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Functional Olefin Metathesis Polymers: Methodology Development and Applications

English title Functional Olefin Metathesis Polymers: Methodology Development and Applications
Applicant Kilbinger Andreas F. M.
Number 134642
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 01.05.2011 - 30.09.2011
Approved amount 54'172.00
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All Disciplines (2)

Discipline
Organic Chemistry
Material Sciences

Keywords (6)

polymers; ring opening metathesis polymerization; block copolymers; end-functional polymers; olefin metathesis; block copolymer microphase separation

Lay Summary (English)

Lead
Lay summary

The first two sub-projects deal withthe development of new synthetic methods that allow the synthesis of polymerchains with precisely defined end-groups. The ends of long polymer chains oftenneed to be chemically different to the rest of the polymer chain in order toallow their attachment to surfaces or to synthesize more complex polymerarchitectures. The ring opening metathesis polymerization (ROMP) usingruthenium carbene initiators developed recently by Grubbs (Nobel Prize inChemistry 2005) allows the synthesis of well-defined polymers. However, onlyfew methods were reported until recently that addressed the functionalizationof the polymer chain ends. The work proposed here deals with the development ofnew synthetic procedures that allow control over the nature of the polymerchain ends in ROMP polymers.

The third sub-project deals with thesynthesis of diblock copolymers, i.e. linear polymer chains that consist of twochemically different strands covalently linked via their chain ends. Suchpolymers often adopt interesting solid state phases because the two chemically linkedstrands try to separate from each other. As they cannot fully separate due totheir chemical linkage, they form periodic patterns in the solid state in whichregions of different chemical composition alternate. Some of these patternedsolid state structures (for example the so called gyroid phase) are envisagedto be of great interest for the fabrication of solar cells and other electronicdevices. However, the synthesis of these more interesting phases is oftendifficult to achieve in a controlled manner. In our sub-project we propose thesynthesis of new polymers that can be altered after the polymerization in sucha way as to target these interesting solid state phases with high confidence.

 

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Associated projects

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

Abstract

One of the fundamental requirements in polymer chemistry today is the control of functionality and functionality placement on various size scales ranging from individual polymer chains to micellar aggregates to self organised phases in the solid state. The three research projects described below address different aspects of this requirement, dealing with the placement of functional polymer end-groups in the first two projects and control over the self assembled solid state phases via post polymerisation functionalisation of block copolymers in the third.The first research project deals with the development of methods for introducing end-groups for olefin metathesis polymers. Since the recent development of very stable and functional group tolerant ruthenium carbene complexes by Grubbs et al., the ring opening metathesis polymerisation (ROMP) has received increased attention. However, one major drawback of this living polymerisation technique compared to most others was, that it didn‘t offer a straightforward synthetic method for introducing functional end-groups. We recently developed several ways to overcome this limitation and hydroxyl, thiol, aldehyde and carboxylic acid groups are now readily available as ROMP end-groups. In this proposal we focus on the introduction of amine or protected amine end-groups via the so-called Sacrificial Synthesis. This technique makes use of cyclic olefins that can later on be cleaved to yield the required functionality at the chain end. Amines are very useful nucleophiles that can readily be further functionalised by reductive alkylation of amide formation. More complex polymeric architectures or polymer conjugates with functional molecules, oligomers or biomolecules are thus readily accessible.Secondly, the synthesis of a universal end-capping reagent is proposed based on functionally substituted vinyl esters or vinyl halides. Very recent reports indicate that such compounds are likely to act as ROMP terminating agents and can easily be synthesised and derivatised. As they carry a readily functionalisable group in addition to a group that forms a non-metathesis active carbene, such compounds will be particularly useful for the attachment to macroscopic surfaces, nanoparticles or functional solid supports. Solid surfaces derivatised in this way will readily react with the polmeric ruthenium carbene such that the polymer block will be transferred onto the surface. In the case of solid supports, the result will be a polymer conjugate with a sequence controlled oligomer prepared on the solid support, for example a peptide.Making use of this functional group tolerance, we propose a third project dealing with the synthesis of functionalisable diblock copolymers via ROMP. This can either be achieved by subsequently polymerising two types of monomers or else via preparing an end-functionalised ROMP polymer that is later on attached to a second polymer chain via its end-group. The second approach heavily relies on methods for end-functionalisation like those already developed in our group and will greatly benefit from further end-functionalisation methodology as proposed above. The diblock copolymers will undergo a microphase separation adopting the well-known solid state phases depending on the volume fraction of the individual polymer blocks. At least one of the two blocks will, however, carry functionalities that can be derivatised in a subsequent reaction. This will allow a post polymerisation volume fraction alteration and hence the possibility to change position in the phase diagram. This will be particularly useful for targeting „difficult phases“ such as the gyroid phase, a bicontinuous phase of two interpenetrating polymer blocks, which takes up only a small area in the phase diagram.
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