Diffraction from polymers with

X-Ray Diffraction from Polymers with Mesomorphic Order... 

Yamamoto has synthesized a variety of zinc porphyrin-containing polymers (29-35) with arylene and aryleneethynylene linkers.42 Arylene groups incorporated included 2,5,-dialkoxy-1,4-phenylene, 3-alkyl-2,5-thiophenyl, and 2-alkyl-3,6-pyridenyl species. Due to their long substituents, these polymers are soluble in THF and have molecular weights of 4600-38,000 Da (A/n, GPC). Powder X-ray diffraction revealed some degree of order in the thin films prepared from polymers with long alkyl substituents. Photoluminescence, thermal analysis, and CV of the new polymers were also reported. 

The as-spun fibers produced from the polymer with a high melt viscosity of MFI = 12 g/10 nun show a highly oriented a-monoclinic structure. As indicated by the X-ray diffraction patterns and equatorial traces, these fibers are more oriented than the fibers produced with MFI = 35 g/10 min. In fact, the subsequent drawing of the fiber produced from the polymer with low melt viscosity leads to high-tenacity fibers. The overall molecular orientation of as-spun fibers from polymer with high melt viscosity is found to be higher than the fibers produced from... 

Donald et al. [2] reported banded structures formed by several thermotropic polymers oriented by shear at temperatures above their softening points. Similar structures were also noted in fibers drawn from polymers with rigid backbones above the softening points. Viney et al. [3] point out that the banded structures observed in shear are due to the variation in the direction of the long molecular axis with respect to the direction of shear. Evidence obtained by both optical microscopy and electron diffraction measurements supports this view. Donald and Windle [4] studied the banded structure by electron microscopy and commented that The near sinusoidal variation in the direction of the principal axis of the refractive index ellipsoid is indeed reflecting the variations in the molecular orientation. Their transmission electron microscopy indicates that the transition from... 

Poly(vinyl fluoride) [24981-14-4] (PVF) is a semicrystaltiae polymer with a planar, zig-zag configuration (50). The degree of crystallinity can vary significantly from 20—60% (51) and is thought to be primarily a function of defect stmctures. Wide-line nmr and x-ray diffraction studies show the unit cell to contain two monomer units and have the dimensions of a = 0.857 nm, b = 0.495 nm, and c = 0.252 nm (52). Similarity to the phase I crystal form of poly (vinytidene fluoride) suggests an orthorhombic crystal (53). 

X-rays. The diffraction from this polycrystalline and disoriented fiber is the sum of the diffraction from all the randomly oriented microcrystallites, and it corresponds to a series of concentric rings, each with its characteristic (/-spacing. The intensity is uniform on a ring, but it varies among rings. This type of diffraction, commonly referred to as a powder pattern, is prevalent among minerals and polymers that have a low degree of polymerization. 

Peak Breadths And Reflection Profile Function. As has been mentioned, the individual reflection profiles tend to be broad for polymers. With both x-ray and neutron radiation the peaks exhibit large peak-widths. In a neutron diffraction pattern of isotactic polypropylene (A. Immirzi, work in progress) the peak width at half maximum, K j, had values ranging from 0.60° at 20= 14° to 1.00° at 26= 43° (X= 1.542 A), whilst, with the same... 

One of the first reports on these materials deals with the reaction of [Rh(CO)2Cl]2 with aromatic diisocyanides to produce two-dimensional (2D) coordination polymers with stacked layer arrangements, as established from their X-ray powder diffraction patterns (Fig. 2).14-16 Related 2D layered... 

Bi(CgH6)Cl3], obtained from a benzene solution of BiClj, has been shown by X-ray diffraction to be a layer polymer with very weak bismuth-benzene a-bonding . 

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