The preparation of cross-linkable polyethylene via coordination copolymerization of ethylene with alkene-derived chlorosilane

A facile and controllable way to prepared silane-crosslinked polyethylene by coordination polymerization was proposed in this article. Four alkene-derived chlorosilanes, trichloro(oct-7-en-1-yl)silane (Oct-TriSi), dichloro(methyl)(oct-7-en-1-yl)silane (Oct-DiSi), chlorodimethyl(oct-7-en-1-yl)silane (Oct-MoSi) and (2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyl)dichloro(methyl)silane (Nor-DiSi) were first synthesized by hydrosilylation and copolymerized with ethylene to prepare cross-linkable polyethylene. The copolymerization results of ethylene/octenyl-silanes indicated monochloro-substituted silane showed lowest crosslinking ability while trichloro-substituted silane showed the lowest copolymerization ability, therefore, their ability to prepare cross-linkable polyethylene was: Oct-DiSi > Oct-TriSi > Oct-MoSi, moreover, Nor-DiSi outcompeted Oct-DiSi as comonomer to obtain higher copolymerization activity, comonomer proportion in copolymer, comonomer conversion and gel content. The crosslinking process was simply finished via alcoholysis with methanol and subsequent hydrolysis catalyzed with DBTDL. Even with a slight addition of Nor-DiSi, the polyethylene was able to be crosslinked, with the gel content ranging from 42.0 to 98.0%. The TGA and DMA tests demonstrated the crosslinked copolymers showed better thermal stability and heat deformation resistance than polyethylene. After crosslinking, the copolymers with an appropriate gel content would have higher yield stress, tensile modulus and tensile stress.