Regular chains and crystallinity

Stereodefects reduce the overall regularity of an isotactic polymer chain and hinder its ability to crystallize. As the concentration of defects increases, the degree of crystallinity falls, resulting in reduced density, reduced melting temperatures, lower heat distortion temperatures, reduced modulus, and reduced yield stress. 

The observed range of the shear modulus varies between 1.5 GPa in filaments of regular count to 3 GPa in microfilaments, which correlates with the degree of orientation and crystalline perfection in the fibres [40]. Compared to the theoretical value of the modulus of shear between two hydrogen-bonded chains of 4.1 GPa, it indicates softening due to the van der Waals bonding between the hydrogen-bonded planes. 

The structural characterization of the PPEs studied by Wrighton et al. revealed that the polymers exhibited different degrees of order and crystallinity, depending on the nature of the side chains. In line with other studies [41,42], it was shown that the polymers with less regular structure (Table 1, entries 6 and 7) were less ordered than the derivatives with regularly spaced linear side chains, which adopted lamellar architectures (Table 1, entries 4 and 5). Wrighton et al. concluded that for the materials studied, higher conductivity was associated with... 

The recommendations embodied in this document are concerned with the terminology relating to the structure of crystalline polymers and the process of macromolecular crystallization. The document is limited to systems exhibiting crystallinity in the classical sense of three-dimensionally periodic regularity. The recommendations deal primarily with crystal structures that are comprised of essentially rectilinear, parallel-packed polymer chains, and secondarily, with those composed of so-called globular macromolecules. Since the latter are biological in nature, they are not covered in detail here. In general, macromolecular systems with mesophases are also omitted, but crystalline polymers with conformational disorder are included. 

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