Chain-Walking Polymerization of Linear Internal Octenes Catalyzed by α-Diimine Nickel Complexes

The chain-walking polymerization of linear internal alkenes (i.e., trans-2-, 3-, and 4-octenes) using α-diimine nickel catalysts activated with modified methylaluminoxane (MMAO) was studied in comparison with the corresponding terminal alkene polymerization. The rates of polymerization were found to decrease in the following order: 1-octene > 4-octene ≥ 2-octene ≫ 3-octene. The obtained branched poly(2-octene)s and poly(4-octene)s with high molecular weight and Mw/Mn less than 2 were amorphous polymers with low glass transition temperature (Tg) of approximately −66 °C. At 0 °C, 4-octene polymerized in a living/controlled manner. The NMR analyses of the polymers showed that the chain-walking polymerization of 4-octene gave periodically branched polymers with the constant branching density, while that of 2-octene gave the polymer possessing fewer branches than the expected value due to monomer-isomerization. The (n+2),(n+3)- and (n+3),(n+2)-insertions of the internal (n+2)-alkene [CH3(CH2)nCH═CH(CH2)mCH3] f...