Polyolefin thermoplastic elastomers from 1-octene chain-walking polymerization

This work reports the polymerization of 1-octene to yield semicrystalline, branched poly(ethylene)-like materials with high molecular weight and narrow molecular weight distribution. The polymerization of 1-octene was catalyzed by an ?-diimine Ni(II) complex [(ArN)C(CH3)-(CH3)C(NAr)]NiBr2 [Ar = 2,6-(iPr)2C6H3], in combination with different aluminum alkyls, i.e., Et2AlCl, MAO and MMAO. The effect of the aluminum alkyl, monomer concentration, polymerization temperature and Al/Ni ratio on the activity, selectivity of monomer insertion, polymers microstructure, and structure/properties is investigated. The results indicate the possibility to tune the polymer microstructure, which in turn strongly affects the structure, thermal and mechanical polymer properties. Mechanical testing carried out by uniaxial stretching until failure and step-cycle tensile experiments served to establish these materials as a new class of polyolefin thermoplastic elastomers with different performances depending on the microstructure and crystallinity.