Download Polymer mediated (PM) interactions between colloidal particles are

Polymer mediated (PM) interactions between colloidal particles are in the core of many biologically
and technologically relevant phenomena such as red blood cell adhesion, DNA mediated depletion
interactions and size-exclusion polymer chromatography. In our group, we study PM interactions by
developing and making use of analytical theoretical methods primarily based on the self-consistent
field theory. Our theoretical calculations help to understand the dependence of the polymermediated forces on the separation between particles, particle size and shape, and properties of the
host polymer systems. Our results show, in agreement with previous Monte Carlo simulations and
experiments, that PM interactions are particularly sensitive to the colloid size and the way in which
the polymers interact with the colloid surfaces. Two representative cases of our theoretical results
illustrating these conclusions are shown in Fig.1 and 2.
Figure 1. Comparison of the potentials of the depletion interactions
acting between nanoparticles, mediated by non-adsorbing
polymers calculated by developed self-consistent field theory (red
line), Monte Carlo simulations (points) and PRISM theory (blue line).
Fig. 1 shows the comparison of our theoretical findings
with the results of Monte Carlo simulations of the
depletion potential mediated by non-adsorbing polymers in the protein limit, where the size of the
colloids is much smaller than the gyration radius RG of polymers. Fig.2 shows the comparison of our
theory with the experiment performed for the opposite case of
large (compared to RG) colloids mediated by irreversibly
adsorbed polymers.
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Figure 2. Comparison of the predictions of the analytic self-consistent field
theory of the polymer mediated force acting between large colloids bearing
irreversibly adsorbed polymer layers with the experiment performed for
adsorbed PEO polymers immersed in toluene for selected molecular weights of
PEO.
These Figures clearly show that the developed analytical self-consistent field theory gives an
adequate description of experiments and simulations. Inspired by the success of the developed
theory in explaining the observed pair polymer mediated interactions between colloids, we have
used our approach to describe the many-body effects on the PM depletion interaction caused by
the presence of hard walls and other colloids. In particular, we have found out that the long range
character of the PM interactions causes significant effect imposed on these interactions by the walls
of the vessel containing a polymer-colloid system. As an immediate extension of the developed
theory, we plan to modify our analytical approach in order to describe PM interactions in dense
polymer systems (e.g. polymer melts) and study the effect of these interactions on the rheological
properties (e.g. shear viscosity) of nano-particle filled dense polymer systems.
1. A.I.Chervanyov, G. Heinrich, Immersion energy and polymer-mediated depletion interactions between
nano-colloids as studied by analytic self-consistent field theory, Phys. Rev. E, xxxx (2012).
2. A.I.Chervanyov, Depletion forces acting on nanoparticles in confined polymer systems: Potential theory,
Phys. Rev. E 83(6), 061801 (2011).
3. M. Horecha, V. Senkovskyy, A. Synytska, M. Stamm, A. I. Chervanyov, A. Kiriy, Ordered Surface Structures
from PNIPAM-Based Loosely Packed Microgel Particles, Soft Matter 6, 5980 (2010).
4. A.I.Chervanyov, G. Heinrich, Potential theory of the depletion interaction in the colloid-polymer mixtures, J.
Chem. Phys. 131, 234907 (2009).
5. A.I.Chervanyov, S.A. Egorov, Interaction between irreversibly adsorbed polymer layers: is the mean field
picture really inadequate?, Phys. Rev. E 69(4), 041801 (2004).