Roughness and ordering at the interface of oxidized polystyrene and water

• For the first time, atomistically detailed molecular dynamics calculations revealed molecular ordering of the water-oxidized atactic polystyrene (aPS) interface. Both ordering of the water molecules and the phenyl rings occur. In addition, the natural roughness of the surface has been simulated and compared to experimental values. The composition of the simulated aPS films is based on spin-coated aPS films that have been oxidized and characterized experimentally. The aPS surfaces are oxidized with ultraviolet-ozone radiation and have been characterized by XPS, AFM, and water contact angle measurements. XPS measurements show that the oxygen content in the sample increases rapidly with exposure and reaches saturation near 24 at. % of oxygen. The molecular dynamics simulations show smoothening of an hydrophobic aPS surface upon transition from vacuum to water. The smoothening decreases with increasing hydrophilicity. The calculations reveal ordering of oxidized phenyl rings for aPS surfaces in water. The order increases with increasing hydrophilicity. Additionally, we investigated the water structure near the aPS-water interface as a function of the surface hydrophilicity. With increasing hydrophilicity, the density of water at the aPS-water interface increases. The water density profile is steeper in the presence of hydrophobic aPS. The water shows an ordered layer near both the hydrophobic and hydrophilic surfaces; the position of this layer shifts toward the interface with increasing hydrophilicity. © 2011 American Chemical Society.

Ämnesord

NATURVETENSKAP  -- Matematik -- Sannolikhetsteori och statistik (hsv//swe)

NATURAL SCIENCES  -- Mathematics -- Probability Theory and Statistics (hsv//eng)

NATURVETENSKAP  -- Matematik (hsv//swe)

NATURAL SCIENCES  -- Mathematics (hsv//eng)

Nyckelord

AFM; Atactic polystyrenes; Density of water; Experimental values; Hydrophobic and hydrophilic; Molecular dynamics calculation; Molecular dynamics simulations; Molecular ordering; Ordered layer; Oxygen content; Phenyl rings; Surface hydrophilicity; Ultraviolet-ozone; Water contact angle measurement; Water density; Water molecule; Water structure; XPS measurements

Angle measurement; Contact angle; Hydrophobicity; Molecular dynamics; Ozone; Polystyrenes; X ray photoelectron spectroscopy

Hydrophilicity

polystyrene derivative; water

article; chemical phenomena; chemistry; conformation; molecular dynamics; oxidation reduction reaction; surface property

Hydrophobic and Hydrophilic Interactions; Molecular Conformation; Molecular Dynamics Simulation; Oxidation-Reduction; Polystyrenes; Surface Properties; Water

Matematik

Mathematics

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