cis14polyisoprenes

cis14polyisoprenes, or cis-1,4-polyisoprenes, are polymers in which the isoprene units are joined predominantly through cis-1,4 linkages. This stereochemistry yields a flexible, non-crystalline backbone that gives natural rubber its characteristic elasticity. Most cis-1,4 polyisoprene contains very little trans-1,4 or 1,2-addition content, typically over 95–98% cis.

Natural occurrence and production: The principal source is latex from Hevea brasiliensis. Biosynthesis proceeds via polyisoprene synthases that assemble isopentenyl diphosphate into long chains with cis-1,4 stereochemistry. Industrially, cis-1,4 polyisoprene is also produced synthetically by polymerizing isoprene under catalysts and conditions that favor cis arrangement, using methods such as coordination polymerization with single-site catalysts or specialized anionic processes.

Properties: The polymer is soft and highly elastic at room temperature, with a very low glass transition temperature and is typically amorphous. It lacks crystallinity unless crosslinked. Vulcanization with sulfur or other crosslinkers forms a network that improves strength, heat resistance, and elasticity, reducing long-term creep and abrasion.

Applications and context: cis-1,4 polyisoprene is the backbone of natural rubber and is used in tires, seals, belts, and molded components. Synthetic cis-1,4 polyisoprene offers a rubber with similar properties for a range of applications, allowing control over purity, additives, and processing characteristics.