Co-reporter:Dr. Kai Yuan;Dr. Xiaodong Zhuang;Ting Hu;Dr. Lei Shi;Dr. Stavroula Sfaelou;Ulrike Polnick;Dr. Michael Forster;Dr. Thomas Pichler;Dr. Thomas Riedl;Dr. Xinliang Feng;Dr. Yiwang Chen;Dr. Ullrich Scherf
ChemElectroChem 2017 Volume 4(Issue 3) pp:709-715
Publication Date(Web):2017/03/01
DOI:10.1002/celc.201600850
AbstractOwing to their unique structure and intriguing properties, 2D transition-metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS2), have attracted tremendous attention. Chemical surface functionalization of TMDs can be used to tune their properties and broaden their application perspective. Unfortunately, covalent functionalization of TMDs into sandwich-type hybrid materials remains challenging, owing to the chemically rather inert basal plane and the poor solution processability of TMDs. Herein, we report an efficient approach for the preparation of MoS2-templated, cobalt-containing conjugated microporous polymer sandwiches (MoS2−Co−MP), starting from basal-plane-functionalized MoS2. The resulting MoS2−Co−CMP hybrids can easily be converted into MoS2-cored, hierarchically porous carbon materials (MoS2−Co−C) of high specific surface area through direct pyrolysis. The MoS2−Co−C 2D materials exhibit excellent oxygen reduction reaction activity, approaching the performance of commercial Pt/C catalysts. Moreover, MoS2−Co−C shows a promising electrochemical energy storage capability, with a high capacitance value up to 288 F g−1 coupled with remarkable cycle stability. Such a promising performance can be attributed to synergistic effects between the MoS2 template and the graphitized, hierarchically porous carbon shells with a homogeneous distribution of nitrogen centres as well as probable involvement of catalytically active Co−N or/and Co−N−C structural motifs.
Co-reporter:Kai Yuan;Ting Hu;Yazhou Xu;Robert Graf;Lei Shi;Michael Forster;Thomas Pichler;Thomas Riedl;Yiwang Chen
Materials Chemistry Frontiers 2017 vol. 1(Issue 2) pp:278-285
Publication Date(Web):2017/02/16
DOI:10.1039/C6QM00012F
Conjugated microporous polymers (CMPs) are considered as promising precursors to fabricate multi-functional porous carbons. However, CMPs are formed under kinetic control, and most of them are obtained as amorphous powders without long-range order. Carbon materials derived from CMPs usually preserve the particular structure of the CMP precursors, thus the direct pyrolysis of CMPs into two-dimensional (2D) porous carbon nanosheets remains a great challenge. In this work, 4-iodophenyl-substituted graphene (RGO-I) is used both as a building block and a structure directing template for the construction of nitrogen–rich graphene–CMP (GMP) sandwiches using a solution-based approach. The 2D structure of RGO-I with its large aspect ratio allows for the growth of uniform CMP shells onto both sides of the graphene sheets. Thereby, aggregation and restacking of the graphene sheets can be effectively suppressed even during high-temperature treatment. Thereby, well-defined nitrogen-doped porous carbon/graphene nanosheets were readily obtained by direct pyrolysis of the GMP sandwiches. The sandwich-like nitrogen-doped porous carbon/graphene nanosheets were used as electrode materials for supercapacitor devices with very promising capacitive performance, superior in comparison to the corresponding porous carbons derived from the graphene-free CMPs. The good 2D electron transport ability of graphene together with the intimate interactions between porous carbon and graphene layers provide a combination of large electrochemically active surface area for charge transfer and minimized ion diffusion paths during the charge/discharge process. This unique set of physical properties effectively boosts the capacitive performance values if applied in supercapacitor devices.
Co-reporter:A. Palma-Cando;D. Woitassek;G. Brunklaus;U. Scherf
Materials Chemistry Frontiers 2017 vol. 1(Issue 6) pp:1118-1124
Publication Date(Web):2017/06/01
DOI:10.1039/C6QM00281A
A series of novel microporous polymer networks (MPNs) have been prepared from tetraphenylethene (TPE)-cored, multifunctional carbazole- or thiophene-based monomers by using chemical and electrochemical oxidative coupling methods. Octafunctional monomers lead to MPNs with a high degree of cross-linking and optimized specific surface areas (SBET) of up to 2200 m2 g−1. Aggregation-induced emission (AIE) activity of the monomers is demonstrated. The MPN films are tested for application in the chemical sensing of nitroaromatic analytes by fluorescence quenching.
Co-reporter:Christian Widling;Michael Forster;Venkata M. Suresh
Science China Chemistry 2017 Volume 60( Issue 8) pp:1103-1106
Publication Date(Web):19 May 2017
DOI:10.1007/s11426-017-9047-8
Multifunctional iodoaryl monomers were used for the catalyst- and solvent-free generation of microporous polymer networks of high surface areas up to 732 m2 g−1. The thermal conversion of the monomers relies on the homolytic cleavage of weak iodine–carbon bonds followed by a C–C coupling of the radicalic intermediates. By using tri- or tetrafunctional monomers and by tuning reaction temperature and time, the optimum reaction conditions allow the formation of the corresponding microporous networks in good yields of 71%–86%. The resulting networks exhibit notable high CO2 and H2 adsorption capacities of up to 8.89 wt% (273 K, 1 bar) and up to 1.31 wt% (77 K, 1 bar), respectively.
Co-reporter:Alex Palma-Co
Macromolecular Chemistry and Physics 2016 Volume 217( Issue 7) pp:827-841
Publication Date(Web):
DOI:10.1002/macp.201500484
Co-reporter:Kim-Julia Kass;Dr. Michael Forster ;Dr. Ullrich Scherf
Angewandte Chemie International Edition 2016 Volume 55( Issue 27) pp:7816-7820
Publication Date(Web):
DOI:10.1002/anie.201600580
Abstract
Incorporation of the donor–acceptor structure of an alternating conjugated copolymer into a rigid ladder polymer backbone is reported. The resulting ladder polymers show optical features typical of rigid ladder polymers, but present an increased Stokes shift if compared to their non-polar counterparts. This behavior reflects the occurrence of charge transfer processes during excitation and leads to a positive solvatochromism.
Co-reporter:Kim-Julia Kass;Dr. Michael Forster ;Dr. Ullrich Scherf
Angewandte Chemie 2016 Volume 128( Issue 27) pp:7947-7951
Publication Date(Web):
DOI:10.1002/ange.201600580
Abstract
Incorporation of the donor–acceptor structure of an alternating conjugated copolymer into a rigid ladder polymer backbone is reported. The resulting ladder polymers show optical features typical of rigid ladder polymers, but present an increased Stokes shift if compared to their non-polar counterparts. This behavior reflects the occurrence of charge transfer processes during excitation and leads to a positive solvatochromism.
Co-reporter:Alex Palma-Cando, Eduard Preis, and Ullrich Scherf
Macromolecules 2016 Volume 49(Issue 21) pp:8041-8047
Publication Date(Web):October 26, 2016
DOI:10.1021/acs.macromol.6b02025
A series of four tetra- or octacarbazolyl-substituted, tetraphenylmethane/-silane monomers have been oxidatively coupled into microporous polymer networks (MPNs). Chemical polymerization with iron(III) chloride gives bulk MPNs with BET surface areas (SBET) of up to 1331 m2 g–1 (for the octacarbazolyl-substituted tetraphenylmethane monomer). Slightly increased SBET values result for the materials made from the octacarbazolyl monomers if compared to the tetracarbazolyl analogues, while the exchange of the central carbon by a silicon atom leads to decreased surface areas. The latter phenomenon might be related to electronic interactions of aromatic substituents through the silicon centers. This may cause a reduced reactivity of the carbazoles after the initial oxidative couplings and finally a reduced cross-linking density of the resulting MPNs. Moreover, electrochemical oxidative coupling enables the formation of thin polymer films on the working electrode. These films also show high SBET values that are only slightly reduced if compared to the corresponding bulk MPNs. Electrochemical quartz microbalance measurements allow for an in-situ characterization of the electrochemical MPN generation. Finally, the electrochemical reduction of a series of nitroaromatic compounds (NACs) on MPN-modified glassy carbon electrodes is studied and applied for high sensitivity NACs detection up to the ppb range.
Co-reporter:Kai Yuan;Yazhou Xu;Johannes Uihlein;Gunther Brunklaus;Lei Shi;Ralf Heiderhoff;Mingming Que;Michael Forster;Thomas Chassé;Thomas Pichler;Thomas Riedl;Yiwang Chen
Advanced Materials 2015 Volume 27( Issue 42) pp:6714-6721
Publication Date(Web):
DOI:10.1002/adma.201503390
Co-reporter:Kai Yuan, Peiyao Guo-Wang, Ting Hu, Lei Shi, Rong Zeng, Michael Forster, Thomas Pichler, Yiwang Chen, and Ullrich Scherf
Chemistry of Materials 2015 Volume 27(Issue 21) pp:7403
Publication Date(Web):October 16, 2015
DOI:10.1021/acs.chemmater.5b03290
Conjugated microporous polymers (CMPs) are usually obtained as amorphous or semicrystalline powders. Their insolubility and nonprocessability are considered as key bottlenecks that impede CMP applications. In this study, light-emitting, nanofibrous films were fabricated by electrospinning CMP/poly(lactic acid) (PLA) mixtures. The resulting nanofibrous films show a high flexibility combined with high porosity and surface-area-to-volume ratios. The CMP-based nanofibrous films have been used as sensitive sensors in the detection of nitroaromatic and benzoquinone vapors as well as oxidizing metal ions. Moreover, 4-iodophenyl-substituted graphene sheets were used as templates for growing CMP/graphene sandwiches. The graphene-based CMP (G-CMP) sandwiches are characterized by high surface areas and aspect ratios. Furthermore, hierarchically porous two-dimensional carbon nanosheets were obtained by pyrolysis of these carbon-rich G-CMP hybrids. The resulting carbon nanomaterials show excellent supercapacitor behavior with a 48% increased capacitance if compared to porous carbons without the graphene template.
Co-reporter:E. Preis, W. Dong, G. Brunklaus and U. Scherf
Journal of Materials Chemistry A 2015 vol. 3(Issue 7) pp:1582-1587
Publication Date(Web):19 Dec 2014
DOI:10.1039/C4TC02664K
Microporous Polymer Networks (MPNs) that contain aggregate-induced emission (AIE) active tetraphenylethylene (TPE) or other tetraarylethylene units have been generated in a reductive polyolefination process starting from four different tris(α,α-dichlorobenzyl)arene derivatives with dicobalt octacarbonyl or chromium(II)acetate as reductive olefination agents. Microporosity with moderately high BET surface areas up to 500 m2 g−1 could be combined with high solid state photoluminescence quantum yields up to 25.3% for polymer network P4. This unique combination should be promising for applications as optical solid state sensors, especially for MPNs with electron-deficient triazine core units.
Co-reporter:Suman Kalyan Samanta, Eduard Preis, Christian W. Lehmann, Richard Goddard, Saientan Bag, Prabal K. Maiti, Gunther Brunklaus and Ullrich Scherf
Chemical Communications 2015 vol. 51(Issue 43) pp:9046-9049
Publication Date(Web):23 Apr 2015
DOI:10.1039/C5CC01654A
One-step synthesis of a cyclic 2,17-dioxo[3,3](4,4′)biphenylophane (MC) was achieved in high yield; its structure was verified by single crystal X-ray analysis. As a first example, a microporous polymer network was formed from macrocycle MC via acid-catalysed cyclotrimerization yielding a BET surface area of ca. 570 m2 g−1.
Co-reporter:Alex Palma-Cando and Ullrich Scherf
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 21) pp:11127
Publication Date(Web):May 6, 2015
DOI:10.1021/acsami.5b02233
Thin films of microporous polymer networks (MPNs) have been generated by electrochemical polymerization of a series of multifunctional carbazole-based monomers. The microporous films show high Brunauer–Emmett–Teller (BET) surface areas up to 1300 m2 g–1 as directly measured by krypton sorption experiments. A correlation between the number of polymerizable carbazole units of the monomer and the resulting surface area is observed. Electrochemical sensing experiments with 1,3,5-trinitrobenzene as prototypical nitroaromatic analyte demonstrate an up to 180 times increased current response of MPN-modified glassy carbon electrodes in relation to the nonmodified electrode. The phenomenon probably involves intermolecular interactions between the electron-poor nitroaromatic analytes and the electron-rich, high surface area microporous deposits, with the electrochemical reduction at the MPN-modified electrodes being an adsorption-controlled process for low scan rates. We expect a high application potential of such MPN-modified electrodes for boosting the sensitivity of electrochemical sensor devices.Keywords: electrochemical reduction; electropolymerization; microporous materials; nitroaromatic analytes; thin films;
Co-reporter:Eduard Preis, Nicole Schindler, Sven Adrian, and Ullrich Scherf
ACS Macro Letters 2015 Volume 4(Issue 11) pp:1268
Publication Date(Web):October 30, 2015
DOI:10.1021/acsmacrolett.5b00726
The cyclotrimerization of commercial, aromatic diisocyanates allows for the formation of monolithic, microporous polymer networks with SBET surface areas up to 1300–1500 m2/g. The process has been up-scaled for production of 100 g batches. The monolithic materials show a promising potential for the removal of lipophilic components from aqueous mixtures.
Co-reporter:Sebastian Kowalski;Sybille Allard
Macromolecular Rapid Communications 2015 Volume 36( Issue 11) pp:1061-1068
Publication Date(Web):
DOI:10.1002/marc.201400557
Co-reporter:Wenyue Dong;Yuyu Pan;Martin Fritsch
Journal of Polymer Science Part A: Polymer Chemistry 2015 Volume 53( Issue 15) pp:1753-1761
Publication Date(Web):
DOI:10.1002/pola.27631
ABSTRACT
Two polytriphenylamines (PTPAs) (P1 and P2) with aggregation induced emission (AIE)-active tetraphenylethylene side groups have been designed and successfully synthesized. Both polymers only faintly emit in dilute solution but show strong emission in aggregated state, meaning that they are AIE-active. The detection of 1,3,5-trinitrobenzene (TNB) vapors has been investigated by photoluminescence (PL) quenching in polymer films. High solid state quantum yields and donor-acceptor interactions of the electron-rich PTPA chains with the TNB analyte, hereby, induce a high sensing sensitivity, both for P1 and P2 films towards TNB vapor. Contacting thin P1 and P2 films with saturated TNB vapor, the PL intensity was quenched by 85% for P1 and 89% for P2 within 600 s, respectively. The sensing process is reversible, >90% of the PL is recovered, also after repeated cycling. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 53, 1753–1761
Co-reporter:Alex Palma-Cando, Gunther Brunklaus, and Ullrich Scherf
Macromolecules 2015 Volume 48(Issue 19) pp:6816-6824
Publication Date(Web):September 18, 2015
DOI:10.1021/acs.macromol.5b01821
Four thiophene-based monomers have been synthesized by Stille- or Suzuki-type couplings followed by chemical or electrochemical polymerization into microporous polymer networks (MPNs) with high BET surface areas (SBET). Similar SBET values of up to 2020 and 2135 m2 g–1 have been determined for tetraphenylmethane-cored bulk MPN powders and thin films, respectively. Electrochemical polymerization in boron trifluoride diethyl etherate (BFEE)/dichloromethane (DCM) mixtures allows for the generation of MPN films with optimized porosity. Moreover, an interesting effect of boron trifluoride on the connectivity of the monomeric units during electropolymerization is observed for 3-thienyl-based monomers. Finally, the electrochemical reduction of 1,3,5-trinitrobenzene at MPN-modified glassy carbon (GC) electrodes shows increased cathodic responses compared to nonmodified GC electrodes due to interaction between electron-deficient nitroaromatic analyte and electron-rich MPN film. The influence of the specific surface area of MPNs on the electrochemical response is also studied for this class of materials.
Co-reporter:Wenyue Dong, Jõao Pina, Yuyu Pan, Eduard Preis, J. Sérgio Seixas de Melo, Ullrich Scherf
Polymer 2015 Volume 76() pp:173-181
Publication Date(Web):12 October 2015
DOI:10.1016/j.polymer.2015.08.064
•Acceptor-substituted polycarbazoles and polytriphenylamines showing both AIE and ICT behavior have been synthesized.•Dispersions containing polymer aggregates have been used for optical detection of 1,3,5-trinitrobenzene.•Amplified PL quenching was observed with a maximum PL quenching constant of 5.5 × 105 M−1.•One polymer (PTPATPAN) was used as PL-sensitive dopant in the Tg-detection of polystyrene.Acceptor-substituted polycarbazoles (PCzTPAN) and polytriphenylamines (PTPATPAN) bearing electron-deficient 2,3,3-triphenylacrylonitrile (TPAN) side groups have been successfully synthesized. Both of them are aggregation-induced emission (AIE)-active and show intramolecular charge transfer (ICT) behavior. PCzTPAN and PTPATPAN aggregates in 90% water/THF were used for the detection of 1,3,5-trinitrobenzene (TNB) as prototypical nitroaromatic compound. They show amplified PL quenching upon addition of TNB with a maximum quenching constant of 5.5 × 105 M−1. As additional application example, the detection of the glass transition temperature of polystyrene (PS) was accomplished for PTPATPAN blended into PS at doping concentrations of 0.1–1.0 wt%.Polycarbazoles (PCzTPAN) or polytriphenylamines (PTPATPAN) decorated with 2,3,3-triphenylacrylonitrile side groups have been synthesized and characterized for the occurrence of aggregation-induced emission (AIE) and intramolecular charge transfer (ICT) effects. PCzTPAN and PTPATPAN dispersions in 90% water/THF were further used for the high sensitivity detection of 1,3,5-trinitrobenzene (TNB) as prototypical nitroaromatic analyte, showing amplified PL quenching with a maximum quenching constant of 5.5 × 105 M−1. Moreover, PTPATPAN was used as AIE-active fluorescent probe for detection of the glass transition temperature of a polystyrene (PS) film, exhibiting a very reliable response to the glass transition of PS, up to low probe concentration of 0.1 wt%.
Co-reporter:Mario Kraft, Sylwia Adamczyk, Andreas Polywka, Kirill Zilberberg, Christ Weijtens, Jens Meyer, Patrick Görrn, Thomas Riedl, and Ullrich Scherf
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 14) pp:11758
Publication Date(Web):July 4, 2014
DOI:10.1021/am5025148
Anionic, conjugated thiophene- and fluorene-based polyelectrolytes with alkylthiosulfate side chains undergo hydrolysis under formation of alkylthiol and dialkyldisulfide functions. The hydrolysis products can be deposited onto gold or silver surfaces by self-assembly from solutions of the anionic conjugated polyelectrolyte (CPE) precursors in polar solvents such as methanol. This procedure allows solution-based surface modifications of gold and silver electrodes using environmentally friendly solvents and enables the formation of conjugated polymer bilayers. The herein presented alkylthiosulfate-substituted CPEs are promising candidates for increasing the work function of gold and silver electrodes thus improving hole injection from such electrode assemblies into organic semiconductors.Keywords: Bunte salts; charge injection interlayer; conjugated polyelectrolytes (CPE); conjugated polymer bilayer; cross-linking; self-assembly
Co-reporter:Wenyue Dong, Teng Fei, Alex Palma-Cando and Ullrich Scherf
Polymer Chemistry 2014 vol. 5(Issue 13) pp:4048-4053
Publication Date(Web):12 Mar 2014
DOI:10.1039/C4PY00251B
Novel conjugated polymers based on 3,6-carbazole repeat units were synthesized by nickel-catalyzed Yamamoto coupling under microwave heating. The resulting poly(3,6-carbazole)s contain tetraphenylethylene (TPE) units in their side chains. The resultant polymers show aggregation induced emission (AIE) behavior. Hereby, the photoluminescence (PL) intensity of PCzTPE0.5 in 90% water–THF is 35 times higher than that in pure THF, connected to the introduction of TPE side chains. The ability of polymer PCzTPE0.5 for explosive sensing was also studied. A maximum Stern–Volmer quenching constant of 1.26 × 106 M−1 was observed for PL quenching of PCzTPE0.5 aggregates by trinitrobenzene (TNB). A solid state paper strip test based on PCzTPE0.5 and PCzTPE also demonstrates effective PL quenching towards both TNB vapor and solution.
Co-reporter:S. Kowalski, S. Allard, K. Zilberberg, T. Riedl, U. Scherf
Progress in Polymer Science 2013 Volume 38(Issue 12) pp:1805-1814
Publication Date(Web):December 2013
DOI:10.1016/j.progpolymsci.2013.04.006
Future application of conjugated (co)polymers, e.g. in electronic devices, requires the availability of up-scalable synthetic procedures. “Conventional” (hetero)aryl-(hetero)aryl coupling schemes often produce toxic or environmentally risky by-products. Here, so-called direct arylation schemes without use of organometallic reagents or related anion equivalents came in the focus of attention as simplified alternative to standard coupling procedures. Now, a couple of structurally defined conjugated (co)polymers can be generated in high yield and molecular weight via direct arylation polycondensation. The promising application potential of these materials as active component of organic solar cells has been demonstrated.
Co-reporter:Eduard Preis, Christian Widling, Gunther Brunklaus, Johannes Schmidt, Arne Thomas, and Ullrich Scherf
ACS Macro Letters 2013 Volume 2(Issue 5) pp:380
Publication Date(Web):April 17, 2013
DOI:10.1021/mz400126f
Acidic self-condensation of 2,7-bis(N-carbazolyl)-9-fluorenone 1 produces microporous polymer networks (MPNs) with high Brunauer–Emmett–Teller (BET) surface areas of up to 2250 m2/g and hydrogen storage capacities of up to 1.7% (at 1 bar) in a fully metal-free condensation regime.
Co-reporter:Jan-Moritz Koenen;Stefan Jung;Abhijit Patra;Anke Helfer
Advanced Materials 2012 Volume 24( Issue 5) pp:681-686
Publication Date(Web):
DOI:10.1002/adma.201102993
Co-reporter:Sebastian Kowalski, Sybille Allard, and Ullrich Scherf
ACS Macro Letters 2012 Volume 1(Issue 4) pp:465
Publication Date(Web):March 20, 2012
DOI:10.1021/mz300093w
Poly(4,4-dialkyl-cyclopenta[2,1-b:3,4-b′]dithiophene-alt-2,1,3-benzothiadiazole) (PCPDTBT), a potentially interesting low bandgap donor copolymer for bulk heterojunction-type organic solar cells with a power conversion efficiency >5.5%, can be now synthesized in a direct arylation scheme starting from 4,4-dialkyl-cyclopenta[2,1-b:3,4-b′]dithiophene (CPDT) and 4,7-dibromo-2,1,3-benzothiadiazole (4,7-dibromo-BT) as monomers. The direct arylation procedure leads to PCPDTBT with an Mn of up to 40 000 and circumvents the use of costly diboronic acid/ester or distannyl monomers.
Co-reporter:Daniel Dolfen;Kristina J. Schottler
Macromolecular Rapid Communications 2012 Volume 33( Issue 18) pp:1542-1548
Publication Date(Web):
DOI:10.1002/marc.201200206
Abstract
A new soluble polyamine with main chain perylene units is synthesized and subsequently converted into cationic or zwitterionic polyelectrolytes. The optical properties of the monomer 1,6,7,12-tetrakis(4-tert-butylphenoxy)-3,4,9,10-tetra(bromomethyl)perylene and the resulting polymers have been studied with special attention to ongoing de/aggregation processes. UV–Vis and PL spectra of the polymers show a distinct concentration and solvent dependency of the optical properties. In contrast to the corresponding monomer complete deaggregation did not occur for the polymers. The environment-sensitive optical properties should allow applications as sensor materials. The perylene-containing polyelectrolytes may be applied in orthogonal processing schemes toward multilayer electronic devices.
Co-reporter:Andrea Gutacker, Chi-Yen Lin, Lei Ying, Thuc-Quyen Nguyen, Ullrich Scherf, and Guillermo C. Bazan
Macromolecules 2012 Volume 45(Issue 11) pp:4441-4446
Publication Date(Web):May 31, 2012
DOI:10.1021/ma202738t
All-conjugated “rod–rod” diblock copolymers are an emerging class of polymeric materials of considerable interest for applications in chemical and biological sensors or as components for optoelectronic devices. Here, we report a novel cationic diblock copolymer containing a neutral polyalkylfluorene block covalently bound to a polar polyfluorene counterpart—poly[9,9-bis(6-trimethylammoniumhexyl)-2,7-fluorene]-b-poly(3-hexyl-2,5-thiophene) (PF6NBr-b-PF8)—which was synthesized in a sequential Suzuki–Miyaura polymerization and was made ionic with trimethylamine in a subsequent quaternization step. The optical properties of this material were investigated by UV/vis and photoluminescence spectroscopies in three different solvents: methanol, THF and THF/methanol 1:1. Atomic force microscopic (AFM) imaging experiments provided evidence for solvent-induced aggregation. The formation of vesicles and spherical particles is observed in layers from THF and methanolic solution.
Co-reporter:Penglei Li, Oliver Fenwick, Seyfullah Yilmaz, Dietrich Breusov, Daren J. Caruana, Sybille Allard, Ullrich Scherf and Franco Cacialli
Chemical Communications 2011 vol. 47(Issue 31) pp:8820-8822
Publication Date(Web):04 Jul 2011
DOI:10.1039/C1CC12752G
We have synthesised and characterised a new low-gap conjugated polymer, with a broad absorption profile. In blends with a C70 derivative we demonstrate power conversion efficiencies of 0.76%. We show electroluminescence from the polymer peaking at 956 nm, and quantum efficiency of 0.02% in a blend.
Co-reporter:Eduard Preis, Christian Widling, Ullrich Scherf, Satish Patil, Gunther Brunklaus, Johannes Schmidt and Arne Thomas
Polymer Chemistry 2011 vol. 2(Issue 10) pp:2186-2189
Publication Date(Web):15 Aug 2011
DOI:10.1039/C1PY00251A
A series of novel, microporous polymer networks (MPNs) have been generated in a simple, acid catalysed Friedel–Crafts-type self-condensation of A2B2- and A2B4-type fluorenone monomers. Two A2B4-type monomers with 2,7-bis(N,N-diphenylamino) A or 2,7-bis[4-(N,N-diphenylamino)phenyl] D substitution of the fluorenone cores lead to MPNs with high SBET surface areas of up to 1400 m2 g−1. Two MPNs made of binary monomer mixtures showed the highest Brunauer–Emmett–Teller (BET) surface areas SBET of our series (SBET of up to 1800 m2 g−1) after washing the powdery samples with supercritical carbon dioxide. Total pore volumes of up to 1.6 cm3 g−1 have been detected. It is observed that the substitution pattern of the monomers is strongly influencing the resulting physicochemical properties of the microporous polymer networks (MPNs).
Co-reporter:Saulius Grigalevicius, Baohua Zhang, Zhiyuan Xie, Michael Forster, Ullrich Scherf
Organic Electronics 2011 Volume 12(Issue 12) pp:2253-2257
Publication Date(Web):December 2011
DOI:10.1016/j.orgel.2011.08.018
Cross-linkable polycarbazole copolymers have been synthesized starting from 3,6-diiodo-9-(2-ethylhexyl)carbazole and 3,6-diodo-9-[6-(3-ethyloxetan-3-ylmethoxy)hexyl]carbazole monomers in a Ni(0)-catalyzed Yamamoto-type aryl–aryl coupling. The synthesized materials were characterized by various techniques including differential scanning calorimetry, thermogravimetry and cyclic voltammetry. Insoluble layers of the copolymers have been obtained by photo-crosslinking thin films of the materials. Organic light emitting diodes using the crosslinked polycarbazole networks as hole transporting layer demonstrated a turn-on voltage of ca. 4 V, a maximum brightness of 15,000 cd/m2, and maximum OLED efficiency of 8.5 cd/A.Graphical abstractLuminous efficiency of the devices: ITO/PEDOT or crosslinked PKOx/GEP/(Ca/Al).Highlights► Cross-linkable polycarbazole copolymers have been synthesized. ► Insoluble layers from the copolymers were obtained by photo-cross-linking. ► OLEDs using the networks demonstrated maximum brightness exceeding 15000 cd/m2. Maximum OLED efficiency was 8.5 cd/A.
Co-reporter:Dr. Ullrich Scherf
Angewandte Chemie 2011 Volume 123( Issue 22) pp:5120-5121
Publication Date(Web):
DOI:10.1002/ange.201101643
Co-reporter:Dr. Ullrich Scherf
Angewandte Chemie International Edition 2011 Volume 50( Issue 22) pp:5016-5017
Publication Date(Web):
DOI:10.1002/anie.201101643
Co-reporter:Andrea Gutacker, Sylwia Adamczyk, Anke Helfer, Logan E. Garner, Rachel C. Evans, Sofia M. Fonseca, Matti Knaapila, Guillermo C. Bazan, Hugh D. Burrows and Ullrich Scherf
Journal of Materials Chemistry A 2010 vol. 20(Issue 8) pp:1423-1430
Publication Date(Web):22 Dec 2009
DOI:10.1039/B918583F
Novel, all-conjugated polyelectrolyte block copolymers of the rod-rod type can be generated in a “grafting from” scheme and exhibit a preferred tendency to self-assemble into layered aggregates both in solution and the solid state. Here, the rigid-rod structure of the individual, complex macromolecules favours the formation of low-curvature vesicular and lamellar aggregates. Our poly(9,9-dialkylfluorene)-b-poly[3-(6-ammoniumhexyl)thiophene] (PF2/6-b-P3TMAHT and PFO-b-P3TMAHT, where PF2/6 and PFO denote 2-(ethyl)hexyl and linear octyl alkyl pendant groups, respectively), and poly(9,9-dialkylfluorene)-b-poly[3-(6-pyridylhexyl)thiophene] (PF2/6-b-P3PyHT and PFO-b-P3PyHT) polyelectrolyte diblock copolymers allow for simple and reliable control of the occurring self-organisation process and the resulting nano-scaled architectures. They are, therefore, promising candidates for application as the active layer in electronic devices or as functional membranes (e.g. for sensor applications). Moreover, the electronic properties of the materials (especially the excitation energy transfer between both blocks) strongly depend on the aggregation state present. Aggregation can be further controlled via addition of oppositely charged surfactants resulting in the formation of ordered polyelectrolyte/surfactant complexes.
Co-reporter:Reiner Sebastian Sprick, Arne Thomas and Ullrich Scherf
Polymer Chemistry 2010 vol. 1(Issue 3) pp:283-285
Publication Date(Web):26 Jan 2010
DOI:10.1039/B9PY00375D
The synthesis of a new class of very rigid, microporous ladder polymers in a cyclotrimerization reaction of bifunctional diketo-s-indacene-type monomers is described. The cyclotrimerization reaction is carried out under Lewis-acidic (TiCl4) or, preferentially, acidic conditions (methanesulfonic acid—MSA) and yields ladder-type, aromatic networks with high BET surface areas of up to 1650 m2 g−1. The synthetic scheme towards the truxene-cored ladder networks also allows for the incorporation of carbonyl functions that may be transformed to other functionalities in further derivatization reactions.
Co-reporter:Christof J. Kudla, Daniel Dolfen, Kristina J. Schottler, Jan-Moritz Koenen, Dietrich Breusov, Sybille Allard, and Ullrich Scherf
Macromolecules 2010 Volume 43(Issue 18) pp:7864-7867
Publication Date(Web):August 30, 2010
DOI:10.1021/ma1014885
Co-reporter:Andrea Gutacker, Nils Koenen, Ullrich Scherf, Sylwia Adamczyk, João Pina, Sofia M. Fonseca, Artur J.M. Valente, Rachel C. Evans, J. Seixas de Melo, Hugh D. Burrows, Matti Knaapila
Polymer 2010 Volume 51(Issue 9) pp:1898-1903
Publication Date(Web):20 April 2010
DOI:10.1016/j.polymer.2010.03.010
Optical spectroscopy and photophysical measurements on cationic fluorene-thiophene diblock copolymers in solution show distinct properties for the two blocks, with clear indications of singlet exciton migration from the polyfluorene to polythiophene blocks. Electrical conductivity measurements and small angle X-ray scattering studies show that different aggregates are formed in water and methanol. This may be associated both with different solubilities of the two blocks and with the effect of solvent on the degree of dissociation of the ionic part. Atomic force microscopy (AFM) shows that different nanostructures are deposited from the two solvents, with large, vesicular structures deposited on mica from methanolic solution. Aggregation behavior is also found to be modulated, and to lead to more rigid thiophene blocks, by addition of the oppositely charged surfactant sodium dodecylsulfate.
Co-reporter:Jan-Moritz Koenen, Askin Bilge, Sybille Allard, Ronald Alle, Klaus Meerholz and Ullrich Scherf
Organic Letters 2009 Volume 11(Issue 10) pp:2149-2152
Publication Date(Web):April 16, 2009
DOI:10.1021/ol900675f
Two swivel cruciform oligothiophenes are investigated for the occurrence of oxidative ring closure reactions. Surprisingly, instead of intramolecular cyclizations, a regioselective side chain oxidation of two of the four α-methylene groups next to the terminal thiophene rings is detected for one of the oligomers. Such side chain oxidations may be one unintended degradation pathway in oligothiophene-based organic semiconductors used as the active layer of organic field effect transistors (OFETs), organic light emitting diodes (OLEDs), and organic solar cells (OSCs).
Co-reporter:Ines Dumsch;Christof J. Kudla
Macromolecular Rapid Communications 2009 Volume 30( Issue 9-10) pp:840-844
Publication Date(Web):
DOI:10.1002/marc.200800557
Co-reporter:Ullrich Scherf;Sylwia Adamczyk;Andrea Gutacker ;Nils Koenen
Macromolecular Rapid Communications 2009 Volume 30( Issue 13) pp:1059-1065
Publication Date(Web):
DOI:10.1002/marc.200900088
Co-reporter:Benjamin Souharce;Christof J. Kudla;Michael Forster;Jürgen Steiger;Ralf Anselmann;Heiko Thiem
Macromolecular Rapid Communications 2009 Volume 30( Issue 14) pp:1258-1262
Publication Date(Web):
DOI:10.1002/marc.200900214
Co-reporter:Ullrich Scherf;Sylwia Adamczyk;Andrea Gutacker ;Nils Koenen
Macromolecular Rapid Communications 2009 Volume 30( Issue 13) pp:
Publication Date(Web):
DOI:10.1002/marc.200990029
Co-reporter:Baoling Wang;Michael Forster;Eduard Preis;Huan Wang;Yuguang Ma
Journal of Polymer Science Part A: Polymer Chemistry 2009 Volume 47( Issue 19) pp:5137-5143
Publication Date(Web):
DOI:10.1002/pola.23565
Abstract
In this study, a simplified route to synthesize soluble, spiro-bridged ladder-type poly(p-phenylene)s (spiro-LPPP) was developed. The new, simplified synthesis route for spiro-LPPP involves two reaction steps: a single-stranded precursor polymer containing diaryloylbenzene building blocks was obtained by the Suzuki reaction, followed by a subsequent twofold cyclization cascade using methanesulfonic acid to form the target spiro-LPPP. Spiro-LPPP shows a well-defined chemical structure, high molecular weight (Mn of 17,500 g/mol with a polydispersity index of 2.0), excellent thermal stability (5% weight loss at 370 °C), and good solubility in common organic solvents. Spiro-LPPP emits blue light (λmax,em = 455 nm) with the high solution PL quantum yield (94%). The spectral properties of spiro-LPPP in the solid state are very similar to the solution properties, thus indicating a low degree of intermolecular aggregation. After annealing a thin film of spiro-LPPP to 120 °C in air for 3 to 24 h, its emission spectrum is unchanged, reflecting excellent thermooxidative stability. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5137–5143, 2009
Co-reporter:M. Carmen G. Hernández and Mikhail G. Zolotukhin, Jose Luis Maldonado, Nina Rehmann and Klaus Meerholz, Simon King and Andrew P. Monkman, Nils Fröhlich, Christof J. Kudla and Ullrich Scherf
Macromolecules 2009 Volume 42(Issue 23) pp:9225-9230
Publication Date(Web):November 10, 2009
DOI:10.1021/ma902061t
Co-reporter:Christof J. Kudla, Nils Koenen, Wojciech Pisula and Ullrich Scherf
Macromolecules 2009 Volume 42(Issue 10) pp:3483-3488
Publication Date(Web):April 22, 2009
DOI:10.1021/ma8028503
Nonsymmetrically substituted chiral 9-alkyl1-9-alkyl2fluorene monomers of the AB type allow for their directed, stereoregular aryl−aryl cross-coupling after Suzuki leading to isotactic poly(9-alkyl1-9-alkyl2fluorene). As expected, the isotactic poly(9-dodecyl-9-methylfluorene) i-PF1-12 of this study shows an increased solid state ordering and distinctly different thermal properties when compared to its corresponding atactic, stereoirregular polyfluorene counterpart a-PF1-12. This and other isotactic polyfluorene derivatives will be interesting building blocks for the generation of chiral, all-conjugated block copolymers.
Co-reporter:Ullrich Scherf, Andrea Gutacker and Nils Koenen
Accounts of Chemical Research 2008 Volume 41(Issue 9) pp:1086
Publication Date(Web):April 11, 2008
DOI:10.1021/ar7002539
All-conjugated block copolymers of the rod−rod type came into the focus of interest because of their unique and attractive combination of nanostructure formation and electronic activity. Potential applications in a next generation of organic polymer materials for photovoltaic devices (“bulk heterojunction”-type solar cells) or (bio)sensors have been proposed. Combining the fascinating self-assembly properties of block copolymers with the active electronic and/or optical function of conjugated polymers in all-conjugated block copolymers is, therefore, a very challenging goal of synthetic polymer chemistry. First examples of such all-conjugated block copolymers from a couple of research groups all over the world demonstrate possible synthetic approaches and the rich application potential in electronic devices. A crucial point in such a development of novel polymer materials is a rational control over their nanostructure formation. All-conjugated di- or triblock copolymers may allow for an organization of the copolymer materials into large-area ordered arrays with a length scale of nanostructure formation of the order of the exciton diffusion length of organic semiconductors (typically ca. 10 nm). Especially for amphiphilic, all-conjugated copolymers the formation of well-defined supramolecular structures (vesicles) has been observed. However, intense further research is necessary toward tailor-made, all-conjugated block copolymers for specific applications. The search for optimized block copolymer materials should consider the electronic as well as the morphological (self-assembly) properties.
Co-reporter:Adam J. Moulé, Argiri Tsami, Torsten W. Bünnagel, Michael Forster, Nils M. Kronenberg, Markus Scharber, Markus Koppe, Mauro Morana, Christoph J. Brabec, Klaus Meerholz and Ullrich Scherf
Chemistry of Materials 2008 Volume 20(Issue 12) pp:4045
Publication Date(Web):May 21, 2008
DOI:10.1021/cm8006638
Polymer/fullerene bulk heterojunctions have recently generated a lot of scientific interest due to their potential in low-cost photovoltaic applications. In this paper we detail the synthesis and characterization of two new low-band-gap polythiophenes, poly[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl-alt-4,7-bis(2-thienyl)-2,1,3-benzothiadiazole-5′,5′′-diyl] (PCPDTTBTT) and poly[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl-alt-2,3-dioctylquinoxaline-5,8-diyl] (PCPDTQ), for use in these applications. The PCPDTQ polymer did not produce efficient solar cells. A high power efficiency of 2.1% under one sun was found for a PCPDTTBTT/fullerene mixture. The high efficiency was achieved by alteration of the morphology using a solvent additive. Analysis of atomic force microscopy phase images shows that material phases with distinct mixing ratios are formed and altered with the addition of the solvent additive.
Co-reporter:Sybille Allard Dr.;Michael Forster Dr.;Benjamin Souharce;Heiko Thiem Dr. Dr.
Angewandte Chemie International Edition 2008 Volume 47( Issue 22) pp:4070-4098
Publication Date(Web):
DOI:10.1002/anie.200701920
Abstract
The cost-effective production of flexible electronic components will profit considerably from the development of solution-processable, organic semiconductor materials. Particular attention is focused on soluble semiconductors for organic field-effect transistors (OFETs). The hitherto differentiation between “small molecules” and polymeric materials no longer plays a role, rather more the ability to process materials from solution to homogeneous semiconducting films with optimal electronic properties (high charge-carrier mobility, low threshold voltage, high on/off ratio) is pivotal. Key classes of materials for this purpose are soluble oligoacenes, soluble oligo- and polythiophenes and their respective copolymers, and oligo- and polytriarylamines. In this context, micro- or nanocrystalline materials have the general advantage of somewhat higher charge-carrier mobilities, which, however, could be offset in the case of amorphous, glassy materials by simpler and more reproducible processing.
Co-reporter:Sybille Allard Dr.;Michael Forster Dr.;Benjamin Souharce;Heiko Thiem Dr. Dr.
Angewandte Chemie 2008 Volume 120( Issue 22) pp:4138-4167
Publication Date(Web):
DOI:10.1002/ange.200701920
Abstract
Die kostengünstige Fertigung flexibler elektronischer Bauelemente dürfte in Zukunft stark von der Entwicklung aus Lösung prozessierbarer, organischer Halbleitermaterialien profitieren. Besondere Aufmerksamkeit gilt dabei zurzeit löslichen Halbleitern für organische Feldeffekttransistoren (OFETs). Die bis vor einiger Zeit vorgenommene Trennung zwischen “kleinen Molekülen” und polymeren Materialien spielt mittlerweile keine Rolle mehr – entscheidend ist vielmehr die Verarbeitbarkeit der Materialien aus Lösung zu homogenen Halbleiterschichten mit optimalen elektronischen Eigenschaften (hohe Ladungsträgermobilität, geringe Schwellspannung, hohes An/Aus-Verhältnis). Die Materialien der Wahl sind hier lösliche Oligoacene, lösliche Oligo- und Polythiophene oder entsprechende Copolymere sowie Oligo- und Polytriarylamine. Mikro- oder nanokristalline Materialien bieten dabei allgemein den Vorteil etwas höherer Ladungsträgermobilitäten; amorphe, glasartige Materialien könnten dies jedoch durch eine einfachere und besser reproduzierbare Verarbeitung wettmachen.
Co-reporter:Argiri Tsami, Torsten W. Bünnagel, Tony Farrell, Markus Scharber, Stelios A. Choulis, Christoph J. Brabec and Ullrich Scherf
Journal of Materials Chemistry A 2007 vol. 17(Issue 14) pp:1353-1355
Publication Date(Web):05 Mar 2007
DOI:10.1039/B700271H
The optical and electronic properties of novel, alternating quinoxaline/oligothiophene donor–acceptor copolymers show an unexpected independence of absorption and photoluminescence, as well as of the HOMO/LUMO energy levels, on the length of the oligothiophene segments in the copolymer main chain.
Co-reporter:Guoli Tu;Askin Bilge;Sylwia Adamczyk;Michael Forster;Ludwig Josef Balk;Ralf Heiderhoff;David Mühlbacher;Mauro Morana;Markus C. Scharber;Stelios A. Choulis;Christoph J. Brabec;Markus Koppe
Macromolecular Rapid Communications 2007 Volume 28(Issue 17) pp:1781-1785
Publication Date(Web):21 AUG 2007
DOI:10.1002/marc.200700239
The hole mobility and power conversion efficiency of bulk heterojunction solar cells based on P3HT-type donor polymers and the soluble fullerene derivative [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as an acceptor both show a strong sensitivity to the introduction of interchain branches into the P3HT backbones. Branched B-P3HT copolymers display a distinctly decreased hole mobility and reduced solar cell power conversion efficiency with increasing amount of interchain 3.3′-bithiophene branches within the polythiophene macromolecules. The results illustrate the primary importance of proper solid state packing towards optimum charge transport and solar cell performance.
Co-reporter:Frank Galbrecht;Torsten W. Bünnagel;Tony Farrell
Macromolecular Rapid Communications 2007 Volume 28(Issue 4) pp:387-394
Publication Date(Web):21 FEB 2007
DOI:10.1002/marc.200600778
Polymeric semiconducting materials are being utilized as components in a new generation of electronic devices. The generation of high quality polymeric semiconductors often involves transition metal-catalyzed cross-coupling reactions, which require long reaction times. Microwave heating can be very efficient in reducing reaction times and consequently leads to increased reaction yields and concomitantly reduces the amount of side products. This microreview aims to summarize the use of microwave heating to prepare conjugated polymers, which are specifically tailored towards applications in optoelectronic and electronic devices. Moreover, microwave heating is a valuable investigative tool for the screening towards novel materials, especially when optimizing the backbone arrangement of unsaturated building blocks.
Co-reporter:Saulius Grigalevicius;Liang Ma;Gang Qian;Zhiyuan Xie;Michael Forster
Macromolecular Chemistry and Physics 2007 Volume 208(Issue 4) pp:349-355
Publication Date(Web):22 FEB 2007
DOI:10.1002/macp.200600498
New carbazole-based copolymers, which contain various concentrations of 9-alkyl-3,6-carbazole fragments in the main chain connected via alkylene spacers, have been synthesized by Ni(0)-catalyzed Yamamoto-type aryl-aryl coupling reactions. Full characterization of the copolymer structure by NMR spectroscopy and elemental analysis is presented. These compounds represent amorphous materials of high thermal stability with glass transition temperatures of 151–162 °C and thermal decomposition starting at temperatures >390 °C. UV-Vis absorption and photoluminescence emission of the copolymers confirmed that the effectively conjugated segment in the 3,6-linked carbazole-type copolymers is limited to dyads (dimeric units). However, copolymers with varying concentrations of the oligocarbazole chromophores demonstrate different charge injection and transport properties in multilayer light-emitting diodes with the copolymers as the hole transport and Alq3 as the electroluminescent/electron transport layer. The device based on a copolymer composed of oligocarbazole blocks with an average length of around four carbazoles exhibited the best overall performance with a turn-on voltage of 3.5 V, a maximal photometric efficiency of 4.1 cd · A−1 and maximum brightness of about 4 200 cd · m−2.
Co-reporter:Askin Bilge, Achmad Zen, Michael Forster, Hongbo Li, Frank Galbrecht, Benjamin S. Nehls, Tony Farrell, Dieter Neher and Ullrich Scherf
Journal of Materials Chemistry A 2006 vol. 16(Issue 31) pp:3177-3182
Publication Date(Web):06 Jul 2006
DOI:10.1039/B605338F
Synthesis and electronic properties of three swivel-cruciform oligothiophene dimers—bis(terthiophene) (BT3), bis(pentathiophene) (BT5) and bis(heptathiophene) (BT7)—with increased solubility in organic solvents are reported. We obtained a field-effect mobility of 3.7 × 10−5 cm2 V−1 s−1 and a current on/off ratio of >103 for a solution-processed OFET device with dimer BT5 as p-type semiconductor.
Co-reporter:Saulius Grigalevicius;Michael Forster;Stefan Ellinger;Katharina Lfester and
Macromolecular Rapid Communications 2006 Volume 27(Issue 3) pp:200-202
Publication Date(Web):23 JAN 2006
DOI:10.1002/marc.200500750
Summary: The first examples of the dye-coated semi-conducting polymer nanoparticles as well as experiments to demonstrate the excitation energy transfer from the excited chromophor of the nanoparticle to the fluorescent dye are described. We have demonstrated that the blue fluorescence of the dye-coated polyfluorene nanoparticles is only slightly quenched after dye deposition. However, a new emission band of the surface-bound dye (Rhodamine 6G or Rhodamine TM) appears in the wavelength region of 530–600 nm. These results clearly indicate an effective excitation energy transfer from the excited PF chromophores to the fluorescent dye.
Co-reporter:Ullrich Scherf;Eduard Preis
Macromolecular Rapid Communications 2006 Volume 27(Issue 14) pp:
Publication Date(Web):24 JUL 2006
DOI:10.1002/marc.200690025
Co-reporter:Eduard Preis
Macromolecular Rapid Communications 2006 Volume 27(Issue 14) pp:1105-1109
Publication Date(Web):20 JUL 2006
DOI:10.1002/marc.200600323
Summary: Semiconducting polymers with moderate HOMO–LUMO energy gaps between 1.5 and 2.0 eV are of increasing attraction as donor components of bulk heterojunction-type organic solar cells. The synthesis and characterization of a novel cross-conjugated, aromatic polymer, poly(diindenonaphthalene) PDIN, with a HOMO-LUMO gap of ca. 1.6 eV (λmax: 724 nm) in comparison to poly(indenofluorene) PIF, a previously described, structurally related polymer, is presented. The replacement of the central benzene ring of PIF by a naphthalene moiety in PDIN leads to an increase of the optical bandgap energy of ca. 0.16 eV.
Co-reporter:Benjamin S. Nehls;Frank Galbrecht;David J. Brauer;Christian W. Lehmann;Tony Farrell
Journal of Polymer Science Part A: Polymer Chemistry 2006 Volume 44(Issue 19) pp:5533-5545
Publication Date(Web):21 AUG 2006
DOI:10.1002/pola.21552
A helical step-ladder polyarylene incorporating chiral (R)-2,2′-dioctoxy-1,1′-binaphthyl units was synthesized for the first time. The first step involved the preparation of a precursor poly(arylene ketone) via a palladium-mediated Suzuki-type cross-coupling reaction with the aid of microwave heating. Two polymer-analog reaction steps, the reduction of the keto groups to tertiary alcohol functionalities and subsequent intramolecular Friedel–Crafts cyclization, gave a step-ladder polymer (6) in good yields with reasonable mean average molecular weights greater than 13,000. The regioselective cyclization pattern in the α position of the naphthalene core was confirmed by a comparison of the NMR data of the polymer with those of the corresponding model ladder oligomers, 12 and 13, and also a single-crystal structure of 13. The optical spectra of the oligomers and polymers indicated that there was little electronic interaction across the binaphthyl units. The circular dichroism spectrum of 6 exhibited a strong bisignate Cotton effect in the π–π* absorption region of the planar chromophores, which reflected the strong exciton coupling within the helical polymer chain. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5533–5545, 2006
Co-reporter:Saulius Grigalevicius;Liang Ma;Zhi-Yuan Xie
Journal of Polymer Science Part A: Polymer Chemistry 2006 Volume 44(Issue 20) pp:5987-5994
Publication Date(Web):6 SEP 2006
DOI:10.1002/pola.21660
2,7-Bis(9-ethylcarbazol-3-yl)-9,9-di(2-ethylhexyl)fluorene and a segmented copolymer composed of the same chromophores alternated with hexamethylene fragments were synthesized. The obtained materials possess good solubility in common organic solvents, high thermal stability with 1% weight loss temperature of 350–370 °C, and suitable glass transition temperatures. Both derivatives show blue fluorescence in dilute solutions as well as in solid state, demonstrating that excimers are not formed in the thin films. The fluorescence spectra of the materials do not show any peaks in the long-wavelength region even after annealing at 200 °C in air. An organic LED with the configuration of ITO/copolymer/Al generates blue electroluminescence with the maximum peak at 416 nm, rather low turn-on voltage (4.0 V), and brightness of about 400 cd/m2. The heterostructure device based on model derivative emitted stable blue light with low operation voltage (100 cd/m2 at ∼11 V) and demonstrated luminescence efficiency of 0.8 cd/A. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5987–5994, 2006
Co-reporter:Frank Galbrecht, Xiao Hui Yang, Benjamin S. Nehls, Dieter Neher, Tony Farrell and Ullrich Scherf
Chemical Communications 2005 (Issue 18) pp:2378-2380
Publication Date(Web):18 Mar 2005
DOI:10.1039/B501297J
The synthesis of statistical fluorene-type copolymers with on-chain Pt–salen phosphorescent units and their use in electrophosphorescent OLEDs is reported.
Co-reporter:Benjamin S. Nehls, Frank Galbrecht, Askin Bilge, David J. Brauer, Christian W. Lehmann, Ullrich Scherf and Tony Farrell
Organic & Biomolecular Chemistry 2005 vol. 3(Issue 17) pp:3213-3219
Publication Date(Web):02 Aug 2005
DOI:10.1039/B508125D
A facile route has been developed for the preparation of a new family of oligophenyls based on a 2,5,2′,5′-tetra-aryl substituted biphenyl structural motif. The cruciform terphenyl dimer 2,5,2′,5′-tetra(4-tert-butylphenyl)-1,1′-biphenyl (2) has been prepared in a two step protocol as a representative of this interesting class of materials. The thermal behaviour of the cruciform was analysed by DSC and shows that 2 forms an amorphous glass when cooled from the isotropic melt. Subsequent heating reveals a glass transition temperature at 130 °C. X-Ray single crystal structure analysis of 2,2′-bis(4-tert-butylphenyl)-1,1′-biphenyl (4) and 2 shows that both these molecules with a quater-phenyl substructure adopt a folded solid-state structure. Examining the 1H NMR spectra of 2 and 4 reveals that the interactions that induce this folding in the solid-state are sufficiently strong to bias foldamer formation also in solution. Consequently, it is reasonable to assume that the folded conformation within the lattice is due to intramolecular π–π interaction rather than being imposed by crystal packing. The optical properties of the cruciform terphenyl dimer 2 are discussed relative to the linear analogue 1,4-bis(4-tert-butylterphenyl)benzene (3).
Co-reporter:B. S. Nehls;U. Asawapirom;S. Füldner;E. Preis;T. Farrell;U. Scherf
Advanced Functional Materials 2004 Volume 14(Issue 4) pp:
Publication Date(Web):19 APR 2004
DOI:10.1002/adfm.200400010
A fully conjugated para-phenylene ladder polymer (P1) and the alternating copolymers {2,7-[9,9-bis(2-ethylhexyl)fluorene]-5,5′-(2,2′-bithiophene)} (P3) and {2,7-[9,9-dioctylfluorene]-5,5′-(2,2′-bithiophene)} (P4) have been prepared via metal-mediated cross-coupling reactions, using microwaves as a heat source. The procedure, which yields polymeric material in ca. ten minutes, has no adverse effects on the quality of the polymers and displays a high degree of reproducibility. Transfer of the optimized conditions to the synthesis of a new naphthalene-based polyarylene-ketone (P2) and a (1,5-dioctoxynaphthylene-2,6-diyl-alt-2,2′-bithiophene-5,5′-diyl) copolymer (P5) confirmed the versatility of the procedure and the dramatic reduction in reaction times compared with conventional heating. In the case of the Stille-type coupling reaction of the electron-rich, less reactive dibromo monomer 1,5-dioctoxy-2,6-dibromo-naphthalene, the microwave-assisted protocol results in a marked increase in both yield and molecular weight.
Co-reporter:Roland Güntner, Tony Farrell, Ullrich Scherf, Tzenka Miteva, Akio Yasuda and Gabi Nelles
Journal of Materials Chemistry A 2004 vol. 14(Issue 17) pp:2622-2626
Publication Date(Web):01 Jul 2004
DOI:10.1039/B406339M
Two novel fluorene-trimers were synthesised following a Suzuki-type cross-coupling reaction. Methyl pendant chains in 9-position of the fluorene building blocks ensured a rod-like backbone of a small molecular diameter while the introduction of terminal, flexible n-octyl and n-hexadecyl alkyl chains in the 2- and 7″-positions causes the occurrence of two different liquid-crystalline (LC) mesophases for both trimers. The terminal chain length was found to strongly affect the phase transition temperatures but not the number and type of LC phases formed. By using several analytical techniques (differential scanning calorimetry DSC, polarizing microscopy, and X-ray diffractometry) the exact nature of the mesophases was determined. The n-hexadecyl- and n-octyl-substituted fluorene-trimers characteristically form smectic LC phases at transition temperatures of 108 and 171 °C, respectively, which when heated further are transformed into lower ordered nematic LC mesophases at 140 and 187 °C, respectively.
Co-reporter:T. Piok;S. Gamerith;C. Gadermaier;H. Plank;F.P. Wenzl;S. Patil;R. Montenegro;T. Kietzke;D. Neher;U. Scherf;K. Lfester and;E.J.W. List
Advanced Materials 2003 Volume 15(Issue 10) pp:
Publication Date(Web):16 MAY 2003
DOI:10.1002/adma.200304253
Co-reporter:S.A. Patil;U. Scherf;A. Kadashchuk
Advanced Functional Materials 2003 Volume 13(Issue 8) pp:
Publication Date(Web):12 AUG 2003
DOI:10.1002/adfm.200304344
A new ladder polymer incorporating a polar carbazole group within the main chain, ladder-type poly(para-phenylene carbazole), LPPPC, was synthesized and characterized by luminescence techniques. Its properties are compared to that of the well-known methyl-substituted ladder-type poly(para-phenylene), MeLPPP. The results obtained evidence a very low energetic disorder in this new polymer, presumably due to its near-perfect intrachain structure and low content of defects. It was found that although the density of states (DOS) distribution for neutral excitations is narrower than in MeLPPP, the manifold of charge-transporting localized states is substantially more energetically disordered due to important dipolar disorder contributions.
Co-reporter:A. Palma-Cando, D. Woitassek, G. Brunklaus and U. Scherf
Inorganic Chemistry Frontiers 2017 - vol. 1(Issue 6) pp:NaN1124-1124
Publication Date(Web):2016/12/16
DOI:10.1039/C6QM00281A
A series of novel microporous polymer networks (MPNs) have been prepared from tetraphenylethene (TPE)-cored, multifunctional carbazole- or thiophene-based monomers by using chemical and electrochemical oxidative coupling methods. Octafunctional monomers lead to MPNs with a high degree of cross-linking and optimized specific surface areas (SBET) of up to 2200 m2 g−1. Aggregation-induced emission (AIE) activity of the monomers is demonstrated. The MPN films are tested for application in the chemical sensing of nitroaromatic analytes by fluorescence quenching.
Co-reporter:Suman Kalyan Samanta, Eduard Preis, Christian W. Lehmann, Richard Goddard, Saientan Bag, Prabal K. Maiti, Gunther Brunklaus and Ullrich Scherf
Chemical Communications 2015 - vol. 51(Issue 43) pp:NaN9049-9049
Publication Date(Web):2015/04/23
DOI:10.1039/C5CC01654A
One-step synthesis of a cyclic 2,17-dioxo[3,3](4,4′)biphenylophane (MC) was achieved in high yield; its structure was verified by single crystal X-ray analysis. As a first example, a microporous polymer network was formed from macrocycle MC via acid-catalysed cyclotrimerization yielding a BET surface area of ca. 570 m2 g−1.
Co-reporter:Argiri Tsami, Torsten W. Bünnagel, Tony Farrell, Markus Scharber, Stelios A. Choulis, Christoph J. Brabec and Ullrich Scherf
Journal of Materials Chemistry A 2007 - vol. 17(Issue 14) pp:NaN1355-1355
Publication Date(Web):2007/03/05
DOI:10.1039/B700271H
The optical and electronic properties of novel, alternating quinoxaline/oligothiophene donor–acceptor copolymers show an unexpected independence of absorption and photoluminescence, as well as of the HOMO/LUMO energy levels, on the length of the oligothiophene segments in the copolymer main chain.
Co-reporter:E. Preis, W. Dong, G. Brunklaus and U. Scherf
Journal of Materials Chemistry A 2015 - vol. 3(Issue 7) pp:NaN1587-1587
Publication Date(Web):2014/12/19
DOI:10.1039/C4TC02664K
Microporous Polymer Networks (MPNs) that contain aggregate-induced emission (AIE) active tetraphenylethylene (TPE) or other tetraarylethylene units have been generated in a reductive polyolefination process starting from four different tris(α,α-dichlorobenzyl)arene derivatives with dicobalt octacarbonyl or chromium(II)acetate as reductive olefination agents. Microporosity with moderately high BET surface areas up to 500 m2 g−1 could be combined with high solid state photoluminescence quantum yields up to 25.3% for polymer network P4. This unique combination should be promising for applications as optical solid state sensors, especially for MPNs with electron-deficient triazine core units.
Co-reporter:Penglei Li, Oliver Fenwick, Seyfullah Yilmaz, Dietrich Breusov, Daren J. Caruana, Sybille Allard, Ullrich Scherf and Franco Cacialli
Chemical Communications 2011 - vol. 47(Issue 31) pp:NaN8822-8822
Publication Date(Web):2011/07/04
DOI:10.1039/C1CC12752G
We have synthesised and characterised a new low-gap conjugated polymer, with a broad absorption profile. In blends with a C70 derivative we demonstrate power conversion efficiencies of 0.76%. We show electroluminescence from the polymer peaking at 956 nm, and quantum efficiency of 0.02% in a blend.
Co-reporter:Kai Yuan, Ting Hu, Yazhou Xu, Robert Graf, Lei Shi, Michael Forster, Thomas Pichler, Thomas Riedl, Yiwang Chen and Ullrich Scherf
Inorganic Chemistry Frontiers 2017 - vol. 1(Issue 2) pp:NaN285-285
Publication Date(Web):2016/08/04
DOI:10.1039/C6QM00012F
Conjugated microporous polymers (CMPs) are considered as promising precursors to fabricate multi-functional porous carbons. However, CMPs are formed under kinetic control, and most of them are obtained as amorphous powders without long-range order. Carbon materials derived from CMPs usually preserve the particular structure of the CMP precursors, thus the direct pyrolysis of CMPs into two-dimensional (2D) porous carbon nanosheets remains a great challenge. In this work, 4-iodophenyl-substituted graphene (RGO-I) is used both as a building block and a structure directing template for the construction of nitrogen–rich graphene–CMP (GMP) sandwiches using a solution-based approach. The 2D structure of RGO-I with its large aspect ratio allows for the growth of uniform CMP shells onto both sides of the graphene sheets. Thereby, aggregation and restacking of the graphene sheets can be effectively suppressed even during high-temperature treatment. Thereby, well-defined nitrogen-doped porous carbon/graphene nanosheets were readily obtained by direct pyrolysis of the GMP sandwiches. The sandwich-like nitrogen-doped porous carbon/graphene nanosheets were used as electrode materials for supercapacitor devices with very promising capacitive performance, superior in comparison to the corresponding porous carbons derived from the graphene-free CMPs. The good 2D electron transport ability of graphene together with the intimate interactions between porous carbon and graphene layers provide a combination of large electrochemically active surface area for charge transfer and minimized ion diffusion paths during the charge/discharge process. This unique set of physical properties effectively boosts the capacitive performance values if applied in supercapacitor devices.
Co-reporter:Andrea Gutacker, Sylwia Adamczyk, Anke Helfer, Logan E. Garner, Rachel C. Evans, Sofia M. Fonseca, Matti Knaapila, Guillermo C. Bazan, Hugh D. Burrows and Ullrich Scherf
Journal of Materials Chemistry A 2010 - vol. 20(Issue 8) pp:NaN1430-1430
Publication Date(Web):2009/12/22
DOI:10.1039/B918583F
Novel, all-conjugated polyelectrolyte block copolymers of the rod-rod type can be generated in a “grafting from” scheme and exhibit a preferred tendency to self-assemble into layered aggregates both in solution and the solid state. Here, the rigid-rod structure of the individual, complex macromolecules favours the formation of low-curvature vesicular and lamellar aggregates. Our poly(9,9-dialkylfluorene)-b-poly[3-(6-ammoniumhexyl)thiophene] (PF2/6-b-P3TMAHT and PFO-b-P3TMAHT, where PF2/6 and PFO denote 2-(ethyl)hexyl and linear octyl alkyl pendant groups, respectively), and poly(9,9-dialkylfluorene)-b-poly[3-(6-pyridylhexyl)thiophene] (PF2/6-b-P3PyHT and PFO-b-P3PyHT) polyelectrolyte diblock copolymers allow for simple and reliable control of the occurring self-organisation process and the resulting nano-scaled architectures. They are, therefore, promising candidates for application as the active layer in electronic devices or as functional membranes (e.g. for sensor applications). Moreover, the electronic properties of the materials (especially the excitation energy transfer between both blocks) strongly depend on the aggregation state present. Aggregation can be further controlled via addition of oppositely charged surfactants resulting in the formation of ordered polyelectrolyte/surfactant complexes.
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