Synthesis of End-Functionalized Poly(norbornene)s via Ring-Opening Metathesis Polymerization

Bielawski, Christopher W.; Benítez, Diego; Morita, Takeharu; Grubbs, Robert H.

doi:10.1021/ma010878q

Cited by 178 publications

(143 citation statements)

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“…Two examples are the acyclic diene metathesis method, which was extensively developed by Wagener's group [8][9][10] and follows a step-growth polymerization mechanism, or ROMP with an irreversible chain transfer in which a cyclic olefin monomer is polymerized in the presence of small quantities of an acyclic olefin. However, such polymerizations cannot be considered to be living, as molecular weight distributions are typically broad and block copolymers cannot be made 11 .…”

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confidence: 99%

Catalytic living ring-opening metathesis polymerization

Nagarkar

Kilbinger

2015

Nature Chem

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In living ring-opening metathesis polymerization (ROMP), a transition-metal-carbene complex polymerizes ring-strained olefins with very good control of the molecular weight of the resulting polymers. Because one molecule of the initiator is required for each polymer chain, however, this type of polymerization is expensive for widespread use. We have now designed a chain-transfer agent (CTA) capable of reducing the required amount of metal complex while still maintaining full control over the living polymerization process. This new method introduces a degenerative transfer process to ROMP. We demonstrate that substituted cyclohexene rings are good CTAs, and thereby preserve the 'living' character of the polymerization using catalytic quantities of the metal complex. The resulting polymers show characteristics of a living polymerization, namely narrow molecular-weight distribution, controlled molecular weights and block copolymer formation. This new technique provides access to well-defined polymers for industrial, biomedical and academic use at a fraction of the current costs and significantly reduced levels of residual ruthenium catalyst. In olefin metathesis reactions, olefinic bonds are rearranged with the help of a transition-metal catalyst 1,2 . In the early days following the discovery of this reaction, ill-defined catalysts 3 were used to carry out this transformation. After Herisson and Chauvin 4 had proposed a reaction mechanism, the olefin metathesis reaction was better understood and soon gained much popularity. Typical catalysts used for olefin metathesis reactions include those based on ruthenium (developed mainly by the Grubbs group 5 ), tungsten and molybdenum (developed mainly by the Schrock group 6 ). Owing to the low oxophilicity of ruthenium compared to those of molybdenum and tungsten, the ruthenium metathesis catalysts (commonly known as Grubbs' catalysts) are more tolerant towards many polar functional groups and residual impurities, as well as to water 7 . Therefore, these catalysts are the catalysts of choice in highly functional organic chemistry transformations as well as for the majority of metathesis polymerizations carried out today. Catalysts G1 (first generation) and G3 (third generation) are the most widely used ruthenium initiators for ring-opening metathesis polymerization (ROMP). In comparison to the G1 initiator, the third-generation catalyst G3 exhibits very fast initiation and propagation rates, and thereby gives polymers with very narrow dispersities and an excellent control over their molecular weights. Owing to its superior stability as well as the favourable polymerization kinetics, the third-generation Grubbs' catalyst G3 was used for this work. ROMP is a polymerization technique that uses the metathesis of cyclic olefins to synthesize linear polymers. Depending on the structure of the monomer, such polymerizations can be controlled perfectly to give polymers with a narrow molecular weight distribution and a controlled average molecular weight. Ring-strained monomers, li...

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confidence: 99%

Catalytic living ring-opening metathesis polymerization

Nagarkar

Kilbinger

2015

Nature Chem

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“…28 Use of PCy 3 (Cy¼cyclohexyl), a bulky and electron-rich phosphine, leads to highly active catalyst 10, 29 which is stable in organic solvents in the presence of water, alcohol and acetic acid, or in a diethyl ether solution of HCl. As a result, they have allowed the synthesis of end-functionalized poly(norbornene)s 30 and block copolymers. 31 Nowadays, various metathesis-active Ru-carbene complexes are available.…”

Section: Intermolecular Chain Transfermentioning

confidence: 99%

Recent advances in ring-opening metathesis polymerization, and application to synthesis of functional materials

Sutthasupa

Shiotsuki

Sanda

2010

Polym J

339

273

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This article reviews the development of catalysts for ring-opening metathesis polymerization (ROMP), synthesis of polymers bearing amino acids and peptides by ROMP of functionalized norbornenes, formation of aggregates and micelles, and applications of the polymers to medical materials. It also describes the control of monomer unit sequences, that is, living polymerization to synthesize block copolymers, and alternating copolymerization that is achieved on the basis of acid-base interactions. Polymer Journal (2010) 42, 905-915; doi:10.1038/pj.2010.94; published online 13 October 2010Keywords: alternating copolymerization; amino acid; block copolymerization; living polymerization; metathesis catalyst; peptide; ROMP INTRODUCTIONOlefin metathesis reactions are metal-mediated carbon-carbon (C-C) double bond exchange processes, 1,2 which were discovered in the mid 1950s. Chauvin proposed the commonly accepted mechanism for metathesis involving a metallacyclobutane, as illustrated in Scheme 1. 3 Initially, olefin metathesis was regarded as an odd reaction, but now it has undoubtedly established the position as one of the most important C-C bond formation reactions applicable to synthesis of a wide variety of useful products. In the early stages, transition metal chlorides were used as catalysts for the reaction, but the transition metal carbene complex catalysts designed by Schrock and Grubbs have remarkably advanced mechanistic analysis and control of catalytic activity by the choice of ligands. In 2005, Chauvin, Grubbs and Schrock were awarded the Nobel Prize in chemistry for development of the metathesis method in organic synthesis.Olefin metathesis polymerization is an application of metathesis reactions to polymer synthesis and includes ring-opening metathesis polymerization (ROMP) and acyclic diene metathesis (ADMET) polycondensation (Scheme 2). ADMET has been extensively developed by Wagener since 1987 4 for the synthesis of polyolefins having regularly spaced functional group branches and high thermal stability and crystallinity. 5,6 ADMET is also useful for synthesizing polymeric materials containing in-chain functionality. Although the general structures of the polymers obtained by ROMP and ADMET are illustratable in the same fashion as shown in Scheme 2, a completely different treatment is necessary from the viewpoint of polymerization kinetics. The former involves chain polymerization, whereas the latter is a step-growth polymerization process.

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“…In addition, the polymerization for the chiral monomer (þ)-1 proceeds in a living fashion 44 : the molecular weights of poly-2 were varied by controlling the molar ratio of monomer to initiator ( The control of the molecular weight is attributed to the fact that for the catalyst 3, k i /k p is high enough that all the chains initiate and grow at a similar rate. 45,46 For this reason, catalyst 3 promotes living ROMP for a novel chiral norbornene (þ)-1 bearing both cyano and ester groups with both higher activity and better molecular weight control.…”

Section: Resultsmentioning

confidence: 99%

Enantioseparation of doubly functionalized polar norbornenes by HPLC and their ruthenium‐catalyzed ring‐opening metathesis polymerization

Nishihara

Doi

Izawa

et al. 2009

J. Polym. Sci. A Polym. Chem.

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Doubly fuctionalized polar norbornenes bearing the cyano and ester groups in 2,3‐positions are synthesized and enantiomers are separated by high performance liquid chromatography (HPLC) with a chiral stationary phase. These optically active monomers are polymerized by ruthenium carbene catalysts, and high yields of the polymers were obtained. The chiral monomer bearing ethyl ester gave an optically active polymer of lower, but opposite sign of optical rotation (monomer [α]D = +61.0°, polymer [α]D = −3.1°). The circular dichroism (CD) of the obtained chiral polymers gave a Cotton effect. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 485–491, 2010

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Synthesis of End-Functionalized Poly(norbornene)s via Ring-Opening Metathesis Polymerization

Cited by 178 publications

References 47 publications

Catalytic living ring-opening metathesis polymerization

Catalytic living ring-opening metathesis polymerization

Recent advances in ring-opening metathesis polymerization, and application to synthesis of functional materials

Enantioseparation of doubly functionalized polar norbornenes by HPLC and their ruthenium‐catalyzed ring‐opening metathesis polymerization

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