Phenyl ring orientation

Polyphenylenevinylidenes and Related Polymers meta-Polyphenylenevinylidenes (PmPV) are rather frequently used for the production of nanotube composite materials. Normally, such derivatives with functional groups ensuring a better wetting are employed (e.g., PmPV ). An exemplary substance commonly used is depicted in Figure 3.92a. The adhesion of the polymer to the nanotube is mainly based on Jt-Jt-interactions with the phenyl rings oriented in parallel to the surface of the tube. The long side chains of substituted PmPV additionally contribute to the interfacial exchange. 

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].

Figure 18.12 The electron-density map is interpreted by fitting into it pieces of a polypeptide chain with known stereochemistry such as peptide groups and phenyl rings. The electron density (blue) is displayed on a graphics screen in combination with a part of the polypeptide chain (red) in an arbitrary orientation (a). The units of the polypeptide chain can then be rotated and translated relative to the electron density until a good fit is obtained (b). Notice that individual atoms are not resolved in such electron densities, there are instead lumps of density corresponding to groups of atoms. [Adapted from A. Jones Methods Enzym. (eds. H.W. Wyckoff, C.H. Hirs, and S.N. Timasheff) 115B 162, New York Academic Press, 1985.]...

Fig. 13 a, b. Possible stacking of macromolecular bilayers in the P form crystals of s-PS. The regular succession of bilayers ABAB. .. gives rise to the ordered P" modification (a) defects, corresponding to pairs of bilayers of the kind AA or BB, would characterize the disordered P modification an AA defect is reported in (b). The symbols (/) and ( ) indicate the orientation of the lines connecting the adjacent phenyl rings of each chain inside the macromolecular bilayers A and B, respectively [29]... 

A disorder of the same kind has been suggested also for the orthorhombic form of s-PS. In fact, in the so-called disordered [V modification the disorder would be in the stacking of ordered macromolecular bilayers and a 3-D long range periodicity would characterize only the mean position and orientation of the phenyl rings [28,29] (Fig. 13). 

This kind of disorder is present, for instance in the hexagonal form of s-PS. The disorder present in the so-called a modification [27,28], would correspond, in fact, to the statistical occurrence of two specific orientations of triplets of tram-planar chains, which leave unaltered the positions of the barycenters of the phenyl rings (Fig. 14) at well-defined positions in the 3-D lattice. 

P2j Z = 2 DX = 1.43 R = 0.067 for 1269 intensities. The uracil residue is in the anti (63.4°) disposition. The conformation of the D-ribosyl group is 2T3 (176.8°, 37.5°). The orientation about the exocyclic, C-4 -C-5 bond is t (—174.2°). The phenyl and uracil ringsofthe same molecule lie in almost parallel planes, 120 pm apart. The phenyl group is disordered. The uracil ring is sandwiched by the phenyl rings, and vice versa. The 0-1 and N-a atoms of the peptide backbone are hydrogen-bonded to 0-4 and N-3 of atranslationally related uracil to form cyclic dimers. Such interactions serve as models for nucleic acid-protein interactions. [Coordinate errors H(02 ) x should be —1574, instead of —1474 H(Na)2 z should be —145 instead of— 645.]... 

The initial step of the adsorption of thiols on a Mo(100) surface is the formation of adsorbed thiolate groups. Phenyl thiolate is formed upon adsorption of thiophenol at 120 K on a clean Mo(110) surface.381 The thiolate intermediate subsequently undergoes competing C-S bond hydrogenolysis to form benzene, or C-S and C-H bond scission to form surface benzyne. The adsorption of thiophenol was also studied on a sulfur-covered Mo surface382 Phenyl disulfide is formed via S-H bond scission and S-S bond formation. The S-S linkage is oriented perpendicular and the phenyl ring parallel to the surface. 

Figure 3 Orientation of the phenyl rings in stretched PET films, with respect to the machine (X,), transverse (X2), and normal (X3) directions, as a function of applied stress, a0, at 90°C. Birefringence results were obtained using refractrometry. Reproduced with permission from Lapersonne et al. [11]. Copyright Elsevier 1994.

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