Jan Rayss

Effect of the support surface on the structure of the film of liquid crystalline stationary phase

Abstract It has been found that the chromatographic properties of the Chromosorb P NAW- p -butyl] p ′-hexanoylazobenzene system largely on the thickness of the liquid crystal film. Modification of the liquid crystal properties by the support surface takes place to a distance of a about 2 nm from the surface. The modified liquid crystal layer reveals a selectivity with respect to n -octane and toluene different from that of the liquid cyrstal in the bulk phase.

Phase transitions in the monomolecular film of N-octadecanol on silica gel surface

Abstract The phenomena occurring in the monomolecular layer of n-octadecanol on a silica gel surface during heating of this system were investigated. It was shown by three independent methods—“inverse” gas chromatography, differential thermal analysis, and contact angle measurements—that the second phase transition occurred in this film except for the solid compact-liquid expanded transition type. This transition can be observed when the amount of n-octadecanol on the adsorbent surface exceeds the monolayer capacity.

On the mechanism of support surface adsorption in gas—liquid chromatographic systems

Abstract The mechanism of support surface adsorption is investigated in gas—liquid chromatogrpahic systems with supports exhibiting strong adsorptive properties. For this purpose the characteristic adsorption isotherm for solute adsorbed on the support is evaluated, using the theoretical method developed previously by the authors. This isotherm is then analyzed on the basis of the third-order interaction theory, which allows the determination of information on the mechanism of support surface adsorption.

Study on the possibility of determining the third gas—solid virial coefficient in physical adsorption by gas chromatography

Abstract Definitions of virial coefficients used in the theory of physical adsorption of gases are discussed. A new method of evaluating the third virial coefficient is developed, based on gas chromatographic measurements. To illustrate this method, the third virial coefficient for carbon tetrachloride adsorbed on graphite was evaluated.

Comparison of the properties of liquid crystal films on silica gel and on a graphite surface

Abstract The effect of the solid surface on the properties of liquid crystal films was studied. The results show that the structure of such films depends strongly on the kind of solid support. An additional phase transition, other than solid-nematic and nematic-isotropic liquid, has been found in films of liquid crystals on a graphite surface. At temperatures higher than the nematic-isotropic liquid transition, the surface film on silica gel is probably the monolayer composed of horizontal molecules. The structure of the surface film on graphite is more complicated.

Estimation of the surface area of adsorbents from the third gas—solid virial coefficient

Abstract A new method is proposed for the estimation of the surface area of adsorbents from the second and third gas—solid virial coefficients. The method is based on a three-dimensional model of physical adsorption, and is in addition an extremely simple one. The data needed can be easily obtained by gas chromatography.

Application of differential thermal analysis to the determination of specific surface area

Abstract On the basis of Serpinets finding that long-chain aliphatic alcohols form strictly defined monolayers on solid surfaces, a new method of specific surface area determination has been worked out. The method involves differential thermal analysis measurements of the amount of heat which is necessary to melt the quantity of n-octadecanol deposited on an adsorbent surface exceeding the quantity necessary to form the monolayer.

Investigations of the retention mechanism in gas—liquid partition chromatography

Abstract A new graphical method is proposed for estimating the retention mechanism in gas—liquid partition chromatographic (GLPC) systems in which adsorption phenomena occur. The proposed method enables the adsorption phenomena accompanying the bulk liquid solution to be investigated unequivocally from gas chromatographic data alone. Moreover, it can be applied even in the very complicated instances of the GLPC systems with heterogeneous, and in addition not totally loaded, support surfaces. The utility of this method is demonstrated for two different GLPC systems with strong adsorption properties.

Temperature dependence of hetp for columns with small amounts of liquid stationary phase

Abstract It was found that the plate number of a column depends strongly on the physical state of th monomolecular layer formed by the liquid stationary phase on the support surface. Phase transitions in the monolayer modify the distribution of liquid in the column packing and, as a result, change the height equivalent to a theoretical plate for a given column.

Adhesion of polymer protective coatings of optical fibers

The effect of optical fiber polymer coatings on the mechanical properties of a fiber was studied. Their adhesion to the optical fiber surface is of special interest. It is also shown how the analysis of electron donor and electron acceptor properties of the surfaces being in contact can predict the adhesion energy. An optical fiber model taking into consideration the pressure exerted on it by the protective coating is also described.