Homo‐ and copolymerization of ethylene and norbornene with bis(β‐diketiminato) titanium complexes activated with methylaluminoxane

Abstract

Homo‐ and copolymerization of ethylene and norbornene were investigated with bis(β‐diketiminato) titanium complexes [ArNC(CR3)CHC(CR3)NAr]2TiCl2 (R = F, Ar = 2,6‐diisopropylphenyl 2a; R = F, Ar = 2,6‐dimethylphenyl 2b; R = H, Ar = 2,6‐diisopropylphenyl 2c; R = H, Ar = 2,6‐dimethylphenyl 2d) in the presence of methylaluminoxane (MAO). The influence of steric and electric effects of complexes on catalytic activity was evaluated. With MAO as cocatalyst, complexes 2a–d are moderately active catalysts for ethylene polymerization producing high‐molecular weight polyethylenes bearing linear structures, but low active catalysts for norbornene polymerization. Moreover, 2a–d are also active ethylene–norbornene (E–N) copolymerization catalysts. The incorporation of norbornene in the E–N copolymer could be controlled by varying the charged norbornene. 13C NMR analyses showed the microstructures of the E–N copolymers were predominantly alternated and isolated norbornene units in copolymer, dyad, and triad sequences of norbornene were detected in the E–N copolymers with high incorporated content of norbornene. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 93–101, 2008

High norbornene incorporation in ethylene-norbornene copolymerization with a bis(α-alkyloxoimine) titanium-MAO catalyst

“…Copolymerization data in Table 3 show that the copolymerization activity and NBE incorporation in the copolymer are affected by the quantities of charged NBE. Unlike bis (pyrrolide-imine) titanium catalysts [22,23], bis(-diketiminato) titanium catalysts [29], and bis(benzoin) titanium catalyst [30], as the quantities of charged NBE increases (and thereby the NBE/E molar ratio increases), the catalytic activity remains practically unchanged and then increases apparently. This result is likely to arise from good performance of bis(-alkyloxoimine) titanium catalyst for NBE polymerization.…”

“…These results further confirm that bis(-alkyloxoimine) titanium catalyst has a good thermal stability. Most previous publications reported that nonmetallocene titanium complexes had no activity or low activity for norbornene homopolymerization [22][23][24][25]29], while bis(-alkyloxoimine) titanium 4 exhibited good activity for NBE polymerization at high temperature. This provides a possibility for synthesis of the ethylene-norbornene copolymer with high norbornene incorporation.…”

“…The signals are assigned according to the previous reports [10,20] and our results [29,30]. As shown in Figure 3(a), the spectrum of the copolymer containing 19% NBE units displays solely eight major peaks respectively at 29.9 ppm (successive E sequences), 30.4 ppm (isolated E + C5/C6), 30.9 ppm (C5/C6 + E sequence), 33.1 ppm (C7), 41.7, 42.2 ppm (C1/C4), 47.4 and 48.0 ppm (C2/C3), which are characteristics of the NBE units existing as alternating (ENEN) and isolated (ENEE) sequences.…”

“…Many non-metallocenes titanium complexes such as bis(pyrrolide-imine) titanium [22,23], bis(imino-indolide) titanium [24], bis(-enaminoketonato) titanium [25], [2-(2,6-dialkylphenylamino)-1-phenylethoxy TiCl 2 ] [26], titanium complexes bearing tridentate [O  NX R ] (X = S, O, Se, P) ligands [27,28], and bis(-diketiminato) titanium [29] were also used to effectively copolymerize ethylene (E) and norbornene (NBE) in the presence of MAO or MMAO. However, fewer successful examples have appeared for the efficient synthesis of random, high-molecular-weight copolymers with high NBE contents (> 50 mol%), which typically possess high T g (> 150 °C).…”

Zirconium complexes with versatile β-diketiminate ligands: Synthesis, structure, and ethylene polymerization

“…Roesky's [40] and Mindiola's [41] groups investigated the stability of b-diketiminate Ti(III) complexes as well as their intermolecular rearrangement reactions. More recently, Wu's [42] and Li's [43] groups prepared the bulky bis(b-diketiminate)titanium complexes with trifluoromethyl-substituted backbone, which displayed moderate activities for the homo-and copolymerization of ethylene and norbornene.…”