Hydrophilic forces

The term "hydrophilic force", literally meaning "love of water" force, was introduced as a complement to "hydrophobic force". Hydrophilic forces are equivalent to polar forces, and polar solvents that interact strongly with water are called hydrophilic solvents. 

Other important forces, including hydration and solvation forces associated with the tendency of molecules or ions to bind tightly to surfaces, as well as hydrophobic and hydrophilic forces and other specific interactions, are present in complex fluids. These forces become important at separations of a couple of nanometers. As discussed in Chapter 7, such forces can influence the rheological properties of suspensions of particles in near contact. 

On the other hand, the amount of water inside the film is not sufficiently large to induce the formation of globules with a water core this is best seen from the curve which corresponds to the 40% deuteration rate. Thus when the temperature is raised of about only 2°C, combined hydrophobe-hydrophile forces tend to favour the existence of a water layer, but the amphiphiles keep a dense packing the temperature change is too small to induce in the surfactant film the disorder necessary for a globular shape. Moreover that water... 

To achieve gelation instead of uncontrolled aggregation and precipitatirMi, a balance needs to be maintained between attractive forces that lead to network formation and hydrophilic forces that solvate the nanofibrils. To generate a hydrated, non-collapsed nanofibrillar network, the nanofibrils should either be stabilized by sufficient swelling and electrostatic repulsion or they must contain intercormected regions with conformational disorder that increase the entropy of the system. The coexistence of soluble and insoluble regions within the nanofibrils makes the nanofibrillar network stable and swollen. 

Ben-Naim, A. (1994) Hydrophobic-Hydrophilic Forces in Protein Folding. In Structure and Reactivity in Aqueous Solutions, C. J. Cramer and D. G. Thrular, Ed. American Chemical Society Washington, D.C., Vol. 568 pp 371-380. 

It may be noted here that the behavior of snrfactants in the mnltiphase and multisurface systems is mainly determined by the balance between the hydrophobic forces and hydrophilic forces of the surfactants (Figures 17.13a through 17.13f). 

Contact angle and surface free energy measurements offer the first insight into the potential use of the PDLC as biomaterial and also provide information about the physical interactions inside the material that determine the droplet anchoring. Usually, for a material to be considered as potentially biocompatible, the water contact angle value must be in the range of 60-90 degrees, which is considered within the domain of moderate wettability (Ikada 1994 Vasile and Pascu 2007). These values ensure an appropriate balance of hydrophobic/hydrophilic forces that will favor cellular adhesion and prevent the rejection of the implanted material. 

For our work the change in dipole moment is a very important feature, since it may change the dielectric constant of the medium in which the dye is located. The better water compatibility may play a role in systems in which a balance of hydrophobic and hydrophilic forces exist. Finally it has to be noted that the over-all dimensions of the dye change upon conversion to the cis form. This too may cause changes in binding properties to macromolecules. 

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