Molecular packing density

Pyroelectricity of several kinds of alternating LB films consisting of phenylpyrazine derivatives and stearic acid was measured by the static method at various temperatures. Effects of thermal expansion and molecular packing density of the film on pyroelectricity were also examined. The following conclusions were derived. 

Figure 10.6. Orientation of adsorbate on the surface and the molecular packing density. (From Ref. 10, with permission from Elsevier.)...

It appeared that the fractional free-volume in filled systems increased in proportion to the polymer fraction in the surface layer, determined independently, and ranging from 0.025 to 0.043. This fact was explained by the diminishing molecular packing density on the surface. There was at the same time a decrease in the temperature Tq-The findings indicate that the criterion of constancy of the free-volume fraction at T% cannot be applied to filled systems because of the influence of the filler on the polymer structure. Thus, even for one and the same polymer, the difference in its physical structure induced by physical actions capable of changing the structure causes polymer behavior to deviate from that predicted within the framework of the iso-firee-volume concept. 

Auger spectroscopy is an important technique in structural investigations [12] all elements except H and He can be detected, usually with limits of detection well below the lowest levels which significantly influence surface behavior elemental Auger signals are readily measured from which atomic, ionic, and molecular packing densities can be obtained. 

Possible explanations for these results involve differences in molecular packing density, velocity of sound, or mobility from one crystallographic direction to another. 

In Equation (6.1), N is the molecular packing density, or the number of molecules per unit volume. In the optical frequency regime, we substitute e = n and obtain the Lorentz-Lorenz equation [2] ... 

Here, N stands for the molecular packing density, h = 3el(2e+ 1) is the cavity field factor, e = (ej + 2e )/3 is the averaged dielectric constant, F is the Onsager reaction field, < //> and are the principal elements of the molecular polarizability tensor. 

PFPE overcoating onto all SAM surfaces increases the wear durability, and the extent of improvement in wear durability depends on the SAM surface properties such as surface wettability, chemical interactions between SAM molecules and PFPE molecules, and molecular packing density and order in the SAM surfaces. The extent of improvement of wear durability is very high when PFPE is coated onto reactive SAM surfaces (such as APTMS and GPTMS SAMs) and is very low when PFPE is coated onto nonpolar OTS SAM. This is mainly due to the differences in the extent of chemical interactions between PFPE and SAM molecules. 

Concentrations of the stmcture elements may be expressed in many units. In senticonductor physics it is coimnon to express the concentrations in number per cm3, xhis has the disadvantage, however, that when two compounds with different molecular (packing) densities contain the same number of defects per cm, the number of defects per molecular unit is different in the two compounds, and vice versa. Furthermore, the molecular unit size (packing density, or unit cell parameters) of a compound changes as a function of its nonstoichiometry and temperature, and in this case the unit of defects per cm does not unequivocally reflect the relative defect concentration per molecular unit or atom site under different conditions. 

Different rings in the central core and the insertion of lateral groups change the molecular packing density, which exerts an essential influence on the shear and the rotational viscosity (Fig. 19) [55, 85], Obviously, the reason for the large differences in the rotational viscosities of alkyl- and alkyloxy-cyanobiphenyls is the different packing density. Other explanations are not very convincing [82]. 

Bn =1.176 cm /nmol, and the Pt Auger signal for the clean surface was measured at 161 eV. Molecular packing density was found from the carbon packing density (for which the precision was generally the best) ... 

Molecular packing density was obtained independently from the ratio of Pt signals for the coated (Ipt) and clean Pt surface (Ipt) ... 

Experimental Conditions, molecular packing density, F, from C signal was employed to calculate nox (oxidation factor) other conditions as in Table 1. 

The molecular packing density from Ic/Ipt data at 1 mM TYR concentration (on the adsorption plateau) was 0.22 nmol/cm, and that from... 

The molecular packing density from Ic/Ipt was 0.35 nmol/cm, and that from Ipt/Xpt was 0.28 nmol/cm. The calculated molecular packing design based upon the model structure shown in Figure 3E is 0.417 nmol/cm (39.8 A /molecule). The packing density of ALA did not reach the limiting value calculated for the model structure when adsorbed from the millimqlar solution employed in the present study. 

Molecular packing density from Ic/Ipt was 0.22 nmol/cm, and from Ipt/Ipt was also 0.22 nmol/cm. The calculated packing density based upon the model structure shown in Figure 3F (catechol ring parallel to the surface) is 0.213 nmol/cm (78.0 A ), while that of the N-bonded orientation is 0.438 nmol/cm2 (37.9 A ). In view of these findings the most probable surface condition is a mixture of the two orientations (ring-parallel and N-bonded) (4m), Figure 3F. 

Auger data, Tables 1 and 2, and Equations 2 and 17-19 indicate absorption with the ring parallel to the Pt surface. Molecular packing density from... 

Molecular packing density based upon Ic/Ipt was found to be 0.20 nmol/cm, and from Ipt/Ipt was 0.22 nmol/cm. The calculated packing density for the model structure in Figure 3H is 0.208 nmol/cm (80.0 AM. 

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