الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
In this study, five nonionic surfactants namely dimethyl alkyl phosphine oxide, where R= decyl, dodecyl-, tetradecyl-, hexadecyl-, and octadecyl alkyl chains, were prepared and characterized using elemental analysis, FTIR and 1H-NMR spectroscopy.
The surface activities and surface parameters of the studied surfactants were described using: surface tension and interfacial tension measurements. The determined surface parameters of the studied surfactants were surface tension, critical micelle concentration, effectiveness, efficiency, maximum surface excess and minimum surface area at 25 oC.
The dependence of surface activities of the nonionic surfactants on the alkyl chain length was studied in distilled water.
The thermodynamic evaluation of the surfactants was performed by calculating the standard free energies of micellization and adsorption.
The structure-corrosion inhibition performance was estimated using potentiodynamic polarization, electrochemical impedance measurements and quantum chemical studies at 25 oC in true sample formation water.
The quantum chemical calculations and molecular dynamics simulations studies of a series of five nonionic surfactants namely: dimethyl alkyl phosphine oxide surfactants (C10-18PO) containing were implemented using the density functional theory (DFT) method to interpret the correlation between the inhibition efficiency and the molecular structure of the different inhibitors in formation water. The global quantities including: highest occupied molecular orbital energy (HOMO), lowest unoccupied molecular orbital energy (LUMO), energy gap (ΔE), dipole moment (μ), total energy (TE), ionization potential (I), electron affinity (A), electronegativity (χ), chemical potential (π), global hardness (η), global softness (σ), global electrophilicity (ω), polarizabilities <α> and fraction of electrons transferred (∆N) were calculated for the different inhibitors in formation water.
Keywords: nonionic surfactants; surface activity; interfacial tension; adsorption; formation water; corrosion inhibition.