Chain alignment

The importance of the alignment of the polymer chains has been recently demonstrated in a study in which PPyCPFs) films have been stretched to 96% [102]. The conductivity parallel to the stretch was increased, while the strain perpendicular to the stretch increased from 1.45 to 2.65% (but with more creep) at the same time very little strain could then be produced parallel to the stretch. The suggestion made was that counter-ions migrated to locations between the oriented polymer chains, producing strain perpendicular to this direction. The nanoscale chain configuration has also been altered by rolling as well as 

A further nanostructured approach which has been undertaken is to establish a degree of anisotropy across a conducting-polymer film, often due to differences created at the inert 

A single-layer PPy film, capable of bending actuation due to its intrinsic anisotropy, but without delamination problems, was constructed by electrochemical synthesis on a steel 

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In the Fischer convention, the ermfigurations of other molecules are described by the descriptors d and L, which are assigned comparison with the reference molecule glyceraldehyde. In ertqrloying the Fischer convention, it is convenient to use projection formulas. These are planar representations defined in such a w as to convey three-dimensional structural information. The molecule is oriented with the major carbon chain aligned vertically in such a marmer that the most oxidized terminal carbon is at the top. The vertical bonds at each carbon are directed back, away fiom the viewer, and the horizontal bonds are directed toward the viewer. The D and L forms of glyceraldehyde are shown below with the equivalent Fischer projection formulas. 

Fig. 1. Schematic representation of the chain alignment of a triple helix. Circles represent o-carbons, that of glycine is denoted number 1. Heavy circles indicate the chain in front, the N-terminal is at the bottom. The intrachain hydrogen bonds are designated by broken lines...

Fig. II (a) View of the crystal structure of [Cr(Cp )2][Ni(a-tpdt)2] along [1 —1 0], where it is possible to see three layers of chains aligned either along [1 —1 0] or [1 1 0], cl correspond to the closest D+A intrachain contacts and c2 to the closest A A interchain interlayer contacts, (b) View of two chain layers along the [1 0 2] direction. The chains of the layer on the right are aligned along [1 — 1 0] and on the left along [1 1 0]. c3 corresponds to the closer interchain contacts within the layers...

Apart from the tunable color emission covering the full visible range, there are several other aspects supporting the interest in PTs for PLEDs. PTs are examples of classical conjugated polymers with intrinsic one-dimensionality of the polymer chain. Alignment can induce anisotropy in macroscopic properties such as electron transport or optical properties. Polarized... 

Jimenez et al. (2002) proposed a molecular model for the insulin protofilament based on these data and on electron cryomicroscopy (cryo-EM) reconstructions of insulin fibrils. The fibrils show a number of twisted morphologies that seem to be alternative packings of similar protofilaments. The protofilaments have cross sections of 30x40 A. The authors suggest a complete conversion to / -structure and model the amyloid monomer as having four jS-strands (Fig. 3B). Each insulin chain contributes two of these jS-strands, and the chains align in a parallel stack, constrained by the interchain disulfide bonds. One pair of stacked /i-stran ds is curved... 

The extended structure of [Mn(ebbg)(OH2)] [N03]3 [50,51], is difficult to ascertain, owing to the five co-ordinate Mn(III) geometry and the non co-planarity of the cations and anions. Approximate sheet architectures can be discerned in planes parallel to (-1 3 1) and (1 -2 -2). The latter is shown in Fig. 25. In this view, the cations form dimeric pairs, which are linked through N03 anions and coordinated H20 molecules to form chains aligned in the [0 1 -1] direction. The... 

Planet interacts with itself and with other Cabinet servers in different ways depending on what relationship is desired. Searching is available by protein chain alignment and ligand structural similarity within Planet itself by selecting similar. En2yme functionality and ligand-structure search across all Cabinet databases is available with the related button. 

FIGURE 18.10 Idealized relationships between the distance from the outer wall and chain alignment. 

In addition to the above effects, the intermolecular interaction may affect polymer dynamics through the thermodynamic force. This force makes chains align parallel with each other, and retards the chain rotational diffusion. This slowing down in the isotropic solution is referred to as the pretransition effect. The thermodynamic force also governs the unique rheological behavior of liquid-crystalline solutions as will be explained in Sect. 9. For rodlike polymer solutions, Doi [100] treated the thermodynamic force effects by adding a self-consistent mean field or a molecular field Vscf (a) to the external field potential h in Eq. (40b). Using the second virial approximation (cf. Sect. 2), he formulated Vscf(a), as follows [4] ... 

This order is associated with chain alignment or, as previously seen, with a reduced mobility of the network strands. 

Such increases of y- and -relaxation temperatures with increasing draw ratio are thought to be due to the limited mobility of molecular chains in the noncrystalline region. As pointed out in the foregoing section, the amorphous molecular chains align fairly well parallel to the drawing direction. Therefore, the conformational versatility and mobility of such molecular chains are considered to be much restricted. 

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