General comments

The materials to be discussed in this book are known by a variety of names. The oldest, rubbers, is not very illuminating since it refers to their relatively unimportant ability to remove pencil or ink marks from paper by an abrasive rubbing action (Treloar, 1975; Eichinger, 1983; Mark, 2005a). Of much greater importance are their elastic properties, and the term elastomers is now much in use. So also is rubberlike materials, which emphasizes the similarities between such substances and natural rubber, which is obtained from the Hevea tree.

Rubberlike materials have long been of extraordinary interest and importance. They find usage in items ranging from automobile tires and conveyor belts to heart valves and gaskets in supersonic jet planes (Gent, 1992). The striking nature of their elastic properties and their relationships to molecular structure has attracted the attention of numerous physical chemists and chemical physicists interested in structure–property relationships, particularly those involving polymeric materials (Flory, 1953; Treloar, 1975; Mark and Erman, 1992; Erman and Mark, 1997; Graessley, 2003; Witten, 2004).

Rubberlike elasticity and its molecular requirements

A useful way to begin a discussion of rubberlike elasticity is to define it and then to list the molecular characteristics required to achieve the very unusual behavior described. This is done in Table 1.1. The definition has two parts: very high deformability and essentially complete recoverability.