The morphologies and dynamics of aggregates formed by surfactant molecules are known to influence strongly performance properties spanning biology, household cleaning, and soil cleanup. Molecular dynamics simulations were used to investigate the morphology and dynamics of a class of surfactants, the gemini or dimeric surfactants, that are of potential importance in several industrial applications. Simulation results show that these surfactants form structures and have dynamic properties that are drastically different from those of single-chain surfactants. At the same weight fraction, single-chain surfactants form spherical micelles whereas gemini surfactants, whose two head groups are coupled by a short hydrophobic spacer, form thread-like micelles. Simulations at different surfactant concentrations indicate the formation of various structures, suggesting an alternative explanation for the unexpected viscosity behavior of gemini surfactants.
Molecular dynamics simulations have been performed on amphiphilic molecules, oil and water to investigate surfactant behavior in water-like and oil-like solvents. Using a simple model for water, oil and surfactant molecules on a powerful parallel computer, we were able to simulate the adsorption of surfactants at the water/oil interface and the self-assembly of surfactant molecules into micelles. Simulations on various classes of surfactant molecules with different headgroup sizes and interactions show a strong dependence of the dynamics and morphology of surfactant aggregates on the surfactant structure. In the presence of an oil droplet, micelles induce the transfer of oil molecules from the oil droplet to the micelles by means of three mechanisms.
A new capillary‐type closed viscometer is described that can be used for many kinds of liquids. The viscometer is of simple design, incorporating a transparent measuring section and a suspended level enabling a flow of liquid under a constant mean hydrostatic head, the value of which is not affected by the total volume of liquid in the instrument. The viscometer is especially suitable for precise measurements with liquids having high vapor pressures, strongly corrosive properties, or showing chemical reactions with the atmosphere. As the viscometer has been used in molten salt research, a short description of the high temperature furnace, which involves an automatic optoelectronic device for recording the efflux time of the liquid, is also given. After a series of calibration experiments with molten
KNO3
, the viscosity of molten
CdCl2
was determined in the temperature range 590°–800°C. Experimental results are given and compared with literature data.
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