Preparation of polybutene-based thermoplastic elastomers through the copolymerization of 1-butene with higher α-olefins

Abstract

A series of 1-butene-based random copolymers were synthesized through the direct copolymerization of 1-butene with higher α-olefins, namely 1-octene (C8), 1-dodecene (C12), 1-hexadecene (C16), and 1-eicosene (C20). Four catalysts, namely rac-Et(Ind)₂ZrCl₂ (Cat.1), rac-Me₂Si(1-Ind)₂ZrCl₂ (Cat.2), Me₂C(Cp)(9-Flu)ZrCl₂ (Cat.3), and dimethyl(pyridyl-amido)hafnium (Cat.4), were adopted to promote the copolymerization upon activation with iBu₃Al/Ph₃CB(C₆F₅)₄. The post-metallocene catalyst, Cat.4, displayed superior catalytic activity (>10⁷ g_polymer mol_Hf⁻¹ h⁻¹) and α-olefin incorporation ability, yielding copolymers with ultra-high molecular weight (M_w > 10³ kDa) and isotactic selectivity (mmmm up to 90%). The copolymerizations in this study enable the synthesis of a series of rigid and tough polybutene-based thermoplastic elastomers under mild conditions, with the copolymers exhibiting impressive tensile strengths ranging from 18 to 31 MPa, elongation at breaks between 480% and 650%, and elastic recoveries ranging from 44.7% to 60.7%.