Temperature dependence, polymer crystal lamellar thickness

Crystallization from the melt also results in chain-folded lamellar crystals and for numerous polymers single lamellae have been studied by SFM approaches. Since typical lamellar thicknesses, depending on the polymer and the crystallization temperature, are in a range of 10 nm to several tens of nanometers, the finite size of the SFM probe tip leads to convoluted data, if lamellae are viewed edge-on (33). Among the coimtless examples are isotactic PS (157,158), PEO (159,160), PP (161-163), PE (164), polycarbonate (PC) (165), etc. 

Melt Crystallized.—Spherulites are observed to consist of radiating fibrils or lamellae which in melt-crystallized polymers are 100—500 A thick, depending on crystallization temperature, and /um in breadth. The c axis, i.e, the chain direction, coincides with the thickness of the lamellae and, by analogy to single crystal morphology, the molecular chain folds backwards into the lamellae. Amorphous polymer fills the regions between lamellae and can account for a substantial amount of the content. Painter et al. have shown that these inter-lamellar regions are very similar to melt-crystallized polymer in their i.r. spectrum. 

For synthetic polymer crystallization it is found that lamellar thickness, and hence crystal stability, depends strongly on preparation conditions such as temperature of crystallization and cooling rate. Future studies may indicate similar relationships for these biopolymer crystals. 

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