Introduction Crystalline and Amorphous Regions in Polymers

11 Factors Affecting the Glass Transition of Polymers Problem Sets 

Solid polymers can occur in the amorphous or crystalline state. Polymers in the amorphous state are characterized by a disordered arrangement of the macromolecular chains, which adopt conformations corresponding to statistical coils. The crystalline state is characterized by a long-range three-dimensional order (order extending to distances of hundreds or thousands 

Many polymers have the capability to crystallize. This capability basically depends on the structure and regularity of the chains and on the interactions between them. The term sernicrystalline state should be used rather than crystalline state, because regions in which the chains or part of them have an ordered and regular spatial arrangement coexist with disordered regions typical of the amorphous state. X-ray diffraction studies of samples of polymers crystallized from the melt reveal diffuse zones, char- 

Flgure 2.1 Conformational differences of polymer chains in the amorphous and crystalline states. Fringed micelle model. Parallel and coiled lines represent, respectively, portions of chains in the crystalline and the amorphous regions. 

In this chapter we study the characteristics that determine the crystallinity of polymers, crystalline morphology, and the factors affecting the crystallization and melting of polymers. We describe the amorphous state, focusing on the glass transition, a fundamental property for defining the mechanical behavior of polymers. The entire description refers exclusively to synthetic polymers. 

---