# Behavior of block-polyampholytes near a charged surface

- 69 Downloads
- 7 Citations

## Abstract.

The behavior of polyampholytes near a charged planar surface is studied by means of Monte Carlo simulations. The investigated polyampholytes are overall electrically neutral and made up of oppositely charged units (called blocks) that are highly charged and of the the same length. The influence of block length and substrate's surface-charge-density on the adsorption behavior is addressed. A detailed structural study, including local monomer concentration, monomer mean height, and transversal chain size, is provided. It is demonstrated that adsorption is favored for long enough blocks and/or high enough Coulomb interface-ion couplings. By explicitly measuring the chain size in the bulk, it is shown that the charged interface induces either a swelling or a shrinkage of the transversal dimension of the chain depending, in a non trivial manner, on the block length.

### PACS.

82.35.Gh Polymers on surfaces; adhesion 82.35.Jk Copolymers, phase transitions, structure 87.15.Aa Theory and modeling; computer simulation## Preview

Unable to display preview. Download preview PDF.

### References

- Y. Watanabe, K. Kubo, S. Sato, Langmuir
**15**, 4157 (1999) CrossRefGoogle Scholar - M. Dreja, K. Heine, B. Tieke, G. Junkers, J. Colloid Interface Sci.
**191**, 131 (1997) CrossRefGoogle Scholar - S. Neyret, L. Ouali, F. Candau, E. Pefferkorn, J. Colloid Interface Sci.
**176**, 86 (1995) CrossRefGoogle Scholar - J.F. Joanny, J. Phys. II
**4**, 1281 (1994) CrossRefGoogle Scholar - B. Mahltig, P. Müller-Buschbaum, M. Wolkenhauer, O. Wunnicke, S. Wiegand, J.F. Gohy, R. Jérôme, M. Stamm, J. Colloid Interface Sci.
**242**, 36 (2001) CrossRefGoogle Scholar - B. Mahltig, J.F. Gohy, R. Jérôme, M. Stamm, J. Polym. Sci. B
**39**, 709 (2001) CrossRefGoogle Scholar - E. Zhulina, A.V. Dobrynin, M. Rubinstein, Eur. Phys. J. E
**5**, 41 (2001) CrossRefGoogle Scholar - A.V. Dobrynin, Phys. Rev. E
**63**, 051802 (2001) CrossRefADSGoogle Scholar - A.V. Dobrynin, M. Rubinstein, J.F. Joanny, Macromolecules
**30**, 4332 (1997) CrossRefGoogle Scholar - N.P. Shusharina, P. Linse, Eur. Phys. J. E
**6**, 147 (2001) CrossRefGoogle Scholar - J. McNamara, C.Y. Kong, M. Muthukumar, J. Chem. Phys.
**117**, 5354 (2002) CrossRefADSGoogle Scholar - A. Akinchina, N.P. Shusharina, P. Linse, Langmuir
**20**, 10351 (2004) CrossRefGoogle Scholar - R. Messina, Phys. Rev. E
**70**, 051802 (2004);**74**, 049906(E) (2006) CrossRefADSMathSciNetGoogle Scholar - R. Messina, J. Chem. Phys.
**124**, 014705 (2006) CrossRefADSGoogle Scholar - Only the monomer-monomer excluded volume interaction was not modeled by a hard-sphere potential. There, a purely repulsive Lennard-Jones potential was used Google Scholar
- A.G. Moreira, R.R. Netz, Europhys. Lett.
**52**, 705 (2000) CrossRefADSGoogle Scholar - Note that in our case where we have only one chain and no contact with a bulk reservoir, so that the monomer density profile will necessarily tend to zero. This means that the density will always show a peak (although very small in practice in case of depletion) Google Scholar
- A. Shafir, D. Andelman, R.R. Netz, J. Chem. Phys.
**119**, 2355 (2003) CrossRefADSGoogle Scholar - P. de Gennes,
*Scaling Concepts in Polymer Physics*(Cornell University Press, Ithaca, New York, 1979) Google Scholar - R. Varoqui, J. Phys. II
**3**, 1097 (1993) CrossRefGoogle Scholar - I. Borukhov, D. Andelman, H. Orland, Macromolecules
**31**, 1665 (1998) CrossRefGoogle Scholar - A. Esztermann, R. Messina, H. Löwen, Europhys. Lett.
**73**, 864 (2006) CrossRefADSGoogle Scholar - To be more explicit, let us consider a diblock PA where the two oppositely charged blocks of length b are characterized by a linear charge density ± ξe (with ξ>0).
*Neglecting*the block-block correlations, the minimum energy configuration E_{stretched}in the adsorbed stretched state is given (in units of k_{B}T) by \(E_{stretched} = \int_0^b \frac{z}{\lambda}\xi dz - \int_b^{2b} \frac{z}{\lambda}\xi dz = -\frac{\xi b^2}{\lambda}\) whereas for the “L” structure we get \(E_{{\rm L}} = -\int_0^b \frac{z}{\lambda}\xi dz = -\frac{\xi b^2}{2\lambda}\) which shows that \(\Delta E = E_{{\rm L}}- E_{stretched} = \frac{\xi b^2}{2\lambda} > 0\). In this reasoning and for the sake of simplicity, we have also ignored the presence of the counterions that ultimately should not change the sign of ΔE Google Scholar