polyisoprene

alt=Pieces of polyisoprene in a jar|thumb|upright|Pieces of polyisoprene in Hutchinson SA|Hutchinson's Research and Innovation center in France

Polyisoprene is, strictly speaking, a collective name for polymers that are produced by polymerization of isoprene. In practice polyisoprene is commonly used to refer to synthetic cis-1,4-polyisoprene, made by the industrial polymerisation of isoprene. Natural forms of polyisoprene are also used in substantial quantities, the most important being "natural rubber" (99.99% cis-1,4-polyisoprene), which is derived from the sap of trees. Both synthetic polyisoprene and natural rubber are highly elastic and consequently used in a variety of applications, such as making tires.