Electrostatic Surface Charging by Water Dewetting

doi:10.1021/acs.langmuir.4c00906

2024-07-05

PRE

Knorr, Nikolaus *

Rosselli, Silvia

Nelles, Gabriele

DOI：10.1021/acs.langmuir.4c00906

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摘要

En 中文

Water dewetting generates static electricity. We reviewed historical experiments of this phenomenon, and we studied the charging of polymer slides and metal electrode supported polymer films withdrawn vertically from a pool of aqueous solutions. For pure water, charging was negative and surface charge densities increased with the speed of dewetting, which we explain by the thermally activated entrainment of nanometer-sized water droplets or clusters charged by unbalanced adsorbed electric double-layer ions. Surface charge densities increased for reduced polymer film thickness following a power law, which we explain by reduced discharge of the entrained water volumes. At low salinity c less than or similar to 10 mu M, charging was proportional to electrokinetic interfacial charge densities: the negative charging was increased for alkaline solutions and for most salts at mu M concentrations and the charge polarity was inversed to positive for a cationic surfactant, a salt with a highly positively charged cation, and for a strong acid at approximately pH 4. Charging was reduced again for c greater than or similar to 100 mu M, especially at high dewetting speeds and for chaotropic ions, which we explain by the entrainment of larger and more discharged droplets. We determined adsorption energies of the charged water clusters on the dewetted surface from thermally stimulated discharge of the charged polymer slides and we show that the surface charge distribution, imaged by charged toner powders and measured microscopically by Kelvin probe force microscopy, is a record of the dewetting process that provides spatial and kinetic information about the three-phase contact line motion.

Keyword:

CONTACT LINE

ELECTROOSMOTIC MOBILITY

HYDROPHOBIC POLYMERS

ELECTRIFICATION

IONS

INTERFACES

DYNAMICS

KINETICS

ENERGY

FILMS