Issue
EPL
Volume 85, Number 5, March 2009
Article Number 58001
Number of page(s) 6
Section Interdisciplinary Physics and Related Areas of Science and Technology
DOI http://dx.doi.org/10.1209/0295-5075/85/58001
Published online 16 March 2009
EPL, 85 (2009) 58001
DOI: 10.1209/0295-5075/85/58001

Phase behaviour and structure of stable complexes of oppositely charged polyelectrolytes

V. Mengarelli1, L. Auvray2 and M. Zeghal1

1   Laboratoire de Physique des Solides, UMR CNRS 8502, Bât. 510 Université Paris-sud - 91405 Orsay, France, EU
2   Institut de Chimie des Matériaux Paris Est UMR CNRS 7182, Equipe Matériaux Polymères aux Interfaces, Université d'Évry - 91025 Évry, France, EU

zeghal@lps.u-psud.fr

received 17 October 2008; accepted in final form 5 February 2009; published March 2009
published online 16 March 2009

Abstract
We study the formation and structure of stable electrostatic complexes between oppositely charged polyelectrolytes, a long polymethacrylic acid and a shorter polyethylenimine, at low pH, where the polyacid is weakly charged. We explore the phase diagram as a function of the charge and concentration ratio of the constituents. In agreement with theory, turbidity and $\zeta $ potential measurements show two distinct regimes of weak and strong complexation, which appear successively as the pH is increased and are separated by a well-defined limit. Weak complexes observed by neutron scattering and contrast matching have an open, non-compact structure, while strong complexes are condensed.

PACS
82.35.Rs - Polyelectrolytes.
61.25.he - Polymers solutions.
61.05.fg - Neutron scattering (including small-angle scattering).

© EPLA 2009