Incorporation of Different End Groups in Conjugated Polymers Using Functional Nickel Initiators

Smeets, Alfons; Bergh, Karlien Van den; Winter, Julien De; Gerbaux, Pascal; Verbiest, Thierry; Koeckelberghs, Guy

doi:10.1021/ma901888h

Cited by 120 publications

(173 citation statements)

References 37 publications

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“…Additional free dppp was used during the KCTP of 1, and a high degree of functional group transfer from the initiator to the polymer (80-95%) was observed. [74] Recently, Doubina et al investigated the influence of the initiator precursor substitution pattern on the initiator incorporation in more detail. Using phosphonate-containing arylchlorides with the methodology illustrated in Scheme 3d, the importance of a substituent ortho to the nickel center was confirmed.…”

Section: Ex Situ (External) Initiationmentioning

confidence: 99%

Kumada Catalyst‐Transfer Polycondensation: Mechanism, Opportunities, and Challenges

Kiriy

Senkovskyy

Sommer

2011

Macromol. Rapid Commun.

225

178

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Kumada catalyst-transfer polycondensation (KCTP) is a new but rapidly developing method with great potential for the preparation of well-defined conjugated polymers (CPs). The recently discovered chain-growth mechanism is unique among the various transition metal-catalyzed polycondensations, and has thus attracted much attention among researchers. Most progress is found in the areas of mechanism and external initiation via new initiators, but also the number of monomers other than thiophene that can be polymerized is steadily increasing. Accordingly, the variety of CP chain architectures is increasing as well, and a considerable contribution of KCTP toward more efficient materials can be expected in the future. This review critically focuses on very recent progress in the synthesis of CPs and the mechanism of KCTP, and is finally aimed at providing a comprehensive picture of this exciting polymerization method.

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Section: Ex Situ (External) Initiationmentioning

confidence: 99%

Kumada Catalyst‐Transfer Polycondensation: Mechanism, Opportunities, and Challenges

Kiriy

Senkovskyy

Sommer

2011

Macromol. Rapid Commun.

225

178

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“…Moreover, it has already been reported that a substituent in the ortho-position to the C-Br bond stabilizes the formed 9,13,[15][16] Therefore, the lack of a -substituent in the P3AOT polymerization is a second reason for the decreased stability of the growing Ni-center in this case. However, in contrast to P3AT [13] , in which the polymerization completely failed when a reversed thiophene monomer (with substituent in meta-position) was used, a polymer is still formed, albeit in a non-controlled fashion.…”

Section: Proposed Polymerization Mechanismmentioning

confidence: 70%

“…[9] Then, another molecule of 3 reacts with 4. In case of 4a, a dimer in a head-to-head fashion is formed.…”

Section: Proposed Polymerization Mechanismmentioning

confidence: 99%

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Ni‐Catalyzed Polymerization of Poly(3‐alkoxythiophene)s

Bergh

Winter

Gerbaux

et al. 2010

Macro Chemistry & Physics

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The Ni-catalyzed polymerization of poly(3-alkoxythiophene)s (P3AOTs) was studied and compared with the controlled chain-growth polymerization of poly(3-alkylthiophene)s (P3ATs). By varying the ratio of the initial monomer concentration to the initiator concentration, no linear dependence of the molar mass was observed, revealing that the polymerization does not proceed via a controlled mechanism. This was also confirmed by analyzing the end-groups of the polymer with MALDI-TOF mass spectrometry. To acquire more information on the polymerization mechanism, the formation of the actual monomer and the polymerization reaction were studied into more detail. These experiments proved that the polymerization proceeds via a chain-growth mechanism, although not in a controlled way. a Supporting information for this article is available at the bottom of the article's abstract page, which can be accessed from the journal's homepage at http://www.macros.wiley-vch.de, or from the author.-2 - IntroductionPoly(3-alkylthiophene)s (P3ATs) are a class of conjugated polymers that has been intensively studied over the past decades. The discovery by McCullough and Yokozawa of the chain-growth polymerization mechanism of P3ATs has led to a renewed interest in the synthesis of these polymers.[1] This chain-growth mechanism is made possible by the 'ringwalking process' of the Ni-catalyst, whereby the Ni(0) species is transferred intramolecularly along a polymer chain to its end where it oxidatively inserts in the C-Br bond. [2] Due to this mechanism, all polymer chains are equipped with the same end-groups, being a bromine and a hydrogen atom (after quenching with acid). It also allows control of the molar mass by adjusting the feed ratio of the monomer to the Ni-catalyst, and the formation of block copolymers by successive monomer addition.[3]The versatility of the quasi-controlled chain-growth polycondensation has also been demonstrated by the use of other monomers, polymerized with Ni-as well as Pd-catalysts. In this way, polyfluorenes [4] , poly(para-phenylenes) [5] and polypyrroles [3d] have been successfully prepared.If the polythiophene backbone is substituted with an alkoxy instead of an alkyl side-chain, a polymer with different characteristics is obtained. Regioregular HT-coupled poly(3-alkoxythiophene)s (P3AOTs) are electronically different and show a significantly higher  max compared to P3ATs. [6] Their Faraday rotation is much larger (Verdet constant up to 3x10 6 T -1 m -1 ) [7] and their magnetic properties differ [8] . Although their properties are interesting, the polymerization behavior of P3AOTs has never been studied in detail.An important finding in this respect is that starting the polymerization of P3AOT with an otolyl nickel initiator complex results in polymers which mainly bear o-tolyl/hydrogen endgroups -as would be formed by a controlled chain-growth mechanism -but also otolyl/bromine and even small amounts of Br/Br, Br/H and H/H end-groups.[9] Although most -3 -polymers were equipped with the initiator u...

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“…Polymers resulting from this initiator had only tolyl/H end groups. Concurrent studies carried out independently by Koeckelberghs et al verified these observations [65]. They found that the PhNi(PPh 3 ) 2 Br initiators were prone to disproportionation to afford biphenyl, Ni, PPh 3 , and Ni(PPh 3 ) 2 Br 2 , which could then initiate another polymerization.…”

Section: Initiation and Catalyst Transfer Propagationmentioning

confidence: 83%

The Synthesis of Conjugated Polythiophenes by K umada Cross‐Coupling

Koch

Heeney

2012

Materials Science and Technology

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Conjugated polymers have been the subject of intensive research efforts over the past few decades. Much of this interest has stemmed from the fact that such materials combine the inherent processibility and mechanical robustness associated with polymers, with the electronic properties more typically associated with inorganic semiconductors. Thus, such materials may allow the fabrication of electronic devices on a variety of flexible or conformable surfaces, by a range of potentially low-cost and large-area deposition techniques such as printing. Possible applications include field effect transistors for display backplanes, organic solar cells, electrochromic displays, chemical sensors, and polymeric light-emitting diodes [1].Within the realms of conjugated polymer research, thiophene-containing materials have been one of the most widely investigated classes for many of the above applications [2,3]. Thiophene is a cheap and widely available electron-rich, planar aromatic heterocycle which is readily functionalized by range of chemistries. As a result, it can be copolymerized with a variety of aromatic comonomers to generate polymers with extended π-electron delocalization along the backbone. The alternating double and single bonds of the delocalized conjugated system are nondegenerate, leading to an energy band gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). For many of the optoelectronic applications outlined above, the absolute energy levels of the HOMO and LUMO, as well as the band gap between them, are important parameters affecting device performance. As such, major research efforts have been devoted to understanding how chemical structure can influence the electronic delocalization of conjugated polymers. Whilst these factors are complex, they can be related to points such as the attachment of electron-donating/-withdrawing substituents to the polymer backbone, the degree of backbone planarity (and, therefore, the π-electron overlap and delocalization), and the nature and aromaticity of any comonomers included in the polymer backbone.

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Incorporation of Different End Groups in Conjugated Polymers Using Functional Nickel Initiators

Cited by 120 publications

References 37 publications

Kumada Catalyst‐Transfer Polycondensation: Mechanism, Opportunities, and Challenges

Kumada Catalyst‐Transfer Polycondensation: Mechanism, Opportunities, and Challenges

Ni‐Catalyzed Polymerization of Poly(3‐alkoxythiophene)s

The Synthesis of Conjugated Polythiophenes by K umada Cross‐Coupling

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