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Université de Fribourg

Functional polymer blends and nanocomposites

Weder, Christoph

In: Chimia, 2009, vol. 63, no. 11, p. 758–763

The broad class of (multi)functional polymers with unusual combinations of optical, electronic, mechanical and other properties is attracting significant interest, because it conceptually combines the advantages of polymers - low cost, ease of processing and a range of attractive mechanical characteristics - with the specific, tailorable properties of functional organic molecules. The caveat is...

Université de Fribourg

Stimuli-responsive mechanically adaptive polymer nanocomposites

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

In: ACS Applied Materials & Interfaces, 2009, vol. 2, no. 1, p. 165–174

A new series of biomimetic stimuli-responsive nanocomposites, which change their mechanical properties upon exposure to physiological conditions, was prepared and investigated. The materials were produced by introducing percolating networks of cellulose nanofibers or “whiskers” derived from tunicates into poly(vinyl acetate) (PVAc), poly(butyl methacrylate) (PBMA), and blends of these...

Université de Fribourg

Influence of temperature on low-power upconversion in rubbery polymer blends

Singh-Rachford, Tanya N. ; Lott, Joseph ; Weder, Christoph ; Castellano, Felix N.

In: Journal of the American Chemical Society, 2009, vol. 131, no. 33, p. 12007–12014

The upconverting properties of a dye cocktail composed of palladium(II) octaethylporphyrin (PdOEP, triplet sensitizer) and 9,10-diphenylanthracene (DPA, triplet acceptor/annihilator) were investigated as a function of temperature in several low glass transition temperature (Tg) polymer hosts including an ethyleneoxide-epichlorohydrin copolymer (EO-EPI) and the polyurethanes...

Université de Fribourg

Supramolecular routes towards liquid crystalline side-chain polymers

Hammond, Matthew R. ; Mezzenga, Raffaele

In: Soft Matter, 2008, vol. 4, p. 952-961

Supramolecular attachment of mesogenic or non-mesogenic side chains to polymer backbones can result in the formation of liquid crystalline morphologies. The various parameters that can be tuned in order to achieve these morphologies, such as the type of non-covalent bonding chemistry (hydrogen bonding, ionic bonding, metal coordination, π–π interactions), the polymeric template architecture,...

Université de Fribourg

Coordination polymer networks with s-block metal ions

Fromm, Katharina M.

In: Coordination Chemistry Reviews, 2008, vol. 252, no. 8-9, p. 856-885

Université de Fribourg

Correlated roughness in polymer films containing Maghemite nanoparticles

Kashem, M. M. Abul ; Perlich, J. ; Schulz, Leander ; Roth, S. V. ; Müller-Buschbaum, P.

In: Macromolecules, 2008, vol. 41, no. 6, p. 2186 -2194

Two different uniform thicknesses (8 and 68 nm) of a nanocomposite film comprising diblock copolymer matrix and magnetic nanoparticles filler have been installed in one sample preparation step under identical condition simultaneously. Long-range interface correlations are investigated. Maghemite (F₂O₃) nanoparticles covered with polystyrene chains are incorporated in...

Université de Fribourg

Relation between directed polymers in random media and random-bond dimer models

Jiang, Ying ; Emig, Thorsten

In: Physical Review B, 2007, vol. 75, p. 134413

We reassess the relation between classical lattice dimer models and the continuum elastic description of a lattice of fluctuating polymers. In the absence of randomness, we determine the density and line tension of the polymers in terms of the bond weights of hard-core dimers on the square and the honeycomb lattice. For the latter, we demonstrate the equivalence of the set of complete dimer...

Université de Fribourg

Liquid-crystalline polymers from cationic dendronized polymer-anionic lipid complexes

Canilho, Nadia ; Kasëmi, Edis ; Mezzenga, Raffaele ; Schlüter, Dieter A.

In: Journal of the American Chemical Society, 2006, vol. 128, no. 43, p. 13998-13999

The use of cationic dendronized polymers as a polyelectrolytic system for templating thermotropic liquid-crystalline phases (LC) via complexation and self-assembly with counter-charged ionic lipids is described. The topology of the LC phases resulting from the self-assembly process, their lattice parameter, and the interpenetration of lipid chains is discussed via birefringency analysis and...

Université de Fribourg

Photocount statistics in mesoscopic optics

Balog, Sandor ; Zakharov, Pavel ; Scheffold, Frank ; Skipetrov, S. E.

In: Physical Review Letters, 2006, vol. 97, p. 103901

We report the first observation of the impact of mesoscopic fluctuations on the photocount statistics of coherent light scattered in a random medium. A Poisson photocount distribution of the incident light widens and gains additional asymmetry upon transmission through a suspension of small dielectric spheres. The effect is only appreciable when the average number of photocounts becomes...