8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Wed 711:10-14:00P5.107Monolayers of microparticles at fluid Interfaces:structure and dynamicsAlma Mendoza, 1 Manuel G. Velarde, 2 Ramon G. Rubio, 1 and Francisco Ortega 11 Universidad Complutense de Madrid, Ciudad Universitaria s/n, 28040, Madrid,Spain2 Instituto Pluridisciplinar, Madrid, SpainMicroparticle dispersions have served as model systems in fundamental studies of intermolecularpotential, structure, dynamics, rheology, fluid flow, etc. The organization of these particles inconfined conditions, 2D or quasi-2D, is relevant in many of applications, particularly in coatingprocesses, wetting, foam and emulsion stability, selective transport through membranes, etc. Inspite of their technological applications, the Statistical Mechanical description of particles at interfacesis far from being clear. In particular, many contradictory results have been reported aboutthe role of hydrodynamic and multibody interactions in the structure of particle monolayers. Thesituation is even worse for the calculation of the interfacial friction coefficient, thus leading tohuge differences between interfacial micro- and microrheology. In our work we will limit the dynamicstudies to the linear regime in order to try to understand the most basic behaviour of particlemonolayers. Our study of these monolayers of particles located at fluid interfaces (gas-liquid andliquid-liquid) has been carried out mainly using video-microscopy and image processing tools, theresults have allowed us to calculate the radial, g(r), and orientational, g 6 (r), distribution functions,the structure factor S(q), the orientational bond correlation function, and the mean squaredisplacement. The experimental results have allowed us: a) to characterize the phase diagram ofthese systems, mainly a transition from fluid to a hexagonal solid, b) to obtain, using integral equations,the interaction potential from the radial distribution functions, and c) to study the variationof the diffusion coefficient, D.107