A new strain-crystallizable rubber via neodymocene-catalyzed regio-, stereo-, and sequence-selective copolymerization of isoprene and ethylene

Abstract

An ansa-neodymocene catalyst previously reported in the literature has been identified to catalyze the title copolymerization to afford poly(1,4-trans-isoprene–ethylene) with 95% selectivity for the major microstructure. Such structural regularity is minimally required for the rubbery product, dubbed isoprene–ethylene rubber (IER), to exhibit prominent strain-induced crystallization (SIC) at 0 °C. The mechanical properties of IER rival those of natural rubber when SIC occurs. The unit cell of the strain-induced crystals is monoclinic with a = 2.21 nm, b = 0.72 nm, c = 1.30 nm, and β = 110.8°. Each unit cell is estimated to contain 12 chains in the ac plane and one repeat unit along the b axis.