ABSTRACT
Conventional vulcanized elastomers, whether natural or synthetic, consist of very long molecules connected into a continuous network by means of occasional crosslinks. High extensibility is possible because the chains are sufficiently flexible and mobile, at temperatures encountered during use, to accommodate large imposed strains without suffering local chain failure. The retractive force following deformation is essentially entropic in origin and depends on the freedom of the chains to undergo very facile thermal motion with respect to one another. Hence elastomers are based on polymeric molecules that at ambient temperatures are far above their glass transition temperatures and are also amorphous (in the unstrained state at least) and relatively free of highly polar or bulky side groups.
