Rawan Omar

Date of Award

January 2019

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

First Advisor

Gudong Du

Abstract

A new series of star-shaped and highly branched poly(β-hydroxybutyrates) (PHBs) with a distinct structure was synthesized by ring-opening polymerization (ROP) of β-butyrolactone (BBL) with amido-oxazolinate zinc catalysts. The ROP of BBL using multifunctional hydroxyl-terminated initiators is an efficient methodology that allowed the preparation of PHBs with not only well-controlled molecular weights (Mn) and narrow dispersity (Đ), but also well-defined end-functional groups. Furthermore, the modifications of star-shaped and highly branched PHBs resulted in various architectures with tailored properties for many applications particularly for the biomedical field. Star-shaped structure is constructed via a core-first approach, in which the multi-functional alcohols will serve as the initiator for ROP. Specifically, three-, four-, and multi-armed star polymers were obtained and thoroughly characterized by various techniques such as nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC), and their thermal and mechanical properties were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). These properties were compared with the linear PHBs since it is expected that branched architectures may have different features. Moreover, the impact of the arm numbers and the arm lengths was studied on thermal properties of the obtained star-shaped PHBs, which strongly depended upon their arm numbers and arm lengths.

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