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71.
The computation of the orientational averages is a great problem in the case of semicrystalline polymers. In a previous communication [1] it has been shown that sin=f() sin describes the orientational changes satisfactorily for a certain class of polymers. In this paper some alternative deformation schemes are also discussed. It has been concluded that birefringence provides a useful guideline in the choice of a deformation scheme. 相似文献
72.
73.
By covalently binding chromophore NPP, N-(4-nitrophenyl)-(L)-prolinol, to a structurallycontrolled cage-like cross-linking polymer (SCCP), a modified nonlinear optical (NLO) polymeric filmprepared by "in situ poling and sol-gel" process successfully overcame the fundamental problem of NPPchromophores subliming out from the cages of the "doped" NLO polymeric film when heated or placed underUV light. Its d_(33) (coefficient of second harmonic generation) is 2.0×10~(-8) esu. measured by IR dichroism. Themodified film has a low decay of the SHG signal and preserves 94% of the initial value after 50 days at roomtemperature. These properties match that of the "doped" film, indicating that the modified film also retainsthe main advantages of the "doped" film. 相似文献
74.
New metallocene catalysts applied to propylene polymerization expand the range of properties of polypropylene (PP), resulting in semi-crystalline materials having crystallinities below 60% up to X-ray amorphous highly elastic ones. To date the origin of the unique elastic mechanical behavior of such low crystalline PP is not completely understood. Therefore, the microscopic orientation of those PPs due to uniaxial stretching was investigated using wide-(WAXS) and small-angle X-ray scattering (SAXS). The aim of this study was to correlate these orientations or changes in the developed fiber textures with the macroscopic stress-strain behavior. This includes efforts to come closer to the main question of the nature of the physical cross-links in these not chemical cross-linked homopolymers, which is the reason for the high elastic behavior. Therefore, high molecular weight metallocene PPs showing different crystallinities (0-36%) were stretched to several elongations and the structural changes during the deformation were recorded by X-ray scattering. Stress-strain measurements show the great potential of these PPs as a thermoplastic rubber material. For quantitative analysis and discussion of the polymer chain orientations, the orientation functions were calculated. Correlations between the orientation functions and the stress-strain curves allow an interpretation of the macroscopic behavior on a microscopic scale. A higher cross-linking density in elongated samples indicates that the network, which is responsible for the elasticity, mainly built up by strain-induced morphology changes and chain orientations. 相似文献
75.
76.
Kenzo Sato 《International Journal of Infrared and Millimeter Waves》1987,8(1):69-102
From analysis of anisotropical lattice bands properties of 50 reflection spectra both of the CO stretching and bending bands measured from some pearl (Ca++CO
3
––
or Ca++HCO
3
––
layer) we discussed following subjects.i) Quantized properties present both in reflectivity and in energy. ii) classifications of the Optical Activity. iii) Polar distributions of the CO3 oscillators in Ca++CO
3
––
surface mono-layer. iv) Force constants of these oscillators. v) Step variation of the dipolemoment and their influences to the degree of Optical Activity. vi) Two types of hysteresis loops of the values of YN (M2Jbend ()/M1Jstret. ()) derived from the oscillators which are at innert-state, at weak active-state and at active-state. 相似文献
77.
We found that the entering position of the bromination in the bay-region (e.g., 1,6,7,12-positions) was precisely determined by the orientation director(s), either individually or cooperatively. In particular, a combination of two directors shows precisely positioning for the third entering bromo with an effect of ‘1+1>2’. 相似文献
78.
79.
D.G. Demers 《Annalen der Physik》2010,522(7):520-523
The recent claim by da Rocha and Rodrigues that the nonassociative orientation congruent algebra (???? algebra) and native Clifford algebra are incompatible with the Clifford bundle approach is false. The new native Clifford bundle approach, in fact, subsumes the ordinary Clifford bundle one. Associativity is an unnecessarily too strong a requirement for physical applications. Consequently, we obtain a new principle of nonassociative irrelevance for physically meaningful formulas. In addition, the adoption of formalisms that respect the native representation of twisted (or odd) objects and physical quantities is required for the advancement of mathematics, physics, and engineering because they allow equations to be written in sign‐invariant form. This perspective simplifies the analysis of, resolves questions about, and ends needless controversies over the signs, orientations, and parities of physical quantities. 相似文献
80.
S. Garbarino A. Ponrouch S. Pronovost J. Gaudet D. Guay 《Electrochemistry communications》2009,11(10):1924-1927
Two types of platinum deposits were obtained by potentiostatic deposition onto Ti substrates, namely platinum black (Pt B) and platinum nanowires (Pt NW) with the latter being achieved through a porous anodic aluminum oxide (AAO) membrane at the solution/substrate interface. Surface characterization of these deposits was performed using scanning electron microscopy (SEM) and cyclic voltammetry (CV) in sulphuric acid solution. Surface properties for Pt NW revealed a predominant presence of (1 0 0) crystallographic planes, not present in Pt B deposit grown in the same conditions. Also, Pt NW exhibits an increased resistance to electrochemically active surface area (EASA) loss upon potential cycling in acidic solution, as compared to Pt B. 相似文献