Proteins & Nanoparticles @ membranes location:Jülich, Germany date:19-22 October 2014
The wetting of anisotropic colloidal particles is of great importance in several applications, including Pickering emulsions, filled foams, and membrane transduction by particles. In the present work, we quantify the variation of the contact angle of prolate ellipsoidal colloids at a liquid−liquid interface as a function of surface chemistry and aspect ratio using Freeze-Fracture Shadow-Casting (FreSCa) cryo-SEM. This method, initially demonstrated for spherical colloids, is extended here to the more general case of ellipsoids. Prolate ellipsoidal particles are prepared from polystyrene and poly(methyl methacrylate) spheres using a well-known film stretching technique in which thorough particle cleaning is of the essence. In order to quantify wetting variations with shape a correction term is introduced into the ideal Young−Laplace equation which expresses the relative importance of line effects relative to surface effects. From this term the contribution of an effective line tension can be extracted. This contribution includes the effects that both surface chemical and topographical heterogeneities have on the contact line and which become increasingly more important for ellipsoids with higher aspect ratios, where the contact line length to contact area ratio increases.