Aluminum salen and salan complexes in the ring-opening polymerization of cyclic esters: Controlled immortal and copolymerization of rac-β-butyrolactone and rac-lactide

Edward D. Cross, Laura E. N. Allan, Andreas Decken, Michael P. Shaver*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Aluminum-based salen and salan complexes mediate the ring-opening polymerization (ROP) of rac-β-butyrolactone (β-BL), rac-lactide, and ε-caprolactone. Al-salen and Al-salan complexes exhibit excellent control over the ROP of rac-β-butyrolactone, yielding atactic poly(3-hydroxybutyrate) (PHB) with narrow PDIs of <1.15 for Al-salen and <1.05 for Al-salan. Kinetic studies reveal pseudo-first-order polymerization kinetics and a linear relationship between molecular weight and percent conversion. These complexes also mediate the immortal ROP of rac-β-BL and rac-lactide, through the addition of excess benzyl alcohol of up to 50 mol eq., with excellent control observed. A novel methyl/adamantyl-substituted Al-salen system further improves control over the ROP of rac-lactide and rac-β-BL, yielding atactic PHB and highly isotactic poly(lactic acid) (Pm = 0.88). Control over the copolymerization of rac-lactide and rac-β-BL was also achieved, yielding poly(lactic acid)-co-poly(3-hydroxybutyrate) with narrow PDIs of <1.10. 1H NMR spectra of the copolymers indicate a strong bias for the insertion of rac-lactide over rac-β-BL.

Original languageEnglish
Pages (from-to)1137-1146
Number of pages10
JournalJournal of Polymer Science Part A: Polymer Chemistry
Volume51
Issue number5
DOIs
Publication statusPublished - 1 Mar 2013

Keywords / Materials (for Non-textual outputs)

  • rac-lactide
  • biodegradable
  • INITIATORS
  • rac-ss-butyrolactone
  • RACEMIC LACTIDE
  • METAL-COMPLEXES
  • BIODEGRADABLE ALIPHATIC POLYESTERS
  • BIOMEDICAL APPLICATIONS
  • STEREOELECTIVE POLYMERIZATION
  • CHAIN-END CONTROL
  • PREDOMINANTLY SYNDIOTACTIC POLY(BETA-HYDROXYBUTYRATE)
  • ring-opening polymerization
  • LACTONES
  • EPSILON-CAPROLACTONE
  • copolymerization

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