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Sustainable polymer chemistry of high-performance materials by mechanochemistry Niamh Curran (21210790) PUREID: 660499656 mechanochemistry sustainable polymer chemistry depolymerisation monobenzoxazine twin-screw extrusion ball milling Mechanochemistry involves the induction of chemical reactions by the direct absorption of mechanical energy. Chapter 1 gives an overview of mechanochemistry and its potential for more environmentally friendly and sustainable chemistry compared to traditional approaches. It also discusses polymer mechanochemistry, and the potential for it to contribute to a sustainable polymer future. <br><br>Chapter 2 describes the synthesis of monobenzoxazines by mechanochemistry using twin-screw extrusion, a continuous method of mechanochemistry, which aimed to further expand and enhance the knowledge and understanding of the way in which these reactions occur by mechanochemistry. The batch reaction process was optimised to gain a set of reactions that could be scaled directly to twin-screw extrusion (TSE). This was then translated and scaled to extrusion. Overall, both batch and TSE monobenzoxazine synthesis achieved 91% conversion when optimised and TSE offered an alternative approach that enabled easy scaling. <br><br>Chapter 3 investigates mechanochemical depolymerisation, which seeks to take advantage of mechanochemical techniques to achieve chemical recycling. The primary focus was the depolymerisation of the low ceiling temperature polymer cyclic poly(phthalaldehyde) (cPPA) in the solid state by mechanochemistry for the first time. The main mechanochemical methods investigated were ball-milling, to determine the differences between a batch mechanochemical method (ball-milling), and a continuous mechanochemical method (TSE), and to investigate the impact of mechanochemistry on a polymer without a second reactant. Ball milling cPPA could achieve 75% conversion to the monomer, when milling conditions were optimised. Liquid-assisted grinding (LAG) was found to hinder the rate of depolymerisation (i.e., “liquid hindered grinding”). Conversely, the opposite effect was found with solid assisted grinding (SAG). TSE was capable of full depolymerisation of cPPA to its monomer at elevated temperatures (at least 90°C). The greater ability of ball milling to depolymerise the polymer at lower temperatures indicates that impact force is important for mechanochemical depolymerisation. <br> 2026-10-01T16:18:31Z Text Thesis 10.17034/32805083.v1 https://figshare.com/articles/thesis/Sustainable_polymer_chemistry_of_high-performance_materials_by_mechanochemistry/32805083 All Rights Reserved