Polyisoprene

Polyisoprene is an elastomeric polymer built from isoprene units. Its cis-1,4 form is the main polymer in natural rubber, while synthetic forms include both cis and trans structures.

Isoprene: Isoprene is a five-carbon conjugated diene that serves as the repeating-unit precursor for polyisoprene. Its carbon skeleton supplies the units joined to form the polymer.
Polymer chain: A polymer chain is a long molecule composed of covalently linked repeating units. Polyisoprene’s macroscopic behavior emerges from the motion of its long chains.
Natural rubber: Natural rubber is a plant-derived elastomer composed chiefly of cis-1,4-polyisoprene. It is the best-known naturally occurring form of polyisoprene.
Tire: A tire is a ring-shaped vehicle component that cushions motion and provides traction on a surface. Polyisoprene is used in tire compounds for its resilience and resistance to fatigue.
Trans-polyisoprene: Trans-polyisoprene is a polyisoprene stereoisomer whose repeat units have trans geometry around the backbone double bonds. Its ordered chains form hard materials rather than the highly elastic cis rubber.
Cis–trans isomerism: Cis–trans isomerism is a form of geometric isomerism caused by restricted rotation around a bond. The geometry of each double bond distinguishes flexible natural rubber from rigid gutta-percha.
Entanglement: Polymer entanglement is the topological interlocking of long chains that restricts their motion without permanent bonds. Entangled chains help prevent uncrosslinked polyisoprene from flowing freely.
Hevea brasiliensis: Hevea brasiliensis is a tropical tree cultivated as the principal commercial source of natural rubber latex. Its latex supplies most natural-rubber polyisoprene used worldwide.
Condom: A condom is a thin sheath worn over the penis or inserted into the vagina to reduce pregnancy and infection risk. Natural-rubber polyisoprene is used to make condoms, including versions without natural-rubber latex proteins.
Styrene-butadiene rubber: Styrene-butadiene rubber is a synthetic copolymer of styrene and butadiene used widely in tires and other rubber goods. It is a major tire-rubber alternative with different monomers and properties.

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