title: Evidence of a two-step process and pathway dependency in the thermodynamics of poly(diallyldimethylammonium chloride)/poly(sodium acrylate) complexation.
abstract: Recent studies have pointed out the importance of polyelectrolyte assembly in the elaboration of innovative nanomaterials. Beyond their structures, many important questions on the thermodynamics of association remain unanswered. Here, we investigate the complexation between poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium acrylate) (PANa) chains using a combination of three techniques: isothermal titration calorimetry (ITC), static and dynamic light scattering and electrophoresis. Upon addition of PDADMAC to PANa or vice-versa, the results obtained by the different techniques agree well with each other, and reveal a two-step process. The primary process is the formation of highly charged polyelectrolyte complexes of size 100 nm. The secondary process is the transition towards a coacervate phase made of rich and poor polymer droplets. The binding isotherms measured are accounted for using a phenomenological model that provides the thermodynamic parameters for each reaction. Small positive enthalpies and large positive entropies consistent with a counterion release scenario are found throughout this study. Furthermore, this work stresses the importance of the underestimated formulation pathway or mixing order in polyelectrolyte complexation.
authors.affiliation: Matière et Systèmes Complexes, UMR 7057 CNRS Université Denis Diderot Paris-VII, Bâtiment Condorcet, 10 rue Alice Domon et Léonie Duquet, 75205 Paris, France. jean-francois.berret@univ-paris-diderot.fr.
authors.forename: L
authors.initials: L
authors.lastname: Vitorazi
authors.forename: N
authors.initials: N
authors.lastname: Ould-Moussa
authors.forename: S
authors.initials: S
authors.lastname: Sekar
authors.forename: J
authors.initials: J
authors.lastname: Fresnais
authors.forename: W
authors.initials: W
authors.lastname: Loh
authors.forename: J-P
authors.initials: JP
authors.lastname: Chapel
authors.forename: J-F
authors.initials: JF
authors.lastname: Berret