Molecular tilt angle

S = (3 is molecular tilt angle to film normal. 

Fig. 11. The dependence of SH intensity (open circle) and molecular tilt angle < > to film normal of the mixed monolayer on the fraction of C18OAZ0NO2.

The values of the envelopes of SH intensity at 45 ° incidence in the mixed monolayers are plotted against the fraction of C180AZ0N02 in Fig.ll. The molecular tilt angle <(> evaluated by the above-mentioned procedure is also shown in this figure. The SH intensity of the single-component monolayer of C180AZ0N02 is very small. This result means that the orientation of amphiphile... 

The MAMs were found to be closely packed. NEXAFS and FTIR spectroscopy studies revealed that the molecular tilting angles relative to the surface normal varied from 4° to 21° as a function of Ax. In wetting studies it was found that the highest water contact angles ( 131°) with the lowest contact angle hysteresis... 

We note that the tilt direction of the molecular distribution can directly be derived from the ratio of the 45° intensities, which are emphasized by the enlarged symbols in Fig. 6.10. The -45° intensity is larger than the 45° intensity for the rubbed polyimide film, which indicates an upwards tilt of the molecular distribution with respect to the rubbing direction. For the ion beam irradiated film, on the other hand, one notices the opposite intensity ratio, which corresponds to a downward tilt of the molecular distribution with respect to the in-plane direction of the ion beam irradiation. One can therefore characterize the anisotropy of the molecular distribution by two ratios the molecular tilt angle is determined by the ratio of the tt intensities observed for a = 45° incidence angle within the plane parallel to the rubbing or ion beam direction. And the ratio of the two normal incidence spectra with the electric field vector in the plane either parallel (sohd squares at a = 90°) or perpendicular to the treatment direction (open circles at a = 90°) reveals the in-plane anisotropy. We will make use of this later. 

Fig. 6.14. Ion beam incidence angular dependence of the liquid crystal pretilt angle (3 and the molecular tilt angle 7 of the polymer segment distribution at the film surface for polyimide (top) and amorphous carbon (bottom). As predicted by the alignment model the liquid crystal pretilt angle / follows the molecular tilt angle 7. The line is a fit to y 0) using a model that assumes finite, but different cross sections for breaking of phenyl rings oriented along or perpendicular to the ion beam direction [35].

Comparing the spectra in the right panel, which characterize the molecular tilt angle, one finds the same polarization dependence for the two ion beam irradiated materials, which is opposite to the one of the rubbed polyimide film. Hence, a downwards liquid crystal pretilt angle is expected for both ion beam treated surfaces. Again, since the overall shape and the tt intensities and their dichroism is comparable for the two ion beam irradiated films, liquid crystals ai e expected to exhibit a technologically sufficient pretilt angle on an ion beam irradiated amorphous carbon layer. 

The molecular tilt angle depends on the surfactant concentration at the interface. In the regime of infinitely small surfactant concentrations, the molecules tend to lay almost flat on the surface. This corresponds to tilt angles of about 90° measured with respect to the surface normal vector. During film compression, the phase transitions towards liquid-expanded and liquid-condensed phases can be characterized by decreasing tilt angles. 

In Figure 3.13, the results of pentacene [45] are shown as an example. For penta-cene (Pn), the values of mj in the F—Xp and F— Ypn directions at 300 K are determined to be 3.02mo and 1.86mo, respectively, by applying Eq. (3.14) to the measured dispersion rdations. This result demonstrates the presence of the anisotropy of the hole mobility in pentacene crystals also at room temperature. Furthermore, by comparing with the other experimental E k) relations in pentacene films [46-48], it was confirmed that the band structure of pentacene films is very sensitive to the minor difference in the film structure, espedally molecular tilt angle, because of bumpy special distribution of MO of the molecule. Tliis was also... 

The differences in the density profiles and the molecular tilt angles for the two force fields can be mainly attributed to the attractive surface interactions in model II. The alkyl chains respond to this potential by aproaching the surface. In addition to the increase in tilt angle, the alkyl chains for model II have an enhanced tendency to the formation of loops which is evident in the secondary peak found in the methyl bead denisty profile. These structural changes are accompanied by a large decrease in the liquid densities for model II, which are approximately 30% lower than those for the Karaborni and Toxvaerd model at the same temperatures. 

Figure 9 with an Ordered SAM and Molecular Tilt Angle of 30° Relative to the Surface Normal ... 

Note that only the P, component of the total polarization is nonvanishing after a symmetry operation, so the measured value of the spontaneous polarization, P, is proportional to the molecular tilt angle, 0 [6,7,15] ... 

These modes can also be observed in ferroelectric liquid crystalline polymers (FLCPs). The soft mode is connected with the change of the molecular tilt angle 0 near the phase transition from an untilted to a tilted phase (e.g., Sm A /Sm C ). For low-molar-mass compounds it usually has a frequency of 10 to 10 Hz. For... 

The threshold for the director deviation can be calculated neglecting distortion of the smectic layers [118]. The angle ip defined in Fig. 6.32 is taken as variable. At a boundary cos rpo = tan fi/ tan fl, where /x is the angle between the smectic layer normal h and the plane of a substrate (xy), n is the molecular tilt angle of a smectic C. The free energy density includes the Frank elastic term... 

Molecular orientational models of SSFLCs have previously been studied, so the orientational states of SSFLCs and their optical properties are fully understood. For example, the smectic layer structures of various SSFLCs have been studied by using higji-resolution X-ray diffraction and the relationship between the layer tilt angle and the optical molecular tilt angle has been confirmed. 

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