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Dissertation
Nano/microstructured materials obtained using photopolymerization induced phase separation
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2020
DOI: 10.17077/etd.005296
Abstract
Photopolymerization can initiate chemical reactions among liquid molecules by exposing them to light in order to fabricate soft or hard polymeric materials. This process is extensively used for industrial purposes because of the advantages offered via photopolymerization (e.g. fast reaction rates, low cost, environmentally friendly). This research exploits a technique called photopolymerization-induced phase separation (PhIPS) to control polymer morphology. PhIPS can also be used to synergistically combine the properties of different components into a single polymer network by controlling phase separation process and polymer morphology, leading to unique physical and mechanical properties. In this work, we utilize two monomers that do not react with each other (e.g. radically and cationically polymerized) in order to favor phase separation during photopolymerization. Altering the light intensity and/or addition multifunctional monomers (i.e. cross-linkers) allows greater control over domain size-scale and phase separated morphologies due to differences in reaction kinetics between radical and cationic monomers. For example, increasing light intensity and the cross-linker concentration results in polymer morphologies with co-continuous or small soft/hard domains. These changes in polymer morphology facilitate enhanced strength and flexibility of the films which lead to overall improved mechanical properties.
Moreover, the effect of polymerization temperature on the development of phase-separated domains for radical/cationic systems is investigated. Our results indicate that photopolymerization at increased temperature allows greater diffusion of the incompatible phases and delays polymer network vitrification. Interestingly, the degree of phase separation increases with polymerization temperature, affecting significantly polymer properties. Furthermore, this project also explores phase separation in acrylate systems that incorporate unreactive small chain polymers (oligomers) with different molecular weight and architecture. For example, increasing the molecular weight or changing the placement of functional groups on the oligomer chain leads to the formation of multiple phase-separated domains and different phase distributions. These changes in the polymer morphology result in more flexible materials and significantly enhanced energy absorption before failure.
This work establishes the fundamental tools that can be used to control polymer morphology via photo-induced phase separation in order to enable tailoring and enhancement of material properties over a wider range than is possible with traditional polymer systems.
Details
- Title: Subtitle
- Nano/microstructured materials obtained using photopolymerization induced phase separation
- Creators
- Erion Hasa
- Contributors
- C. Allan Guymon (Advisor)Julie L. P. Jessop (Committee Member)Jeffrey W. Stansbury (Committee Member)Syed Mubeen (Committee Member)Alexei V. Tivanski (Committee Member)Joe Gomes (Committee Member) - University of Iowa, Chemical and Biochemical Engineering
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Chemical and Biochemical Engineering
- Date degree season
- Spring 2020
- Publisher
- University of Iowa
- DOI
- 10.17077/etd.005296
- Number of pages
- xix, 212 pages
- Copyright
- Copyright 2020 Erion Hasa
- Language
- English
- Description illustrations
- color illustrations
- Description bibliographic
- Includes bibliographical references (pages 200-212).
- Academic Unit
- Chemical and Biochemical Engineering
- Record Identifier
- 9983956197602771
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