Interphase structural analysis

Glass fibers sized with polyurethane and polyvinyl acetate formed different interfaces. This was due to the differences in reactivity and miscibility. Polyurethane forms a stronger interface because it is reactive and miscible with epoxy resin. " Surface tension of glass surface in a molten state correlates with the interface formation with polymer. The diffusion at interface contributes to a complex structure controlling properties of the interphase. The analysis of the diffusion at the interphase has helped to develop an understanding of the formation of metal-polymer interfaces and plastic welding. 

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. 

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. 

The crystalline structure of composite materials can be highly varied. The measurements of crystallinity show how the combined interference of the various components of the composite influences the structure. Filled material is composed of crystalline and amorphous regions separated by an interphase which is a diffuse boundary between these two states. The crystallinity of the binder material depends on the fraction of crystalline structures and on their size. Filler may affect both the fraction and the size of crystallites. But, those two measures of crystalline structure are often insufficient and the measurement of crystallinity may give confusing in-f ormation if the results are taken without further analysis of the fine structure of the material. Table 10.1 gives examples of the effect of fillers on material crystallinity from the current literature. ... 

The measurement of the diflFusion coeflBcient is an excellent tool for investigating subtle changes in polymer structure. Both the interphase in styrene-butadiene-styrene block copolymers and the morphology of polyethylene have been investigated using this method of diflFusion analysis. 

ZnS toluene colloidal dispersions have been synthesized by an interphase interaction of toluene zinc oleate solution and aqueous solution of hydrogen sulfide. XRD analysis shows the crystal cubic structure of ZnS particles. According to TEM their size varies between 2 and 10 nm. The UV-vis absorption spectra indicate the prepared nanoparticles to have a narrow size distribution and show the maximum at 280 nm. PL intensity of nanoparticles could be enhanced with capping agents such as aromatic thiols and aromatic polymers. 

In the case of metallic adsorbates (metal deposits, underpotentially deposited upd-layers, catalytically active metal deposits), the type of coordination to surface sites (one-, two- or three-fold) and the distance to these sites may be of interest. Vice versa the same type of data may be of importance in the case of adsorbed ions on metal electrodes or about the atomic environment of a given atom/ion in an interphase. Analysis of the fine structure of X-ray absorption (EXAFS, XANES) close to the X-ray absorption edge of the species (atom) of interest will yield this data provided the sample can be prepared in a very thin layer in order to exclude unwanted bulk interference. Otherwise the experiment can be done in reflection (SEXAFS). Information about the distance between the atom of interest and its first and sometimes even second shell of surrounding species can be derived from the spectra [95]. Availability of a suitable light source, generally a synchrotron (for details see p. 15), is an experimental prerequisite. The method has been applied in studies of passive and corrosion layers on various metals [96-102] and of molecular and ionic adsorbates on single crystal surfaces [103]. 

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