10.1002/macp.202400506© 2025 The Author(s). Macromolecular Chemistry and Physicspublished by Wiley-VCH GmbH. This is an open access article under theterms of the Creative Commons Attribution-NonCommercial-NoDerivsLicense, which permits use and distribution in any medium, provided theoriginal work is properly cited, the use is non-commercial and nomodifications or adaptations are made.DOI: 10.1002/macp.202400506Organic light-emitting diodes (OLEDs),[2–4]organic photovoltaics (OPVs),[5–7] and or-ganic field-effect transistors (OFETs)[7,8] arerepresentative semiconducting-polymer ap-plications. These semiconducting polymershave mainly been synthesized by poly-condensation using cross-coupling reac-tions such as the Suzuki−Miyaura[9] andMigita−Kosugi-Stille coupling reactions.[10]In recent years, polycondensation via di-rect arylation (C–H/C–X coupling, X =halogen) has been developed as an al-ternative to conventional methods.[11] Di-rect arylation polycondensation has advan-tages in terms of short synthetic processesand environmental impacts because thereaction does not require organometallicmonomers and, therefore, gives no metal-containing by-products. In direct arylationpolycondensation, there are several potential risks associatedwith the formation of structural defects in the polymer mainchain. The reaction of the undesired C–H moieties causesbranching or crosslinking defects.[12–16] Additionally, side reac-tions involving the C–H/C–H or C–Br/C–Br homocoupling re-actions cause defects in the alternating structure, which are re-ferred to as homocoupling defects.[12,14,16–22] These defect struc-tures degrade the semiconducting properties.[17,18,21] Detailed op-timization of the reaction conditions by several research groupsover a decade succeeded in avoiding the formation of such defectstructures in direct arylation polycondensation.[11,16,23–30] Indeed,the direct arylation polycondensation yields polymers with fewerdefect structures than the conventional Migita−Kosugi−Stillepolycondensation, which causes 10% homocoupling defects.[30]In contrast to intensive research on the accuracy of the mainchain, control of the terminal structure has received relatively lit-tle attention in direct arylation polycondensation,[27,31] althoughthe terminal structures of the polymer materials affect theirphysical properties such as crystallinity,[32,33] hole mobility,[34–36]and photoelectric conversion properties.[32,36–39] In our previ-ous study, luminescence properties were affected by the termi-nal defect structure caused by side reactions.[31] The purposeof this study was to synthesize semiconducting polymers withcontrolled terminal structures and defect-free main chains us-ing direct arylation polycondensation. An investigation of themonomer feed ratio and terminal treatment methods enabledMacromol. Chem. Phys. 2025, 226, 2400506 2400506 (1 of 8) © 2025 The Author(s). Macromolecular Chemistry and Physics published by Wiley-VCH GmbHhttp://www.mcp-journal.demailto:kanbara@ims.tsukuba.ac.jpmailto:kuwabara@ims.tsukuba.ac.jphttps://doi.org/10.1002/macp.202400506http://creativecommons.org/licenses/by-nc-nd/4.0/http://crossmark.crossref.org/dialog/?doi=10.1002%2Fmacp.202400506&domain=pdf&date_stamp=2025-02-20www.advancedsciencenews.com www.mcp-journal.deScheme 1. Polycondensation of TPD and Br2-DOF.the synthesis of three polymers with nearly complete control ofboth terminals. The influence of the terminals on the photophys-ical properties was elucidated by evaluating the optical and OLEDproperties of polymers with the same main-chain structure butdifferent terminal groups.2. Results and Discussion2.1. Polymerization and Terminal Structure Control5-(2-Ethylhexyl)thieno[3,4-c]-pyrrole-4,6-dione (TPD) was se-lected as the monomer for this investigation owing to itsfavorable reactivity of the C─H bonds for direct arylation.[27,40,41]Our group reported the optimal reaction conditions for TPDusing a low-polarity solvent with a PCy3 (tricyclohexylphosphine)ligand.[27] The use of the Pd(0) catalyst, Pd(PCy3)2, instead of acombination of Pd(OAc)2 and PCy3 is important for preventinghomocoupling defects during the initiation of the catalyticreaction.[29] To modify both polymer terminals with TPD units,polycondensation reactions of TPD with 2,7-dibromo-9,9-dioctylfluorene (Br2-DOF) were performed with excess TPD(Scheme 1, Table 1). The reaction with excess TPD yieldedpolymers with suppressed molecular weights, in accordancewith the Carothers equation.[42] Matrix-assisted laser desorp-tion/ionization time-of-flight mass spectrometry (MALDI-TOFMS) provides direct information on terminal structures. Themass spectra of the polymers synthesized in Entries 1 and 2 showpeaks corresponding to the alternating structure with both TPDterminals (Figures S1 and S2, Supporting Information). Theseresults indicate that the polycondensation reaction can be usedto synthesize polymers with no structural defects in the mainchain, unified terminals, and controlled molecular weights.Table 1. Results of polycondensation.Entry TPD:Br2-DOF Yielda) Mn (Mw/Mn)1 1.05:1 42% 14 500 (1.5)2 1.01:1 96% 70 000 (2.3)3 1:1 91% 98 700 (2.0)a)Yields of the CHCl3-soluble and hexane-insoluble parts.Figure 1. a) Chemical structure and b) crystal structure of the Pd(II) cata-lyst precursor. One of the disordered structures is presented.Interestingly, even in the case of polymerization with a 1:1molar ratio (Table 1, Entry 3), TPD-terminated structures weredominant (Figure S3, Supporting Information). In principle,both the TPD and fluorene terminals should be observed. Suchselective modification of both terminals occurs when a Pd cata-lyst is transferred intramolecularly and reacts sequentially.[43–45]In this case, after the reaction with one Br group of Br2-DOFproceeds, the Pd catalyst may transfer to the other Br through afluorene unit and react sequentially. To confirm the intramolec-ular catalyst transfer, polycondensation reactions of TPD andBr2-DOF under conditions with an excess of Br2-DOF wereperformed because polycondensation involving intramolecularcatalyst transfer would give a high-molecular-weight polymer,even in the presence of excess amounts of Br2-DOF (Table S1,Supporting Information Entry 1). Polymerization gave polymersof higher molecular weight than the calculated molecular weightfrom the Carothers equation, confirming that the intramolec-ular catalytic transfer occurred. However, the reaction with alarge excess of Br2-DOF (Table S1, Supporting InformationEntry 2) yielded a relatively low-molecular-weight polymer withbromofluorene terminals, indicating that the intramolecular cat-alytic transfer is preferentially occurred, but a certain percentageof intermolecular reactions also occurred.2.2. Modification of Terminals with MethylthiopheneFor the modification of the TPD terminals, methylthiophene wasselected as the electron-rich terminal group to compare the prop-erties of the electron-poor TPD terminal group. Although Pd(0)catalysts are effective in preventing side reactions,[29] they are un-stable in air and difficult to handle. To smoothly introduce themethylthiophene units at the chain terminals, a new Pd(II) cat-alyst precursor bearing a methylthiophene moiety was synthe-sized (Figure 1; Scheme S1, Supporting Information). This cata-lyst is stable and easy to handle in the air, facilitating the additionof a Pd catalyst for terminal modification during the reaction.[46]The Pd(II) catalyst precursor should generate an active Pd(0)species when reacting with the C−H terminals of the polymer.Macromol. Chem. Phys. 2025, 226, 2400506 2400506 (2 of 8) © 2025 The Author(s). Macromolecular Chemistry and Physics published by Wiley-VCH GmbH 15213935, 2025, 10, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/macp.202400506 by National Institute For, Wiley Online Library on [19/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.mcp-journal.dewww.advancedsciencenews.com www.mcp-journal.deFigure 2. MALDI-TOF-MS tracking the terminal modification process.Single-crystal X-ray diffraction analysis confirmed the expectedstructures (Figure 1b).The catalytic activity of the Pd(II) catalyst precursor wasinvestigated for terminal modification of the TPD-terminatedpolymer synthesized in the previous section (Table 1, Entry1). The progress of terminal modification was tracked usingMALDI-TOF-MS (Figure 2). Before modification, the spectrumshowed only peaks corresponding to the TPD-terminated poly-mer (A). The spectrum of the sample after the reaction for 2 hshowed peaks corresponding to polymers with one terminalmodified (B) and polymers with both terminalsmodified (C). Theintensity of peak C increased with time, and eventually, only peakC was observed. The structure of the terminally modified poly-mer was confirmed by 1H NMR spectroscopy (Figure S4, Sup-porting Information). Similar results were obtained when themodification was conducted with Pd(PCy3)2, which is highly ac-tive but unstable in the air (Figure S5, Supporting Information).The Pd(II) catalyst precursor exhibited a terminal modificationcomparable to that of the Pd(0) catalyst, with the added advan-Scheme 2. Synthesis of Br-terminated polymer (P-Br).tages of air stability and ease of handling. The Pd(II) catalystprecursor facilitated both polycondensation and terminal modi-fication, producing the corresponding polymers with methylth-iophene terminals (Scheme S2, Supporting Information). Al-though there are many examples of terminal modification inpolycondensation reactions using conventional cross-couplingreactions,[47–49] a unique feature of this system is that both termi-nals can be modified nearly completely. Complete terminal mod-ification is possible because the C─H bond is more stable thanthe carbon−metal bond used in conventional cross-coupling re-actions and does not decompose during the reaction. Direct ary-lation reactions can be used to synthesize polymers with well-controlled terminals.2.3. Synthesis of the Polymers with Different Terminal UnitsTo evaluate the effect of terminal groups on the physical prop-erties, a polymer with bromofluorene terminals was prepared.Normally, a reaction with a small excess of Br2-DOF would yielda polymer with bromofluorene terminals; however, owing to theaforementioned intramolecular catalyst transfer, the formation ofthe TPD terminal takes precedence. Several trials revealed thata large excess of Br2-DOF (1.33 times) was required to obtain apolymer with the desired terminal structure (Scheme 2). Becauseof the large excess of monomers, the molecular weight was only16 900. MALDI-TOF MS revealed the presence of polymers withboth bromofluorene terminals and polymers with one TPD ter-minal (Figure 3).Polymers with methylthiophene (P-Th) and TPD terminals (P-TPD) bearingmolecular weights similar toP-Brwere synthesizedusing the method described in the previous section. P-TPD wasobtained via the polycondensation under the condition of a 5%excess TPD monomer (Scheme 3). P-Th was prepared via poly-condensation and subsequent terminal modification in a one-pot manner. The molecular weights from GPC measurementsand yields are listed in Table 2. The molecular weight of P-Th(17600) was calculated from the integral ratio of the main chainand terminal unit in the 1H NMR spectrum. This value is ingood agreement with that obtained fromGPC (17900). The termi-nal structures were confirmed usingMALDI-TOF-MS (Figure 3).These results indicate that the three polymers have the sameMacromol. Chem. Phys. 2025, 226, 2400506 2400506 (3 of 8) © 2025 The Author(s). Macromolecular Chemistry and Physics published by Wiley-VCH GmbH 15213935, 2025, 10, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/macp.202400506 by National Institute For, Wiley Online Library on [19/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.mcp-journal.dewww.advancedsciencenews.com www.mcp-journal.deFigure 3. MALDI-TOF-MS for P-Th, P-TPD, and P-Br.Scheme 3. Synthesis of P-TPD and P-Th.Table 2.Molecular weight and yield of the polymers.Terminal structure Mn Mw/Mn YieldP-Th Methylthiophene 17 900 1.9 84%P-TPD TPD 17 500 2.0 77%P-Br a) Br 16 900 1.8 65%a)P-Br contains minor TPD terminal units.main chain, are free of defects, and contain controlled terminalgroups with similar molecular weights.2.4. Evaluation of Photophysical Properties and DevicePerformanceThe UV−vis absorption and photoluminescence (PL) spectra ofthe three polymers were measured in solution and thin-filmstates. The absorption spectra of the polymers are nearly identical(Figure S12, Supporting Information). The PL spectra in the solu-tion state are very similar because the emission is predominantlyfrom the main chain (Figure 4a). In contrast, the spectra in thethin-film state show different ratios of the first (495 nm) and sec-ond (530 nm) maximum peaks (Figure 4b). Although the mecha-nism by which the terminal structures affect the intensity ratio ofthe two peaks derived from the vibrational structure is unknown,but it is found that the effects of the terminals are pronouncedin the film state. In terms of photoluminescence quantum yield(PLQY), P-Th had a relatively low value (Table 3). The three poly-mers have identical optical bandgap (2.53 eV) and HOMO level(−6.2 eV), which are estimated from the absorption edges in thethin film states and by photoelectron yield spectroscopy (PYS),respectively. These identical values reveal that the main chainstructure dominantly determines the energy levels and that theterminal structures have minimal effect.OLEDs containing these polymers were fabricated with thesame configuration (details are provided in the Experimental sec-tion). Figure 5 shows the current density–voltage plots and exter-nal quantum efficiency (EQE)–current density characteristics ofthe fabricated OLEDs. The results are summarized in Table 3.The device with P-TPD exhibited a higher EQE than those withP-Th and P-Br. The low EQE of the OLED with P-Th was proba-bly owing to its low PLQY (Table 3). Although the PLQYs of P-Brand P-TPD were similar, the OLED with P-Br exhibited a lowerEQE than the OLED with P-TPD. In the current density–voltageplots, the OLEDwith P-Br showed a relatively low current densityat the same voltage compared with the others (Figure 5a), whichMacromol. Chem. Phys. 2025, 226, 2400506 2400506 (4 of 8) © 2025 The Author(s). Macromolecular Chemistry and Physics published by Wiley-VCH GmbH 15213935, 2025, 10, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/macp.202400506 by National Institute For, Wiley Online Library on [19/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.mcp-journal.dewww.advancedsciencenews.com www.mcp-journal.deFigure 4. a) PL spectra of P-Th, P-TPD, and P-Br in solution state (CHCl3,5 μM, 𝜆ex = 400 nm) and b) in thin-film state (𝜆ex = 440 nm).Table 3. PLQY in the thin film state and OLED properties.PLQY a) / % EQE b) / % Max luminance c) / cd m−2P-Th 22 1.05 9760P-TPD 27 1.25 9740P-Br 28 1.01 2970a)Photoluminescence quantum yield in the thin film state;b)External quantumefficiency of the OLEDs. Configuration: glass/ITO/PEDOT:PSS (40 nm)/ poly(9-vinylcarbazole) (PVK) (30 nm)/Polymer (30 nm)/ 2,2′,2′’-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) (30 nm)/LiF (1 nm)/Al (100 nm);c)Maximumluminance of the OLEDs.Figure 5. a) Current density–voltage plots and b) EQE–current den-sity characteristics of the OLEDs fabricated with glass/ITO/PEDOT:PSS(40 nm)/PVK (30 nm)/Polymer (30 nm)/TPBi (30 nm)/LiF (1 nm)/Al(100 nm).implies that P-Br has a large resistance. As has been previouslyreported,[34,36–38] the Br terminals are likely to be carrier trappingsites, which lead to high resistivity and exciton quenching dueto carrier-exciton interactions, resulting in the low EQE.[50] Re-lated to this, the OLED with P-Br has a lower maximum lumi-nance value (Table 3; Figure S13, Supporting Information). TheTPD terminals in P-TPD were superior to the other terminalsin terms of the PLQY and efficient carrier transport, resultingin the highest EQE and contributing to the lower driving volt-age. Notably, the same polymer with high molecular weight (MnMacromol. Chem. Phys. 2025, 226, 2400506 2400506 (5 of 8) © 2025 The Author(s). Macromolecular Chemistry and Physics published by Wiley-VCH GmbH 15213935, 2025, 10, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/macp.202400506 by National Institute For, Wiley Online Library on [19/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.mcp-journal.dewww.advancedsciencenews.com www.mcp-journal.de= 176 800) was evaluated in the same device configuration andshowed a high EQE (2.04%) in a previous study.[31] This suggeststhat all the terminal groups can have negative effects on deviceperformance, and high-molecular-weight materials are desirablein OLED materials to reduce the number of terminal units.3. ConclusionWe successfully synthesized conjugated polymers with defect-free main chains and controlled their terminal structures via di-rect arylation polycondensation. A Pd(II) catalyst precursor wasdeveloped and used as an air-stable catalyst for terminal modi-fication. An investigation of the optical and OLED properties ofthe three polymers with nearly complete control of both termi-nals revealed that the terminal structures affected the PLQY inthe thin-film state and carrier transport properties in the OLEDs.The small percentage of terminal groups in the polymer materialcan produce a 20% difference in EQE of OLEDs. This researchhighlights the potential for improving device properties throughterminal group control and provides valuable insights for the fu-ture development of organic optoelectronic materials.4. Experimental SectionMaterials: Pd(PCy3)2 was purchased from BLDpharm and stored un-der a N2 atmosphere. Anhydrous toluene was purchased from KantoChemical and used as a dry solvent. Other chemicals were receivedfrom commercial suppliers and used without further purification. 5-(2-Ethylhexyl)thieno[3,4-c]-pyrrole-4,6-dione (TPD) was prepared accordingto previously reported methods.[51,52]General Measurements and Characterization: NMR spectra wererecorded by AVANCE-400 and AVANCE-600 NMR spectrometers (Bruker).Elemental analyses were carried out with a Yanaco MT-5 CHN au-torecorder at A-Rabbit-Science Japan Co., Ltd. MALDI-TOF-MS spectrawere recorded on a MALDI TOF/TOF 5800 (AB SCIEX) using trans-2-[3-(4-t-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) as ma-trix. UV–vis absorption spectra in solution states were recorded on aHitachi U-3900H or a JASCO V-630. PL spectra in solution states wererecorded on a Hitachi F-2700 fluorescence spectrophotometer. UV–vis ab-sorption spectra and PL spectra for the spin-coated films were recordedon a Hitachi U-3010 and JASCO FP-6500 spectrophotometer, respectively.PLQYs of the spin-coated films were measured using a JASCO FP-6500spectrophotometer with an integrating sphere. The HOMO energy lev-els were estimated by PYS using an AC-3 spectrometer (Riken Keiki). Allthe manipulations for the reactions were carried out under an N2 atmo-sphere using a glove box or standard Schlenk technique. Intensity datafor crystal structure determination were collected on a Bruker SMARTAPEX II ULTRA with Mo K𝛼 radiation. A full matrix least-squares refine-ment was used for non-hydrogen atoms with anisotropic thermal param-eters using the SHELXL-97 program. CCDC 2409877 contains the sup-plementary crystallo-graphic data for this paper. These data can be ob-tained free of charge via www.ccdc.cam.ac.uk/data_request/cif , by email-ing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crys-tallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:+44 1223 336033.Synthesis of the Pd(II) Catalyst Precursor: To a 25 mL Schlenk tube witha stirrer chip were added Pd2(dba)3 (91.6 mg, 0.10 mmol), PCy3 (140 mg,0.50mmol), dry toluene (6.5mL), and 2-bromo-5-methylthiophene (68 μL,0.60 mmol) in a Glove box. The mixture was stirred at 60 °C for 24 h. Af-ter cooling to room temperature, the mixture was filtered using a syringefilter. The filtrate was concentrated under reduced pressure. Recrystalliza-tion with toluene and diethyl ether gave light yellow crystals. The crystalswere dried under vacuum (79.1 mg, 47%).1H NMR spectrum (400 MHz, CDCl3): 𝛿 6.59 (d, J = 3.1 Hz, 1H), 6.30(d, J = 3.4 Hz, 1H), 2.43 (s, 3H), 1.98 (m, 22H), 1.64 (m, 22H), 1.14(m, 22H). 13C{1H} NMR spectrum (100 MHz, CDCl3): 𝛿 140.47, 130.35,126.17, 33.86, 30.31, 27.76, 27.17, 15.42. 31P NMR spectrum (162 MHz,CDCl3): 𝛿 22.61 (s, 2P). Anal Calcd. for C41H71BrP2PdS: C 58.32, H 8.48,S 3.80; found: C 58.25, H 8.53, S 3.69.Synthesis of P-Th: A solution of Pd(PCy3)2 (2.7 mg, 0.0040 mmol)in dry toluene (1 mL) was prepared in a glove box. 2,7-Dibromo-9,9-dioctylfluorene (Br2-DOF) (106.4 mg, 0.194 mmol), Cs2CO3 (163 mg,0.50 mmol), 5-(2-ethylhexyl)-thieno[3,4-c]pyrrole-4,6-dione (TPD) (53 mg,0.20 mmol) was added to a 25 mL Schlenk tube with a stirrer chip. Thesolution of the Pd catalyst was added to the Schlenk tube in the glove box.The pivalic acid (6.9 μL, 0.060mmol) was added under the N2 atmosphereoutside of the glove box. The mixture was stirred at 100 °C for 24 h. ThePd(II) catalyst precursor (6.8 mg, 0.0080mmol), dry toluene (3.5 mL), and2-bromo-5-methylthiophene (4.6 μL, 0.040 mmol) were added to the mix-ture under N2. The mixture was stirred at 100 °C for 24 h. After cooling toroom temperature, volatiles were removed under vacuum. The productswere dissolved in CHCl3 (100 mL) and an aqueous solution of sodium di-ethyldithiocarbamate (0.1 m, 150 mL) was added. The mixture was stirredfor 16 h at room temperature. After separation, the organic layer waswashed with water (3 times) and brine. The organic layer was dried withNa2SO4 and was concentrated. The solution was poured into vigorouslystirred MeOH (200 mL) and stirred overnight. The solid was filtered andwashed with hexane (150 mL) for 1 h. P-Th was isolated as a yellow solidafter drying under vacuum (109.4 mg, 84%).1H NMR spectrum (600 MHz, 373 K, C2D2Cl4): 𝛿 8.33 (s, 2H), 8.26 (d,J = 8.4 Hz, 2H), 7.91 (d, J = 8.1 Hz, 2H), 3.72 (br, 2H), 2.23 (br, 4H), 2.01(t, J = 6.3 Hz, 1H), 1.54-1.46 (br, 8H), 1.26-1.21 (br, 20H), 1.07-0.99 (m,6H), 0.88 (10H, overlapped); Terminal groups: 8.31 (br), 8.23 (br), 7.88(br), 6.88 (s), 3.67 (br), 2.62 (s)Mn = 17 900,Mw/Mn = 1.9.Synthesis of P-TPD: A solution of Pd(PCy3)2 (2.7 mg, 0.0040 mmol)in dry toluene (1 mL) was prepared in a glove box. Br2-DOF (106.4 mg,0.194 mmol), Cs2CO3 (163 mg, 0.50 mmol), TPD (53 mg, 0.20 mmol)were added to a 25 mL Schlenk tube with a stirrer chip. The solution ofthe Pd catalyst was added to the Schlenk tube in the glove box. The pi-valic acid (6.9 μL, 0.060 mmol) was added under the N2 atmosphere out-side of the glove box. The mixture was stirred at 100 °C for 24 h. Aftercooling to room temperature, volatiles were removed under vacuum. Theproducts were dissolved in CHCl3 (100 mL) and an aqueous solution ofsodium diethyldithiocarbamate (0.1 m, 150 mL) was added. The mixturewas stirred for 16 h at room temperature. After separation, the organiclayer was washed with water (3 times) and brine. The organic layer wasdried with Na2SO4 and was concentrated. The solution was poured intovigorously stirred MeOH (200 mL), and stirred overnight. The solid wasfiltered and washed with hexane (150 mL) for 1 h. P-TPD was isolated asa yellow solid after drying under vacuum (101.1 mg, 77%).1H NMR spectrum (600 MHz, 373 K, C2D2Cl4): 𝛿 8.32 (s, 2H), 8.26 (d,J = 8.3 Hz, 2H), 7.91 (d, J = 8.1 Hz, 2H), 3.72 (br, 2H), 2.23 (br, 4H), 2.00(t, J = 6.1 Hz, 1H), 1.52-1.44 (br, 8H), 1.25-1.21 (br, 20H), 1.07-0.98 (m,6H), 0.91-0.83 (10H, overlapped); Terminal groups: 8.30 (br), 8.20 (br),7.88 (br), 7.75 (s), 3.65 (br)Mn = 17 500Mw/Mn = 2.0.Synthesis of P-Br: A solution of Pd(PCy3)2 (2.7 mg, 0.0040 mmol) indry toluene (1 mL) was prepared in a glove box. Br2-DOF (109.7 mg,0.20 mmol), Cs2CO3 (163 mg, 0.50 mmol), TPD (39.8 mg, 0.15 mmol)were added to a 25 mL Schlenk tube with a stirrer chip. The solution ofthe Pd catalyst was added to the Schlenk tube in the glove box. The pi-valic acid (6.9 μL, 0.060 mmol) was added under the N2 atmosphere out-side of the glove box. The mixture was stirred at 100 °C for 24 h. Aftercooling to room temperature, volatiles were removed under vacuum. Theproducts were dissolved in CHCl3 (100 mL) and an aqueous solution ofsodium diethyldithiocarbamate (0.1 m, 150 mL) was added. The mixturewas stirred for 16 h at room temperature. After separation, the organiclayer was washed with water (3 times) and brine. The organic layer wasdried with Na2SO4 and was concentrated. The solution was poured intovigorously stirred MeOH (200 mL), and stirred overnight. The solid wasfiltered and washed with hexane (150 mL) for 1 h. P-Br was isolated as ayellow solid after drying under vacuum (84.5 mg, 65%).Macromol. Chem. Phys. 2025, 226, 2400506 2400506 (6 of 8) © 2025 The Author(s). Macromolecular Chemistry and Physics published by Wiley-VCH GmbH 15213935, 2025, 10, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/macp.202400506 by National Institute For, Wiley Online Library on [19/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.mcp-journal.dehttps://www.ccdc.cam.ac.uk/services/structures?id=doi:10.1002/macp.202400506http://www.ccdc.cam.ac.uk/data_request/cifwww.advancedsciencenews.com www.mcp-journal.de1H NMR spectrum (600 MHz, 373 K, C2D2Cl4): 𝛿 8.33 (s, 2H, s), 8.26(d, J = 8.4 Hz, 2H), 7.91 (d, J = 7.7 Hz, 2H), 3.72 (br, 2H), 2.24 (br, 2H),2.00 (d, J = 6.2 Hz, 1H), 1.55-1.45 (br, 8H), 1.30-1.19 (br, 20H), 1.07-1.00(m, 6H), 0.89 (10H, overlapped); Terminal groups: 8.31 (br), 8.20 (br),7.81 (br), 7.66 (d, J = 8.3 Hz), 7.59 (s), 7.56 (d, J = 9.5 Hz), 7.52 (s)Mn =16 900,Mw/Mn = 1.8.Fabrication and Characterization of OLEDs: OLEDs were fabricatedin the following configuration: Glass/ITO/PEDOT:PSS (40 nm)/PVK (30nm)/Polymer (30 nm)/TPBi (30 nm)/LiF (1 nm)/Al (100 nm) The pat-terned indium tin oxide (ITO) glass (conductivity: 10 Ω/square) was pre-cleaned in an ultrasonic bath of acetone and ethanol and then treated in anultraviolet-ozone chamber. A thin layer (40 nm) of PEDOT:PSS was spin-coated onto the ITO at 3000 rpm and air-dried at 110 °C for 10 min ona hot plate. The substrate was then transferred to a N2-filled glove boxwhere it was re-dried at 110 °C for 10 min on a hot plate. A chloroformsolution of PVK (3 mg 1 mL−1) was subsequently spin-coated onto thePEDOT:PSS surface to form the hole transport layer (30 nm), followed bya baking process for 10 min at 150 °C. A toluene solution of polymer (5mg 1 mL−1) was subsequently spin-coated onto the PVK surface to formthe light-emitting layer (30 nm), followed with an annealing process for10 min at 80 °C. TPBi was placed in a Mo boat, and LiF and Al in a W boat,and the boats were heated by applying suitable current to the boats. TPBi(30 nm), LiF (1 nm), and Al (100 nm) were then deposited onto the activelayer at a chamber pressure lower than 5× 10−4 Pa, which provided the de-vices with an active area of 2 × 2 mm2. Current-voltage characteristics andluminance of the OLED were simultaneously measured using an ADCMT6245 DC voltage current source/monitor (ADC CORPORATION) and anLS-100 luminance meter (KONICA MINOLTA, INC.), respectively. The ELspectra were measured using an array spectrometer (MCPD-9800-311C,Otsuka Electronics Co, Ltd.).Supporting InformationSupporting Information is available from the Wiley Online Library or fromthe author.AcknowledgementsThe authors thank the Chemical Analysis Center of the University ofTsukuba for the measurements of NMR, elemental analyses, and thesingle-crystal X-ray diffraction analysis. The authors are grateful to RikenKeiki Co. Ltd. for measurements of photoelectron yield spectroscopy us-ing an AC-3 spectrometer. The authors also thank to Prof. A. Takai andtheMolecular Design and Function Group, National Institute forMaterialsScience (NIMS) for theMALDI-TOF-MS. This work was partially supportedby JSPS KAKENHI Grant Number JP22K05075, JP23K04884, JP23K04835,and the Joint Usage/Research Project for Catalysis (No. 23ES0313 and24DS0629).Conflict of InterestThe authors declare no conflict of interest.Data Availability StatementThe data that support the findings of this study are available from the cor-responding author upon reasonable request.Keywordsconjugated polymers, direct arylation polycondensation, organic light-emitting diodes, semiconducting polymers, terminal groupReceived: December 17, 2024Revised: February 10, 2025Published online: February 20, 2025[1] I. McCulloch, M. Chabinyc, C. Brabec, C. B. Nielsen, S. E. Watkins,Nat. Mater. 2023, 22, 1304.[2] A. C. Grimsdale, K. L. Chan, R. E. Martin, P. G. Jokisz, A. B. Holmes,Chem. Rev. 2009, 109, 897.[3] T. Jiang, Y. Liu, Z. Ren, S. Yan, Polym. Chem. 2020, 11, 1555.[4] W. Liu, H. Chen, S. Zhang, P. Li, W. Wu,Macromol. Chem. Phys. 2024,225, 2300325.[5] S. Holliday, Y. Li, C. K. Luscombe, Prog. 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Galeotti, Dyes Pigments 2015, 114, 138.Macromol. Chem. Phys. 2025, 226, 2400506 2400506 (8 of 8) © 2025 The Author(s). Macromolecular Chemistry and Physics published by Wiley-VCH GmbH 15213935, 2025, 10, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/macp.202400506 by National Institute For, Wiley Online Library on [19/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.mcp-journal.de Synthesis of Conjugated Polymers with Controlled Terminal Structures by Direct Arylation Polycondensation and Correlation Between Terminal Structures and Emission Properties 1. Introduction 2. Results and Discussion 2.1. Polymerization and Terminal Structure Control 2.2. Modification of Terminals with Methylthiophene 2.3. Synthesis of the Polymers with Different Terminal Units 2.4. Evaluation of Photophysical Properties and Device Performance 3. Conclusion 4. Experimental Section Supporting Information Acknowledgements Conflict of Interest Data Availability Statement Keywords