Efficient ring-opening polymerization and copolymerization of epsilon-caprolactone and omega-pentadecalactone catalyzed by Candida antartica lipase B

In this paper, Novozyme-435-catalyzed omega-pentadecalactone and omega-pent adecalactone/epsilon-caprolactone polymerizations were investigated. Novozy me-435-catalyzed omega-pentadecalactone polymerizations were studied in bul k and at omega-pentadecalactone-to-toluene ratios from 1:1 to 1:10 (wt/vol) . By carrying out polymerizations with w-pentadecalactone to toluene 1:1 wt /vol instead of in bulk, the monomer conversion (32 to 90%) and product M-n (22 x 10(3) to 86 x 10(3) g/mol) increased. Effects of reaction temperatur e on monomer conversion and product molecular weights also were studied, om ega-Pentadecalactone polymerization at 90 degrees C in toluene (1:2 omega-p entadecalactone to toluene wt/vol) resulted in the fastest kinetics thus fa r reported for lipase-catalyzed polyester production. However, reduction of the polymerization temperature from 90 to 55 degrees C gave polypentadecal actone with increased M-n (66 x 10(3) to 81 x 10(3) g/mol). Novozyme-435-ca talyzed omega-pentadecalactone/epsilon-caprolactone copolymerizations condu cted at 70 degrees C in toluene occurred at unexpectedly rapid rates. Studi es of monomer coreactivity ratios (r(1) = 1.742 and r(2) = 0.135) showed th at w-pentadecalactone reacted 13 times faster than epsilon-caprolactone, C- 13 NMR studies showed that copolymers with random repeat unit sequence dist ributions were formed after 10 min at monomer conversions greater than or e qual to 44%). We believe that Novozyme-435 actively promotes interchain tra nsesterification reactions that tend to randomize the repeat unit sequence distribution.