Multilamella Structures

 

 Under many conditions, particularly during crystallization from concentrated solution or the melt, branched and/or multilayered lamellar structures appear.

 When crystallization is carried out at higher concentrations (>0.1% w/v) with little or no prenucleation (selfseeding), multilamellar structures usually result.

 

   Multilamellar Structures include :

          - dendrites

          - hedrites (or axialites) and

          - spherulites.

 

   Molecular weight dependence in isothermal crystallization :

          low molecular weight              axialites

          moderate molecular weights    sheet-like structures

          high molecular weights            spherulites

          very high (> 2×106) molecular weights    randomly positioned lamellas

 

Fig. 1. A schematic representation of lamella in spherulite.

 

Fig. 2. Polymer chain orientation in the lamellar ribbons of a prespherulitic structure.