Face-on orientation

For a detailed study of the structural properties of LMW and HMW fraction thin films t 10-200 nm) grazing-incidence diffraction techniques [25] have been employed. As mentioned above, P3HT films show mostly lamellae structure with possible edge-on and face-on orientation [21]. The scattering scheme is shown in Figure 10.1. This set-up allows measurement of a momentum trans-... 

Aida et al. have shown that o-phenylene octamers can be used as surface modifiers to obtain homeotropic ordering of a variety of DLCs [116]. The octa-meric o-phenylenes are known to fold helically into a cylindrical architecture that resembles to a pi-stacked column of DLCs. It has been found that the oligomers adhere to the glass substrate with its cylindrical axis orthogonal to the surface. Therefore it is speculated that this face-on orientation of the octamer likely nucleates the homeotropic ordering of the liquid crystalline discotic materials. 

The relative intensity enhancement of the out of plane bands suggests that the corresponding vibrations are mainly parallel to the normal of the incident radiation. Thus, the macrocycle complexes have a preferential face-on orientation... 

The corresponding in-plane vibrations at 1,273, 1,380, 1,480 and 1,514 cm undergo a relative intensity decrease. All the above results suggest that the coordination plane of the complex is face-on oriented on the metal. On the other hand, the observation of an enhancement in bands at 1,176 and 1,237 cm, attributed to in-plane CH phenyl modes, and at 1,453,1,548,1,590 and 1,630 cm attributable to the vCC of the phenyl substituents, or to modes in which this group is involved, supports the idea of a perpendicular orientation of these groups with... 

The SERS spectrum of CUN4 on Ag colloid (Figure 14.36b) indicates that the complex adopts a face-on orientation on the metal as deduced also for the Ni complex. 

On Au film (Figure 14.36c) a marked intensification of the in-plane modes of the 1,500-1,650 cm region is also observed along with a relative increase of the band at 3,056 cm However, the presence of prominent bands at 470, 603 and 637 cm , suggests the existence of face-on oriented macrocycles. The simul-... 

Thiebaut, O. Bock, H. Clrelet, E. Face-on oriented bilayer of two discotic columnar liquid crystals for organic donor-acceptor heterojunction. J. Am. Chem. Soc. 2010,132, 6886-6887. 

Generally aromatic molecules tend to adsorb in a face-on orientation on metallic and HOPG surfaces due to the favorable interactions with the extended tt-system of the... 

Hydrophobic HBC-discs with six hydrophihc oligo(ethylene oxide) chains exhibit highly ordered columnar structures with enhanced molecular segregation in the bulk state [78]. The hydrophilic periphery forces a face-on orientation at the air/ water interface and homeotropic alignment in cluster-separated thin layers after transfer by the LB-method. 

F. 16 Molecular (mentation of P3HT in thin layers, with fast charge transport expected parallel to the chain axis and in the x-stacking direction, while the side chains act as barriers (a) edge-on oii tation, (b) face-on orientation, and (c) standing chains. Image courtesy of Florian Fischer... 

Besides the deposition conditions, the nature of the substrate can have a significant influence on the texture. Substrate treatment with self-assembled monolayers (SAMs) such as octadecyltrichlorosilane, hexamethyldisilazane, and Y-aminopropyltriethoxysUane results in an edge-on texture [72, 103-105]. By contrast, Chow and coworkers reported the formation of a face-on oriented P3HT... 

Fig. 19 Molecular orientation of P3HT on different surfaces with (a) edge-on and (b) face-on orientation [105], (c) Height and (e) phase AFM images of P3HT on a NH2-terminated SAM. (d) Height and (f) phase AFM images of P3HT on a CH3-terminated SAM [104], (Reprinted with permission from Kim et al. [105], Copyright (2005) American Chemical Society. And reprinted with permission from Kim et al. [104]. (Copyright (2005) Wiley-VCH)...

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