title: Structure of colloidal gels at intermediate concentrations: the role of competing interactions.
abstract: Colloidal gels formed by colloid-polymer mixtures with an intermediate volume fraction (ϕc≈ 0.4) are investigated by confocal microscopy. In addition, we have performed Monte Carlo simulations based on a simple effective pair potential that includes a short-range attractive contribution representing depletion interactions, and a longer-range repulsive contribution describing the electrostatic interactions due to the presence of residual charges. Despite neglecting non-equilibrium effects, experiments and simulations yield similar gel structures, characterised by, e.g., the pair, angular and bond distribution functions. We find that the structure hardly depends on the strength of the attraction if the electrostatic contribution is fixed, but changes significantly if the electrostatic screening is changed. This delicate balance between attractions and repulsions, which we quantify by the second virial coefficient, also determines the location of the gelation boundary.
authors: Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstr. 1, 40225 Düsseldorf, Germany.
authors: Ronja F
authors: RF
authors: Capellmann
authors: División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, Lomas del Campestre, 37150 León, Guanajuato, Mexico. mlaurati@fisica.ugto.mx ramoncp@fisica.ugto.mx.
authors: Néstor E
authors: NE
authors: Valadez-Pérez
authors: Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstr. 1, 40225 Düsseldorf, Germany.
authors: Benedikt
authors: B
authors: Simon
authors: Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstr. 1, 40225 Düsseldorf, Germany.
authors: Stefan U
authors: SU
authors: Egelhaaf
authors: Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstr. 1, 40225 Düsseldorf, Germany and División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, Lomas del Campestre, 37150 León, Guanajuato, Mexico. mlaurati@fisica.ugto.mx ramoncp@fisica.ugto.mx.
authors: Marco
authors: M
authors: Laurati
authors: División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, Lomas del Campestre, 37150 León, Guanajuato, Mexico. mlaurati@fisica.ugto.mx ramoncp@fisica.ugto.mx.
authors: Ramón
authors: R
authors: Castañeda-Priego