Suzuki Polycondensation Research Articles

Synthesis of Porphyrin‐Appended Poly(fluorene‐alt‐triphenylamine)s: Effect of Appending Groups on Optical and Electrochemical Properties

AbstractSeries of poly(fluorene‐alt‐triphenylamine)s having 5 and 10% equivalent of porphyrin appended through oxyethylene spacer in carbazole and aldehyde as side chain in triphenylamine unit (P2‐P5 CHO) were synthesized using Suzuki polycondensation. The synthesized polymers were compared with their parent polymer (P1 CHO). The effect of side chains in polymer backbone was studied by using aldehyde and dicyanomethane as side chain in triphenylamine moiety of polymer. Further, the role of spatial arrangement of appended porphyrin group on the polymer's optical and electrochemical properties was also studied. Thermal studies of the polymers showed that, these polymers were thermally stable up to 200 °C. Optical absorption studies of the porphyrin appended polymers showed absorption maxima at around 301 nm, 375 nm, and 421 nm with Q bands of porphyrin. As thin film, photoluminescence emission studies of the polymers showed emission maxima at around 650 and 719 nm. Electrochemical study reveals that m‐phenyloxy trisphenylporphyrin appended polymers showed HOMO energy level at around −5.45 eV and LUMO energy level at around −3.45 eV. While, p‐phenyloxy trisphenylporphyrin appended polymers showed a marginal shift in HOMO and LUMO energy levels. Photovoltaic studies of the porphyrin appended polymer showed up to 0.1% power conversion efficiency with an open circuit voltage of 0.76 V and the details are reported.

Trifluoromethyl-Substituted Large Band-Gap Polytriphenylamines for Polymer Solar Cells with High Open-Circuit Voltages.

Two large band-gap polymers (PTPACF and PTPA2CF) based on polytriphenylamine derivatives with the introduction of electron-withdrawing trifluoromethyl groups were designed and prepared by Suzuki polycondensation reaction. The chemical structures, thermal, optical and electrochemical properties were characterized in detail. From the UV-visible absorption spectra, the PTPACF and PTPA2CF showed the optical band gaps of 2.01 and 2.07 eV, respectively. The cyclic voltammetry (CV) measurement displayed the deep highest occupied molecular orbital (HOMO) energy levels of −5.33 and −5.38 eV for PTPACF and PTPA2CF, respectively. The hole mobilities, determined by field-effect transistor characterization, were 2.5 × 10−3 and 1.1 × 10−3 cm2 V−1 S−1 for PTPACF and PTPA2CF, respectively. The polymer solar cells (PSCs) were tested under the conventional device structure of ITO/PEDOT:PSS/polymer:PC71BM/PFN/Al. All of the PSCs showed the high open circuit voltages (Vocs) with the values approaching 1 V. The PTPACF and PTPA2CF based PSCs gave the power conversion efficiencies (PCEs) of 3.24% and 2.40%, respectively. Hence, it is a reliable methodology to develop high-performance large band-gap polymer donors with high Vocs through the feasible side-chain modification.

Design and synthesis of N-substituted perylene diimide based low band gap polymers for organic solar cell applications.

In this study, we report on the synthesis and device studies of a series of new copolymers containing N-substituted perylene dimide and dioctylfluorene units as part of the main backbone. A facile synthetic approach avoiding non-selective bromination was used to synthesize the monomer M1 by the reaction of perylene-3,4,9,10-tetracarboxylic dianhydride with 2-amino-7-bromo-9,9-dioctylfluorene. The copolymers P1 and P2 were synthesized by Suzuki polycondensation of M1 with 2,2′-(9,9-dioctyl-9H-fluoren-2,7-diyl)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) M2 and 9-(heptadecan-9-yl)-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole M3, respectively. The copolymer P3 was synthesized by direct arylation polymerization of M1 with 4,7-bis(4-octylthiophen-2-yl)benzo[c]-1,2,5-thiadiazole M4. All the copolymers showed thermal stability greater than 380 °C as evidenced from thermogravimetric analysis. The copolymers exhibited a narrow optical band gap (1.80–2.08 eV) with their UV-visible absorption spectra extending up to the NIR region and they are found to be suitable for use in OSC applications. The molecular weights of the polymers P1–P3 were found to be in the range of 10.68 to 16.02 kg mol−1 as measured from GPC analysis. The surface morphology of the active layers based on P1/P2/P3:P3HT blend films was investigated by AFM and the rms values from height images range from 0.65 to 2.90 nm. The polymers were blended with P3HT to fabricate BHJ solar cells in three different weight ratios i.e. 1 : 1, 1.5 : 1 and 2 : 1 and the best power conversion efficiency was observed for the binary film of P3:P3HT blend device in a 1 : 1 weight ratio which reached up to 1.96% with a Voc of 0.55 V, Jsc of 10.12 mA cm−2 and FF of 34.63% which is among the highest reported for BHJ solar cells with N-substituted PDI based acceptors.

Polyfluorene copolymers containing 2,5-difluoro-1,4-phenylene chains and carbazole conjugates with 1,8-naphthalimides for stable blue OLEDs

Polyfluorene copolymers containing 33 mol% of 2,5-difluoro-1,4-phenylene units and other comonomers comprising chargetransporting triphenylamine, carbazole, and 1,8-naphthalimide groups were synthesized by the Suzuki polycondensation under microwave irradiation. On heating the obtained copolymers to 180 °C, their photoluminescence spectra remain stable. The best sample herein obtained provided the OLED brightness of 2830 cd m–2, current efficiency of 0.5 cd A–1 and CIE coordinates of x = 0.168 and y = 0.228.

Benzoyl side-chains push the open-circuit voltage of PCDTBT/PCBM solar cells beyond 1 V

Abstract The synthesis, characterization and solar cell performance of PCDTBT and its highly soluble analogue hexyl-PCDTBT with cross-conjugated benzoyl moieties at the carbazole comonomer are presented. Through the use of both model reactions and time-controlled microwave-assisted Suzuki polycondensation, the base-induced cleavage of the benzoyl group from the polymer backbone has been successfully suppressed. Compared to the commonly used symmetrically branched alkyl motif, the benzoyl substituent lowers the energy levels of PCDTBT as well as the band gap, and consequently increases energy of the charge transfer state in blends with PC 71 BM. As a result, photovoltaic diodes with high-open circuit voltage of above 1 V are realized.

Interaction of Polar and Nonpolar Polyfluorenes with Layers of Two-Dimensional Titanium Carbide (MXene): Intercalation and Pseudocapacitance

This article provides insight into the interaction of synthetic conjugated polymers [polyfluorene derivatives (PFDs)] with layers of two-dimensional titanium carbide (Ti3C2Tx). Three derivatives with nonpolar, polar, and charged nitrogen-containing functionalities were synthesized via the Suzuki polycondensation reaction. The organic–inorganic PFD/Ti3C2Tx hybrids were prepared and characterized using X-ray diffraction and a range of microscopic and spectroscopic techniques to elucidate the host–guest interaction mechanism. We show that polar polymers with charged nitrogen-containing ends have the strongest interaction with the Ti3C2Tx layers, yielding an increase in interlayer spacing and large shifts in spectroscopic peaks. Furthermore, the effect of polymer backbone juxtaposition between Ti3C2Tx layers on pseudocapacitance is discussed in detail. Our results suggest that new organic materials capable of intercalation between the layers of Ti3C2Tx and other MXenes may be used in the design of hybrid stru...

A Green Route to Conjugated Polyelectrolyte Interlayers for High-Performance Solar Cells.

Synthesis of fluorene-based conjugated polyelectrolytes was achieved via Suzuki polycondensation in water and completely open to air. The polyelectrolytes were conveniently purified by dialysis and analysis of the materials showed properties expected for fluorene-based conjugated polyelectrolytes. The materials were then employed in solar cell devices as an interlayer in conjunction with ZnO. The double interlayer led to enhanced power conversion efficiency of 10.75 % and 15.1 % for polymer and perovskite solar cells, respectively.

A Green Route to Conjugated Polyelectrolyte Interlayers for High‐Performance Solar Cells

AbstractSynthesis of fluorene‐based conjugated polyelectrolytes was achieved via Suzuki polycondensation in water and completely open to air. The polyelectrolytes were conveniently purified by dialysis and analysis of the materials showed properties expected for fluorene‐based conjugated polyelectrolytes. The materials were then employed in solar cell devices as an interlayer in conjunction with ZnO. The double interlayer led to enhanced power conversion efficiency of 10.75 % and 15.1 % for polymer and perovskite solar cells, respectively.

Tensile Behavior of a Substituted Poly(m‐,p‐phenylene) versus Its Parent Counterpart and Synthesis of Related Polyarylenes

In a recent report, a poly(m,p‐phenylene) with acid‐cleavable trialkylsilyl side chains is synthesized by Suzuki polycondensation in a molecular weight of Mw = 300 kDa determined by gel permeation chromatography (GPC). Such a high value suggests this polymer as a potentially attractive material for strong films and fibers both in the presence and absence of the side chains. After confirming these molecular weights by static light scattering, the polymer is processed into thin films for tensile stress measurements. Above the glass transition, thus >180 °C, the material shows an extended plasticity, which is used to obtain elongated samples of draw ratios ranging from 1.5 to 6. The elongated samples show a Young's modulus of up to 5 GPa and a yield strength of 140 MPa. Upon removal of the solubilizing side chains, these values further increase to a Young's modulus of 7.5 GPa in the direction of drawing and a maximum strength of 300 MPa. Motivated by these findings, the scope of this polymer class is broadened by synthesizing two new high molecular weight poly(m,p‐phenylene)s. The structural variation allows to tune the glass transition temperatures between 125 and 240 °C depending on the amount of the meta connected phenylene units. image

Mechanochemical Suzuki polycondensation – from linear to hyperbranched polyphenylenes

Mechanochemical Suzuki polycondensation offers a sustainable alternative to classical solvent based approaches, affording high yields and short reaction times.

Blue light-emitting polymers containing ortho-linking carbazole-based benzothiophene-S, S-dioxide derivative

The blue light-emitting polymers PF-CzBTOs and PCz-CzBTOs were synthesized by Suzuki polycondensation via introducing ortho-linking N-(2-decyltetradecyl) carbazole bis- [2,3-b,6,7-b]benzo[d]thiophene-S,S-dioxide (CzBTO) into the polyfluorene (PF) and polycarbazole (PCz) backbone, respectively. All the resulted copolymers showed high thermal stability with the glass transition temperatures (Tg) of over 130 °C. The fluorescence quantum yields (ФPL) are in the range of 41%–59% and 20%–31% for PF-CzBTOs and PCz-CzBTOs, respectively. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of the copolymers are basically unchanged with the increase of CzBTO content in the copolymers. The PL spectra of copolymers showed only a faint broadening with the increase of CzBTO content in the copolymers, and with the increase of the solvent polarities, indicating no remarkable ICT effect in polymers containing ortho-linking CzBTO moiety. The copolymers showed a pure blue emission with a CIE coordinates of (0.15, 0.11) for the PF-CzBTO10, and a CIE coordinates of (0.17, 0.18) for PCz-CzBTO15. The results indicated that the strategy of introducing ortho-linking CzBTO unit into the polyfluorene or polycarbazole backbone can effectively restrain ICT effect and result in the pure blue emission.

Dibenzopyran-Based Wide Band Gap Conjugated Copolymers: Structural Design and Application for Polymer Solar Cells

With the efficient synthesis of the crucial dibenzopyran building block, a series of PDBPTBT polymers containing different alkyl side chains and/or fluorine substitution were designed and synthesized via the microwave-assisted Suzuki polycondensation. Quantum chemistry calculations based on density functional theory indicated that different substitutions have significant impacts on the planarity and rigidity of the polymer backbones. Interestingly, the alkyloxy chains of PDBPTBT-4 tend to stay in the same plane with the benzothiadiazole unit, but the others appear to be out of plane. With the S···O and F···H/F···S supramolecular interactions, the conformations of the four polymers will be locked in different ways as predicted by the quantum chemistry calculation. Such structural variation resulted in varied solid stacking and photophysical properties as well as the final photovoltaic performances. Conventional devices based on these four polymers were fabricated, and PDBPTBT-5 displayed the best PCE of 5.32%. After optimization of the additive types, ratios, and the interlayers at the cathode, a high PCE of 7.06% (Voc = 0.96 V, Jsc = 11.09 mA/cm2, and FF = 0.67) is obtained for PDBPTBT-5 with 2.0% DIO as the additive and PFN-OX as the electron-transporting layer. These results indicated DBP-based conjugated polymers are promising wide band gap polymer donors for high-efficiency polymer solar cells.

Stimuli-responsive coil-rod-coil block copolymers synthesized by using a bis-alkoxyamine-functionalized poly(para-phenylene) macro initiator

The preparation of coil-rod-coil block copolymers possessing a rigid poly(para-phenylene) middle segment surrounded by either temperature- or pH-responsive blocks is described. First, the bis-alkoxyamine terminated macro initiator was synthesized using microwave-accelerated Suzuki polycondensation (SPC). Afterwards the macro initiator was applied for the nitroxide-mediated radical polymerization (NMRP) of N-isopropyl acrylamide (NIPAAm) and 2-vinyl pyridine (2VP), respectively, to attach defined thermo- or pH-sensitive blocks. Macro initiator and block copolymer molecular weight and molecular weight distribution determinations were conducted via size exclusion chromatography (SEC). In addition 1H NMR spectroscopy was used to determine block ratios and molecular weights complementary. Further block copolymer characterization was performed by DSC, AFM, SEM measurements as well as turbidity and titration experiments. Critical transition values were found to be little different than for respective homo polymers.

Dithienopyrrole-based monomers as an acceptor unit building for synthesis of donor – acceptor conjugated polymers

A new monomer of N-benzoyl dithieno[2,3-b:2’,3’-d]pyrrole (BDP), has been successfully prepared via copper-catalyzed amidation. Then, this monomer was brominated to form 2,6-dibromo-n-benzoyl dithieno[2,3-b:2’,3’-d]pyrrole (DiBDP) monomer. The structures of monomers were confirmed via the nuclear magnetic resonance (1HNMR) and Fourier transform infrared (FT-IR). BDP and DiBDP monomers will be used as monomers for Suzuki polycondensation reaction to synthesize the donor-acceptor (D-A) conjugated polymers.

Poly(fluorene phenylene) Graft Copolymer As a Novel Binder with Polyvinylpyrrolidone for High-Capacity Silicon Anode in Lithium-Ion Batteries

Rechargeable lithium ion batteries (LIB) have been vastly used in portable devices like cellular phones, laptops, tablets and also in electric vehicles because of their relatively high energy density, good power performance and cycle life. Carbonaceous negative electrode materials, especially graphitic carbons are conventionally used as anode materials at LIBs due to their good cycle-ability and low stable discharge voltage plateau. However, graphite has a low Li atomic density at full Li capacity in carbon intercalation compound (LiC6) which leads to lower theoretical capacity (372 mAh/g). Therefore, different types of anode active materials have been investigated as an alternative to graphite in order to achieve higher capacities. Among them, silicon (Si) is one of the most promising candidate as an anode active material because of its high theoretical capacity (more than 3500 mAh/g at room temperature) and low average discharge potential (∼0.5 V vs Li/Li+).Unfortunately, huge volume expansion (310% at full lithiation of Si) due to the lithium ion diffusion during the lithiation/delithiation process causes drastic capacity fade because of the high internal stresses, loss of electrical contact and the formation of non-electronic and ionic conductive passivation film between the anode surface and electrolyte. Low electrical conductivity of silicon is also another problem that remarkably hinders the rate performance. In the present work, above mentioned shortcomings are overwhelmed by incorporating tri(ethylene glycol) (TEG) groups over phenylene base units as side chains on the framework of the PFP based conductive polymer. Polyvinylpyrrolidone (PVP) was also used as adhesive to enhance the property of binding, thus decreasing stress-induced cracks. The synthesis was achieved through Suzuki polycondensation reaction in the presence of Pd(PPh3)4 catalyst by using independently prepared TEG functionalized dibromo benzene in conjunction with dioctylfluorene-diboronic acid bis(1,3-propanediol) ester. The obtained conductive and flexible polymer was used as a binder for Si-anode with high performance. It was demonstrated that the designed and fabricated binder polymer with multi-functionality displays a high electronic conductivity, mechanical strength, high polarity, adhesion, and more importantly, the electrolyte uptake arising from its excellent ductility. Figure 1

High molecular weight broad band-gap polymers based on indolo[3,2-b]carbazole and thiazolo[5,4-d]thiazole derivatives for solar cells

Two broad band-gap high molecular weight polymers, poly[(5,11-di(9’-heptadecanyl)-indolo[3,2-b]carbazole-alt-2,5-bis(3-n-octylthiophene-2-yl)-thiazolo[5,4-d]thiazole (PICzOTzTz) and poly[(5,11-di(9’-heptadecanyl)-indolo[3,2-b]carbazole-alt-2,5-bis(3-n-n-dodecylthiophene-2-yl)-thiazolo[5,4-d]thiazole]) (PICzDOTzTz), consisting of indolo[3,2-b]carbazole (ICz) and thiazolo[5,4-d]thiazole (TzTz) derivatives were synthesized by Suzuki polycondensation. Their physical, electrochemical and optical properties were characterized in details. The thermogravimetric analysis displayed high thermal stability, and 5% degradation temperatures of PICzOTzTz and PICzDOTzTz were 427 and 435°C, respectively. The optical band gaps of PICzOTzTz and PICzDOTzTz were 2.13 and 2.07 eV, respectively. The hole mobilities of PICzOTzTz and PICzDOTzTz were investigated by the space charge limited current (SCLC) method, which gave the mobility values of 7.21 × 10–5 and 1.57 × 10–4 cm2/(V s) for each polymer, respectively. Through the photo-voltaic characterization in polymer solar cells, they showed that the power conversion efficiencies of PICzOTzTz and PICzDOTzTz were 0.64 and 0.99%, respectively.

The effect of meta-substituted or para-substituted phenyl as side chains on the performance of polymer solar cells

Two donor-acceptor alternative copolymers (P1 and P2) with carbazole group as the donor unit and 2,3-diphenylquinoxaline group as the acceptor unit were designed and synthesized by Suzuki polycondensation reaction. Alkoxy groups were linked to meta-position or para-position of phenyl rings, which were attached on the 2,3-position of quinoxaline group to investigate the effect of the alkoxy position at phenyl rings on the resulting polymer optical, electrochemical and photovoltaic properties. GIWAXS experiments revealed that para-substituted polymer P2 possesses closer packing properties in the solid state. The absorption spectra of para-substituted polymer P2 also displayed larger red-shift than that of meta-substituted polymer P1 when it went from solution to the film, which was beneficial to improve the hole mobilities and short circuit current density (Jsc). When used as the donor materials, devices based on P2:PC71BM exhibited a PCE of 3.33%, which was obviously higher than that based on P1:PC71BM. Our results revealed that the slightly structure change of polymer has a significant influence on the photovoltaic properties of polymer solar cells and adopting para-substituted phenyl ring as the side groups gave superior photovoltaic performance in donor materials based on carbazole and quinoxaline.

Nickel-Catalyzed Suzuki Polycondensation for Controlled Synthesis of Ester-Functionalized Conjugated Polymers

Controlled synthesis of conjugated polymers with functional side chains is of great importance, affording well-defined optoelectronic materials possessing enhanced stability and tunability as compared to their alkyl-substituted counterparts. Herein, a chain-growth Suzuki polycondensation of an ester-functionalized thiophene is described using commercially available nickel precatalysts. Model compound studies were used to identify suitable catalysts, and these experiments provided guidance for the polymerization of the ester-substituted monomer. This is the first report of nickel-catalyzed Suzuki cross-coupling for catalyst-transfer polycondensation, and to further illustrate the versatility of this method, block and alternating copolymers with 3-hexylthiophene were synthesized. The presented protocol should serve as an entry point into the synthesis of other electron-deficient polymers and donor–acceptor copolymers with controlled molecular weights and low dispersity.

Syntheses, electrochemical and spectroelectrochemical characterization of benzothiadiazole and benzoselenadiazole based random copolymers

ABSTRACTThree novel donor-acceptor-donor type random copolymers based on benzothiadiazole (BTh) and benzoselenadiazole (BSe) were synthesized via Pd (0) catalyzed Suzuki polycondensation reaction. The two acceptor units were coupled with electron rich moieties which are carbazole (CZ), fluorene (FL) and silafluorene (SiFL). Monomers were characterized using 1H and 13C-NMR spectroscopy. The number and weight average molecular weights of the polymers were calculated using gel permeation chromatography (GPC). All three polymers were electrochemically and spectroelectrochemically characterized. PBThBSeCZ, PBThBSeFL and PBThBSeSiFL showed only p-dopable character and their doping/dedoping potentials were determined as 1.4 V/1.2 V, 1.53 V/1.27 V and 1.8 V/1.3 V, respectively. Corresponding HOMO energy levels were calculated as −5.85 eV, −6.05 eV and −6.15 eV whereas LUMO energy levels were found to be −3.67 eV, −3.84 eV and −3.77 eV, respectively. PBThBSeCZ had lower HOMO level and band gap than PBThBSeFL and PBThBSeSiFL due to its increased electron donating capability of nitrogen atom in carbazole unit.

Development of a High-Performance Donor–Acceptor Conjugated Polymer: Synergy in Materials and Device Optimization

The development of a high-performance polymer PBDT-BT for bulk heterojunction solar cell devices is summarized. The polymer was first synthesized by Stille polycondensation, and solar cell devices in conventional geometry were optimized through the use of a lithium salt cathode interlayer reaching 6% power conversion efficiency. Improvements were made to the synthesis of the polymer using Suzuki polycondensation giving high-molecular-weight material in the Mn = 100 kg/mol range. Further device optimization in inverted geometry gave power conversion efficiency of over 9%. The synthesis scalability as well as the batch-to-batch reproducibility of the polymer were extensively investigated.