Polymer crystals solution-grown

Polymer crystals most commonly take the form of folded-chain lamellae. Figure 3 sketches single polymer crystals grown from dilute solution and illustrates two possible modes of chain re-entry. Similar stmctures exist in bulk-crystallized polymers, although the lamellae are usually thicker. Individual lamellae are held together by tie molecules that pass irregularly between lamellae. This explains why it is difficult to obtain a completely crystalline polymer. Tie molecules and material in the folds at the lamellae surfaces cannot readily fit into a lattice. 

Preparation of solution-grown crystals (including so-called single crystals ) of linear polymers [2-4,8,10-13]... 

The solution-grown crystal (SGC) from dilute solution forms diamond-like crystals of lateral dimension up to several micrometres, but their thickness is about 10 nm in which polymer chains are folded. The chain axes are parallel to the thickness direction of these lamellar crystals. In SGC materials precipitated from dilute solutions (Figure 3A), the lamellae are stacked and oriented parallel to the material surface. 

Fu, B., Hsiao, B., Chen, G., Zhou J., Koyfman, I., Jamiolkowski D. D. and Dormier E., Structure and property studies of bioabsorbable poly(glycolide-co-lactide) fiber during processing and in vitro degradation. Polymer, 43,5527,2002. Fischer, E. W., Sterzel, H. J. and Wegner, G., Investigation of the structure of solution grown crystals of lactide copolymers by means of chemical reactions, Kolloid-Z. Z. Polym., 251,980. 1973. 

Fig. 5.8 A schematic diagram of chain folding in a solution-grown single crystal of polyethylene. (Reproduced from The Vibrational Spectroscopy of Polymers by D. I. Bower and W. F. Maddams.

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