Degree Type

Dissertation

Date of Award

2016

Degree Name

Doctor of Philosophy

Department

Chemical and Biological Engineering

Major

Chemical Engineering

First Advisor

Eric W. Cochran

Abstract

Hyperbranched polymer produced from triglycerides have been polymerized via reversible addition-fragmentation chain transfer polymerization (RAFT). Triglyceride is one of the main components in vegetable oils and has been considered stable, non-toxic and environmental friendly. Additionally, the unsaturation of fatty acid chains makes triglycerides competitive as monomer. Therefore, triglycerides are considered one of the most important bio-based chemical resources. The resulting hyperbranched polymers have great potential in coating, drug delivery, and etc.. Chemical modification has been applied to increase chemical activities of double bonds by introducing acrylate groups. Due to the high unsaturation of modified triglycerides ( ~ 2.6 functionality per molecule) , radical polymerization leads to macro-gelation at low conversion according to the classic Flory-Stockmayer theory. However, this work demonstrates that gelation process is easily affected or even avoid by simply tuning reaction conditions, which affect the competition of inter-/intra molecular reactions. The intra-molecular reactions decrease the efficiency of polymerization and lead the cyclings to form within macromolecules. The increased proportion of intra-molecular reactions not only suppresses the gelation process, but also leads to heterogeneity in structure. The less homogeneous structures deviate their chain relaxation dynamics from classic models. Zimm model and Rouse model have been successfully used to describe relaxation dynamics for hyperbranched polymers. Due to the high density of side chains, main chain entanglement is largely restricted. Furthermore, the side chains also interact with the main chains, may or may not providing drag or friction, leading the relaxation process obeying Zimm model or Rouse model. In this work, a close study of hyperbranched PAESO relaxation process has been done. Discussion about how branches and cyclings deviates the process from ideal Zimm model has given. Furthermore, in this work, a study of different triglyceride compositions has been done, i.e. what oleic/linoleic/linolenic fatty acids behave in reaction and affect physical properties. Lastly, preliminary data obtained from morphology study of hyperbranched PAESO has been displayed. Overall, this work connects the rheology properties with hyperbranched PAESO structures and synthesis conditions. It may provide insights in hyperbranched PAESO application.

DOI

https://doi.org/10.31274/etd-180810-5475

Copyright Owner

Mengguo Yan

Language

en

File Format

application/pdf

File Size

129 pages

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