Plastic–rubber diblock copolymers obtained from copolymerization of dimethyl-1,3-butadiene and butadiene using rare-earth metal catalysts†

Coordination polymerization of 2,3-dimethyl-1,3-butadiene (DMB) has been investigated by using rare-earth metal catalysts. Of which, the ligand-free gadolinium dibenzyl chloride precursor exhibits the highest activity and perfect cis-1,4 selectivity for DMB homopolymerization and copolymerization with butadiene (BD) to afford plastic poly(2,3-dimethyl-1,3-butadiene) (PDMB) and the plastic–rubber diblock copolymer PDMB-b-PBD, respectively. In solution, PDMB-b-PBD self-assembles into a “core–shell” morphology with the crystalline cis-1,4 regulated PDMB segment as the core and the amorphous cis-1,4 stereoregular PBD unit as the shell, while in the melt state, the PDMB block forms physical cross-linking in the PBD rubbery matrix, endowing the material with unusually high stress accompanied by excellent elongation.