Ring-opening polymerisation of β-butyrolactone catalysed by distannoxane complexes:: study of the mechanism

The mechanism of the ring-opening polymerisation of beta-butyrolactones was studied. The ring-opening polymerisation of BL catalysed by distannoxane complexes is of a living nature. The polymerization of racemic BL gave a predominantly syndiotactic P(3HB). The temperature effect on syndiospecificity was used to determine the activation energy (Delta E = E-syndiotactic-E-isotactic) for syndiotactic versus isotactic diad placement. The SE value was obtained as -1.49 kcal/mol. The steric control leading to the observed syndiospecificity is due predominantly to diastereomeric interactions between the Sn-coordinated P(3HB) chain end, having a specific chain end stereochemistry, and the incoming BL enantiomeric monomers. The catalytic cycle derived from the mechanism of the polymerisation was proposed. (C) 1999 Elsevier Science B.V. All rights reserved.