An old tool to obtain new polymers from renewable resources: [OSSO]-type titanium-catalysed ethylene and myrcene copolymers

The copolymerization of β-myrcene (M) with ethylene (E) and isoprene (I) was successfully promoted by a dichloro{1,4-dithiabutanediyl-2,2'-bis(4,6-di-alkylphenoxy)}titanium complex (1) activated by methylaluminoxane (MAO). The catalytic system afforded well-defined PME copolymers and novel PMEI terpolymers with controlled compositions (up to 49% of terpene incorporated in the case of PME). Microstructural analysis demonstrated high stereoselectivity of 1, with 1,4-<i>trans</i> insertion predominating for both isoprene (97%) and myrcene (94%). A comprehensive analysis by ¹³C and 2D NMR techniques confirmed a multi-block architecture for the novel synthesized copolymers. Notably, PMEI terpolymers exhibited a strong tendency toward forming alternating ethylene-isoprene (E-I) sequences. The thin film morphology, investigated by tapping mode atomic force microscopy (AFM), for the PME and PMEI copolymers, evidenced a phase-separated morphology consisting of soft and hard phases, respectively, ascribed to polydienic and polyethylenic domains. The materials displayed glass transition temperatures ranging from -62 to -74 °C, demonstrating their potential as sustainable and high-performance elastomers.