Phase structure interphase

Model of a supramolecular structure of polymolecular ensembles or clusters, determined by interaction and mutual arrangement of the forming molecules. At this level, the specific mechanisms of supramolecular chemistry, including molecular recognition, self-assembly, etc. [4] can be allocated. In most cases, it is possible to limit this area to objects with the sizes under 1 to 2 nm, since further increase in the sizes admits application of statistical concepts like phase and interphase surface. 

The eukaryotic cell cycle (see Fig. 12-41) produces remarkable changes in the structure of chromosomes (Fig. 24-25). In nondividing eukaryotic cells (in GO) and those in interphase (Gl, S, and G2), the chromosomal material, chromatin, is amorphous and appears to be randomly dispersed in certain parts of the nucleus. In the S phase of interphase the DNA in this amorphous state replicates, each chromosome producing two sister chromosomes (called sister chromatids) that remain associated with each other after replication is complete. The chromosomes become much more condensed during prophase of mitosis, taking the form of a species-specific number of well-defined pairs of sister chromatids (Fig. 24-5). 

Molecular Weight Dependence of Phase Structure. Similar line shape analysis was performed for samples with molecular weight over a very wide range that had been crystallized from the melt. In some samples, an additional crystalline line appears at 34.4 ppm which can be assigned to trans-trans methylene sequences in a monoclinic crystal form. Therefore the spectrum was analyzed in terms of four Lorentzian functions with different peak positions and line widths i.e. for two crystalline and two noncrystalline lines. Reasonable curve fitting was also obtained in these cases. The results are plotted by solid circles on the data of the broad-line H NMR in Fig. 3. The mass fractions of the crystalline, amorphous phases and the crystalline-amorphous interphase are in good accord with those of the broad, narrow, and intermediate components from the broad-line NMR analysis. 

As can be seen, the crystalline fraction (orthorhombic plus monoclinic) decreases from 0.70 to 0.54 at a draw ratio of 50 times and increases to 0.82 at the largest draw ratio. The amorphous phase that appears at a lower draw ratio decreases with increasing draw ratio, accompanying the decrease of the interphase. Such phase structure as elucidated here will reflect on the various macroscopic properties of samples. 

Phase structure. It was confirmed in the previous section that the bulk iPP crystal consists of three phases the crystalline, noncrystalline amorphous phase and crystalline-amorphous interphase. Hence, it is also assumed that the bulk sPP crystal forms a three-phase structure in a similar manner. The question here is whether the sPP crystal involves such a phase structure in forming a gel or not In order to study this problem, we have analyzed 13C NMR spectra of the sPP gel. The noncrystalline contributions to each resonance of CH2, CH and CH3 carbons in the DD/MAS 13C NMR spectrum of the gel can be seen, as indicated by the arrows in Fig. 27, where their assignment as noncrystalline resonances was confirmed by the spin-lattice and spin-spin relaxation times as described above with relation to the results in Table 13. We carried out the line-decomposition analysis of the resonance lines of the methine and methyl carbons, since these resonances are most pertinent for the present purpose because of the simplicity of the spectral shape. 

On the other hand, in the solid-state high resolution 13C NMR, elementary line shape of each phase could be plausibly determined using magnetic relaxation phenomenon generally for crystalline polymers. When the amorphous phase is in a glassy state, such as isotactic or syndiotactic polypropylene at room temperature, the determination of the elementary line shapes of the amorphous and crystalline-amorphous interphases was not so easy because of the very broad line width of both the elementary line shapes. However, the line-decomposition analysis could plausibly be carried out referring to that at higher temperatures where the amorphous phase is in the rubbery state. Thus, the component analysis of the spectrum could be performed and the information about each phase structure such as the mass fraction, molecular conformation and mobility could be obtained for various polymers, whose character differs widely. 

In this overview, we will first discuss how transmission electron microscopy (TEM) techniques can be used to determine the presence or absence of intergranular amorphous phases at interphase boundaries in structural... 

Aside from the selectivity criterion that is essential to all ion specific electrodes, the principal objective of applied design is to physically and chemically control the phase and interphase boundaries across the multiple layers that comprise the electrode structure. The conduction path of electrical charge across all the phases including the solid conductors and external measurement circuitry, as well as the chemical charge across polymeric and solution phases, may be represented by the schematic illustrated in Figure 4. 

Phase structure. It was confirmed in the previous section that the bulk iPP crystal consists of three phases the crystalline, noncrystalline amorphous phase and crystalline-amorphous interphase. Hence, it is also assumed that the bulk sPP crystal forms a three-phase structure in a similar manner. The question here is whether the sPP crystal involves such a phase structure in forming a gel or not In order to study this problem, we have analyzed NMR spectra of the sPP gel. 

The fourth example is the controlled solidification of germanium (or silicon) to produce semiconductor grade materials. The solid phase structure and composition depend strongly upon the interphase exchange processes which can enhance incorporation into the solid or into the liquid depending upon This example implicitly includes the production of most of the metallic structural materials. 

The permeation of gases in such a complex structure is very difficult to model due to the lack of information on the phase structures and properties, as well as the complexity of such modelling. Qualitatively, the reduced mobility and the chain orientation in semi-ordered interphases due to the stiff and ordered crystallites would make the permeability smaller. For the Pebax grades with shorter polyether blocks and longer polyamide blocks, the tortuosity of the diffusion path will increase sharply when the polyether and amorphous PA phases become finely divided by the crystalhne phase. Nevertheless, we tried to use the PA phase crystallinity to simulate the CO2 and nitrogen permeabilities in Pebax films with the simple resistance model [35] to estimate the influence of the Pebax structure on the permeability. 

The data cannot be fitted at all for T > 100 C, since a high-temperature plateau is seen in the copolymer melt while the component homopolymers have no plateau whatever, being homogeneous liquids. We believe these data are not arti-factual, but rather indicate the presence of solid-like structure in the melt above the softening point of the continuous phase. As discussed elsewhere (23), this is probably a manifestation of a liquid yield stress arising from thermodynamic forces associated with the interphase and the continued existence of two-phase structure as long as T < T. ... 

Kitamam R, Horii F, Murayama K (1986) Phase structure of lamellar crystalline polyethylene by solid-state high-resolution 13C NMR detection of the crystalline-amorphous interphase. 

To determine the role of stationary phase structure in the retention process, it is of primary importance to understand its structure in various solvent environments. Studies of the interphase region using deuterium NMR have shown that it is the mobile phase composition that determines the structure of the stationary phase (d). Results have shown that water does not associate strongly wdth the alkyl chains. However, acetonitrile can associate strongly, even at low mole fractions because of the microheterogeneous environments that exist for the binary mixture. Previous in situ studies of the alkyl stationary phases using surface enhanced Raman spectroscopy have also concluded that little conformational change occurs with the addition of a polar solvent to the interface (7). 

Polymer alloys may be considered as independent composite materials because they have many common features similar to filled systems such as two-phase structure and interphase layer. Considering the reinforcement of pol5Tner alloys, one should have in mind a very complicated structure of the matrix, consisting conventionally of three phases. The distribution of particulate filler in such a system will be dependent both on the structure of various regions and on their composition, determining the affinity of the matrix to the filler surface. In its turn, as shown below, the filler may influence the formation of the alloy structure, which is especially important when reinforcing with fibrous fillers. 

Block copolymers composed of incompatible components of A and B form in general a "pseudo two-phase" structure in solid state as a consequence of microphase separation in solidification process. There exists interfacial domain boundary region of a certain thickness where the incompatible components are mixed in between the regions composed of pure A and B segments. Origin of such interphase has recently been studied intensively on the basis of statistical thermodynamics by Meier(l), Helfand(2), and others. Number of works on the mechanical properties of block and graft copolymers have also proposed the existence of the interphase(3-9). 

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