Crystallite Size and Disorder

In addition with the level of crystallinity in a polymer, characteristics of the crystals that make up the crystalline regions also determine the performance of polymers. These characteristics include changes in the unit cell dimensions, crystallite size, and crystalline defects. These characteristics can be evaluated from the positions of the diffraction peaks, from the width of the diffraction peaks, and from the increase in the width of the diffraction peaks with q, respectively, as discussed below. 

The width of the crystalline peaks is a measure of the size (L) of the crystals, which can be determined from the Scherrer equation  

Two kinds of crystalline disorder can be identified in XRD data. The disorder of the first kind refers to the imperfections 

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Though the crystallinity of cw-polyacetylene is remarkably high, there are strong indications of disorder. It is generally accepted that diffraction line broadening is a combined result of crystallite size and disorder in polyacetylene, A quantitative evaluation of the separate contributions is hardly feasible due to the limited number of separate reflections, but it is common practice to consider the number obtained from the Scherrer equation to be a diffraction coherence length rather than a crystallite size. No more than approximately 10 peaks are observed in diffraction, and there is considerable overlap of reflections.. The number of higher layer lines observable in oriented patterns is only... 

Due to discovery of these, the onerous step of polymer deashing is no longer necessary. These compounds have to be used in combination with a triether aluminum. They have large surface area, small crystallite size, and disordered crystal structure. Due to this many Mg ions, coordinatively unsaturated, become available. On these sites TiCU can be easily adsorbed and interact. MgCl2 and TiCU undergo solid solution due to a similarity of their layer lattice structure and ionic radii. This greatly increases catalytic activity electron donation by Mg to active Ti species promotes the polymerization propagation rate constant. 

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