Polystyrene, isotactic crystal lamella

The morphology of crystalline isotactic polystyrene, i-PS, has been investigated by others, and they have concluded that i-PS normally crystallizes as stacks of folded chain lamellae which are arranged in volume filling spherulites. The melting point of lamellar polymer crystals depends on the lamella thickness, L, as follows (28 )... 

Fig. 13. A graph showing the variation of growth rate with the inverse of film thickness Ud) for isotactic polystyrene crystals grown at 180 C in nltrathin films. A step in the behavior can be seen at a thickness of 8 nm. At this temperature, this corresponds to the thickness of the single lamella, showing a change in thickness dependence once the film is thinner than the growing crystal. Reprinted from Ref. 98. Copyright (2002), with permission from Marcel Dekker, Inc.

Figure 12 Hexagonal lamellae of isotactic polystyrene crystallized from the melt at 228 °C, illustrating preservation of...

Isotactic polystyrene, however, constitutes a system which has none of the problems and limitations described above. Not only do polystyrene lamellae tend to adopt a simple, planar hexagonal habit under a wide range of crystallization conditions, such that complex hierarchical morphologies are not observed, but also the melt is easily quenched into the glassy state. Thus polystyrene constitutes a system which is structurally simple, and, therefore, amenable to investigation. 

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