Copolymerization of 1,3‐butadiene and isoprene with cobalt dichloride/methylaluminoxane in the presence of triphenylphosphine

Abstract

The homopolymerization and copolymerization of 1,3‐butadiene and isoprene were achieved at 0 °C with cobalt dichloride in combination with methylaluminoxane and triphenylphosphine (Ph3P). For 1,3‐butadiene, highly cis‐specific and 1,2‐syndiospecific polymerization proceeded in the absence or presence of Ph3P, respectively, although the activity with Ph3P was much higher than that without Ph3P. Only a trace of the polymer was, however, obtained in isoprene polymerization when Ph3P had been added. For copolymerization, the polymer yield in the presence of Ph3P was about three times higher than that in its absence. Copolymerization in the presence of Ph3P was, therefore, investigated in more detail. Unimodal gel permeation chromatography elution curves with narrower polydispersity (weight‐average molecular weight/number‐average molecular weight ≈ 1.5) indicated that the propagation reaction proceeded by single‐site active species. Both the yield and molecular weight of the copolymer decreased with an increasing amount of isoprene in the feed, and this was followed by an increase in the isoprene content in the copolymer. The monomer reactivity ratios, r1 (1,3‐butadiene) and r2 (isoprene), were estimated to be 2.8 and 0.15, respectively. Although the 1,3‐butadiene content in the copolymer was strongly dependent on the comonomer composition in the feed, the ratio of 1,2‐inserted units to 1,4‐inserted units of 1,3‐butadiene was constant. Concerning the isoprene unit, the percentage of 1,2‐ and 3,4‐inserted units was increased at the expense of 1,4‐inserted units with an increasing isoprene content in the feed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3086–3092, 2002

Stereospecific polymerization of 1,3-butadiene catalyzed by cobalt complexes bearing N-containing diphosphine PNP ligands

“…It is interesting to notice that much higher conversion of butadiene was obtained when the imino group in ligand L3 was reduced to amino group (ligand L4), comparing complex 3 (conversion: 12.7%) with complex 4 (conversion: 46.1%) although the nitrogen atoms were not coordinated to the cobalt center (entries 4 and 5 in Table 1). Similar to the results reported in the literature [16,17], the 5/MAO system produced much more amount of 1,2-PBD (1,2-vinyl content: 76.9%) than cis-1,4-PBD (cis-1,4 content: 20.6%) because the nature of PPh 3 as a strong s-donor makes it more preferable to gain a high content of 1,2-PBD (entry 6 in Table 1). However, for the chelate complexes 1a, 1b, and 2e4/ MAO systems, the cis-1,4-PBD as the main product ranging from 75.7% to 88.8% was obtained along with a relatively higher content (9.0%e20.6%) of 1,2-PBD formed.…”

Analysis of solution polybutadiene polymerizations performed with a neodymium catalyst

“…In the past years, distinct catalyst systems (Ni [11, 12], Co [13, 14], Nd [1–10, 15–17], Ti [18, 19], and Sm [20–22]) have been developed for 1,3‐diene polymerizations using methylaluminoxane (MAO) [2–4], borate [16], and alkylaluminum/halides [1–10] as cocatalysts. Titanocene/MAO [18–19] and samarocene/AlR 3 /borane [20–22] catalysts present single‐active catalyst sites and are able to produce high cis ‐1,4 polybutadienes (PB) with the simultaneous control of the MWD and stereoregularity of the obtained polymer material; however, these catalysts require large amounts of MAO to scavenge impurities and activate the catalyst.…”

Synthesis and properties of syndiotactic 1,2‐polybutadiene catalyzed by iron catalyst with phosphate as additive

“…Yet, the considerable discrepancy in mechanism for diene polymerization leads to stereochemistry difficult to understand. The efforts to control the 1,2‐stereoselectivity by judicious choice of the ancillary ligand, consequently, has gained limited progress, and only a few transition metal chromium, 23,24 molybdenum, 25 and cobalt 26–32 catalysts actually exhibit syndiotactic stereospecificity.…”