Poly electron diffraction pattern

Structure of the Collapsed Monolayers. IR spectra of specimens prepared from air dried collapsed monolayers were typical of specimens in the a-helical conformation with no indication of any p conformation. Electron diffraction patterns gave a similar result. The patterns for poly-(L-leucine) and poly(L-norleucine) are similar to poly(L-norvaline) (12) with low crystallinity. A strong equatorial reflection at 10.94 0.10 A is observed in poly(L-leucine). If we assume as previously (5) that this is the 100 reflection from a hexagonal cell, the calculated area per residue in the monolayer is 17.3 A, assuming the molecular separation is the same as in the collapsed film. This figure is in agreement with the observed area of 16 A in view of the difficulties encountered in spreading the monolayer. 

Figure 4. Electron diffraction patterns from collapsed monolayers, (a) Poly(i.-methionine). The outermost reflection at 1.49 A is not visible on this photograph the sharp meridional reflection is 006. (b) 1 1 poly(i.-alanine) + poly(i>-...

Electron diffraction patterns have been obtained from collapsed monolayers of poly (alanine) and poly (y-benzyl glutamate). The enantiomorphic forms of the other two polymers give patterns with very poor crystallinity, and their racemic mixtures have not therefore yet been investigated. The principal features of the diffraction pattern of poly-... 

Figure 6.4 Electron diffraction patterns (a) schematic diagram showing the formation of an electron diffraction pattern in an electron microscope (b) an electron diffraction pattern from WNbi2033, resembling a plane section through the reciprocal lattice (c) a spotty electron diffraction ring pattern from a poly crystalline Ti02 photocatalyst...

Figures 10 and 11 show the thin-film morphology and electron diffraction pattern, respectively, of poly TDCN prepared in the same manner.

Fig. 9-11 shows an X-Ray diffraction pattern for a form of P(Ac) prepared as mlcrofiibrils which have dien been stretched 8-fold and Ij-doped. The strong meridional reflections seen actually correspond to poly(iodine) colunms of repeat distance 5 nm, which however betray a corresponding order in the P(Ac). A good example of the enhanced crystallinity observed with drawing is the case of the 16-fold stretched poly(thienylene vinylene) (P(TV)) fiber shown in Fig. 9-7. An X-Ray pattern of a CP with some crystalline domains in an overall amorphous CP matrix usually appears as diffraction spots situated in a diftiise halo, [204] e.g. for poly(3-alkylthiophenes). A stark improvement in crystallinity has been observed in going from undrawn P(TV)-precursor fiber to 8-fold stretched P(TV) fiber. Electron diffraction patterns closely correspond to X-Ray patterns.

Figure 33 Fractal seaweed aggregate from an ultrathin molten film of poly(trifiuoroethylene) crystallized at 140°C. The insert is an electron diffraction pattern demonstrating that the selected area of ca. 10 gm diameter is a single crystal. From Lovinger and Cais [4] with permission from the American Chemical Society.

Figure 8.14 (a) Electron diffraction pattern of an oriented film of poly(9,9-di-octyl-2,7-fluorene-diyl) (PFO) prodnced by directional epitaxy in trichlorobenzene, subsequently annealed at 210°C for 10 minntes and cooled at 0.4°C/inin. (b) Dark field of the PFO film, imaged through the 008 reflection. The crystalline lamellae of PFO are separated by narrow grain boundaries (darker lines), (c) Calculated diffraction pattern nsing the structural model of part (d). Reproduced from Reference [93] with permission of Brinkmann/L actuahte Chimique. 

The arrangement of helices in the solid and liquid crystalline states of poly(a-phenylethyl isocyanide) were determined by X-ray and electron diffraction. Well-defined diffraction patterns were obtained from oriented films using selected area electron diffraction. Intermolecular and intramolecular patterns were calculated from the five Debye-Scherrer rings. All the reflections were indexed in terms of a pseudo-hexagonal triclinic unit cell, with... 

The electron diffraction data have been reevaluated in support of a new proposal in a more recent paper by Murthy et al. [188]. A hexagonal structure, meanwhile presented for Li- and Na-doped polyacetylene as well as for Na-doped poly(pora-plienylene vinylene), is found to describe the diffraction patterns of PPP-Na rather well, as illustrated in Figure 1,24, The ions reside in channels within columns of three-fold symmetry (Figure 1,25). A compatible space group is P62m with a = 8.6 A, but the symmetry may be lower, for instance due to non-coplanarity of the rings. This may remain hidden in disorder. The authors pay considerable attention to the implications of the hexagonal structure... 

Warren et al. [240] have explored some twenty ditferent sulphonates, mostly aromatic, in the preparation of films of polypyrrole as well as poly(3-methylthiophene), from aqueous solution and from acetonitrile solution. Only PPy-/ TS films from an aqueous medium show the splitting of diffraction peaks this is not interpreted further. Rather, the degree of order is estimated from the intensity of the diffraction peak. Benzenesulphonate ranks first in this respect. Dodecylbenzenesulphonate is also effective, and additionally shows a small-angle peak. This suggests that especially alkyl chains are effective in arranging themselves in a domain of hydrophobic character. (Dodecylbenzenesulphonic acid has been found to be an excellent surfactant for polyaniline and to facilitate its processing see Section 6.4.1.) Some of the films give spot patterns in electron diffraction. Warren et al. [240] state, however, that cell data cannot be derived from these. 

It was reported recently, that polymeric can also form quasicrystals. Hayashida et al. [50] demonstrated that certain blends of polyisoprene, polystyrene, and poly(2-vinylpyridine) form starshaped copolymers that assemble into quaskrystals. By probing the samples with transmission electron microscopy and X-ray diffraction methods, they conclude that the films are composed of periodic patterns of triangles and squares that exhibit 12-fold symmetry. These are signs of quasicrystalline ordering. Such ordering differ from conventional crystals lack of periodic structures yet are well-ordered, as indicated by the sharp diffraction patterns they generate. Quasi-crystals also differ from ordinary crystals in another fundamental way. They exhibit rotational symmetries (often five or tenfold). There are still some basic questions about their stracture. 

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