Polarity of solids

One aspect of the research will examine equilibrium aspects of solvation at hydro-phobic and hydrophilic interfaces. In these experiments, solvent dependent shifts in chromophore absorption spectra will be used to infer interfacial polarity. Preliminary results from these studies are presented. The polarity of solid-liquid interfaces arises from a complicated balance of anisotropic, intermolecular forces. It is hoped that results from these studies can aid in developing a general, predictive understanding of dielectric properties in inhomogeneous environments. 

To rate the polarity of solid surfaces from their heats of immersion in simple organic liquids having different peripheral dipole moments. For the first time, this technique allows an experimentally derived number to be put on the average force field emanating from solid surfaces. 

Determination of the polarity of solid surfaces 135 Study of surface modification 137 Assessment of the site-energy distribution 138 Assessment of structural modifications of the adsorbent 139 Assessment of microporosity 139 Assessment of surface area 139... 

The n transition energy of a spiropyran zwitterion of the type described in Section 4.4.2 [(27a) (27b)] has been used by de Mayo et al. to characterize the polarity of solid oxide surfaces such as that of silica gel [217]. 

V. Daniels. Trans. Faraday Soc. 54, 1834-46 (1958). Polarization of solid, long-chain alcohols explained by disorder in H bonding. 

Zettlemoyer, A.C., Chessick, J.J., and HoUabaugh, C.M. (1958). Estimation of the surface polarity of solids from heat of wetting measurements. Phys. Chem., 62, 489-90. Morimoto, T. and Suda, Y. (1985). Heat of immersion of zinc oxide in organic liquids. 1. Effect of surface hydroxyls on the electrostatic field strength. Langmuir, 1, 239—43. 

This commentary on the current status of research on heats of immersion begins where our review written in 1958 concludes [6]. The classification of heats of immersion of solids into liquids as a function of precoverage is expanded to include two new types of curves. Several difficulties in heat of immersion research are discussed. Then, current applications of heats of immersion to determine the average polarity of solid surfaces, heterogeneities on solid surfaces, wetting by surfactants, hydrophilicity of solid surfaces, and thermodynamics of the specific interaction of molecules from solution onto solid surfaces are described. 

The average polarity of solid surfaces can be estimated from heats of immersion into selected liquids, usually n-butyl derivatives possessing... 

Figure 3, Determination of polarity of solid surface (rutile)...

The so-called atomic polarization arises from the shifts of differently charged atoms with respct to each other. In salt, NaCl, for example, which is an ionic solid, an applied external field causes the positive sodium atoms to shift their positions slightly with respct to their negative counterparts. Normally such a contribution to the dielectric polarization of solids is low, about 1/7 that noted for the electronic polarization in organic materials. In rare cases, atomic polarization can be quite large. Witness, for example the perovskite minerals such as BaTi03. It may, if prepared carefully, have a remarkably high relative dielectric constant of, say, 4000. 

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