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Structure of polyelectrolyte brushes studied by coarse grain simulations


As an example of a very low friction system, Monte Carlo Brownian dynamics simulations have been used to calculate equilibrium structures of a polyelectrolyte brush grafted onto planes. The polymers were calculated in a semi-flexible coarse-grain model that is appropriate to treat the charge density of the polyion. The effect of linear charge density on the polyion ξ, the surface negative charge, and added salts were studied. In salt-free solution, scaling theories predicted the structure well in the low — region. In the high ξ region, additional shrinkage was found from the theories due to counterion condensation. The effect of surface charge showed not only the repulsion of the polyion from the surface but also the shrinkage in the high ξ region due to the additional counterions required for electrical neutrality. The addition of salts led to the shrinkage of the brush heights, and in the high ξ region, additional extension was found. The computational strategy for calculating the friction dynamics of the system is also discussed.


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Correspondence to Hitoshi Washizu.

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This article is published with open access at

A preliminary version of this work was presented at the 3rd International Symposium on Tribology of IFToMM, Luleå, Sweden, 2013.

Hitoshi WASHIZU. He received his M.A. and Ph. D degrees in Physical Chemistry from the University of Tokyo, Japan, in 1998 and 2001 respectively. He joined Toyota Central R&D Labs., Inc., from 2001. His current position is a leader of Washizu Research Group, Forintier Research Center of the TCRD. He is also a delegate of his research group in the Elements Strategy Initiative for Catalysts and Batteries, Kyoto University. His research areas cover computational chemistry of surfaces in tribology, polymer science, and electrochemistry.

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Washizu, H., Kinjo, T. & Yoshida, H. Structure of polyelectrolyte brushes studied by coarse grain simulations. Friction 2, 73–81 (2014).

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  • polyelectrolyte brush
  • friction
  • Monte Carlo Brownian dynamics simulation
  • soft materials
  • automotive tribology