In situ X-ray absorption fine structure study on the polymerization of isoprene assisted by Nd-based ternary catalysts

Abstract

Polymerization processes of isoprene catalyzed by four catalysts with different alkylaluminums were detected by in situ XAFS technique. The catalytic mechanism of the neodymium-based ternary catalyst was discussed based on the structure information.

Triisobutylaluminium-promoted formation of lanthanide hydrides

“…3–4 alkyl ligands at the neodymium centre, with a Nd–C distance of 2.58 Å, whereas addition of extra diisobutylaluminium chloride led to detection of two Al “neighbours” at a distance of 3.14 Å. 28 Compared to our work, this may suggest that two aluminato units may be involved. Further, the comparison of interatomic distances clearly shows similarities of 1 Nd with the calculated parameters reported by Guo et al 26,28 They describe substitution of the Nd–O for Nd–C bonds, which are in the range of 2.57–2.58 Å.…”

“…28 Compared to our work, this may suggest that two aluminato units may be involved. Further, the comparison of interatomic distances clearly shows similarities of 1 Nd with the calculated parameters reported by Guo et al 26,28 They describe substitution of the Nd–O for Nd–C bonds, which are in the range of 2.57–2.58 Å. We observed strikingly similar Nd–C interatomic distances in the range of 2.542–2.763 Å for 1 Nd .…”

“…Additionally, the Nd---Al distances in 1 Nd are 2.999(2) and 3.243(2) Å, which is comparable to the metrics for two aluminium neighbours given with average 3.14 Å. 28…”

“…It is noteworthy that previous investigations into the active species, which are formed in mixtures of neodymium carboxylate Nd(vers) 3 (vers = neodecanoato), TIBA, and diisobutylaluminium chloride, using MALDITOF and XAFS techniques do not consider the formation of hydride species but very well alkylation. 27,28 Theoretical optimization of the EXAFS data assumes the presence of approx. 3–4 alkyl ligands at the neodymium centre, with a Nd–C distance of 2.58 Å, whereas addition of extra diisobutylaluminium chloride led to detection of two Al “neighbours” at a distance of 3.14 Å.…”

Catalysts for the Controlled Polymerization of Conjugated Dienes

“…The 3,4-polydienes do not exist in the natural state, their preparation was synthetically developed later, and they have recently been shown to be potentially useful for improving tire performance, thanks to their excellent skid resistance and their low rolling resistance [8]. Nowadays, there is a better understanding of the polymerization mechanism and involves allyl-active species, thanks in particular to the support of more and more efficient calculations methods [9][10][11]. Since the beginning of the 2000s, there has also been a tendency for statistical copolymerization of 1,3-dienes with olefin or styrene comonomers to produce statistical, alternating, and block copolymers [12], while access to multiblock and stereoblock copolymers is currently made possible by the innovative approaches of coordinative chain transfer polymerization [13].…”