The polymer backbone, also called the main chain, is the part of a polymer where the pieces of the polymer link together.
In many polymers, the backbone is made of carbon atoms. Vinyl polymers have an all-carbon backbone. Different types of polymer can have different chemical elements in their backbone: polyesters and polyethers have both carbon and oxygen, polyamides have carbon and nitrogen, and polyurethanes have all three of these elements. Other polymers, like silicones, do not have any carbon in their backbone.
In polymers with cross-links, there is more than one backbone. These separate backbones are linked together when the cross-links form.
