Metallocene-catalyzed synthesis of polyethylenes with side-chain triarylamines: Effects of catalyst structure and triarylamine functionality

The copolymerization of ethylene with 8-triarylamine (TAA) substituted 1-octene monomers (TAA = triphenylamine (M1), N,N-diphenyl-m-tolylamine (M2), N,N-diphenyl-1-naphthylamine (M3)) using various types of group 4 single-site catalytic systems (Cp₂ZrCl₂ (C1), rac-EBIZrCl₂ (C2), rac-SBIZrCl₂ (C3), i-PrCpFluZrCl₂ (C4), Me₂Si(η⁵-C₅Me₄)(η¹-N-^tBu)TiCl₂ (C5)) was investigated to prepare functionalized polyethylene with side-chain TAA groups. The metallocene/methylaluminoxane (MAO) catalytic systems (C1-C4) efficiently lead to the production of high-molecular-weight poly(ethylene-co-M1). While the C4/MAO catalytic system shows the highest comonomer response, the C5/MAO system exhibits the poor compatibility with the M1 comonomer. Copolymerization results of ethylene with M1-M3 using C4/MAO indicate that M1-M3 are well tolerated by both the cationic active species of C4 and MAO cocatalyst, giving rise to the copolymers with high levels of activity and molecular weight. Inspection of the aliphatic region of the ¹³C NMR spectra of the copolymers (P1-P3) having ca. 11 mol% of M1-M3, respectively, reveals the presence of isolated comonomer units with prevailing EEMEE] monomer sequences in the polymer chain. UV-vis absorption and PL spectra exhibit an apparent low-energy band broadening for P1 and P2 indicative of intrachain aggregate formation. Whereas P2 and P3 undergo completely reversible one-electron oxidation process, P1 shows relatively poor oxidational stability.