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IRTG / Soft Matter Science
Freiburger Materialforschungszentrum
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79104 Freiburg, Germany

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You are here: Home Events Prof. Dimitris Vlassopoulos "Comb and star macromolecules : some rheological consequences of macromolecular topology"

Prof. Dimitris Vlassopoulos "Comb and star macromolecules : some rheological consequences of macromolecular topology"

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FORTH, Institute of Electronic Structure & Laser, and University of Crete, Department of Materials Science & Technology, Heraklion, Crete, Greece

What
  • Seminar
When Sep 01, 2015
from 10:30 AM to 11:15 AM
Where ICS Strasbourg - Amphithéâtre Henri Benoît
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Branching is known to play a key role in the properties of entangled polymers. At the same time, high level of branching leads to molecular structures such as hyperbranched polymers, dendritic Cayley-tree types of polymers etc, which can also be viewed as soft colloids. We discuss our efforts attempting at bridging the interesting gap between polymers and colloids by accessing highly functionalized well-characterized polymers and exploring their properties with emphasis on dynamics and rheology. We show two examples. (i) Regular entangled comb polymers exhibit interesting nonlinear rheological properties in shear (thinning) and uniaxial extension (hardening). We show that the concept of dynamic dilution provides a framework for understanding them. (ii) High-molar mass star polymers with changing functionality can respond as regular entangled stars or soft colloids either in solution or in melt. In solution in particular they exhibit intriguing properties and their (ultra)softness is responsible for a variety of new metastable states and transitions at high fractions in molecular or polymeric solvents. We discuss here an interesting thermoreversible melting phenomenon of a depletion gel in star-linear polymer mixtures. Finally, we close with some thoughts on a relatively new class of hyperbranched polymers, dendronized polymers. They are similar to bottlebrushes but each branch is a dendrimer. By varying the molar mass of the backbone and the dendrimer generation it is possible to switch from polymer-dominated to colloid-like response, hence these systems offer tunability as well as complexity.

These examples demonstrate that polymer chemistry holds the premise for exploring and understanding exciting novel properties of soft matter.

Work in collaboration with J. Roovers (Ottawa), N. Hadhichristidis (KAUST), M. Gauthier (Waterloo), K. Matyjaszewski (Carnegie-Mellon) and A. D. Schlüter (ETH Zürich).

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