Ring‐opening polymerization of lactones using RuCl₂(PPh₃)₃ as initiator: Effect of hydroxylic transfer agents

Abstract

-Caprolactone and ␦-valerolactone were polymerized in bulk at 150°C using the ruthenium(II) complex RuCl 2 (PPh 3 ) 3 as initiator in the presence of 1,3-propanediol (PD) with a series of alcohols as coinitiators. Polymerization of lactones proceeds via ruthenium(II) alkoxide active centers.1 H-NMR analysis revealed that the ruthenium complex reacted with the alcohol, generating in situ a ruthenium alkoxide. This species became a more active initiator of ring-opening polymerization than was RuCl 2 (PPh 3 ) 3 . The obtained polylactones were characterized by 1 H-and 13 C-NMR and matrixassisted laser desorption ionization time-of-flight (MALDI-TOF). The results showed the formation had occurred of ␣,-telechelic PCL and PVL diols, in which PD had been incorporated into the polymer backbone. Depending on the nature of the alcohol used as coinitiator, PCLs with different end groups could be synthesized. Insertion of an alcohol as an end group (benzyl alcohol, n-octanol, or isopropanol) or into the polymeric backbone (propanediol) provided support for the conclusion that a classical coordination-insertion mechanism was operating during lactone polymerization.

Ring‐opening polymerization of ϵ‐caprolactone initiated with different ruthenium derivatives: Kinetics and mechanism studies

“…When alcohols are used in the polymerization as transfer agents, an accelerating effect is observed (reaction times in the order of 30 h are commonly observed using hydroxylic transfer agents). Presence of alcohols also exerts control of end‐group functionality and final polyester number‐average molecular weight ( M n ), which depends on the initial initiator/transfer agent ratio 22. However, it is convenient to compare the catalytic activity of RuCl 2 (PPh 3 ) 3 with other ruthenium complexes.…”

“…Presence of alcohols also exerts control of end-group functionality and final polyester number-average molecular weight (M n ), which depends on the initial initiator/transfer agent ratio. 22 However, it is convenient to compare the catalytic activity of RuCl 2 (PPh 3 ) 3 with other ruthenium complexes. In particular, TpRu(L)(L 0 ) complexes have received significant attention, as they are able to systematically control the steric and electronic features of the metal coordination sphere via variation of L and L 0 ligands nature.…”

“…α,ω‐ Telechelic polycaprolactone (PCL) and polyvalerolactone (PVL) diols, in which 1,3‐propanediol had been incorporated into the polymer backbone, can be obtained with good yields. Depending on the nature of the alcohol used as coinitiator, PCLs with different end groups can be synthesized 22. Following in this line of investigation, we report hereby a comparative study of the catalytic behavior of four different ruthenium complexes TpRuCl(L)(L′) (L, L′ = PPh 3 , PHPh 2 , PMe 2 Ph) in the ROP of CL (Scheme ).…”

“…Depending on the nature of the alcohol used as coinitiator, PCLs with different end groups can be synthesized. 22 Following in this line of investigation, we report hereby a comparative study of the catalytic behavior of four different ruthenium complexes TpRuCl(L)(L 0 ) (L, L 0 ¼ PPh 3 , PHPh 2 , PMe 2 Ph) in the ROP of CL (Scheme 1). Characterization of intermediates leads us to propose a coordination-insertion mechanism.…”

Electronic and steric effects of methyl substituent in Samarium (III) phenolates on their initiation activities in polymerization of ϵ‐caprolactone

“…[6][7][8][9][10] Although some coordination complexes, including Sm (III) complexes, have been utilized in ROP of CL and its copolymerization with lactide (LA), some easily obtained and cheap phenols, such as 2-methylphenol, 4-methylphenol, 2-tertbutyl-4-methylphenol, etc., have never been used to prepare initiators of this kind. [11][12][13][14][15] Besides, there has never been any systematic study published on Sm (III) phenolates, leaving alone studies concentrated on the correlation between phenols' structures and initiation activities of corresponding phenolates. Considering plenty of phenols' possible structures and their much divergent costs, this kind of study could contribute to more rational initiator design.…”