1-Octene copolymers with 1-decene and cyclopentene by an alpha-diimine Ni(II)/AlEt2Cl catalyst: synthesis, thermal and mechanical behavior

In our recent work we investigated the polymerization of 1-octene catalyzed by an ?-diimine Ni(II) complex [(ArN)C(CH3)-(CH3)C(NAr)]NiBr2 [Ar = 2,6-(iPr)2C6H3] (Ni-1) in combination with different aluminum alkyls.[1]Branched poly(ethylene)-like materials with high molecular weight, narrow molecular weight distribution, and low crystallinity were obtained. The tensile tests showed that the resulting polymers behave as thermoplastic elastomers (TPEs) with properties close to those reported for ethylene/1-octene copolymers, and generally outperform the 1-dodecene/ethylene di- and tri-block copolymers in terms of elastic recovery.[2] We found that by suitably choosing the type of aluminum alkyl, monomer concentration, and polymerization temperature it was possible to tune the polymer (micro)structure (i.e., total branching, branch-type, and crystallinity) which in turn strongly affects the polymer thermal and mechanical properties. We have been searching for alternative routes to easily tune the (micro)structure of the polymers from of 1-octene, allowing access to TPEs with improved mechanical properties. In this respect we are now reporting on the copolymerization of 1-octene with 1-decene and cyclopentene catalyzed by Ni-1 in combination with AlEt2Cl (Scheme 1). The effect of the type and the feedstock concentration of the comonomer on the microstructure, the total branching and the branch-type distribution was evaluated by 1H and 13C NMR spectroscopy. Moreover, a comprehensive investigation on the mechanical behavior by uniaxial stretching until failure, step-cycle and creep tensile tests was carried out. The results obtained clearly indicated that this approach can be considered a novel, convenient way to fabricate innovative TPEs from readily accessible starting materials. References 1. Leone G., Mauri, M., Pierro I., Ricci G., Canetti M., Bertini F. Polymer 2016, 100, 37. 2. Leone G., Mauri M., Bertini F., Canetti M., Piovani D., Ricci G. Macromolecules 2015, 48, 1304.