Rapid Polymerization via Photothermal Synthesis

Open Access
- Author:
- Phillips, Sarah
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 02, 2024
- Committee Members:
- Kenneth Knappenberger, Program Head/Chair
Benjamin Lear, Co-Chair & Dissertation Advisor
Elizabeth Elacqua, Major Field Member
Raymond Schaak, Major Field Member
Bellamarie Ludwig, Co-Chair & Dissertation Advisor
Bryan Vogt, Outside Unit & Field Member - Keywords:
- photothermal
polymer
polyurethane
polydimethyl siloxane
fouling release - Abstract:
- The photothermal effect of nanoparticles provides an alternative heating method to conventional heat sources (ovens, hot-plates, etc.) that allows for control of the distribution of thermal energy with both nanometer and nanosecond precision. Photothermal heating can drive reactions at rates that would not be possible using conventional heat sources without degrading the material. This dissertation examines the use of photothermal heat to rapidly synthesize polymers using carbon black and a continuous-wave laser. Carbon black is a common filler used to reinforce polymers, such as increasing the mechanical strength of rubber in tires. The strong absorption by carbon black across a broad range of wavelengths leads to its excellent photothermal properties, generating nanoscale heat and bulk temperature increases. First, the photothermal synthesis of polyurethane from blocked isocyanates is demonstrated. It was shown, for the first time, that photothermal heat can de-block isocyanates and drive the formation of polyurethane. The photothermal approach produced cross-linked polyurethane in 10 seconds that was spectroscopically identical by 1H NMR to oven heated polyurethane. Next, the generality of the photothermal approach was demosntrated by the curing of a different polymer chemistry, siloxane. Again using carbon black as the photothermal agent, polydimethylsiloxane was cured in 5 seconds to the same degree as samples cured for 5 days under ambient conditions (22 °C) as measured by a differential scanning calorimeter. The effects of carbon black concentration and photothermal heating on the kinetics of the curing reaction and the mechanical properties of the cured polymer were also examined. A potential application of rapid photothermal polymerization, marine coatings, was also investigated. A procedure to photothermally cure smooth polydimethylsiloxane fouling-release coatings was developed. Contact angle measurements, removal strength tests, and salt/fog chamber experiments showed that a photothermal approach can rapidly cure a marine-relevant polymer, without reducing its protective properties or functional abilities. Future directions for this research were also discussed, including strategies to increase the interaction between carbon black and the polymer network and the use of coal as alternative photothermal agent.