MOLECULAR-SCALE CONTROL OVER REACTION RATE AND MATERIAL PROPERTIES OF PHOTOTHERMALLY CURED SILICONE

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- Author:
- Fortenbaugh, Robert
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 21, 2019
- Committee Members:
- Benjamin James Lear, Dissertation Advisor/Co-Advisor
Benjamin James Lear, Committee Chair/Co-Chair
Paul S Cremer, Committee Member
Ayusman Sen, Committee Member
Venkatraman Gopalan, Outside Member - Keywords:
- Photothermal
photothermal effect
nanoparticles
silicone
photothermal heat
PDMS
polymer
3D printing
paints and coatings
thermoset polymer - Abstract:
- The photothermal effect of nanoparticles produces extremely localized heat that can be harnessed to drive large scale chemical reactions by simultaneously generating many individual reactions on the nanoscale. We use the photothermal effect to enhance the curing rate of polydimethylsiloxane (PDMS) by a factor of 4.9 x 10^9. Photothermal curing occurs via crosslinking reactions between vinyl and Si-H groups of the pre-polymer, and the course of the reaction was followed by monitoring the disappearance of infrared bands associated with these functional groups. Using mass spectroscopy, we verify that the major polymer m/z peaks are identical for both traditionally and photothermally cured polymers, indicating that the photothermal effect of nanoparticles is an effective way in which to supply on-demand curing of PDMS. Photothermal curing was also shown to affect the desirable chemical and physical properties of the cured polymer. The swelling, gel fraction, and Young’s modulus for PDMS cured under a variety of photothermal and traditional conditions are reported using swelling and tensile measurements. We find that all of these properties can be tuned via the intensity of light and the loading of the photothermal agent and that the crosslink density within the thermoset decreases with increasing intensity of light during curing. Collectively, this work provides a greater understanding of the ability of the photothermal effect to drive chemical reactions and control the final material properties of the cured polymer.
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