Crystalline polymers long-range periodicity

Crystallinity is a state of molecular structure referring to a long-range periodic geometric pattern of atomic spacings. In semi-crystalline polymers, such as polyethylene (PE), the degree of crystallinity (% crystallinity) influences the degree of stiffness, hardness, and... 

It is well known that the stacked lamellae of semi-crystalline polymers result in the long period which usually gives two (or three) diffuse Bragg reflections. We will focus on the first reflection (named LI) and the secondary reflection (named L2) at two (/-ranges, denoted as qu and qu, respectively [30,31]. 

Some polymers manifest liquid crystalline ordering, which does not have the full long-range three-dimensional periodicity of crystallinity but is far more ordered than amorphicity. Since many excellent books and articles have been published on such polymers and the author does not have much that is new to add to this background information, very little will be said about polymer liquid crystallinity in this book. Van Krevelen [3] has reviewed liquid crystallinity in polymers in a readable manner and discussed its effects on properties for which quantitative structure-property relationships are available. Adams et al [41] have published a valuable compendium of articles covering the theory, synthesis, physical chemistry, processing and properties of liquid crystalline polymers. Woodward [42] has discussed and illustrated liquid crystallinity in polymers with many beautiful micrographs. 

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