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 C-13 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.