Orientation out-of-plane

At higher fiber contents, we must also consider the relationship between fiber aspect ratio and the theoretical maximum achievable volume fraction. As fibers are laid down randomly in a plane, the probability of fibers crossing each other and thus being oriented out of plane increases as the fiber length and concentration are increased. This will result in a lower sti ess in the X-Y plane and a subsequent increase in stiffness in the Z direction. For instance, it has been shown [2] that, in the fiber aspect ratio range of 300-lKX), the maximum achievable volume fi action in a two-dimensional random in-plane laminate is 18-20% v/v. If the laminate volxune fraction is greater than this, then there are a number... 

In a similar system, we simulated the effect of the chemical structure of the polymer and the polymer chain density on the liquid crystal orientation [87]. To see the effect on the orientation of the polymer structure, we compared the liquid crystal orientation (out-of-plane tilting and in-plane orientation) on a polyamide surface that had the same surface density as the above-described PMDA-PPD. Even though the polyamide is similar to PMDA-PPD, the adsorption energy of the 8CB molecules is only about 2/3 as high. 

Because the fibers generally are anisotropic, they tend to be deposited on the wire in layers under shear. There is Htde tendency for fibers to be oriented in an out-of-plane direction, except for small undulations where one fiber crosses or passes beneath another. The layered stmcture results in the different properties measured in the thickness direction as compared to those measured in the in-plane direction. The orthotropic behavior of paper is observed in most paper properties and especially in the electrical and mechanical properties. 

The upper panel in Fig. 5.17 compares the experimentally determined PVDOS for the oriented array of Fe(TPP)(NO) crystals with that for Fe(TPP)(NO) powder. The crystal data is recorded with the incident X-ray beam 6° above the mean porphyrin plane. Since the NIS measurement is only sensitive to Fe motion along a probe direction, the spectral contribution of modes with predominantly in-plane Fe motion are enhanced, and the contribution of out-of-plane modes is suppressed in the oriented crystal data. 

Fig. 5.17 Comparison of the experimental PVDOS determined from NIS measurements on Fe (TPP)(NO) (upper panel) with the PVDOS predicted on the basis of DFT calculations using the B3LYP (center panel) and BP86 (lower panel) functionals. Blue traces represent the PPVDOS Dp (v)for oriented crystals (see Appendix 2, Part III, 3 of CD-ROM), scaled by a factor of 3 for comparison with the total PVDOS Dpe(v)of unoriented polycrystalline powder (red traces). Since the X-ray beam direction k lies 6° from the porphyrin plane, modes involving Fe motion in the plane of the porphyrin are enhanced, and modes with Fe motion primarily normal to the plane are suppressed, in the scaled oriented crystal PVDOS relative to the powder PVDOS. In-plane Fe modes dominate the 200-500 cm range of the data, while Fe motion in modes observed at 74, 128, and 539 cm is predominantly out-of-plane. Crosshatching in the upper panel indicates the area attributable to acoustic modes. In the lower two panels, the Fe-NO bend/stretch modes predicted at 386 and 623 cm , have been artificially shifted to the observed 539 cm frequency to facilitate comparison with the experimental results. Predicted PVDOS are convolved with a 10 cm Gaussian (taken from [101])...

FIG. 2 Molecular orientation angles at liquid interfaces for rodlike molecules. The out-of-plane motion is a rotation away from the OZ axis, whereas the in-plane motion is performed with the OX, OY) plane. 

FIG. 3 Solvation dynamics dependence of coumarin 314 probe molecule orientation at the air-water interface. Signals are generated with a 420 nm pump photon and probed by surface second harmonic signal with 840 nm (SH at 420), x Sx element. The normalized change in SH field is plotted vs. pump delay, r is derived from a single exponential fit to the data, (a) Pump polarization S (inplane), (b) Pump polarization P (out-of-plane). (Reprinted from Ref 24 with permission from the American Chemical Society.)... 

A detailed analysis of Ni11 complexes with mew-substituted porphyrins bearing zero, one, two, or four /-butyl groups revealed that both the out-of-plane and in-plane distortion depend on the perturbation symmetry of the peripheral substituents (number and position of substitutents), and their orientation.1775 These results have implications for understanding the role of nonplanar distortions in the function of metalloproteins containing nonplanar porphyrins.1776... 

In contrast to the above cases, the spectra in the four geometries are necessary for samples showing biaxial orientation. The information along the ND is accessible because under p-polarization, the electric field has components both in-plane (Z or X) and out-of-plane (Y) with respect to the sample. Although the details are beyond the scope of this chapter, Everall and Bibby have shown how to determine directly the different (P2mn) values (m, n — 0 or 2) by measuring the four absorbances of Equation (28) for two bands with different [j angles [32],... 

Pi Each pi bond has one axial nodal plane (p-like shape) and the longitudinal profile, (Figs. 4.24(b) and (c)) to be expected from 7t-type overlap of d orbitals. The two pi bonds are labeled 7tw(o) (out of plane) or 7Tww(l) (in plane) to distinguish their orientation with respect to the molecular plane. 

The lack of clear-cut hallucinogen-type activity for the 2-aminotetralins could be explained in several ways. The known deleterious effect of molecular bulk in the alpha-position would seem to direct attention to the steric effect of the reduced ring of the tetralins as detrimental to activity. In 18b, however, it has been noted (156) that the 5-methoxy group is forced out of plane by the adjacent 6-methyl and 4-methylene groups. The importance to activity of maintaining the methoxy groups coplanar with the aromatic ring has been emphasized earlier. Both substituent orientation and N-alkylation must also be important to activity, and it may not be realistic to make direct comparisons between the phenethyl-amines and the 2-aminotetralins. 

Orientation angles (degree) of the hydrocarbon chain axis y and the transition moment of the 4>-H out-of-plane bending vibration Jt(-H) around the surface normal in 11-monolayer LB films of CmAzoCn and CmAzoCn-Ba [4]. 

The molecular orientation and interactions of redox chromophores are very important in controlling photoresponses at the molecular level. Absorption and fluorescence spectra will give important information on them. We have studied, photoresponses, specific interactions, in-plane and out-of-plane orientation of various chomophores in LB films composed of amphiphiles shown in Figure 1 [3-12]. 

The out-of-plane orientation of chromophores can be more easily controlled in LB films as compared with the in-plane orientation. Many chromophores are known to show anisotropic orientation in the surface normal direction. The molecular structure of chromophores and their position in amphiphile molecules, the surface pressure, the subphase conditions are among those affect their out-of-plane orientation. The out-of-plane orientation has been studied by dichroic ratio at 45° incidence, absorbance ratio at normal and 45° incidence, and incident angle dependence of p-polarized absorption [3,4,27,33-41]. The evaluation of the out-of-plane orientation in LB films is given below using amphipathic porphyrin (AMP) as an example [5,10,12]. 

As the isoquinoline molecule reorients in the order listed above, the absorption of infrared radiation by the in-plane vibrational modes would be expected to increase, while that of the out-of-plane modes would be predicted to decrease (in accordance with the surface selection rule as described above). In the flat orientation there is no component of the dipole moment perpendicular to the surface for the in-plane modes, and under the surface selection rule these modes will not be able to absorb any of the incident radiation. However, as mentioned above, infrared active modes (and in some cases infrared forbidden transitions) can still be observed due to field-induced vibronic coupled infrared absorption (16-20). We have determined that this type of interaction is present in this particular system. 

In many planar metal complexes it is not possible to record an ENDOR spectrum which only contains contributions from Bo orientations in the complex plane. This is due to the fact that in the powder EPR spectrum the high- or low-field turning points may arise from extra absorption peakssl which do not correspond to directions of the principal axes. ENDOR spectra observed near the in-plane region of such a powder EPR spectrum are due to molecules oriented along a large number of B0 directions (in- and out-of-plane), so that the orientation selection technique is no longer effective. 

Two orientations have been chosen (Fig. 17) for polarized excitation spectroscopy. The first is used to distinguish between in-plane and out-of-plane effects, while the second one allows a comparison of the two in-plane directions. 

Fig. 17. The structure of the ketone (1) molecule as determined by r-ray crystallography shown in the (approximate) orientations used in the polarization measurements. In (a) the in-plano versus out-of-plane polarization directions are compared. The in-plane extinction direction shown is nearly parallel to the Cl—C2 double bond, being tipped just 5°out of plane. In (b) the two directions in plane arc compared. The long axis extinction direction shown is exactly in plane and makes an angle of 40° with the Cl—C2 double bond, (From Jones, Kearns, and Wing, Ref, 9))...

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