ABSTRACT
This chapter covers the basic components that influence polymer shape or morphology. It describes the structure of both synthetic and natural polymers in terms of four levels of structure. The primary structure describes the precise sequence of the individual atoms that compose the polymer chain. For polymers where there is only an average structure, such as proteins, polysaccharides, and nucleic acids, a representative chain structure is often given. The secondary structure describes the molecular shape or conformation of the polymer chain. The tertiary structure describes the shaping or folding of polymer. Finally, the quaternary structure represents the overall shape of groups of tertiary structures where the tertiary structures may be similar or different. The chapter then discusses the typical properties of straight-chain hydrocarbons and types of commercial polyethylene. Most polymers consist of a combination of crystalline and amorphous regions. Even within polymer crystals such as spherulites, the regions between the ordered folded crystalline lamellae are less ordered, approximating amorphous regions.
