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Université de Fribourg

Crystal structure of highly concentrated, ionic microgel suspensions studied by neutron scattering

Gasser, Urs ; Sierra-Martin, B. ; Fernandez-Nieves, A.

In: Physical Review, 2009, vol. 79, no. 5, p. 051403

We present a neutron-scattering investigation of the crystal structure formed by pH-sensitive poly(2-vinylpyridine) microgel particles with 5 wt % of cross-linker. We focus on highly swollen particles and explore concentrations ranging from below close packing to well above close packing, where the particles are forced to shrink and/or interpenetrate. The crystal structure is found to be random...

Université de Fribourg

Novel phase morphologies in a microphase-separated dendritic polymer melt

Lee, Won Bo ; Elliott, Richard ; Mezzenga, Raffaele ; Fredrickson, Glenn H.

In: Macromolecules, 2009, vol. 42, no. 3, p. 849–859

Equilibrium phase morphologies of two different dendritic block copolymer melts are calculated and compared. These copolymers have a pitchfork-like architecture and consist of three distinct blocks that correspond roughly to the handle, the connecting middle dendron structure, and the attached tines of a pitchfork. The first melt considered consists of a copolymer that has a simple Y-junction...

Université de Fribourg

Linear-to-branched micelles transition: a rheometry and diffusing wave spectroscopy (DWS) study

Oelschlaeger, C. ; Schopferer, M. ; Scheffold, Frank ; Willenbacher, N.

In: Langmuir, 2009, vol. 25, no. 2, p. 716–723

The frequency-dependent shear modulus of aqueous wormlike micellar solutions of cetylpyridinium chloride (CPyCl) and sodium salicylate (NaSal) has been measured over a broad frequency range from 10⁻² to 10⁶ rad/s using diffusing wave spectroscopy (DWS) based tracer microrheology as well as mechanical techniques including rotational rheometry and oscillatory squeeze flow. Good agreement...

Université de Fribourg

Synthesis and characterization of novel functional electrosterically stabilized colloidal particles prepared by emulsion polymerization using a strongly ionized amphiphilic diblock copolymer

Mohanty, Priti S. ; Dietsch, Hervé ; Rubatat, Laurent ; Stradner, Anna ; Matsumoto, K. ; Matsuoka, H. ; Schurtenberger, Peter

In: Langmuir, 2009, vol. 25, no. 4, p. 1940–1948

Amphiphilic diblock copolymers such as poly(styrene)-block-poly(styrene sulfonate) (PS-b-PSS) (Matsuoka, H.; Maeda, S.; Kaewsaiha, P.; Matsumoto, K. Langmuir 2004, 20, 7412), belong to a class of new polymeric surfactants that ionize strongly in aqueous media. We investigated their self-assembly behavior in aqueous solutions and used them as an emulsifier to...

Université de Fribourg

Functional columnar liquid crystalline phases from ionic complexes of dendronized polymers and sulfate alkyl tails

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

In: Macromolecular Symposia, 2008, vol. 270, no. 1, p. 58 - 64

We describe how cationic dendronized polymers of generations 1, and 2 and anionic monoalkyl tails can be combined by supramolecular ionic complexation into comb-like liquid crystalline polymers. The final structures in bulk of these supramolecular complexes were studied by differential scanning calorimetry (DSC), cross-polarized optical microscopy (CPOM), small angle x-rays scattering (SAXS) and...

Université de Fribourg

Real space imaging and molecular packing of dendronized polymer-lipid supramolecular complexes

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

In: Macromolecules, 2007, vol. 40, no. 21, p. 7609 -7616

The present work describes the molecular structure and the topology in real space of self-assembled comblike liquid crystalline polymers based on supramolecular ionic complexation of dendronized polymers and lipids. The molecular organization was studied as a function of the generation of the dendronized polymers and the length of the lipid tails, both parameters being known to strongly influence...

Université de Fribourg

Comblike liquid-crystalline polymers from ionic complexation of dendronized polymers and lipids

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

In: Macromolecules, 2007, vol. 40, no. 8, p. 2822 -2830

This work describes the self-assembly behavior, the structure, the state, and phase diagrams of comblike liquid-crystalline polymers obtained by supramolecular ionic complexation of cationic dendronized polymers (PG1-PG3) and anionic sulfonated lipid surfactants. In order to characterize the influence of both the polymer and the surfactant on the microphase separation of...

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...