Fringe micelle

Fringed micelle model Frings acetator Frisium Frit... 

Figure 3.6. Two-dimensional representation of molecules in a crystalline polymer according to the fringed micelle theory showing ordered regions (crystallites) embedded in an amorphous matrix.

The fringed micelle theory has been less favoured recently following research on the subject of polymer single crystals. This work has led to the suggestion that polymer crystallisation takes place by single molecules folding themselves at intervals of about 10 nm to form lamellae as shown in Figure 3.3b. These lamellae appear to be the fundamental structures of crystalline polymers. 

Figure 3.3 Arrangements of molecules in crystalline polymers according to (a) fringed micelle and (b) lamellae theories...

If the ordered, crystalline regions are cross sections of bundles of chains and the chains go from one bundle to the next (although not necessarily in the same plane), this is the older fringe-micelle model. If the emerging chains repeatedly fold buck and reenter the same bundle in this or a different plane, this is the folded-chain model. In either case the mechanical deformation behavior of such complex structures is varied and difficult to unravel unambiguously on a molecular or microscopic scale. In many respects the behavior of crystalline polymers is like that of two-ph ise systems as predicted by the fringed-micelle- model illustrated in Figure 7, in which there is a distinct crystalline phase embedded in an amorphous phase (134). 

Figure 8 Fringe-micelle model of crystalline polymers. (PramRef. 131,)...

It has been suggested that glass transition is an important physicochemical event that controls the phase transition process of starch (Biliaderis, 1998). According to Biliaderis (1998), the "fringe-micelle" model (Fig. 5.16) does not permit assignment of a definite Tg for most starches. This is because the change in heat capacity during phase... 

The fringed micelle picture is not particularly suitable for describing synthetic polymers crystallized from solution or melt. However, the fibrils of many nat-... 

Fig. 7. Schematic representation of the fringed micelle model of crastalline polymers... 

However, with naturally occurring macromolecules, such as cellulose, the older fringed micelle concept is believed to apply. This represents a crystalline polymer, (it would be more correct to speak of semicrystalline or partially crystalline polymers since a material consisting of chain molecules can never be completely ordered), made up of ordered (crystalline) domains interspersed with disordered (amorphous) domains, so that each polymer chain passes through several crystalline and amorphous regions (Figure 4). 

Figure 4. Schematic presentation of a partially crystalline material ( fringed micelle )...

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