Université de Fribourg

Light-Activated Healing of Metallosupramolecular Polymers

Fiore, Gina L. ; Rowan, Stuart J. ; Weder, Christoph

In: CHIMIA International Journal for Chemistry, 2011, vol. 65, no. 9, p. 745

Université de Fribourg

Stress transfer in cellulose nanowhisker composites—Influence of whisker aspect ratio and surface charge

Rusli, Rafeadah ; Shanmuganathan, Kadhiravan ; Rowan, Stuart J. ; Weder, Christoph ; Eichhorn, Stephen J.

In: Biomacromolecules, 2011, vol. 12, no. 4, p. 1363–1369

The mechanically induced molecular deformation of cellulose nanowhiskers embedded in subpercolation concentration in an epoxy resin matrix was monitored through Raman spectroscopy. Cellulose nanowhiskers isolated by sulfuric acid hydrolysis from tunicates and by sulfuric acid hydrolysis and hydrochloric acid hydrolysis from cotton were used to study how the aspect ratio (ca. 76 for tunicate and...

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

In vivo deployment of mechanically adaptive nanocomposites for intracortical microelectrodes

Harris, J. P. ; Hess, Andreas E. ; Rowan, Stuart J. ; Weder, Christoph ; Zorman, C. A. ; Tyler, D. J. ; Capadona, Jeffrey R.

In: Journal of Neural Engineering, 2011, vol. 8, no. 4, p. 046010

We recently introduced a series of stimuli-responsive, mechanically adaptive polymer nanocomposites. Here, we report the first application of these bio-inspired materials as substrates for intracortical microelectrodes. Our hypothesis is that the ideal electrode should be initially stiff to facilitate minimal trauma during insertion into the cortex, yet become mechanically compliant to match the...

Université de Fribourg

Bioinspired mechanically adaptive polymer nanocomposites with water-activated shape-memory effect

Mendez, Julie ; Annamalai, Pratheep K. ; Eichhorn, Stephen J. ; Rusli, Rafeadah ; Rowan, Stuart J. ; Foster, E. Johan ; Weder, Christoph

In: Macromolecules, 2011, vol. 44, no. 17, p. 6827–6835

New biomimetic, stimuli-responsive mechanically adaptive nanocomposites, which change their mechanical properties upon exposure to water and display a water-activated shape-memory effect, were investigated. These materials were produced by introducing rigid cotton cellulose nanowhiskers (CNWs) into a rubbery polyurethane (PU) matrix. A series of materials with CNW concentrations of 2–20% v/v...

Université de Fribourg

Self-assembly and alignment of semiconductor nanoparticles on cellulose nanocrystals

Padalkar, Sonal ; Capadona, Jeff R. ; Rowan, Stuart J. ; Weder, Christoph ; Moon, Robert J. ; Stanciu, Lia A.

In: Journal of Materials Science, 2011, vol. 46, no. 17, p. 5672-5679

The synthesis of cadmium sulfide (CdS), zinc sulfide (ZnS), and lead sulfide (PbS) nanoparticle chains on cellulose nanocrystal (CNC) templates can be accomplished by the reaction of the precursor salts. The use of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), was critical for the synthesis of well-defined semiconductor nanoparticle chains on the surface of the CNCs. The...

Université de Fribourg

Stress-transfer in anisotropic and environmentally adaptive cellulose whisker nanocomposites

Rusli, Rafeadah ; Shanmuganathan, Kadhiravan ; Rowan, Stuart J. ; Weder, Christoph ; Eichhorn, Stephen J.

In: Biomacromolecules, 2010, vol. 11, no. 3, p. 762–768

Quantitative insights into the stress-transfer mechanisms that determine the mechanical properties of tunicate cellulose whisker/poly(vinyl acetate) nanocomposites were gained by Raman spectroscopy. The extent of stress-transfer is influenced by local orientation (or anisotropy) of the whiskers, which in turn is governed by the processing conditions used to fabricate the nanocomposites....

Université de Fribourg

Biomimetic mechanically adaptive nanocomposites

Shanmuganathan, Kadhiravan ; Capadona, Jeffrey R. ; Rowan, Stuart J. ; Weder, Christoph

In: Progress in Polymer Science, 2010, vol. 35, no. 1-2, p. 212–222

The development of a new class of mechanically adaptive nanocomposites has been inspired by biological creatures such as sea cucumbers, which have the ability to reversibly change the stiffness of their dermis. Several recent studies have related this dynamic mechanical behaviour to the distinctive nanocomposite architecture of the collagenous tissue, in which interactions among rigid collagen...

Université de Fribourg

Bio-inspired mechanically-adaptive nanocomposites derived from cotton cellulose whiskers

Shanmuganathan, Kadhiravan ; Capadona, Jeffrey R. ; Rowan, Stuart J. ; Weder, Christoph

In: Journal of Materials Chemistry, 2010, vol. 20, p. 180-186

A new series of biomimetic, stimuli-responsive nanocomposites, which change their mechanical properties upon exposure to physiological conditions, was investigated. The materials were produced by introducing percolating networks of cellulose whiskers isolated from cotton into poly(vinyl acetate). Below the glass-transition temperature (Tg∼ 63 °C), the tensile storage moduli...