Dienes and rubber
Some molecule contain more than one c=c double bond, those with two c=c bond are called dienes.
Two important examples of dienes, butadiene and isoprene (figure 9.30) from rubbery polymers. Elastomers are polymers with elastic or rubberlike properties (they can stretch and recover). Until comparatively, they only known elastomer was natural rubber, known since ancient times. Then chemists developed the first synthetic elastomers in 1937. Usually elastomers are lightly crosslinked in a process called vulcanization that improves their strength and elasticity.