Stereo-polymerization of 1,3-Butadiene by Cobalt Catalysts in the Presence of External Donor: Access to 1,2-Syndiotactic Polybutadiene with Tunable Properties

Disulfide carbon (CS 2 ) and triphenyl phosphine (TPP) were tested as donors for cobalt ( Co1, Co2, and Co3 )-catalyzed 1,2-syndiotactic polymerization of butadiene. With CS 2, a 1,2-selectivity of 96.8% and syndiotacticity ( rr ) up to 97% were achieved by Co1 – Co3 /Al i Bu 3 /CS 2, yielding highly crystallized polybutadiene resin. Variations on polymerization temperature (0–80 °C), catalyst loading, and polymerization time did not significantly affect the 1,2-incorporation and syndiotactic conformation of the resulting polymers, highlighting the excellent 1,2-stereoselectivity of active species stabilized by CS 2 . With external donor TPP, the formed Co1 – Co3 /MAO/TPP have regioselectivities of 65.2–89.2% and syndiotacticities of 32.1–65.5%. Thus, an array of polybutadienes differing in chemoenchainment and 1,2-stereoenchainment is accessible with the present cobalt catalysts in combination with different donors. AFM measurements were performed to distinguish the morphology of two types of 1,2- syn -polybutadiene. Elucidation on the plausible role of CS 2 and TPP in the stereoselective polymerization reaction was also made.