Anisotropic segment

Prices for the different material groups (F —F ) are largely influenced by product size and shape and the quantity of production. Apart from product shape, the main price-determining factor is the performance factor K Prices for the powder, a sintered anisotropic ring, and a sintered anisotropic segment are roughly on the order of 1, 2, and 5, respectively. 

Figure 7.7 Fast but anisotropic segmental motion results in a solid-like contribution to the NMR signal. This contribution is expressed in terms of a fractional contribution q of the second moment M2 of the rigid lattice line of a single chain or residual dipolar interactions between protons. The line splitting caused by the dipole-dipole interaction depends on the orientation angle q of the internuclear vector of the coupling protons in the magnetic field B(). The distribution of orientation angles changes with the...

The depolarized spectrum is dominated by local fluctuations of the optical anisotropy owing to an overall orientation of stiff molecules, local motions of optically anisotropic segments or internal Ronse-Zimm modes for flexible chain molecnles. The depolarized spectrum thus reflects dynamics of collective molec-nlar orientation when the interaction between translation and rotation can be neglected. 

To consider the relative permittivity tensor of polymeric system, one makes use of the heuristic model of a macromolecule as freely-jointed segments each macromolecule consists of z segments and is surrounded by solvent molecules (Sect. 2.1). Then, the simple old-fashion [111, 112] speculations allow us to determine the relative permittivity tensor of polymeric system in terms of the mean orientation of anisotropic segments of the macromolecules (6,6 ). The relative permittivity tensor is formulated below to within first-order terms in the orientation tensor... 

Making the usual assumption that the birefringence arising from the deformation of swollen elastomer is a result of the orientation of optically anisotropic segments, then the mean macroscopic polarizability remains constant, (a, + + Oj) = 3o where... 

HDH/DHD interface. If the motion of the polymer was the same for each portion of the molecule, i.e., isotropic, the concentration of deuterium across the interface would remain constant. However, if the monomer motion is anisotropic, such as with reptation, where the chain ends lead the centers, a high amplitude ripple in the concentration profile, as described below will be displayed. For a reptating chain, lateral motion of the central segment of the chain is permitted up to depths approximating the tube diameter, after which the central segments must follow the chain ends in a snake-like fashion. 

The cross-peak coordinates represent two frequency values, va and vp, where va + vp=2v, and v is the proton frequency. When plotted in the coordinates v2a and v2p, the contour lineshape is transformed into a straight line segment. An extrapolation of this straight line permits the determination of the hyperfine tensors. A curve obtained by choosing some frequencies in the range will intersect the line defined by the squares of the values v2a and v2p in two points. The values where the curve intersects the experimental data are (val, vpi) and (va2, vp2), where va=A/2 + v, and vp= Vj-A/2. This gives two values of the anisotropic coupling tensor, Ar... 

A few examples of the moduli of systems with simple symmetry will be discussed. Figure 1A illustrates one type of anisotropic system, known as uniaxial orthotropic. The lines in the figure could represent oriented segments of polymer chains, or they could be fibers in a composite material. This uniaxially oriented system has five independent elastic moduli if the lines (or fibers) ara randomly spaced when viewed from the end. Uniaxial systems have six moduli if the ends of the fibers arc packed in a pattern such as cubic or hexagonal packing. The five engineering moduli are il-... 

Figure 23. Radial segment density profile through a cross-section of a highly curved spherical vesicle. The origin is at r = 0, and the vesicle radius is very small, i.e. approximately r = 25 (in units of segment sizes). The head-group units, the hydrocarbons of the tails and the ends of the hydrocarbon tails are indicated. Calculations were done on a slightly more simplified system of DPPC molecules in the RIS scheme method (third-order Markov approximation), i.e. without the anisotropic field contributions...

From a practical point of view, the deviation from main-chain continuity is the most interesting one. Especially the concept of the so-called parallel offset of the main chain is favorized. It is realized in a commercial product made from 4-hydroxybenzoic acid and 2,6-hydroxynaphthalenecarboxylic acid. The incorporation of small amounts of 2,6-hydroxynaphthalenecarboxylic acid causes a discontinuity in the main chain but only in form of a parallel offset of some chain segments. Thus, the ability to form liquid crystalline states is largely maintained as well as the anisotropic properties of the molten and solid polyester. Instead, the melting point is significantly reduced, as desired. 

Fig. 9. Phase diagrams of quasi-ternary systems containing two different molecular weight samples a PHIC-toluene with (Ni, N2) = (4.46,0.38) [73] b schizophyllan-water system with (Nt, N2) = (0.930, 0.0765) [75,76]. (O, A) experimental coexisting isotropic phase ( , , ) experimental coexisting anisotropic phase dashed segments, experimental tie lines the shadowed triangular region, the IAA triphasic region thick full curves, theoretical binodals thin full segments, theoretical tie lines...

Jerry and Monnerie l " have proposed a modified theory of rubber elasticity which includes anisotropic intermolecular interactions U12 (favoring the alignment of neighbouring chain segments) in the form U,2 = ZUL(r12) PL(0i) PL(02), where r,2 is the intermolecular distance, 0X and 02 are the angles between the molecular axes... 

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