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Université de Fribourg

Synthesis of nanometer-sized rod–coil block copolymers

König, Hannah M. ; Kilbinger, Andreas F. M.

In: CHIMIA International Journal for Chemistry, 2013, vol. 67, no. 11, p. 788–790

We present the solid-supported synthesis of a linear rigid rod-like tetradeca(p-benzamide) nanorod as well as a pentadeca( p -benzamide) nanorod carrying an amide N-hexyl side chain at the center of the rod (on the 8th amino acid of the molecule). These nanorods were conjugated with solubilizing poly(ethylene glycol) chains and their solution aggregation was investigated. Both rod–coil block...

Université de Fribourg

Mono-telechelic polymers by catalytic living ring-opening metathesis polymerization with second-generation Hoveyda–Grubbs catalyst

Liu, Peng ; Dong, Zhenghao ; Kilbinger, Andreas F. M.

In: Materials Chemistry Frontiers, 2020, vol. 4, no. 9, p. 2791–2796

The second-generation Hoveyda–Grubbs (HG2) catalyst, which has a small initiation to propagation rate ratio (ki/kp) in ring-opening metathesis polymerization (ROMP), was successfully used in a recently developed catalytic living ROMP. This proved that slow-initiating catalysts can enable ROMP in a living fashion to produce polymers with narrow dispersity and controlled molecular weight. The...

Université de Fribourg

Catalytic living ring opening metathesis polymerisation: the importance of ring strain in chain transfer agents

Liu, Peng ; Yasir, Mohammad ; Kilbinger, Andreas F. M.

In: Angewandte Chemie International Edition, 2019, vol. 58, no. 43, p. 15278–15282

A recently developed catalytic living ring opening metathesis polymerisation (ROMP) was investigated using a series of reversible chain transfer agents (CTA) carrying either cyclopentene or cyclohexene rings, differing only in ring strain. All cyclopentene derivatives examined showed significantly faster reaction rates than the corresponding cyclohexene derivatives. This resulted in lower...

Université de Fribourg

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.

In: Journal of Polymer Science Part A: Polymer Chemistry, 2017, vol. 55, no. 18, p. 2983–2990

Functional enolethers have previously been used to introduce functional end groups at the chain end of ruthenium carbene complex initiated living ring opening metathesis polymers. Here, we investigated whether the weaker π-donating enolesters could equally be used in regio selective reactions with ruthenium carbene complexes and thus as polymer end-functionalization reagents. Enolesters such as...

Université de Fribourg

Degradable precision polynorbornenes via ring-opening metathesis polymerization

Moatsou, Dafni ; Nagarkar, Amit ; Kilbinger, Andreas F. M. ; O'Reilly, Rachel K.

In: Journal of Polymer Science Part A: Polymer Chemistry, 2016, vol. 54, no. 9, p. 1236–1242

In an attempt to introduce monomer sequence control in a growing polynorbornene via ring-opening metathesis polymerization, we employ dioxepins to efficiently determine the location of the monomers on the macromolecule backbone. Owing to the acid-labile acetal group, dioxepins allow scission of the polymer at the point of the dioxepin insertion and thus provide an indirect way to determine...

Université de Fribourg

Tandem ring‐opening–ring‐closing metathesis for functional metathesis catalysts

Nagarkar, Amit A. ; Yasir, Mohammad ; Crochet, Aurélien ; Fromm, Katharina M. ; Kilbinger, Andreas F. M.

In: Angewandte Chemie International Edition, 2016, vol. 55, no. 40, p. 12343–12346

Use of a tandem ring-opening–ring-closing metathesis (RORCM) strategy for the synthesis of functional metathesis catalysts is reported. Ring opening of 7-substituted norbornenes and subsequent ring-closing metathesis forming a thermodynamically stable 6-membered ring lead to a very efficient synthesis of new catalysts from commercially available Grubbs’ catalysts. Hydroxy functionalized...

Université de Fribourg

Catalytic living ring-opening metathesis polymerization

Nagarkar, Amit A. ; Kilbinger, Andreas F. M.

In: Nature Chemistry, 2015, vol. 7, no. 9, p. 718–723

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)...

Université de Fribourg

Efficient amine end-functionalization of living ring-Opening metathesis polymers

Nagarkar, Amit A. ; Crochet, Aurélien ; Fromm, Katharina M. ; Kilbinger, Andreas F. M.

In: Macromolecules, 2012, vol. 45, no. 11, p. 4447–4453

An efficient strategy for the synthesis of monoamine end-functionalized living polymers using ring-opening metathesis polymerization with ruthenium initiators is reported. A new end-capping agent for this purpose was synthesized, and its efficiency for end-functionalization was evaluated using two common ruthenium-based initiators. Finally, terminal cross-metathesis was also explored as...

Université de Fribourg

Telechelics based on catalytic alternating ring-opening metathesis polymerization

Pal, Subhajit ; Alizadeh, Mahshid ; Kilbinger, Andreas F. M.

In: ACS Macro Letters, 2019, vol. 8, no. 10, p. 1396–1401

We describe a protocol to synthesize alternating telechelic ROMP copolymers of 7- oxa-norbornene derivatives and cycloalkenes under catalytic conditions. These copolymers were synthesized using Grubbs’ second-generation catalyst. The sterically less hindered backbone double bonds of the resulting alternating copolymers facilitate the chain transfer (secondary metathesis) reactions. In the ...

Université de Fribourg

Functional metathesis catalyst through ring closing enyne metathesis: one pot protocol for living heterotelechelic polymers

Pal, Subhajit ; Lucarini, Fiorella ; Ruggi, Albert ; Kilbinger, Andreas F. M.

In: Journal of the American Chemical Society, 2018, vol. 140, no. 9, p. 3181–3185

Enyne ring closing metathesis has been used to synthesize functional group carrying metathesis catalysts from a commercial (Ru-benzylidene) Grubbs’ catalysts. The new Grubbs-type ruthenium carbene was used to synthesize living heterotelechelic ROMP polymers without any intermediate purification. Olefin metathesis with a mono substituted alkyne followed by ring closing metathesis with an...