Influence of the Composition on Crystal Phase and Thermal Behavior of trans‐1,4‐Butadiene/Isoprene Copolymers

Abstract Butadiene/isoprene copolymers were prepared using the catalyst system V(acac) 3 ‐MAO. The structure of the comonomers is trans ‐1,4 and the butadiene and isoprene units are statistically distributed along the polymer chain. The attitude of the butadiene sequences to crystallize in the monoclinic form and to evolve in the hexagonal form is preserved in the copolymer for a certain range of composition. The temperature interval between the two endothermic events is progressively reduced by increasing the isoprene content. The monoclinic/hexagonal transition produces a considerable increase in the lamellar thickness of the polymers. Thermal degradation of the copolymers is influenced by the composition and takes place in two different stages: a series of cyclization and cross‐linking reactions occur before the decomposition step. magnified image