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Fluorinated polyhedral oligomeric silsesquioxane (F-POSS) nanoparticles have been widely used to enhance the hydrophobicity or oleophobicity of polymer films via constructing the specific micro/nanoscale roughness. In this work, we study the oleophobicity of pure and F-POSS-decorated poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) films using a dynamic density functional theory approach. The role of nanoparticle size and coverage and the chemical features of F-POSS and the polymer film in the wetting behavior of diiodomethane droplets has been integrated to the remaining ratio of surface potential to quantitatively characterize the corner effect. It is shown that, on the basis of universal force field parameters, the theoretically predicted contact angles are in general agreement with the available experimental data.

Because of the atomic thinness of graphene, its integration into a device will always involve its interaction with at least one supporting substrate, making the surface energy of graphene critical to its real-life applications. In the current paper, the contact angle of graphene synthesized by chemical vapor deposition (CVD) was monitored temporally after synthesis using water, diiodomethane, ethylene glycol, and glycerol. The surface energy was then calculated based on the contact angle data by the Fowkes, Owens-Wendt (extended Fowkes), and Neumann models. The surface energy of fresh CVD graphene grown on a copper substrate (G/Cu) immediately after synthesis was determined to be 62.2 ± 3.1 mJ/m(2) (Fowkes), 53.0 ± 4.3 mJ/m(2) (Owens-Wendt) and 63.8 ± 2.0 mJ/m(2) (Neumann), which decreased to 45.6 ± 3.9, 37.5 ± 2.3, and 57.4 ± 2.1 mJ/m(2), respectively, after 24 h of air exposure. The ellipsometry characterization indicates that the surface energy of G/Cu is affected by airborne hydrocarbon contamination. G/Cu exhibits the highest surface energy immediately after synthesis, and the surface energy decreases after airborne contamination occurs. The root cause of intrinsically mild polarity of G/Cu surface is discussed.

Ordered, hierarchical (triple-scale), superhydrophobic, oleophobic, superoleophobic, and amphiphilic surfaces on poly(methyl methacrylate) PMMA polymer substrates are fabricated using polystyrene (PS) microparticle colloidal lithography, followed by oxygen plasma etching-nanotexturing (for amphiphilic surfaces) and optional subsequent fluorocarbon plasma deposition (for amphiphobic surfaces). The PS colloidal microparticles were assembled by spin-coating. After etching/nanotexturing, the PMMA plates are amphiphilic and exhibit hierarchical (triple-scale) roughness with microscale ordered columns, and dual-scale (hundred nano/ten nano meter) nanoscale texture on the particles (top of the column) and on the etched PMMA surface. The spacing, diameter, height, and reentrant profile of the microcolumns are controlled with the etching process. Following the design requirements for superamphiphobic surfaces, we demonstrate enhancement of both hydrophobicity and oleophobicity as a result of hierarchical (triple-scale) and re-entrant topography. After fluorocarbon film deposition, we demonstrate superhydrophobic surfaces (contact angle for water 168°, compared to 110° for a flat surface), as well as superoleophobic surfaces (153° for diiodomethane, compared to 80° for a flat surface).

An investigation of energetic properties of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) layers deposited on glass, mica, and PMMA (poly(methyl methacrylate)) surfaces was carried out by means of contact angles measurements (advancing and receding) for three probe liquids (diiodomethane, water, and formamide). DPPC was deposited on the surfaces from water (on glass and mica) or methanol (on PMMA) solutions. The topography of the tested surfaces was determined with a help of scanning electron microscopy (SEM) and atomic force microscopy (AFM). Using the measured contact angles, the total apparent surface free energy and its components of the studied layers were determined from van Oss et al.'s (Lifshitz-van der Waals and acid-base components, LWAB) and contact angle hysteresis (CAH) approaches. It allowed us to learn about changes in the surface free energy of the layers (hydrophobicity/hydrophilicity) depending on their number and kind of support. It was found that the changes in the energy greatly depended on the surface properties of the substrate as well as the statistical number of monolayers of DPPC. However, principal changes took place for first three monolayers.

Contact angle measurements for water, glycerol, formamide, ethylene glycol, diiodomethane, α-bromonaphthalene, tricresyl phosphate, dimethylsulfoxide (DMSO), and bromoform on polymethyl methacrylate (PMMA) covered with adsorptive and gelatinized gelatin films were made. Adsorption was performed from solutions in the 0−25 g/L concentration range. A gelatinized gelatin film was created from solutions of 40−100 g/L concentrations. It was found that the biggest changes of the contact angles were up to monolayer coverage of the PMMA surface. For all liquids (besides water) the contact angle was almost constant above the gelatin concentration 50 g/L. Very high contact angles (∼134°) were obtained for water on a gelatinized gelatin film obtained from a solution of 100 g/L concentration. From the obtained contact angles, the Lifshitz−van der Waals components and the values of the electron−acceptor and electron−donor parameters of the acid−base components of the films were calculated for the glycerol−ethylene glyc...

We have investigated the extent to which alkylbenzenes exhibit surfactant properties in diiodomethane (DIM) as solvent. As a result of its dipole moment and high refractive index, DIM has a high cohesive energy density arising from dipole−dipole and dispersion forces. DIM has a high affinity for the benzene group of an alkylbenzene solute but low affinity for the alkyl chain. These different affinities endow alkylbenzenes with amphiphilic properties in DIM solution, causing them to adsorb at the DIM−air surface and to aggregate. Surface tensiometry measurements show that the adsorption of alkylbenzenes at the DIM−air surface increases with the alkylbenzene chain length, consistent with the notion that the antipathy between the DIM solvent and the alkyl chain of the alkylbenzene provides the main driving force for adsorption. Ellipsometry measurements confirm the adsorption of octyl- and hexylbenzenes at the DIM−air surface and also indicate multilayer adsorption of octylbenzene at high concentrations. Usi...

An atomic force microscope has been employed to measure the force of interaction between a micron-sized colloidal sphere and a flat plate, both coated with a copolymer of perfluoro(2,2-dimethyl-1,3-dioxole) and tetrafluoroethylene (Teflon AF1600) in water, glycerol, formamide, ethylene glycol, ethylammonium nitrate, formic acid, ethanol, methanol, diiodomethane, 1-bromonaphthalene, hexadecane, and hexane. A long-range force of attraction was measured in water and, with the exception of the n-alkanols and n-alkanes, all the organic liquids. The results indicate that there is a macroscopic long-range attraction between solvophobic surfaces that has a different origin from that of the hydrophobic interaction observed at the molecular level. The results also indicate that there is a “solvophobic force” that is not due to either orientational ordering propagated by hydrogen bonds, electrostatic (or polarization) effects, or condensates of “loosely attached” surface material; all mechanisms that have been invok...

The repulsive and attractive interactions between silicon nitride and silica across diiodomethane and 1-bromonaphtalene were measured using an atomic force microscope (AFM). By combining measuremne ...

Although surface chemistry fundamentals of semisoluble minerals have been studied by many researchers, detailed understanding of these systems is still incomplete. In situ Fourier transform infrared internal reflection spectroscopy (FT-IR/IRS) techniques have recently been used to successfully describe the adsorption of carboxylates at semisoluble mineral surfaces. The wetting characteristics of these adsorbed films, however, require further consideration. In this regard, the hydrophobicity and stability of transferred Langmuir-Blodgett (LB) monolayers of fatty acids at fluorite and calcite surfaces have been studied by contact angle measurements with water and diiodomethane. Generally, it was found that the transferred LB monolayers of fatty acids at a calcite surface are unstable whereas such monolayers transferred onto a fluorite surface are stable, as revealed from advancing and receding contact angle measurements. These results are believed to be due to incomplete reaction of the fatty acid monolayer at the calcite surface. In addition it was found that a closely packed well-ordered stearate monolayer similar to that of a transferred LB monolayer can be formed at fluorite surfaces by spontaneous adsorption and self-assembly from aqueous solutions. 41 refs., 13 figs., 1 tab.

The thin-layer wicking technique was used to determine the solid surface free energy components for thin-layer chromatography silica (Merck) by the Washburn equation. It has been found that wick-wetting is a reproducible process and the results of the wetting rates expressed as the relationship of the penetrated distances squared, x2 , are a linear function of time, t. However, in some systems an inflection appeared at a distance 3 5 x 5 5 cm, giving thus two straight-line sections with somewhat different slopes. nAlkanes, diiodomethane, water, and formamide were used as the penetrating liquids. Van Oss et al.'s approach to the surface free energy was applied. Thus, apolar, ysLw, and polar electron donor, ys, and electron acceptor, ys+, components were determined for both the laboratory-made glass plates with a deposited Si02 thin layer as well as commercial ones. Practically the same value of ysLw was obtained for both kinds of plates. However, the commercial plates showed higher values of the yscomponent. It is probably due to the presence of some adhesive additives. The polar ys+ component is small for both plates. It is believed that this technique and the approach to the surface free energy components are very useful for testing the wetting properties of solids by liquids.

Mixed self-assembled monolayers (SAMs) of 4‘-methyl-4-mercaptobiphenyl and 4‘-hydroxy-4-mercaptobiphenyl were prepared on gold (111) surfaces. The composition of the mixed SAMs could be precisely determined by external reflection Fourier transform infrared (ER−FTIR) spectroscopy and showed direct correlation with their wetting properties. Contact angles of water, glycerol and diiodomethane showed small hysteresis, and their values did not change after 1 month, suggesting that these mixed SAMs are stable and can be utilized as model systems for the study of surface phenomena.