title: Tuning the Structure and Rheology of Polystyrene Particles at the Air-Water Interface by Varying the pH.
abstract: We form films of carboxylated polystyrene particles (C-PS) at the air-water interface and investigate the effect of subphase pH on their structure and rheology by using a suite of complementary experimental techniques. Our results suggest that electrostatic interactions drive the stability and the structural order of the films. In particular, we show that by increasing the pH of the subphase from 9 up to 13, the films exhibit a gradual transition from solid to liquidlike, which is accompanied by a loss of the long-range order (that characterizes them at lower values of pH). Direct optical visualization of the layers, scanning electron microscopy, and surface pressure isotherms indicate that the particles deposited at the interface form three-dimensional structures involving clusters, with the latter being suppressed and a quasi-2D particle configuration eventually reached at the highest pH values. Evidently, the properties of colloidal films can be tailored significantly by altering the pH of the subphase.
authors.affiliation: FO.R.T.H, Institute of Electronic Structure and Laser, Heraklion, Crete, Greece.|Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS, Université de Montpellier , Montpellier, France.
authors.forename: Domenico
authors.initials: D
authors.lastname: Truzzolillo
authors.affiliation: Department of Chemistry and Biology, University of Siegen , Adolf-Reichwein-Strasse 2, AR-G 213 Siegen, Germany.
authors.forename: Hossameldeen
authors.initials: H
authors.lastname: Sharaf
authors.affiliation: FO.R.T.H, Institute of Electronic Structure and Laser, Heraklion, Crete, Greece.|Department of Chemistry and Biology, University of Siegen , Adolf-Reichwein-Strasse 2, AR-G 213 Siegen, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Jonas
authors.affiliation: FO.R.T.H, Institute of Electronic Structure and Laser, Heraklion, Crete, Greece.
authors.forename: Benoit
authors.initials: B
authors.lastname: Loppinet
authors.affiliation: FO.R.T.H, Institute of Electronic Structure and Laser, Heraklion, Crete, Greece.|Department of Materials Science and Technology, University of Crete , Heraklion, Crete, Greece.
authors.forename: Dimitris
authors.initials: D
authors.lastname: Vlassopoulos