Polyelectrolyte adsorption on a charged surface. A study by Monte Carlo simulations

C.F. NARAMBUENA, D. M. BELTRAMO AND E. P.M. LEIVA

MACROMOLECULES

ACS Publications

Lugar: Washington; Año: 2007 vol. 40 p. 7336 - 7342

0024-9297

In the present work, we develop a grand canonical Monte Carlo study of polyelectrolyte (PE) adsorption on a charged surface by means of a primitive model for the PE and the ions. Charge reversal upon PE adsorption was obtained by using a model that only retains the electrostatic interactions. Free energy changes for the adsorption process were calculated and different contributions to this quantity were analyzed. Among them, the entropic gain due to ion release, the conformational changes of the PE, and enthalpic changes were considered. The results suggest that the entropic contribution is the driving force of this phenomenon, stemming from the release of counterions from the double layers of the PE and the charged surface. The positive enthalpy value obtained is rationalized in terms of the decrease of the number of ionic pairs upon adsorption.