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Université de Fribourg

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

Nagarkar, Amit A. ; Yasir, Mohammad ; Crochet, Aurelien ; 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

Mechanically induced cis-to-trans isomerization of carbon–carbon double bonds using atomic force microscopy

Radiom, Milad ; Kong, Phally ; Maroni, Plinio ; Schäfer, Mark ; Kilbinger, Andreas F. M. ; Borkovec, Michal

In: Physical Chemistry Chemical Physics, 2016, vol. 18, no. 45, p. 31202–31210

Cis-to-trans isomerization of carbon–carbon double bonds can be induced by the application of mechanical force. Using single molecule force spectroscopy by means of atomic force microscopy (AFM) we pulled polymer molecules which contained cis double bonds in the backbone. In the force versus extension profiles of these polymers, a sudden extension increase is observed which is due to the...

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

Branched polymers via ROMP of termimers

Hanik, Nils ; Kilbinger, Andreas F. M.

In: Macromolecular Rapid Communications, 2016, vol. 37, no. 6, p. 532–538

Today's olefin metathesis catalysts show high reactivity, selectivity, and functional group tolerance and allow the design of new syntheses of precisely functionalized polymers. Here the synthesis of a new end-capping reagent is investigated allowing the introduction of a highly reactive activated ester end-group at the polymer chain end as well as its prefunctionalization to directly...

Université de Fribourg

The role of mass and length in the sonochemistry of polymers

Schaefer, Mark ; Icli, Burcak ; Weder, Christoph ; Lattuada, Marco ; Kilbinger, Andreas F. M. ; Simon, Yoan C.

In: Macromolecules, 2016, vol. 49, no. 5, p. 1630–1636

The ultrasound-induced cleavage of macromolecules has become a routine experiment in the emerging field of polymer mechanochemistry. To date, it has not been conclusively proven whether the molecular weight of a polymer or its contour length is the determining factor for chain scission upon ultrasonication. Here we report comparative experiments that confirm unequivocally that the contour length...

Université de Fribourg

Toward large tubular helices based on the polymerization of tri(benzamide)s

Schulze, Maren ; Kilbinger, Andreas F. M.

In: Journal of Polymer Science Part A: Polymer Chemistry, 2016, p. -

Herein we present the synthesis and polycondensation of mono- and di-N-protected, bis-substituted tri(benzamide)s with the aim to create large, tubular helices. We synthesized 2,4-dimethoxy and 2,5-bis-TEGylated aminobenzoic acid derivatives as bent and linear monomers and introduced p-methoxybenzyl (PMB) amide protecting groups to the oligobenzamide backbone. An iterative coupling strategy...

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

Transient anions of cis- and trans-cyclooctene studied by electron-impact spectroscopy

Regeta, Khrystyna ; Nagarka, Amit ; Kilbinger, Andreas F. M. ; Allan, Michael

In: Physical Chemistry Chemical Physics, 2015, vol. 17, no. 6, p. 4696–4700

The effect which deformation of the double bond in trans-cyclooctene (TCO), compared to cis-cyclooctene (CCO), has on its negative ion – and indirectly on the π* virtual orbital – was studied by electron-impact spectroscopy. Differential elastic and vibrational excitation cross sections were measured at a scattering angle of θ = 135°. The vertical attachment energy (VAE) derived from the...

Université de Fribourg

Polyvinyl alcohol as a biocompatible alternative for the passivation of gold nanorods

Kinnear, Calum ; Burnand, David ; Clift, Martin J. D. ; Kilbinger, Andreas F. M. ; Rothen-Rutishauser, Barbara ; Petri-Fink, Alke

In: Angewandte Chemie International Edition, 2014, vol. 53, no. 46, p. 12613–12617

The functionalization of gold nanorods (GNRs) with polymers is essential for both their colloidal stability and biocompatibility. However, a bilayer of the toxic cationic surfactant cetyl trimethylammonium bromide (CTAB) adsorbed on the nanorods complicates this process. Herein, we report on a strategy for the biocompatible functionalization of GNRs with a hydrophobic polymeric precursor,...