The yttrium-catalyzed heteroatom-assisted terpolymerization of ortho-alkoxystyrene, isoprene and butadiene with high regio- and stereoselectivity

The use of coordination polymerization to synthesize functional styrene-isoprene-butadiene rubber (SIBR) is a theoretical challenge in the field of polymer science, since functional monomers are usually poisonous to the employed catalysts. Herein, we report the coordination terpolymerization of polar ortho-alkoxystyrene (oAOS), isoprene (IP), and butadiene (BD) via pyridyl-functionalized tetramethyl-cyclopentadiene-ligated rare-earth-metal bis(allyl) complexes [(C5Me4C5H4N)Ln(eta(3)-C3H5)(2)] [(Ln = Sc (1); Ln = Y (2)] Complex 1 was poisoned by polar groups, while complex 2 realized the first successful terpolymerization of ortho-methoxystyrene (oMOS), IP, and BD with high syndio- and cis-1,4-regioselectivity via a heteroatom-assisted olefin polymerization strategy. We were able to tune the concentration of inserted oMOS in a wide range, specifically 5.6-50.7 mol%, via changing the feed ratios. The gradient microstructure of the resultant poly(oMOS-IP-BD)s was confirmed from the results of NMR measurements and a kinetics study. By switching to ortho-ethoxystyrene (oEOS), random poly(oEOS-IP-BD)s with a single T-g could be afforded, and it exhibited remarkable elasticity.

Automated summary

This study demonstrates the successful coordination terpolymerization of polar ortho-alkoxystyrene (oAOS), isoprene (IP), and butadiene (BD), showing the ability to tune the concentration of monomers in the resulting polymers by changing the feed ratios. This results in varying microstructures of the poly(oAOS-IP-BD) copolymers.