Polyolefin thermoplastic elastomers from 1-octene chain-walking polymerization. (25th September 2016) - Leone, Giuseppe
Abstract: 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 α-diimine Ni(II) complex [(ArN)C(CH3 )–(CH3 )C(NAr)]NiBr2 [Ar = 2, 6-( i Pr)2 C6 H3 ], in combination with different aluminum alkyls, i.e ., Et2 AlCl, 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. Graphical abstract: Highlights: Ni(II) α-diimine based catalysts polymerize 1-octene to branched poly(ethylene)s. The polymerization conditions affect the polymers branching type and distribution. The thermal properties and crystallinity of poly(1-octene)s are influenced by microstructure. A synthesized sample retains the strain recovery about 80% under the applied stain of 1200%. Mechanical testing served to establish these materials as a new TPEs class.