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

The copolymerization of norbornene (NB) and various alpha-olefins [1-octene (O), 1-decene (De), and 1-dodecene (Do)] was achieved with high activity using ((t)BuNSiMe(2)Flu)TiMe2 (1)-[Ph3C][B(C6F5)(4)] and 2,6-bis(1,1-dimethylethyl)-4-methylphenol (BHT)-treated tri-i-butylaluminum ((Bu3Al)-Bu-i) or tri-n-octylaluminum (Oct(3)Al) as a scavenger. The catalytic systems gave NB/alpha-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 alpha-olefin-rich terminal because of the difference of the monomer reactivity ratios between NB and alpha-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 alpha-olefin accompanied by a decrease in strength. The tensile properties of the copolymers are controlled by the NB content and the M-n value. The copolymer films showed transmittance of up to 80% in the visible-light range.