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Catalytic Living Ring Opening Metathesis Polymerization

English title Catalytic Living Ring Opening Metathesis Polymerization
Applicant Kilbinger Andreas F. M.
Number 160192
Funding scheme Project funding (Div. I-III)
Research institution Département de Chimie Université de Fribourg
Institution of higher education University of Fribourg - FR
Main discipline Organic Chemistry
Start/End 01.10.2015 - 30.09.2019
Approved amount 543'847.00
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All Disciplines (2)

Discipline
Organic Chemistry
Material Sciences

Keywords (5)

end-functional polymers; living polymerization; catalytic polymerization; olefin metathesis; ring opening metathesis polymerization

Lay Summary (German)

Lead
Die lebende Ringöffnende Olefinmetathese-Polymerisation ist eine gut untersuchte Polymersationsmethode, welche es gestattet, das Molekulargewicht, sowie die Breite der Polymer-Massenverteilung genau zu kontrollieren. Ein entscheidender Nachteil der Methode ist, dass relativ hohe Mengen eines Rutheniumkomplexes als Initiator der Polymerisation eingesetzt werden müssen. Das vorliegende Forschungsprojekt untersucht daher Methoden, welche es erlauben, den Rutheniumgehalt stark zu vermindern, ohne jedoch die Kontrolle über die Polymersation zu verlieren.
Lay summary

Bei der Ringöffnenden Olefinmetathese Polymeriation (ROMP) handelt es sich um eine Kettenwachstums-Polymerisation. Bei diesem Polymersationstyp werden die Monomere eines nach dem anderen an das Kettenende einer bereits gebildeten Polymerkette angehängt. Um dies zu gewährleisten, ist an das Kettenende des Polymers ein Rutheniumkomplex angebunden, der genau diese Aufgabe übernimmt. Man benötigt daher genau einen Rutheniumkomplex pro Polymerkette.

Die Rutheniumkomplexe, welche diese Aufgabe übernehmen können sind relativ teuer, was gerade bei der Herstellung kurzer Polymerketten zu hohen Kosten führt. Zudem sind diese Komplexe stark gefärbt, so dass die Polymere ebenfalls eine Färbung aufweisen, was für bestimmte Anwendungen von Nachteil ist. 

Im vorliegenden Forschungsprojekt wollen wir eine von uns gefundene Methode weiterentwickeln, die es erlaubt, den Rutheniumgehalt während der Polymerisation um den Faktor 50 zu reduzieren. Dies bedeutet, dass ein Rutheniumkomplex nun für das Kettenwachstum von durchschnittlich 50 Polymerketten verantwortlich ist. Dies können wir durch den Zusatz sog. reversibler Kettentransferreagenzien erreichen. Diese binden sich an die Enden aller Polymerketten an und erlauben es dem Rutheniumkomplex kontinuierlich von einem Kettenende zum anderen zu wechseln, so dass im zeitlichen Mittel alle Polymerketten ungefähr gleich schnell wachsen.

Für solch einen Polymersationsmechanismus benötigt man prinzipiell keine gut definierten bzw. langlebigen Rutheniumkomplexe. Theoretisch könnten auch kurzlebige und schlecht definierte bzw. undefinierte Katalysatoren anderer Übergangsmetalle verwendet werden, ohne die Kontrolle über die Polymersation einzubüssen. 

Die Entwicklung neuer reversibler Kettentransferreagenzien und die Ausweitung der Methode auf undefinierte Katalysatoren hoher Reaktivität wird in diesem Forschungsprojekt bearbeitet werden.

 

Direct link to Lay Summary Last update: 19.08.2015

Responsible applicant and co-applicants

Employees

Publications

Publication
Catalytic Living Ring Opening Metathesis Polymerisation: The Importance of Ring Strain in Chain Transfer Agents.
Liu Peng, Yasir Mohammad, Kilbinger Andreas F M (2019), Catalytic Living Ring Opening Metathesis Polymerisation: The Importance of Ring Strain in Chain Transfer Agents., in Angewandte Chemie (International ed. in English).
Functional End Groups in Living Ring-Opening Metathesis Polymerization
Kilbinger Andreas F. M. (2019), Functional End Groups in Living Ring-Opening Metathesis Polymerization, in Synlett.
Catalytic living ring-opening metathesis polymerization with Grubbs’ second- and third-generation catalysts
Yasir Mohammad, Liu Peng, Tennie Iris K., Kilbinger Andreas F. M. (2019), Catalytic living ring-opening metathesis polymerization with Grubbs’ second- and third-generation catalysts, in Nature Chemistry, 11(5), 488-494.
Heterotelechelic Polymers by Ring-Opening Metathesis and Regioselective Chain Transfer.
Liu Peng, Yasir Mohammad, Ruggi Albert, Kilbinger Andreas F M (2018), Heterotelechelic Polymers by Ring-Opening Metathesis and Regioselective Chain Transfer., in Angewandte Chemie (International ed. in English), 57(4), 914-917.
Enolesters as chain end-functionalizing agents for the living ring opening metathesis polymerization
Liu Peng, Yasir Mohammad, Kurzen Helena, Hanik Nils, Schäfer Mark, Kilbinger Andreas F. M. (2017), Enolesters as chain end-functionalizing agents for the living ring opening metathesis polymerization, in Journal of Polymer Science Part A: Polymer Chemistry, 55(18), 2983-2990.
Tandem Ring-Opening-Ring-Closing Metathesis for Functional Metathesis Catalysts.
Nagarkar Amit A, Yasir Mohammad, Crochet Aurelien, Fromm Katharina M, Kilbinger Andreas F M (2016), Tandem Ring-Opening-Ring-Closing Metathesis for Functional Metathesis Catalysts., in Angewandte Chemie (International ed. in English), 55(40), 12343-6.

Collaboration

Group / person Country
Types of collaboration
FriMat (Fribourg Center of Nanomaterials) Switzerland (Europe)
- Research Infrastructure
Adolphe Merkle Institute, Fribourg Switzerland (Europe)
- Research Infrastructure

Associated projects

Number Title Start Funding scheme
182059 Synthesis of precision polymers 01.10.2019 Project funding (Div. I-III)
137775 Functional Living Olefin Metathesis Polymers: Methodology Development and Applications 01.10.2011 Project funding (Div. I-III)

Abstract

Living polymerizations consist of two key reaction steps: initiation and propagation. Steps such as termination or irreversible chain transfer reactions must not occur for a polymerization to be called “living”. The one polymerization that comes closest to fulfilling this definition is the anionic polymerization for which chain transfer and termination reactions can be avoided. Living cationic polymerizations and living radical polymerizations were developed much later than living anionic polymerization. These latter polymerizations can be controlled because an equilibrium of active and inactive species reduces the concentration of the active propagating species thereby reducing bimolecular termination reactions.The ring opening metathesis polymerization (ROMP) can be considered a living polymerization method for several types of monomers which prevent chain transfer reactions to the polymer (secondary metathesis reactions). The propagating species located at the polymer chain end is a transition metal carbene (here a ruthenium carbene) which can undergo a formal 2+2 cycloaddition with strained cyclic olefins. For living ROMP, each polymer chain carries one transition metal complex at the chain end. Thus, the existing process requires equimolar amounts of transition metal complex. The high cost of ruthenium metal is one reason why living ROMP has not received much attention in an industrial context.Very recently, the applicant’s research group discovered a synthetic procedure that allows the preparation of living ROMP polymers using only catalytic amounts of a ruthenium carbene complex. The principle of this unpublished method is similar to that described for the RAFT process, i.e. relying on a reversible chain transfer agent. The reversible chain transfer agent for ROMP allows at least a 1:50 reduction in catalyst loading compared to the classical living process. We believe that this new catalytic living ROMP process represents a very important milestone in the development of olefin metathesis polymerizations and will have a great impact on academic and industrial materials chemistry. As the polymerization is catalytic in ruthenium complex the polymers produced benefit from exceptionally low discoloration. In addition to reduced coloration and lower cost, areas in which low residual transition metal loadings are important such as medicinal polymer research will benefit primarily from this invention. Within the research project proposed here we want to explore the limits of our process and answer the following questions: What is the upper molecular weight limit for this polymerization process that still allows control over the molecular weight distribution and full end-functionality? What is the lowest catalyst loading that can still give living ROMP polymers? What new reversible chain transfer agents can be synthesized and what structural criteria do they need to fulfill? All previous work has focused on well-defined ruthenium based carbene complexes. Industrially, ill-defined transition metal complexes are, however, the typical choice for ROMP polymerizations today. These ill-defined catalysts consist of mixtures of carbene complexes of greatly differing metathesis activity. This leads to greatly different initiation and propagation characteristics and the resulting polymers can no longer be considered “living”. We will therefore also investigate the use of our newly developed chain transfer agents in the presence of ill-defined catalyst systems and compare the results to those of the well-defined catalysts. The question addressed in this context is: Can cheaper ill-defined catalyst systems be controlled using a living ROMP chain transfer polymerization? Polymerizations that are not living can not produce narrow molecular weight distributions, allow the formation of block-copolymers or the selective synthesis of mono-end functional polymers. Industrially, the ability to prepare block copolymer structures is important as this gives access to new materials properties. This research proposal investigates the mechanism and structural requirements for a fundamentally new olefin metathesis polymerization mechanism that may have a significant impact on academic and industrial polymer research.
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