Lyophobe

These equations imply that A132 will exceed A12 if A33 is larger than A13 + A23. This effect, termed lyophobic bonding, occurs if the solvent-surface interaction is weaker than that between the solvent molecules. More interestingly, the dispersion interaction will be repulsive (A 132 < 0) when An and/or A23 are sufficiently large. Israelachvili [1] tabulates a number of Am values Awhw Ahwh 0-4X 10 erg, Apwp 1 x 10" erg, and Aqwq = O.SX -IO erg, where W, H, P, and Q denote water, hydrocarbon, polystyrene and quartz respectively. 

The idealized reverse micelle sketched in figure C2.3.1 is an aggregate of a double-tail surfactant. In such systems the solvent is more compatible with the lyophobic part of the surfactant than with the headgroup. This preference... 

Verwey E J W and Overbeek J Th G 1948 Theory of the Stabiiity of Lyophobic Coiioids (New York Elsevier)... 

Lyophobic colloids Lyotropic liquid crystals Lyotropic mesophases Lyotropic polymers Lyral [31906-04-4]... 

There are two general theories of the stabUity of lyophobic coUoids, or, more precisely, two general mechanisms controlling the dispersion and flocculation of these coUoids. Both theories regard adsorption of dissolved species as a key process in stabilization. However, one theory is based on a consideration of ionic forces near the interface, whereas the other is based on steric forces. The two theories complement each other and are in no sense contradictory. In some systems, one mechanism may be predominant, and in others both mechanisms may operate simultaneously. The fundamental kinetic considerations common to both theories are based on Smoluchowski s classical theory of the coagulation of coUoids. 

Dispersion forces are ubiquitous and are present in all molecular interactions. They can occur in isolation, but are always present even when other types of interaction dominate. Typically, the interactions between hydrocarbons are exclusively dispersive and, because of them, hexane, at S.T.P., is a liquid boiling at 68.7°C and is not a gas. Dispersive interactions are sometimes referred to as hydrophobic or lyophobic particularly in the fields of biotechnology and biochemistry. These terms appear to have arisen because dispersive substances, e.g., the aliphatic hydrocarbons, do not dissolve readily in water. Biochemical terms for molecular interactions in relation to the physical chemical terms will be discussed later. 

Lyophobic Referring to vinyl dispersions, no affinity or attraction for... 

Derjaguin, B.V. and Landau, L., 1941. The stability of strongly charged lyophobic sols and the adhesion of strongly charged particles in solutions of electrolytes. Acta Physicochim, UPSS, 14, 633-662. 

Lymph-gefass, n. lymphatic vessel, -korper-chen, n. lymph corpuscle, leucocyte, lyo-pbil, a. lyophile, lyophil(ic). -phob, a. lyophobe, lyophobic. -trop, a. lyotrope, lyotropic. 

For convenience, colloids are divided into two main groups, designated as lyophobic and lyophilic colloids. The chief properties of each class are summarised in Table 11.1, although it must be emphasised that the distinction is not an absolute one, since some gelatinous precipitates (e.g. aluminium hydroxide and other metallic hydroxides) have properties intermediate between those of lyophobic and lyophilic colloids. 

Lyophobic colloids, ordinarily, have an electric charge of definite sign, which can be changed only by special methods. 

The stability of lyophobic colloids is intimately associated with the electrical charge on the particles. Thus in the formation of an arsenic(III) sulphide sol... 

Cobalt, sepn. of from nickel, (cm) 532 Codeine and morphine, D. of 740 Coefficient of variation 135 Colloidal state 418 See also Lyophilic, Lyophobic Colorimeters light filters for, 661 photoelectric, 645, 666 Colorimetric analysis 645 criteria for, 672 general remarks on, 645, 672 procedure, 675 solvent selection, 674 titration, 652... 

Liquid junction potential 63, 549 Literature of analytical chemistry 6, 122, 156, 251, 253, 498, 499, 640, 641, 813, 815 Lithium, D. of as aluminate, (g) 459 Litmus 265 Litre xxix, 78 Littrow mounting 661 Logarithms four figure, 843 Lovibond comparator 655 Low voltage d.c. arc 763, 771 Lubricants for glass stopcocks 85 Lyophilic colloids 419 Lyophobic colloids 419 stability of, 419... 

The four terms that need discussion are (1) "hydrophobic interactions", (2)"lyophobic interactions", (3)"hydrophilic interactions" and (4) "lyophilic interactions". 

The reasons for the introduction of the terms "lyophobic" (meaning fear of lye) and "lyophilic" (meaning love of lye) are even more obscure and appear irrelevant as they are virtually alternatives to the terms hydrophobic and hydrophilic. The terms originated in the early soap industry during the mid-to-late nineteenth century. In about 1850 soap was prepared by boiling a vegetable oil with an alkaline solution obtained from leaching wood ash with water. 

The alkaline product from the wood ash was a crude solution of sodium and potassium carbonates called "lye". On boiling the vegetable oil with the lye, the soap (sodium and potassium salts of long chained fatty acids) separated from the lye due to the dispersive interactions between the of the fatty acid alkane chains and were thus, called "lyophobic". It follows that "lyophobic", from a physical chemical point of view, would be the same as "hydrophobic", and interactions between hydrophobic and lyophobic materials are dominantly dispersive. The other product of the soap making industry was glycerol which remained in the lye and was consequently, termed "lyophilic". Thus, glycerol mixes with water because of its many hydroxyl groups and is very polar and hence a "hydrophilic" or "lyophilic" substance. 

EJV Verwey and J Th G Overbeek, Theory of the Stability of Lyophobic Colloids, Elsevier, Amsterdam, 1948. 

REFERENCE VERWEY AND OVERBEEK THEORY OF THE STABILITY OF LYOPHOBIC COLLOIDS... 

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