Models for the Crystalline Structure of Polymers

6 MODELS FOR THE CRYSTALLINE STRUCTURE OF POLYMERS 4.6.1 Fringed Micelle Model 

FIGURE 4.4 The fringed micelle model (a) unoriented (b) chains oriented by applied stress. 

The fringed micelle model has been superseded as new information has led to the development of more advanced models. Nevertheless, it still does a good job of qualitatively predicting the effects of crystallinity on the mechanical properties of the polymers. 

Example 4.2 Because the monomer vinyl alcohol is unstable, poly vinyl alcohol, PVA, is made by polymerization of vinyl acetate followed by the hydrolysis of poly vinyl acetate to form OH side groups  

The extent of reaction may be controlled to yield polymers with anywhere from 0% to 100% of the original acetate groups hydrolyzed. Pure poly(vinyl acetate), 0% hydrolyzed, is insoluble in water. It has been observed, however, that as the extent of hydrolysis is increased, the polymers become more water soluble, up to about 87% hydrolysis, after which further hydrolysis decreases water solubility at room temperature. Explain briefly. 

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