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Synthesis of PDMS-based polyHIPEs with controlled properties using thiol-ene click reactions

McKenzie, Tucker
http://orcid.org/0000-0003-2781-8462
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1704206097490175

Abstract Details

2023, PhD, University of Cincinnati, Arts and Sciences: Chemistry.
Polydimethylsiloxanes (PDMS) are a versatile class of elastomeric polymers that have properties such as chemical resistance and high strain at break making them suitable for applications including biomaterials, soft robotics, and wearable electronics. Furthermore, the introduction of porosity to PDMS-based elastomers provides additional properties making them advantageous in applications such as separation membranes, strain sensors, and sound dampening acoustics. Specific to acoustic materials, the stiffness and porosity of the material are the two key properties that can be targeted to control the acoustic dampening capabilities. Currently, designing porous PDMS with a range of stiffness is a challenge, and there is a need to develop such systems to access a wider range of acoustic properties that are currently inaccessible. This dissertation provides synthesis routes to obtain porous PDMS materials with the goal of systematically controlling properties such as porosity, pore morphology, and moduli. This goal was achieved by coupling polymerized high internal phase emulsions (polyHIPEs) with thiol-ene click reactions. Each Chapter of this dissertation investigates individual aspects of the polyHIPE process to develop knowledge in the relationship between the emulsion template with the final properties of the materials. We first established how the volume fraction of the aqueous internal phase, surfactant concentration, and thiol-ene ratio of the PDMS-based polymer network impacted the polyHIPE’s porosity, pore size, and storage moduli. We show that these low-moduli porous PDMSs were suitable as materials for ultrasonic sound damping by achieving longitudinal sound speeds of ~ 40 m/sec. We expanded these results by investigating a wider range of thiol-ene ratios of the polymer network at a single porosity to obtain larger differences in the moduli of the PDMS polyHIPEs, and obtained low sound speeds of ~ 40-55 m/sec. We next leveraged the orthogonal nature of thiol-ene reactions to design emulsion patterning methods to prepare layered-porosity PDMS-polyHIPEs by a one-step UV-initiated polymerization process and showed that the interface of these materials was well-defined and mechanically robust. We adapted this layering process to prepare polyHIPE-hydrogel composites using two thiol-ene polymer networks. One-step UV-initiated thiol-ene reactions in both polyHIPE- and hydrogel-layers resulted in defined, multi-layered polyHIPE-hydrogel composites for the first time. Lastly, we show that the pore morphology of PDMS-based polyHIPEs can be controlled by the chemistry of the surfactant by synthesizing a library of ABA triblock copolymers using reversible addition-fragmentation chain transfer polymerizations (RAFT). We found that the pore size, pore interconnectivity, and total porosity could be controlled using the triblock surfactants. Additionally, the storage modulus could be controlled by introducing thiol moieties to the surfactant as reactive functional groups, and these materials showed low sound speeds of ~ 35 m/sec at ultra sonic frequency at porosity values over 70%. In conclusion, the results of this dissertation show synthesis routes to obtain polyHIPEs that have a range of mechanical properties for acoustic applications. Furthermore, we have developed a platform for the preparation of layered polyHIPEs using UV-initiated thiol-ene reactions that can be easily adapted to other related click chemistries to access new polyHIPE composite materials.
Neil Ayres, Ph.D. (Committee Chair)
David Smithrud, Ph.D. (Committee Member)
Hairong Guan, Ph.D. (Committee Member)
206 p.
Chemistry
emulsion templated polymerizations; Acoustic materials; polyHIPE; Thiol-ene click reactions; PDMS; porous elastomers

Recommended Citations

Citations

  • McKenzie, T. (2023). Synthesis of PDMS-based polyHIPEs with controlled properties using thiol-ene click reactions [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1704206097490175

    APA Style (7th edition)

  • McKenzie, Tucker. Synthesis of PDMS-based polyHIPEs with controlled properties using thiol-ene click reactions. 2023. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1704206097490175.

    MLA Style (8th edition)

  • McKenzie, Tucker. "Synthesis of PDMS-based polyHIPEs with controlled properties using thiol-ene click reactions." Doctoral dissertation, University of Cincinnati, 2023. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1704206097490175

    Chicago Manual of Style (17th edition)

ucin1704206097490175
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This open access ETD is published by University of Cincinnati and OhioLINK.