Dr. Marie Haddou

Complexes of polyelectrolytes (PECs) are oppositely charged polymers assemblies held together by electrostatic interaction. As the non-covalent assembly of macromolecules/colloids in solution has been thoroughly investigated over the last decade with a particular emphasis put on the morphology of the final aggregates as a function of the building blocks-chemistry, the objective of this thesis is to come to a better understanding of the influence of interaction strength between polyelectrolytes on complexes morphologies, as well as kinetics and thermodynamics of the complexation. For this study, weakly and strongly interacting systems given rise to coacervate and precipitate phases has been elected. Those systems have been studied on a wide charge ratio scale (Z[+]/[-]) to span several physical states of the PECs (soluble and colloidal PECs, dense phases). Morphologies of assemblies are assessed by microscopy (optical, fluorescence, atomic force) and scattering techniques (neutron, light). Kinetics and thermodynamics of the complexation process are studied by use of a stopped-flow mixing device and an isothermal titration calorimeter. Results gave us keys to discriminate strongly interacting systems from weakly interacting ones. In particular, the ‘strong systems’ are showed to be non-equilibrium assemblies, ie. the formulation pathway or the way these different macromolecules are coming into contact is then a key step. Another important aspect that could explain the complexation process behavior is the hydration energy of the polyelectrolytes. Calorimetry measurements have been performed for numerous polyelectrolytes and then correlated to complexes properties.

Les complexes de polyelectrolytes (PECs) sont typiquement formes par interaction electrostatique entre deux polyelectrolytes de charge opposee. Alors que de nombreuses etudes ont ete consacrees aux proprietes de ces complexes, l'objectif de la these est de mieux comprendre le role de l’intensite de l’interaction entre deux polyelectrolytes sur la morphologie des complexes ainsi que la cinetique et la thermodynamique de la complexation. Differents systemes complexants, faibles et forts, donnant lieu a la formation de coacervats ou de precipites ont ete choisis et etudies sur une large gamme de rapport de charges (Z[+]/[-]) afin d'obtenir differents etats physiques (soluble, colloidal, phase dense). La morphologie des complexes a ete determinee par microscopie (optique, fluorescence, force atomique) et diffusion de rayonnement (lumiere, neutrons). La cinetique et la thermodynamique de complexation ont ete etudiees par utilisation respective d'un melangeur a flux stoppe et ...

Submitted for the MAR16 Meeting of The American Physical Society Early Stage Kinetics in Polyelectrolyte Complexation Studied in a Stopped-Flow Configuration XIAOQING LIU, MARIE HADDOU, JOANNA GIERMANSKA, Centre de Recherche Paul Pascal (CRPP), UPR CNRS 8641, Universit Bordeaux, 33600 Pessac, France, CHRISTOPHE SCHATZ, Laboratoire de Chimie des Polymres Organiques, Ecole Nationale Suprieure de Chimie de Biologie et de Physique, 33600 Pessac, France, JEAN-PAUL CHAPEL, Centre de Recherche Paul Pascal (CRPP), UPR CNRS 8641, Universit Bordeaux, 33600 Pessac, France — Polyelectrolyte complexes (PECs) are the association complexes formed between oppositely charged macromolecules. A large body of work has been devoted to the preparation and morphology characterizations of PECs. Much less attention was paid on formation kinetics of PECs, which often occurs under nonequilibrium conditions. Stopped-flow technique combined with light scattering was used to investigate the early stage complexat...

We systematically investigate in this work the surface activity of polyelectrolyte complex (PECs) suspensions as a function of the molar charge ratio Z (= [-]/[+]) from two model systems: the weakly and strongly interacting poly (diallyldimethylammonium chloride)/poly (acrylic acid sodium salt) (PDADMAC/PANa) and poly (diallyldimethylammonium chloride)/poly (sodium 4- styrenesulfonate) (PDADMAC/PSSNa) pairs, respectively. For both systems, the PEC surface tension decreases as the system approaches charge stoichiometry (Z = 1) whenever the complexation occurs in the presence of excess PDADMAC (Z < 1) or excess polyanion (Z > 1) consistent with an increased level of charge neutralization of PEs forming increasingly hydrophobic and neutral surface-active species. The behavior at stoichiometry (Z = 1) is also particularly informative about the physical nature of the complexes. The PDADMAC/PANa system undergoes a liquid–liquid phase transition through the formation of coacervate mi...