Orientation-induced

A somewhat curious effect arises when additional water is dosed on top of this synthetic inner layer, in that the work function is observed to exhibit substantial further decreases. This implies that the water molecules in the multilayers above the inner layer assume some measure of preferential orientation, induced by the presence of the adsorbed bromide in the first layer. This result is probably connected to structure making and structure breaking, or hydrophobic and hydrophilic, properties of soild surfaces, but will not be discussed in detail here. 

Yamane H, Yabuuchi Y, Fukagawa H, Kera S, Okudaira KK, Ueno N (2006) Does the molecular orientation induce an electric dipole in Cu-phthalocyanine thin films J Appl Phys 99 5... 

In addition to the nature of particulate platelet orientation induced during injection moulding, the associated consequences on molecular orientation and crystalline order of the host thermoplastic matrix have also been reported with particular regard to various flake-filled polypropylenes [174], together with an attempt to interrelate these higher order structural parameters with physical properties of the composites [175]. 

Equilibrium electrostatic interactions between a solute and a solvent are always nonpositive - tliey are zero if the solute is characterized by no electrical moments (e.g., a noble gas atom) and negative otherwise, i.e., attractive. It is easiest to visualize the electrostatic interactions as developing in a stepwise fashion. Consider a solute A characterized by electrical moments for simplicity, consider only die dipole moment. When A passes from the gas phase into a solvent, the solvent molecules, if diey have permanent moments of their own, reorient so that, averaged over thermal fluctuations, their own dipole moments oppose that of the solute. In an isotropic liquid with solvent molecules undergoing random thermal motion, the average electric field at any point will be zero however, the net orientation induced by the solute changes this, and the lield induced by introduction of the solute is sometimes called the reaction field . 

The orientation induced by drawing has also been followed for partially oriented PET fibers. In this case where unaxial orientation can be presumed, it is possible to calculate the relative amounts of the trans and gauche isomers. The measurements indicate that increased orientation of the amorphous phase leads to an increase in the trans isomer 288). 

Figure 20 presents mesophase rods produced by extrusion alone and by a light draw after extrusion. As Jenkins and Jenkins observed (34), the strong preferred orientation induced by extrusion was easily disturbed by pyrolysis bubbles or even by small flow irregularities. However, modest draws (e.g., draw ratio = 2) after extrusion produced fibrous morphologies with good uniformity. At these draw levels, the nodes and crosses characteristic of wedge disclinations could be resolved on transverse sections. 

Transient turbidity is an optical technique for measuring the size of magnetic particles [63,64], It does this by aligning particles in an electric field, removing the field, and following their return to random orientation induced by Brownian motion. Their relaxation is measured by turbidity and this can be related to particle size distribution if assumptions are made... 

Since, in HRS, there is no preferred orientation induced by an additional static field, there is the possibility of varying the experimental conditions in order to increase the number of independent observables. The number of theoretically possible independent observations, and hence the number of tensor components that can be obtained by HRS, is at most five. For parametric light scattering, this number is six, due to the possibility of distinguishing between the two optical fundamental fields [20]. The experimental difficulty has precluded the determination of this number of components. What is experimentally realistic in HRS is an additional depolarization measurement, apart from the classical measurement of the intensity of the second-order incoherent scattered light. The two measurements, the total intensity measurement and the depolarization ratio (or two intensity measurements, one with parallel and one with perpendicular polarization for fundamental and second harmonic), represent two independent observables and allow the experimental determination of two tensor components. For molecules of C2 symmetry, these are and P xxy resulting for the total intensity measurement in Eqn. (21),... 

Figure 12.8 Cryo-TEM micrographs of 5-nm-diameter wormy micelles in 0.05 M CTAC with added (a) 0.05 M NaSal and (b) 0.10 M NaSal. All samples were squeezed to form thin films. Orientation induced by squeezing was allowed time to relax in (a), but not in (b). Bar =100 nm. (Reprinted with permission from Clausen et al., Journal of Physical Chemistry 96 474 Copyright < lyy2, American Chemical Society.)...

In this chapter, I discuss the phenomenon of molecular orientation induced by photoisomerization whereby experiment merges with theory to assess molecular movement during isomerization. The theory unifies photochemistry with optics, and it provides rigourous analytical tools for powerful quantification of coupled photoisomerization and photo-orientation. Experiments on spectrally distinguishable isomers detail the mechanisms of chromophore reorientation during photo- and thermal isomerization. In particular, I... 

Thus, one comer remains non-shared and can be oriented either up or down relative to the plane of the sheet. The possibility of different orientations induces the appearance of orientational geometrical isomers shown in Fig. 65. By analogy with the geometrical isomers described above, the isomers under discussion can be described using u and d symbols of tetrahedra orientation. The isomer shown in Figs. 65a and b can be described as a (u)(d) isomer (its orientation matrix has the 1x2 dimensions), whereas the isomer shown in Figs. 65c and d is a (ud) isomer (matrix dimensions are 2x1). The same type of isomerism is found for the actinyl sulfate sheets shown in Fig. 66. a b... 

In molecular systems the polarization P results from the individual molecular dipoles and has two main contributions. One is associated with the average orientation induced by an external field in the distribution of permanent molecular dipoles. The other results from the dipoles induced in each individual molecule by the local electrostatic field. The characteristic timescale associated with the first effect is that of nuclear orientational relaxation, x , typically 10 " s for small molecule fluids at room temperature. The other effect arises mostly from the distortion of the molecular electronic charge distribution by the external field, and its typical... 

Ug expresses the electronic response (induced dipoles), oi is associated with the average orientation induced in the distribution of permanent molecular dipoles, and as denotes the total response. These contributions can in principle be monitored experimentally Immediately following a sudden switch-on of an external field T>, the instantaneous locally averaged induced dipole is zero, however after a time large relative to Xg but small with respect to Xn the polarization becomes Pg = ag D. Equation (1.237) is satisfied only after a time long relative to r . Similarly we can define two dielectric constants, Sg and Sg such that 5 = and Pg = [(sg —... 

M are fast compared with the random changes in particle orientation induced by the thermal agitation of the surrounding fluid molecules. 

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