Hydrophilic polymers liquid water immersion

When a dry polymer film is immersed into liquid water, an opposite process to what described above takes place. Hydrophilic groups migrate to the interface, and hydrophobic moieties move to the inner part of the surface state of a polymer. The main driving force for these movements is the interfacial tension. The greater the interfacial tension, the greater is the surface configuration change. 

Since a lot of new SPI structures have been prepared, it was necessary to develop a fast and easy to reproduce stability test to avoid a time- and material-consuming fuel cell test. Polyimides are known to be sensitive to hydrolysis [182]. The introduction of sulfonate groups along the polymer chains increases the overall hydrophilicity and thus the water diffusion within the structure, which favors the hydrolytic process. Two different tests are now commonly used in the literature (1) the membrane is immersed in liquid water at 80 °C to test the stability against hydrolysis [35,61] and (2) the mem-... 

It has been observed the formation of continuous liquids on high-energy solid surfaces, such as mica, quartz, and silica, when those surfaces are subjected to immersion and emersion in water [13,14]. A continuous film of water on a hydrophilic (i.e., high energy) plasma polymer-coated glass slide moments after it was immersed to a depth of 3 cm in a beaker of DDI water is shown in Figure 26.21A. The water film remained continuous as it receded to the bottom of the plate. After about 2 min the water film front receded to approximately 1 cm from the bottom of the plate, as shown in Figure 26.21B. The presence and stability of a continuous water film can be detected and quantified by the Wilhelmy method [15]. 

With emulsifiable concentrates, emulsions and microemulsion, the surfactant adsorbs at the oil/water interface, with the hydrophilic head group immersed in the aqueous phase, leaving the hydrocarbon chain in the oil phase. Again, the mechanism of stabilization of emulsions and microemulsions depends on the adsorption and orientation of the surfactant molecules at the liquid/liquid interface. As we will see, macromolecular surfactants (polymers) are nowadays used to stabilize emulsions and hence it is essential to understand their adsorption at the interface. Suffice to say that, at this stage, surfactant adsorption is relatively simpler than polymer adsorption. This is because surfactants consist of a small number of units and they are mostly reversibly adsorbed, allowing one to apply some thermodynamic treatments. In this case, it is possible to describe the adsorption in terms of various interaction parameters such as chain/surface, chain solvent and surface solvent. Moreover, the configuration of the surfactant molecule can be simply described in terms of these possible interactions. In contrast, polymer adsorption is fairly complicated. In addition to the usual adsorption considerations described... 

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