Synthesis Of Cyclic And Linear Poly(hydroxybutyrates) By Ring-opening Polymerization Of β-Butyrolactone With Amido-Oxazolinate Zinc Catalysts
Date of Award
Master of Science (MS)
A series of amido-oxazolinate zinc complexes have been employed for the ring opening polymerization of β-butyrolactone (BBL). Experimental results show that these complexes efficiently catalyze the reactions, yielding cyclic poly(hydroxybutyrate)s (PHBs) with high molecular weights (Mn up to 196 kg/mol) and low dispersity. In contrast, in the presence of alcohol co-catalysts, the zinc-catalyzed ring-opening polymerization (ROP) reactions lead to the formation of linear PHBs end-capped by the alcohol initiator and hydroxylbutyrate. A possible mechanism for cyclic PHBs is proposed, in which the zinc catalysts function as a loose Lewis pair at elevated temperature, followed by a fast propagation through a zwitterionic intermediate. Use of diols such as 1,4-cyclohexane diol and 1,4-benzenedimethanol results in the formation of polyester diols. The thermal properties were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) to differentiate between the cyclic and linear polyesters.
Shaik, Muneer, "Synthesis Of Cyclic And Linear Poly(hydroxybutyrates) By Ring-opening Polymerization Of β-Butyrolactone With Amido-Oxazolinate Zinc Catalysts" (2018). Theses and Dissertations. 2344.