Interfacial free energy mature crystallite

Mendelkem [42] noted that there are three different interfacial free energies that are characteristic of crystallites. One, is for the equilibrium extended chain crystallite, a second one a c represents the mature, but nOTi-eqiulibrium crystallite, and the third one is Uen is the interfacial free energy involved in forming a nucleus. These quantities caimot be identified with one another. Because only portions of the polymeric chains participate in the formations of crystallites, the section or sections of the chains of x length that participate in crystallite formation can be designated as (e and the sections of the chains that remain in disorder and amorphous, as x — Ce -... 

The respective interfacial free energies, aun and (Ten, are those appropriate to forming a nucleus. They should not be identified either with the quantities cr c and aec characteristic of the actual mature crystallite that develops or with (Tee, which is appropriate to the equilibrium crystallite. It should be noted that, in either case, no assumption has been made with regard to the chain conformation within the nucleus. The formal expression for AG does not depend on the chain stmcture within the nucleus. 

One method that has been used to effect this separation is to invoke the Gibbs-Thomson relation. The interfacial free energy, a c, associated with the basal plane of the mature lamellar crystallite is obtained from the relation between the melting temperature and crystaUite thickness for bulk crystallized polymers. The inherent assumption is then made that a c for the mature crystallite can be identified with of the nucleus. In this manner the separation of the product of interfacial free energy can be achieved. This rather drastic assumption has not been substantiated. There is no requirement that the interfacial structure of a mature crystallite repUcates that of the initiating nucleus. In fact this situation is highly unlikely. 

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