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Synthesis and Characterization of Repeating Sequence Copolyesters

Weiss, Ryan (2017) Synthesis and Characterization of Repeating Sequence Copolyesters. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Abstract

Sequence in copolymers is underexploited in synthetic copolymer design despite the overwhelming evidence of the importance of sequence in controlling polymer properties that is seen in biological polymers. A series of poly(-hydroxy acid)s consisting of lactic (L); glycolic (G) and caprolactone-derived (C) units has been prepared using segmer assembly polymerization (SAP). The segmers, which consist of the targeted repeat unit, e.g. LGC, are first prepared by the coupling of orthogonally protected building blocks. The periodic copolymers, e.g., (LGC)n were then prepared by a step-growth condensation reaction. The retention of the sequence in the copolymers was confirmed by NMR analysis and the chemical shifts were compared with those previously assigned based on the analysis of statistical copolymers. Thermal properties, Tg and Tm were found to depend both on composition and, in a few cases, sequence. Selected poly(lactic-co¬-glycolic acid)s (PLGAs) with embedded stereosequences (LS vs. LR), were found to form crystalline stereocomplexes, in some cases as blends and in others as homopolymers that included both stereoisomers as mini-blocks. The sequence fidelity of PLGAs was defined and determined for a series of copolymers with controlled levels and types of errors. Both NMR and Matrix-Assisted Laser Desorption/Ionization (MALDI) mass spectrometry were used to quantify the error level. An alternate synthetic method for sequenced PLGAs, based on Entropy-Driven Ring-Opening Metathesis Polymerization (ED-ROMP) was developed. Embedding the target sequence in an unstrained macrocycle bearing an olefinic reactive group allowed for ED-ROMP and produced sequenced copolymers with improved molecular weight control relative to SAP. Kinetic studies were consistent with an entropy-driven process. Copolymers comprised of repeating sequences were synthesized by SAP and ED-ROMP and their properties were then characterized.

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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Weiss, Ryanrmw39@pitt.edurmw39
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairMeyer, Taratmeyer@pitt.edutmeyer
Committee MemberStar, Alexanderastar@pitt.eduastar
Committee MemberHorne, W. Sethhorne@pitt.eduhorne
Committee MemberMarra, Kaceymarrak@upmc.edumarrak
Date: 2 July 2017
Date Type: Publication
Defense Date: 5 August 2016
Approval Date: 2 July 2017
Submission Date: 7 December 2016
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 300
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: PLGA, poly(lactic-co-glycolic acid), sequence, copolymer
Date Deposited: 02 Jul 2017 20:58
Last Modified: 02 Jul 2017 20:58
URI: http://d-scholarship.pitt.edu/id/eprint/31373

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