Conjugated Polymer Synthesis and Materials Applications (eBook)

Yoshiki Chujo (Herausgeber)

eBook Download: EPUB

2025
565 Seiten
Wiley-VCH (Verlag)
978-3-527-84943-7 (ISBN)

Infos

Comprehensive reference exploring the synthesis, preparation, and applications of new and novel conjugated polymers

Conjugated Polymer Synthesis and Materials Applications summarizes the fundamentals and major developments in the synthesis of new conjugated polymers. The book explores novel methodologies for the preparation of inorganic-elements containing conjugated polymers and reviews recent applications of conjugated polymers in the electrical, optical, and biomedical fields.

In each of the chapters, all of them written by internationally acclaimed experts, the book covers the whole spectrum of a specific conjugated polymer from fundamentals to materials applications.

Conjugated Polymer Synthesis and Materials Applications explores topics including:

• Living conjugated polymers
• Optically active through-space conjugated polymers
• Solid-state luminescent conjugated polymers containing boron element-blocks
• Carborane-containing conjugated polymers for optoelectronic materials
• Polymers with three-dimensional conjugated molecules
• Conjugated polymers with controlled higher-order structures
• Conjugated polymers for energy storage devices
• Low bandgap conjugated polymers
• Advances in organic solar cell performance
• Conjugated polymers for biomedical applications

Conjugated Polymer Synthesis and Materials Applications is an essential up-to-date reference on the subject for students and researchers in the field as well as professionals in related industries.

Yoshiki Chujo is a Professor Emeritus of Kyoto University. His research interests focus on polymer synthesis and organic-inorganic hybrid materials. He has received numerous awards throughout his career, including the Award of the Society of Polymer Science, Japan (SPSJ), the Scientific Award of the Chemical Society of Japan (CSJ), the Award of the CSJ, the SPSJ Award for Outstanding Achievement in Polymer Science and Technology, and the Medal with Purple Ribbon from Emperor.

Textauszug

Chapter 1
Transition Metal-catalyzed Polycondensation

Takaki Kanbara1, and Junpei Kuwabara2

1Institute of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan

2Tsukuba Research Center for Energy Materials Science (TREMS), Institute of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan

1.1 Introduction

Transition metal-catalyzed homo- and cross-coupling reactions have emerged as versatile synthetic methodologies that are widely employed for the synthesis of a variety of organic compounds [1–9]. Cross-coupling reactions of various organometallic (Mg, Zn, Sn, B, and Si) reagents and aryl halides are suitable for bond formation at sp2 and sp carbons. Profs. Negishi, Suzuki, and Heck were awarded the Nobel Prize in Chemistry in 2010 for their pioneering work on Pd-catalyzed cross-coupling reactions in organic synthesis [10–13].

Scheme 1.1 shows the general mechanism of cross-coupling reactions. Ni- and Pd-based complexes are commonly employed as transition metal catalysts. In general, cross-coupling reactions involve three steps: an oxidative addition reaction across the carbon–halogen bond as an electrophile, transmetalation with the main group in the organometallic reagents acting as nucleophiles, and reductive elimination, resulting in the formation of the carbon–carbon bonds and regeneration of the active catalyst. Various organometallic reagents, including Grignard reagents (Kumada–Tamao–Corriu), zinc (Negishi), stannane (Migita–Kosugi–Stille), boron (Suzuki–Miyaura), silane (Hiyama), copper (Sonogashira), lithium, and mercury compounds, can be used [1–13].

Scheme 1.1 General mechanism of metal-catalyzed cross-coupling reaction. Ar1 and Ar2 denote aromatic units, M and M′ represent an organometallic moiety, and X represents halogen or pseudo-halogen.

In terms of polymer synthesis, various -conjugated polymers have been designed and developed by the transition metal-catalyzed homo- and cross-coupling polycondensation over the last few decades [14–17]. This chapter describes a fundamental overview of the transition metal-catalyzed homo- and cross-coupling polymerization reactions used in the synthesis of various -conjugated polymers. The utilization of transition metal-catalyzed bond functionalization and carbon–nitrogen bond formations in synthesizing -conjugated polymers is also involved.

1.2 Ni-catalyzed Polycondensation

The utilization of transition metal-catalyzed cross-coupling reactions to -conjugated polymers was first reported by Yamamoto et al. in the synthesis of poly(-phenylene), which was prepared by Ni-catalyzed Grignard coupling of 1,4-dibromobenzene [14, 18, 19]. One of the bonds reacts with Mg to form the Grignard reagent and undergoes further coupling reactions based on the Kumada–Tamao–Corriu cross-coupling reaction (Scheme 1.2a). Polythiophene (PTh) and poly(3-alkylthiophene)s (PRThs) were synthesized using the same protocol (Scheme 1.2b) [20].

Scheme 1.2 Ni-catalyzed Grignard coupling polycondensation of (a) 1,4-dibromobenzene and (b) 2,5-dibromo-3-alkylthiophene.

While the reactions are simple and provide several -conjugated polymers, the regioregularity cannot be controlled using the conventional protocol (Scheme 1.3). The synthesis of regioregular PRThs involving head-to-tail (HT) repeating units can be realized by the Ni-catalyzed polycondensation of regio-controlled organometallic monomers (Scheme 1.4). The reaction of 2,5-dibromo-3-alkylthiophene with metallic Mg or Zn was shown to give the organometallic species at the 5-position. Further addition of the Ni catalyst initiated polymerization to give PRThs with high HT regioregularity (HT-P3RTh, Schemes 1.4a, b) [21–23]. The active monomers for regioregular PRThs were also generated by deprotonation of 2-bromo-3-alkylthiophene with Knochel–Hauser base, 2,2,6,6-tetramethyl piperidinyl magnesium chloride lithium chloride complex (TMPMgCl·LiCl) (Scheme 1.4c) [23]. Regioregular PRThs have been of particular interest because regioregular polymers exhibit remarkable physical properties such as higher crystallinity and electrical conductivity in the solid state than regio-random PRThs [14, 24]. It should be noted that the polymerization reaction in Scheme 1.4 could proceed in a chain-growth manner, in which propagation occurs at the polymer end, despite the reaction being based on a polycondensation. Thus, the reaction allows the control of the molecular weight with a narrow molecular weight distribution and the formation of block copolymers by successive monomer additions [23, 25–30]. Chapter 2 will provide a detailed description of the chain-growth polycondensation.

Scheme 1.3 Synthesis of regioirregular PRTh.

Scheme 1.4 Synthesis of regioregular PRTh mediated by (a) Grignard reagent, (b) Rieke zinc, and (c) Knochel–Hauser base.

Dehalogenative homo-coupling polycondensation of dihaloaromatic monomers using zerovalent Ni complexes (Ni(0)Lm) such as Ni(PPh3)4 and Ni(cod)2 (cod = 1,5-cyclooctadiene), has also contributed to design various -conjugated polymers (Scheme 1.5a) [14, 18]. The protocol proceeds under mild conditions and enables the polycondensation of dihaloaromatic monomers, such as 2,5-dibromopyridine and 1,4-dichloroanthracene, which has not been achieved by other polycondensation methods. While the reaction generally requires a stoichiometric amount of Ni(0) complex, the Ni(0)Lm complexes formed in situ by chemical (e.g. by Zn, NaH, and hydrazine hydrate) or electrochemical reduction of Ni(II) compounds are available for polycondensation [31–35] thus facilitating the following catalytic reactions (Scheme 1.5b).

Scheme 1.5 Dehalogenative homo-coupling polycondensation using (a) a stoichiometric amount of Ni(0) complex and (b) Ni(0) complexes formed by chemical and electrochemical reduction.

1.3 Pd-catalyzed Polycondensation

Pd complexes are known as useful catalysts for various coupling reactions, particularly the Pd-catalyzed Migita–Kosugi–Stille, Suzuki–Miyaura, Sonogashira, and Mizoroki–Heck coupling reactions have been utilized for polycondensation giving various -conjugated polymers [14–17]. This is due to some inherent advantages such as increased diversity and tenability of the catalysts, oxidative and aqueous stability, and relatively facile isolation and structural analysis of the complexes, which aid their mechanistic and methodological developments. With the development of these cross-coupling reactions utilized polycondensation, -conjugated polymers consisting of alternating aromatic units have been prepared easily, and the variation of the -conjugated polymers has been dramatically increased.

The Migita–Kosugi–Stille coupling reaction is a Pd-catalyzed cross-coupling reaction between aryl halides and organostannic compounds and the Suzuki–Miyaura coupling reaction is a versatile bond formation reaction between aryl halides and organoboronic acids. One important difference between the cross-coupling reactions is that the Suzuki–Miyaura coupling reaction requires the activation of the organoboronic acid with a base. This activation facilitated transmetalation (Scheme 1.6). The major advantage of these cross-coupling reactions is that they can tolerate various functional groups and proceed under mild conditions. The Suzuki–Miyaura coupling reaction can even be conducted in aqueous media. The feature of the coupling reactions offers the opportunity to design a variety of -conjugated polymers with functional moieties manifesting many highly desirable properties (Scheme 1.7a, b) [14–17, 36, 37]. In addition, these cross-coupling polymerization protocols also proceed in a chain-growth polymerization manner from the initiator unit derived from the Pd catalyst [25–30]; the details are to be described in Chapter 2.

Scheme 1.6 Reaction mechanism of the Suzuki–Miyaura coupling reaction. Ar1 and Ar2 denote aromatic units and X denotes halogen or pseudo-halogen.

Scheme 1.7 Pd-catalyzed polycondensation via (a) Migita–Kosugi–Stille, (b) Suzuki–Miyaura, and (c) Sonogashira coupling reactions.

The Pd-catalyzed cross-coupling of aryl halides with terminal alkynes employing co-catalytic Cu(I) halides and an amine base is referred as the Sonogashira coupling reaction [9]. The polycondensation reactions between dihaloaromatic monomers and diethynyl aromatic monomers give poly(arylene ethynylene) type -conjugated polymers (Scheme 1.7c) [38]. In this reaction, the Cu(I) halides react with the terminal alkyne to produce a Cu(I) acetylide, which serves as an activated species for the coupling reaction. Transmetalation proceeded in the usual manner for the Pd complex (Scheme 1.1). A Cu-co-catalyzed mechanism for the Sonogashira coupling reaction was also proposed since the rate of the reaction was affected by the nature of the substituent and the halide of the copper(I) salt as well as the aryl halide [39].

The Mizoroki–Heck...

Produkt-Details

• Erscheint lt. Verlag: 11.12.2025
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Chemie ► Organische Chemie
• Schlagworte: 3d conjugated polymers • carborane conjugated polymers • conjugated polymers applications • conjugated polymers synthesis • conjugated polymers with element-blocks • Energy Storage Devices • living conjugated polymers • luminescent conjugated polymers • Optoelectronic materials • organic solar cell performance
• ISBN-10: 3-527-84943-2 / 3527849432
• ISBN-13: 978-3-527-84943-7 / 9783527849437