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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

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

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

Speckle-visibility spectroscopy of depolarized dynamic light scattering

Bossert, David ; Natterodt, Jens ; Urban, Dominic A. ; Weder, Christoph ; Petri-Fink, Alke

In: The Journal of Physical Chemistry B, 2017, vol. 121, no. 33, p. 7999–8007

We show that the statistical analysis of photon counts in depolarized dynamic light scattering experiments allows for the accurate characterization of the rotational Brownian dynamics of particles. Unlike photon correlation spectroscopy, the technique is accurate even at low temporal resolution and enables discontinuous data acquisition, which offers several advantages. To demonstrate the...

Université de Fribourg

Optically healable supramolecular polymers

Burnworth, Mark ; Tang, Liming ; Kumpfer, Justin R. ; Duncan, Andrew J. ; Beyer, Frederick L. ; Fiore, Gina L. ; Rowan, Stuart J. ; Weder, Christoph

In: Nature, 2011, vol. 472, p. 334–337

Polymers with the ability to repair themselves after sustaining damage could extend the lifetimes of materials used in many applications. Most approaches to healable materials require heating the damaged area. Here we present metallosupramolecular polymers that can be mended through exposure to light. They consist of telechelic, rubbery, low-molecular-mass polymers with ligand end groups that are...

Université de Fribourg

Approaches to Polymeric Mechanochromic Materials

Calvino, Céline ; Neumann, Laura ; Weder, Christoph ; Schrettl, Stephen

In: Journal of Polymer Science, Part A: Polymer Chemistry, 2017, p. 640-652

Université de Fribourg

Elucidating the potential biological impact of cellulose nanocrystals

Camarero-Espinosa, Sandra ; Endes, Carola ; Mueller, Silvana ; Petri-Fink, Alke ; Rothen-Rutishauser, Barbara ; Weder, Christoph ; Clift, Martin James David ; Foster, E. Johan

In: Fibers, 2016, vol. 4, no. 3, p. 21

Cellulose nanocrystals exhibit an interesting combination of mechanical properties and physical characteristics, which make them potentially useful for a wide range of consumer applications. However, as the usage of these bio-based nanofibers increases, a greater understanding of human exposure addressing their potential health issues should be gained. The aim of this perspective is to...

Université de Fribourg

Not just fundamental research: education, equal opportunities, knowledge and technology transfer, and communication at the nccr bio-inspired materials

Capper, Scott ; Haskal, Eliav ; Kilbinger, Andreas ; Montero de Espinosa, Lucas ; Rothen-Rutishauser, Barbara ; Rüegg, Curzio ; Weder, Christoph

In: CHIMIA International Journal for Chemistry, 2019, vol. 73, no. 1, p. 86–89

Besides conducting excellent fundamental research in domains of strategic importance, the National Centers of Competence in Research (NCCRs) also aim to become centers of reference for education, equal opportunities, and knowledge and technology transfer. These activities are supported by a communication strategy focused on specific target groups. This article describes some of the main...