Anionic coordinated polymerization ofɛ-caprolactone with aluminium, zirconium and some rare earths alkoxides as initiators in the presence of alcohols

Abstract

SUMMARY: The kinetics of the polymerization of e-caprolactone initiated with various Lewis acid metal alkoxides (Al, Zr and rare earths such as Y, Sm, Nd) in the presence of excess alcohol has been investigated. Whatever the metal, the activity depends strongly on the [Alcohol]/[Metal] ratio and goes through a maximum, except for Zr, for which the increase of alcohol concentration leads to a continuous decrease of the reaction rate. The activities obtained for zirconium butoxide as initiator are lower than for aluminium isopropoxide at room temperature but the activation energy is higher. No transesterification reactions have been noticed during polymerization. The polymerization can be described according to a living process with fast transfer reaction, so that the molecular weight is easily controlled by the [Monomer]/[Alcohol] ratio. Rare earths alkoxides (Y, Sm, Nd) result in higher activities. Although some transesterification reactions are observed if leaving the polymer chains in contact with the active centers, functionalized oligomers can be obtained within less than 5 min with yttrium or samarium isopropoxide as initiators and benzyl alcohol in excess.

In Situ Preparation of a Compatibilized Poly(cis‐1,4‐butadiene)/Poly(ε‐caprolactone) Blend

“…Since Nd alkoxides are known to polymerize CL, [19] the Nd alkoxide species attached to a high cis-1,4-BR building block will yield the desired block copolymer.…”

Poly[ethylene‐co‐(vinyl alcohol)]‐graft‐poly(ε‐caprolactone) Synthesis by Reactive Extrusion, 1 ‐ Structural and Kinetic Study

“…The 1 H NMR characterization of EVOH‐ g ‐PCL required the previous assignments of both PCL and EVOH spectra under the same conditions (temperature and solvent). The PCL and EVO chemical shifts are well known,4, 18, 28 and are composed of two well resolved resonance regions, between 1–2 ppm for methylene protons and between 2.8–4.6 ppm for both methine and alcohol protons. The addition of trifluoroacetic acid (TFA) shifts the labile hydrogen (OH) to low field >10 ppm and shows consequently the three methine dyads.…”

“…The main reasons for this interest are the possibility of controlling the ring opening polymerization with suitable organometallic catalysts or initiators1 and because polycaprolactone (PCL) is biodegradable. Among catalysts and initiators, tin carboxylates or titanium and aluminium alkoxydes2–4 were often used. To improve their reactivity, organic molecules or polymers containing one or more alcohol functions were added as co‐initiators.…”

Bismuth‐Triflate‐Catalyzed Polymerizations of ε‐Caprolactone

“…For the technical production of homo‐ and copolyesters of lactides and lactones, tin(II) 2‐ethylhexanoate (SnOct 2 ) is the standard catalyst, because it was accepted by the American Food and Drug Administration as a food additive, despite its high cytotoxicity. To avoid toxicity problems several research group have examined the usefulness of non‐toxic metal‐salts, metal complexes, and enzymes as alternatives of SnOct 2 1–29…”