Polybutadiene

Polybutadiene is a synthetic rubber formed by polymerizing the monomer butadiene. The polymer chain is based on repeating units that can exhibit different microstructures, mainly cis-1,4, trans-1,4, and 1,2-vinyl configurations. The arrangement of these units depends on the catalyst and conditions used during polymerization, and it strongly influences the material’s properties.

The 1,4-addition structures produce a flexible backbone, with cis-1,4 polybutadiene giving high elasticity and a very low glass transition temperature, while trans-1,4 polybutadiene tends to be tougher and more crystalline. The 1,2-vinyl configuration introduces pendant vinyl groups that disrupt crystallinity and modify processing and mechanical behavior. Commercial grades often consist of blends of these microstructures to balance strength, elasticity, and processability.

Production methods include anionic polymerization, typically in hydrocarbon solvents with organolithium initiators, which allows control over microstructure; and emulsion or solution polymerization using various catalysts to tailor trans or cis content. Highly pure cis-1,4 polybutadiene is a specialty grade, while more common materials are mixtures of microstructures that suit general rubber applications.

Properties and applications: polybutadiene is an elastomer with excellent resilience, low-temperature flexibility, and good abrasion resistance. It vulcanizes readily with sulfur or peroxides. It is a major component of synthetic rubbers, notably styrene-butadiene rubber (SBR), which combines with styrene to meet tire and footwear performance requirements. It also serves as a base polymer in latexes, seals, coatings, and as a modifier in plastics and blends with natural rubber or other elastomers.