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You are here: Home Events Prof. Tatiana Birshtein "Layered structure of planar dendron brushes"

Prof. Tatiana Birshtein "Layered structure of planar dendron brushes"

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Institute of Macromolecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia and St. Petersburg State University, Physics Department

What
  • Seminar
When Nov 26, 2015
from 02:00 PM to 03:00 PM
Where ICS - Amphithéâtre Henri Benoît, 23 Rue du Loess, 67034 Strasbourg
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The talk is devoted to theoretical study of structure and properties of dendron brushes – i.e. monolayers of tree-like macromolecules, or dendrons, densely grafted onto some substrate via the “root spacer” of each dendron – immersed into a solvent. The peculiarity of the dendron brush structure is connected with the increase of the effective thickness of an extended dendron from its root to the top and with the force balance in branching points. The a priori creation of an adequate model for such a structure becomes a rather difficult (or even virtually impossible) task. We were able to develop the general picture of the brush structure a posteriori on the basis of the results obtained by using the Scheutjens-Fleer numerical self-consistent field (SF-SCF) method.

One of the most fascinating properties peculiar to the planar dendron brushes is their layered, or stratified, structure, where dendrons are divided into two or more “populations” with different degree of extension. For example, in a brush made of arm-grafted stars, called “the star brush”, partition of stars between two populations may occur, which results in the two-layer structure of the brush. The effect is connected with the non-linear elasticity and finite extensibility of the stem. A relatively thin brush has a one-layer structure, whereas a relatively thick brush consists of two layers. We developed a simple mean-field theory of the star brush based on a box-like model of the brush and more elaborated analytical self-consistent field model; both approaches take the two-layer structure of the star brush.

We show that by adding a single grafted “probe” linear chain into a two-layered star brush one can construct a molecular switch. The chain admixed to the two-layer star brush can undergo a first order conformational transition from the “coil” conformation close to the grafting surface to the “flower” conformation consisting of an extended "stem", immersed into the brush connected to a coil-like “crown” on the top of the brush. This transition can be provoked by changing either stars grafting density, chain length, or the solvent quality. On the contrary, in a thin one-layer star brush as well as in a conventional brush made of linear chains this transition occurs continuously.


Key publications:
1. A. Polotsky, T. Gillich, O. Borisov, F. Leermakers, M. Textor, T. Birshtein. Dendritic versus Linear Polymer Brushes: Self-Consistent Field Modeling, Scaling Theory, and Experiments, Macromolecules 2010, 43 (22), 9555-9566.
2. A.A. Polotsky, F. A. M. Leermakers, E.B. Zhulina, T.M. Birshtein. On the two-population structure of brushes made of arm-grafted polymer stars. Macromolecules 2012, 45 (17), 7260-7273.
3. O.V. Borisov, A.A. Polotsky, O.V.Rud, E.B. Zhulina, F.A.M. Leermakers, T.M. Birshtein
Dendron brushes and dendronized polymers: a theoretical outlook. Soft Matter 2014, 10 (13), 2093-2101.
4. E.B. Zhulina, V.M. Amoskov, A.A. Polotsky, T.M. Birshtein. Analytical self-consistent field model of arm-grafted starlike polymers in nonlinear elasticity regime, Polymer 2014, 55(20), 5160-5167.
5. E.B. Zhulina, O.V. Borisov, A.A. Polotsky, F.A.M.Leermakers, T.M.Birshtein. Interactions between Brushes of Root-tethered Dendrons, Macromolecules 2014, 47(19), 6932−6945.
6. A.A. Polotsky, A.K. Misorin, E.B. Zhulina, and T.M. Birshtein. Star Brushes under Deformation: Structure and Thermodynamics. Macromolecular Symposia, 2015, 348 (1), 33-43.
7. A.A. Polotsky, F.A.M. Leermakers, and T.M. Birshtein. Structure of Mixed Brushes Made of Arm-grafted Polymer Stars and Linear Chains. Macromolecules 2015, 48 (7), pp 2263–2276.


invited by Dr. Maxim Dolgushev and Dr. Joachim Wittmer

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