Compression and Structure of Monolayers of Charged Latex Particles at Air/Water and Octane/Water Interfaces

作者：Robert Aveyard, John H. Clint, Dieter Nees, Vesselin N. Paunov · 发表于：Langmuir · 年份：1999 · DOI：10.1021/la990887g · 被引用次数：440 · 研究领域：Pickering emulsions and particle stabilization、Surfactants and Colloidal Systems、Proteins in Food Systems

We have studied the compression and structure of compressed monolayers of sulfate polystyrene latex particles on air/water and octane/water interfaces. If compressed sufficiently (on a Langmuir trough) the monolayers at air/water surfaces give rafts of hexagonally packed particles, while those at oil/water interfaces undergo a transition from the originally hexagonal to a rhombohedral structure. We have found that beyond collapse the particle monolayers on both air/water and octane/water interfaces fold and corrugate, and there is no expulsion of individual particles or particle aggregates from the interface. In the case of air/water interfaces, the structuring of particle monolayers (below collapse) was found to be very sensitive to the electrolyte concentration in the aqueous phase. At low electrolyte concentration, a fairly ordered structure resulting from the interparticle repulsion was observed, while at high electrolyte concentration, the particles form 2D clusters. In marked contrast, particle monolayers at octane/water interfaces remain highly ordered as a result of long-range repulsion, even on concentrated electrolyte solution. We attribute the enhanced lateral repulsion between the latex particles at the octane/water interface to the existence of residual surface charges at the particle/octane interface. We propose a simple model, which describes the electrostatic interaction between the adsorbed particles and includes the effect of image forces. From this we have ...