Author: Jasmine Pople
Pople, Jasmine, 2024 Synthesis and applications of poly(trisulfides), Flinders University, College of Science and Engineering
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High sulfur content polymers have garnered significant interest in the past decade due to their excellent properties including high refractive index and electrochemical capacitance, and their low-cost feedstocks. These polysulfides are predominantly synthesised through inverse vulcanisation, an operationally simple polymerisation technique. Through inverse vulcanisation, a range of high-value polysulfides with applications in gold sorbents and lenses for infrared thermal imaging can be produced. However, inverse vulcanisation presents several challenges, including operational hazards and the production of ill-defined materials, making it difficult to scale up the production of polysulfides.
This thesis reports a novel method to produce poly(trisulfides), using electrochemistry to achieve mild and safe reaction conditions. Using well-defined sulfur containing monomers, linear poly(trisulfides) were produced through an electrochemically-initiated ring-opening polymerisation. Through computational and experimental studies, the synthesis of linear poly(trisulfides) with a known sulfur rank of three was demonstrated for the first time. Additionally, a key poly(trisulfide) was shown to be fully recyclable back to its monomer unit, allowing for a closed-loop recycling system.
Upscaling of the electrochemical synthesis of poly(trisulfides) was validated through the design of large-scale batch and continuous flow electrochemical reactors, achieving a 20-fold increase in reaction output. With sustainability in mind, the electrolyte solution was shown to be recyclable.
High sulfur content polymers have shown excellent metal binding properties. A water- soluble poly(trisulfide) with a known sulfur rank was produced for the first time and exhibited enhanced metal binding properties compared to non-water soluble polysulfides. Another key poly(trisulfide) was explored as a fully recyclable gold sorbent. This development was a significant achievement in polysulfide applications, as typical polysulfides produced through inverse vulcanisation cannot be recycled due to cross-linking and their ill-defined structure.
The photochemical production of linear poly(trisulfides) was developed to establish a method for producing high molecular weight materials. This was achieved by controlling the amount of light irradiation through a continuous flow photochemical reactor. Photochemical continuous flow synthesis offered the production of poly(trisulfides) on a large scale.
Water-soluble poly(trisulfides) were shown to exhibit antimicrobial and antifungal properties. This marked the first exploration of the biocidal properties of high sulfur content polymers with a well-defined structure and a known sulfur rank of three.
These achievements demonstrated the ability to produce polysulfides using safe and sustainable techniques that employ electrochemical or photochemical initiation. By polymerising fully characterised sulfur-containing monomers, well-defined polysulfides with a known sulfur rank of three were produced. The recyclability of poly(trisulfides) and their abundant starting material enhances the sustainability of these polysulfides. Key poly(trisulfides) were validated in a range of applications which was enabled by their well-defined linear structure. The upscaling of both electrochemical and photochemical polymerisation resulted in the safe multi-gram production of poly(trisulfides).
Keywords: sulfur, polymer, poly(trisulfides), recyclable
Subject: Chemistry thesis
Thesis type: Doctor of Philosophy
Completed: 2024
School: College of Science and Engineering
Supervisor: Justin Chalker