Synthesis and Properties of Gradient Copolymers Composed of Norbornene and Higher α-Olefins Using an <i>ansa</i>-Fluorenylamidodimethyltitanium-[Ph₃C][B(C₆F₅)₄] Catalyst System

Abstract

The copolymerization of norbornene (NB) and various α-olefins [1-octene (O), 1-decene (De), and 1-dodecene (Do)] was achieved with high activity using (tBuNSiMe2Flu)TiMe2 (1)-[Ph3C][B(C6F5)4] and 2,6-bis(1,1-dimethylethyl)-4-methylphenol (BHT)-treated tri-i-butylaluminum (iBu3Al) or tri-n-octylaluminum (Oct3Al) as a scavenger. The catalytic systems gave NB/α-olefin copolymers with number-average molecular weights over 100,000 and polydispersity indices below 1.3. The copolymers possessed the gradient structure starting from the NB-rich segment to the α-olefin-rich terminal because of the difference of the monomer reactivity ratios between NB and α-olefins. Films of the copolymers were successfully molded using a melt-pressing procedure. The strain at the break of the copolymer films increased with the length of the alkyl group of the α-olefin accompanied by a decrease in strength. The tensile properties of the copolymers are controlled by the NB content and the Mn value. The copolymer films showed transmittance of up to 80% in the visible-light range.