Ethylene/Myrcene Copolymers as New Bio-Based Elastomers Prepared by Coordination Polymerization Using Titanium Catalysts

The synthesis of ethylene/myrcene copolymers was performed using half-titanocene catalysts in the presence of a methylaluminoxane (MAO) cocatalyst. Cyclopentadienyl-phenoxide catalysts, Cp*TiCl2(O-2,6-iPr2-4-RC6H2) [R = H (1), SiEt3 (2)], showed rather efficient myrcene (My) incorporation to afford high-molecular-weight (semicrystalline or amorphous, depending on the My content) copolymers, which possess unimodal molecular weight distributions as well as uniform compositions. Microstructural analysis of poly(ethylene-co-My)s by NMR spectroscopy revealed that the resultant copolymers possessed cyclopentane units with a My pendant arm (−CH2CH═CMe2), formed by 2,1- or 1,4-My insertion and subsequent cyclization after ethylene insertion. The resultant copolymer showed promising elastic properties; the elongation at break increased upon increasing the My content, accompanied by a decrease in the tensile strength and toughness.