Toward More Sustainable Elastomers: Stereoselective Copolymerization of Linear Terpenes with Butadiene

The copolymerization of renewable monomers such as ocimene (O), myrcene (M), and farnesene (F) with butadiene (B), promoted by dichloro­{1,4-dithiabutanediyl-2,2′-bis­[4,6-bis­(2-phenyl-2-propyl)­phenoxy]}­titanium (1) activated by modified methylalumoxane (m-MAO) under mild reaction conditions, was investigated. Copolymers in a wide range of compositions were obtained through a judicious control of the alimentation feed (up to 85% of terpene incorporated in the case of poly­(ocimene–butadiene) (POB)). Analysis of POB, poly­(myrcene–butadiene) (PMB), and poly­(farnesene–butadiene) (PFB) microstructures revealed the good stereoselectivity of 1, both in the butadiene (up to 95%) and in the terpene (up to 92%, 71%, and 86% for O, M, and F, respectively) insertion. For all these new materials, a complete ¹³C NMR assignment was performed, revealing a multiblock structure. A sample of POB was also evaluated as a component in a model tread compound leading to improved mechanical properties with respect to the corresponding plain butadiene rubbers.