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Université de Fribourg

Azo-Containing Polymers with Degradation On-Demand Feature

Ayer, Mathieu A. ; Simon, Yoan C. ; Weder, Christoph

In: Macromolecules, 2016, vol. 49, p. 2917–2927

Molecules comprising aliphatic azo moieties are widely used as radical polymerization initiators, but only a few studies have explored their usefulness as stimuli-responsive motifs in macromolecular constructs. The controlled degradation of azo-containing polymers has indeed remained largely unexplored. Here we present the syntheses of linear azo-containing polyamides and polyurethanes and...

Université de Fribourg

Functional polymers through mechanochemistry

Schrettl, Stephen ; Balkenendea, Diederik W. R. ; Calvino, Céline ; Karman, Marc ; Lavrenova, Anna ; Neumann, Laura N. ; Sagaraa, Yoshimitsu ; Verde-Sestoa, Ester ; Giannantonio, Michela di ; Simon, Yoan C. ; Fromm, Katharina M. ; Lattuada, Marco ; Weder, Christoph

In: CHIMIA International Journal for Chemistry, 2019, vol. 73, no. 1, p. 7–11

While coupling mechanical and chemical processes is widespread in living organisms, the idea to harness the mechanically induced dissociation of weak covalent and non- covalent bonds to create artificial materials that respond to mechanical stimulation has only recently gained attention. Here we summarize our activities that mainly revolve around the exploitation of non-covalent interactions...

Université de Fribourg

Healable Supramolecular Polymer Solids

Montero de Espinosa, Lucas ; Fiore, Gina L. ; Weder, Christoph ; Foster, E. Johan ; Simon, Yoan C.

In: Progress in Polymer Science, 2015, vol. 49-50, p. 60-78

The reversible nature of non-covalent interactions between constituting building blocks permits one to tem¬po¬ra¬rily disassemble supramolecular polymers through the application of an appro¬pri¬ate external stimulus “on command”. This framework has recently emerged as a general design strategy for the development of healable polymer systems. The approach exploits that the temporary...

Université de Fribourg

Light-responsive azo-containing organogels

Ayer, Mathieu A. ; Schrettl , Stephen ; Balog, Sandor ; Simon, Yoan C. ; Weder, Christoph

In: Soft Matter, 2017, vol. 13, no. 22, p. 4017-4023

While azo compounds are widely employed as radical initiators, they have rarely been used as stimuli-responsive motifs in macromolecular constructs. In this study, an azo-based cross-linker was prepared and reacted with poly(vinyl alcohol) to afford a series of stimuli-responsive organogels. Irradiation of these materials with UV light causes de-cross-linking and triggers a solid-to-liquid phase...

Université de Fribourg

A mechano- and thermoresponsive luminescent cyclophane

Sagara, Yoshimitsu ; Simon, Yoan C. ; Tamaoki, Nobuyuki ; Weder, Christoph

In: Chemical Communications, 2016, vol. 52, p. 5694–5697

The first fluorescent cyclophane with mechano- and thermoresponsive solid-state fluorescence characteristics is reported. The new cyclophane comprises two 9,10-bis(phenylethynyl)anthracene moieties that are bridged by tetraethylene glycol spacers. The stimuli-responsiveness is based on molecular assembly changes.

Université de Fribourg

Mechanochemistry in polymers with supramolecular mechanophores

Haehnel, Alexander P. ; Sagara, Yoshimitsu ; Simon, Yoan C. ; Weder, Christoph

In: Topics in current chemistry, 2015, vol. 369, p. 345-375

Mechanochemistry is a burgeoning field of materials science. Inspired by nature, many scientists have looked at different ways to introduce weak bonds into polymeric materials to impart them with function and in particular mechano-responsiveness. In the following sections, the incorporation of some of the weakest bonds, i.e. non-covalent bonds, into polymeric solids is being surveyed. This review...

Université de Fribourg

Mechanochemistry with Metallosupramolecular Polymers

Balkenende, Diederik W. R. ; Coulibaly, Souleymane ; Balog, Sandor ; Simon, Yoan C. ; Fiore, Gina L. ; Weder, Christoph

In: Journal of the American Chemical Society, 2014, vol. 136, no. 29, p. 10493-10498

The transduction of mechanical force into useful chemical reactions is an emerging design approach to impart soft materials with new functions. Here, we report that mechanochemical transductions can be achieved in metallo-supramolecular polymers. We show that both reversible and irreversible reactions are possible and useful to create me-chanically responsive materials that display new...

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...