Effect of Swelling of a Polymer Surface on Advancing and Receding Contact Angles (original) (raw)
Related papers
Effect of temperature on the dynamic contact angle
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1998
The temperature influence on the contact angle relaxation of partially wetting drops is measured for squalane on poly(ethyleneterephthalate). The results are analyzed with the molecular kinetic model, a hydrodynamic model and a model that combines the two previous ones. For each temperature all three approaches can fit our experiments well, but only the molecular kinetic approach leads to physically meaningful parameters. The associated free energy of wetting, introduced by that approach, increases weakly with temperature.
The Journal of Chemical Physics, 1999
The behavior of both flexible and semiflexible polymers near a liquid-liquid interface is investigated with the aid of the self-consistent-field theory as developed by Scheutjens and Fleer. A ternary system (A/B N /C) is studied near the wetting transition. In a symmetric system, i.e., AB ϭ BC ϭ, a change in the interaction parameter introduces a wetting transition. The ratio of the interfacial width of the binary A/C system and the coil size of the polymer determines the order of this transition. Beyond a certain chain length N c ͑at fixed ͒ the wetting transition is of first order, whereas it is of second order for NϽN c. The characteristics of the prewetting line, including the prewetting critical point, are discussed in some detail. The nontrivial N-dependence of the position of this critical point is analyzed in terms of a crude thermodynamic model. For a semiflexible polymer an increase of the chain stiffness at a certain value of is sufficient to introduce a wetting transition.
Journal of Petroleum Science and Engineering, 2007
The goal of this research was to study the effect of advancing velocity and liquid viscosity on the dynamic contact angle between a solid surface and various hydrocarbons. The Wilhelmy plate technique was used to measure the dynamic contact angle at advancing velocities between 20 and 264 μm/s. In addition to hydrocarbons, two silicon oils were also tested for comparison purposes. The results indicate that advancing velocity and oil viscosity have a significant effect on the dynamic contact angle for both hydrocarbon and silicon oils. For example, the advancing contact angle for viscous (1540 mPa s at 15°C) oils was up to 2 times higher at 200 μm/s than at 20 μm/s. As a result, it is recommended that when values for dynamic contact angles are reported, the advancing velocity at which they were measured be indicated. This will ensure correct data interpretation, meaningful comparison between various studies, and better prediction of multiphase flow or adhesion processes that depend on the dynamic contact angle.
Langmuir : the ACS journal of surfaces and colloids, 2017
Measuring truly equilibrium adhesion energies or contact angles to obtain the thermodynamic values are experimentally difficult because they require loading/unloading or advancing/receding boundaries to be measured at rates that can be slower than 1 nm/s. We have measured advancing-receding contact angles and loading-unloading energies for various systems and geometries involving molecularly smooth and chemically homogeneous surfaces moving at different but steady velocities in both directions, ±V, focusing on the thermodynamic limit of ±V → 0. We have used the Bell Theory (1978) to derive expressions for the dynamic (velocity-dependent) adhesion energies and contact angles suitable for both (i) dynamic adhesion measurements using the classic Johnson-Kendall-Roberts (JKR, 1971) theory of 'contact mechanics', and (ii) dynamic contact angle hysteresis measurements of both rolling droplets and syringe-controlled (sessile) droplets on various surfaces. We present our results for...
Probing polymer surface and interface dynamics
Surface and Interface Analysis, 1986
Polymeric materials generally exhibit various molecular motions and relaxations. Such relaxation processes, which include the glass transition temperature, have significant effects on physical and mechanical behavior. Polymer molecules and segments at surfaces and interfaces also exhibit motions and relaxations. In air or vacuum, such motions 'permit' the surface to restructure to minimize the surface free energy. In aqueous solution, the polymer surface restructures and reorients to optimally interact with the aqueous solvent, thereby minimizing the interfacial free energy. XPS and related high vacuum techniques probe the vacuum-equilibrated surface. The best way to probe the polymer-liquid interface is via dynamic contact angle or wetting methods. A number of issues and concerns are discussed: (1) the size or hierarchy of structures; (2) the time course of surface dynamic processes; (3) theory, modeling, and simulation of surface dynamics; and (4) experimental methods.
Comparison of contact angle hysteresis of different probe liquids on the same solid surface
Colloid and Polymer Science, 2012
Advancing and receding contact angles of water, formamide and diiodomethane were measured on 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) layers deposited on three different solid supports-glass, mica and poly (methyl methacrylate). Up to five statistical monolayers were deposited on the surfaces by spreading DPPC solution. It was found that even on five statistical DPPC monolayers, the hysteresis of a given liquid depends on the kind of solid support. Also on the same solid support the contact angle hysteresis is different for each probe liquid used. The AFM images show that the heights of roughness of the DPPC films cannot be the primary cause of the observed hysteresis because the heights are too small to cause the observed hystereses. It is believed that the hysteresis is due to the liquid film present right behind the three-phase solid surface/liquid drop/gas (vapour) contact line and the presence of Derjaguin pressure. The value of contact angle hysteresis depends on both the solid surface and liquid properties as well as on intermolecular interactions between them.
Dependency of Contact Angle Hysteresis on Crystallinity for n- Alkane Substrates
The Journal of Physical Chemistry C, 2009
Changes in dynamic contact angle for the wetting of heat-treated paraffin wax surfaces were reported. It was observed that the advancing angle remains relatively stable while the receding angle decreases with greater treatment. These changes appear to result primarily from a reduction in crystallinity, which was gauged via differential scanning calorimetry and X-ray diffraction. Surface roughness is also found to decrease with heat treatment, but its role in the reported phenomenon appears to be minimal. This is demonstrated by normalizing the roughness of coated plates with cold pressing. Along with global changes in crystallinity, modifications to the local crystallinity were observed using Raman confocal microscopy. Specifically, it is shown that the heat treatment increased the heterogeneities of the wax surfaces by producing micrometer-scale amorphous regions. These regions are believed to act as hydrophilic defects on the wetted surface, impacting almost exclusively receding angle measurements. The findings raise concerns over the use of semicrystalline oligomeric and polymeric materials as model substrates in wetting experiments. Results also identify a possible method for estimating the order of packing of straight-chain hydrocarbon derivatives at surfaces using dynamic contact angle measurements.
Langmuir, 2006
The wetting properties of a substrate can be changed by chemical reaction. Here, we studied simple materials with acid-base properties, by preparing poly(vinyl chloride) films containing lauric acid. These substrates constitute simple polymeric surfaces the wettability of which can be easily controlled by the acid-base equilibrium. The roughness of the material was then varied by adding Aerosil (hydrophobic fumed silica). We then studied the wettability of these materials toward aqueous buffer solutions between pH 2 and 12 from contact angle measurements. The variation of the contact angle of a droplet of buffer solution with the pH of the solution was described by a simple thermodynamic model requiring only two parameters. Thus, we could characterize the acid polymer by an effective surface acid dissociation constant the value of which was consistent with those obtained with a similar surface. We showed that the behavior of any substrate could be described even if the surface geometry was not well-known.
Drop size dependence of contact angles on two fluoropolymers
Colloid and Polymer Science, 2009
Young's equation predicts that the contact angle of a liquid drop is independent of its size. Nevertheless, large drop size dependences of contact angles have been observed, especially for millimetre-sized drops, on a variety of solid surfaces. We report new measurements of drop size dependence of contact angles for several liquids on two fluoropolymer surfaces, Teflon AF 1600 and EGC-1700. We demonstrate a new strategy for contact angle measurement that allows detection of approximately 0.1°changes in the contact angle during the growth of a drop. We find that on the surfaces examined, drop size dependence of contact angles is ten times smaller than on all previously studied fluoropolymers at the millimetre scale. The data are insensitive to various attempted surface modifications. We discuss the interpretation of the data and possible physical sources.
Contact Angle, Wettability, and Adhesion, Volume 6
Contact Angle, Wettability and Adhesion Volume 6, 2009
The porosity and wettability properties of hydrogen ion treated poly(tetrafluoroethylene) (PTFE) materials are related using contact angle, scanning electron microscopy (SEM) and ellipsometry techniques. PTFE samples are irradiated using a low-energy hydrogen ion shower (LEHIS) produced by a Gas Discharge Ion Source (GDIS). The plasma discharge current (Id) is varied at intervals of 1 mA. Results show that treatment using lower Id improved the hydrophobic property of the PTFE material with water contact angle increasing from 102◦ to 119◦. It also becomes less porous as indicated by the increase in the index of refraction, decrease in optical transmittance, and increased fissures and striations in the SEM images. Opposite effects are observed for higher Id.