engleski

Spreading of organic droplets at a charged interface

Although spreading and wetting are common phenomena in everyday life, and are important in industrial processes, their mechanisms are still poorly understood1,2. We propose a new approach to investigation of spreading and wetting at aqueous/mercury electrode interface where the attractive interactions are controled by applied potential. Mercury electrode surface is atomically smooth, fluid and chemically inert, surface charge densities and interfacial tensions are well known and the critical interfacial tension of wetting3 can be determined experimentally4. Spreading and wetting mechanisms were investigated by observing the shape of n-hexadecane droplets at mercury pool/aqueous electrolyte interface. Attachment and shape of droplets depends on potential and reflects wetting equilibrium as a results of complex interfacial interactions on three boundaries, as well as of buoyancy and kinetics of spreading. By changing potential toward the critical value of wetting, shape of droplets is changed from lense through sphere to an elongated shape with a foot. The shape of droplets and range of attachment potentials depend on type and size of droplets, ionic strength of solution, specific adsorption of anions and organic molecules. Detachment of adhered droplets occured only with high overpotential. Pronounced hysteresis and complex shapes observed could not be predicted from wetting equilibrium in the system mercury-water-n-hexadecane.

organic droplets; interfacial properties; attachment; charged interface

nije evidentirano