title: PMLABe diol synthesized by ring-opening polymerization of racemic benzyl β-malolactonate initiated by rare-earth trisborohydride complexes: an experimental and DFT study.
abstract: Polymer diols are a class of polymeric building blocks of high interest for the synthesis of complex macromolecular edifices. Rare-earth borohydride complexes are known as efficient initiators for the ring-opening polymerization (ROP) of cyclic esters, directly affording α,ω-dihydroxy-telechelic polyesters. Here, were report the direct synthesis of poly(benzyl β-malolactonate) (PMLABe) diols, from the ROP of racemic (benzyl β-malolactonate) (rac-MLABe), a valuable and renewable monomer, initiated by the homoleptic [Ln(BH4 )3 (thf)3 ] (Ln=La, Nd, and Sm) complexes. These initiators enabled the controlled ROP of this β-lactone, affording well-defined syndiotactic-enriched (Pr ≈0.83) PMLABes (Mn up to 21 300 g mol(-1) , ÐM ≈1.5) as evidenced by size exclusion chromatography, (1) H and (13) C NMR spectroscopy, and MALDI-ToF mass spectrometry analyses. The first and second insertions of rac-MLABe, as assessed by DFT calculations, revealed more favorable stationary front-side than migratory back-side insertions, the thermodynamically and kinetically competitive ROP on two distinct arms with that on a one arm-only, and the thermodynamically slightly favored formation of syndiotactic-enriched PMLABes.
authors.affiliation: Institut des Sciences Chimiques de Rennes, Organometallics, Materials and Catalysis, UMR 6226 CNRS-Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France).
authors.forename: Cédric G
authors.initials: CG
authors.lastname: Jaffredo
authors.forename: Matthias
authors.initials: M
authors.lastname: Schmid
authors.forename: Iker
authors.initials: I
authors.lastname: Del Rosal
authors.forename: Teddy
authors.initials: T
authors.lastname: Mevel
authors.forename: Peter W
authors.initials: PW
authors.lastname: Roesky
authors.forename: Laurent
authors.initials: L
authors.lastname: Maron
authors.forename: Sophie M
authors.initials: SM
authors.lastname: Guillaume
keywords: density functional calculations; diols; poly(hydroxyalkanoate)s; rare earths; ring-opening polymerization; telechelic