Poly(hydroxybutyrate), as a biodegradable and biocompatible polymer, has received an increasing amount of attention over the last decades due to its significance in a wide variety of applications, ranging from packaging industries to biomedical and drug delivery applications. To tailor the final physical properties of these polymers through controlling the backbone microstructure, several chemical synthetic routes such as ring opening polymerization (ROP) of strained cyclic ester, β-butyrolactone (BBL), based on metallic catalysts have been reported. We have recently shown that chiral alkyl zinc complex (NNiOtBu)Zn(CH2CH3) forms moderately syndiotactic PHBs (Macromolecules 2015 48 (18), 6672-6681). In this work, syndiotactically enriched PHB (Pr up to 0.71) is synthesized from ring opening polymerization of rac-BBL using series of chiral alkoxy zinc complexes. During polymerization, all the complexes are very reactive and have very good control over the molecular weight and form monodispersed syndio-enriched PHBs. This is also the case in the presence of high loadings of alcohols. Detailed investigations have been also carried out to address the polymerization mechanism. Mechanical and thermorheological properties of these polymers are also studied through investigation of the effect of backbone microstructure and molecular weight on the tensile and melt viscoelastic properties of syndiotactically enriched PHBs.

Highly active and syndioselective zinc complexes for the immortal ring-opening polymerization of β-butyrolactone

251st National Meeting (2016)

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