cis14polyisopren

cis-14Polyisopren, more commonly referred to as cis-1,4-polyisoprene, is a polymer formed from isoprene units with cis-1,4 configuration. This arrangement yields a highly flexible, amorphous elastomer renowned for its elasticity and resilience. In nature, the major source is the latex of Hevea brasiliensis, from which natural rubber is produced; other rubber-yielding plants also contribute smaller amounts of cis-1,4-polyisoprene. Synthetic variants can be produced by polymerizing isoprene with catalysts that favor cis-1,4 linkages, yielding materials that closely resemble natural rubber.

The polymer chain consists of repeating isoprene units with methyl groups pendant along the backbone. The cis geometry creates a kinked chain that blocks crystallization, giving a rubbery material at room temperature with a low glass transition temperature.

Properties include high elasticity, good tensile strength after vulcanization, and excellent damping characteristics. Natural cis-1,4-polyisoprene is relatively impermeable to gases and hydrophobic. Unvulcanized rubber is prone to creep and ozone cracking; vulcanization with sulfur or other crosslinkers improves strength, elasticity, heat resistance, and aging resistance. The material is typically processed into sheets and compounds, then used in tires, belts, seals, hoses, medical gloves, footwear, and a range of elastomeric products.

Historically, natural rubber gained prominence in the 19th century after the vulcanization process was developed by Goodyear, which transformed it into a durable elastomer. Cis-1,4-polyisoprene remains the dominant structure in natural rubber and serves as a benchmark for synthetic elastomers.