Aluminum salen and salan complexes in the ring‐opening polymerization of cyclic esters: Controlled immortal and copolymerization of rac‐β‐butyrolactone and rac‐lactide. Issue 5 (5th December 2012)

• Record Type: Journal Article
• Authors: Cross, Edward D.; Allan, Laura E. N.; Decken, Andreas; Shaver, Michael P.
• Is Part Of: Journal of polymer science. Volume 51:Issue 5(2013:Mar.)
• Page Start: 1137
• Page End: 1146
• Publication Date: 2012-12-05
• Subjects: 547
• DOI: 10.1002/pola.26476
• Languages: English
• ISSNs: 0887-624X

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Aluminum‐based salen and salan complexes mediate the ring‐opening polymerization (ROP) of <italic>rac</italic>‐β‐butyrolactone (β‐BL), <italic>rac</italic>‐lactide, and ε‐caprolactone. Al‐salen and Al‐salan complexes exhibit excellent control over the ROP of <italic>rac</italic>‐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 <italic>rac</italic>‐β‐BL and <italic>rac</italic>‐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 <italic>rac</italic>‐lactide and <italic>rac</italic>‐β‐BL, yielding atactic PHB and highly isotactic poly(lactic acid) (<italic>P</italic><sub><italic>m</italic></sub> = 0.88). Control over the copolymerization of <italic>rac</italic>‐lactide and <italic>rac</italic>‐β‐BL was also achieved, yielding poly(lactic acid)‐<italic>co</italic>‐poly(3‐hydroxybutyrate) with narrow PDIs of <1.10. <sup>1</sup>H NMR spectra of the copolymers indicate a strong bias for the insertion of <italic>rac</italic>‐lactide over <italic>rac</italic>‐β‐BL. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013</p> </abstract>