title: Impact of electrostatics on the adsorption of microgels at the interface of Pickering emulsions.
abstract: The importance of electrostatics on microgel adsorption at a liquid interface is studied, as well as its consequence on emulsion stabilization. In this work, poly(N-isopropylacrylamide) (pNIPAM) microgels bearing different numbers of charges and various distribution profiles are studied, both in solution and at the oil-water interface of emulsion drops. Charged microgels are compared to neutral ones, and electrostatic interactions are screened by adding salt to the aqueous solution. In solution, electrostatics has a significant impact on microgel swelling, as induced by the osmotic pressure exerted by mobile counterions in the gel network. At the interface of drops, microgels pack in a hexagonal array, whose lattice parameter is independent of the number of charges and range of electrostatic interactions. Microgel morphology and packing are ruled only by the adsorption of the pNIPAM chain at the interface. Conversely, decreasing the charge density of microgels by the protonation of the carboxylic groups leads to unstable emulsions, possibly as a result of the impact of hydrogen bonding on microgel deformability.
authors.affiliation: Université de Bordeaux, ISM, CNRS, ENSCBP , 16 Avenue Pey Berland, 33607 Pessac Cedex, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Massé
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Sellier
authors.forename: Véronique
authors.initials: V
authors.lastname: Schmitt
authors.forename: Valérie
authors.initials: V
authors.lastname: Ravaine