Applications of the novel bio-derived solvent Cyrene™ in polymer chemistry

Polar aprotic solvents such as N-methyl-2-pyrrolidone, N,N’-dimethylformamide and N,N’-dimethylacetamide are under regulatory pressure worldwide due to their toxicity. Cyrene™, a bio-based solvent first developed by the University of York in collaboration with Circa Group made from cellulosic biomass, represents a promising alternative to polar aprotic solvents with chronic toxicity or other health-related concerns. This thesis explores the use of Cyrene as polar aprotic solvents replacement in polymer dissolution for graffiti removal, extractions of flavonoids, dispersion of carbon nanotubes, polymerisation and/or production of poly(amide-imide) wire enamels and production of filtration membranes. Cyrene proved a good cleaning agent for acrylic and cellulose-based graffiti aerosols, giving comparable results to N-methyl-2-pyrrolidone, without the latter’s chronic toxicity and chemical contamination concerns. Poly(amide-imide) enamels synthesised with Cyrene were chemical resistant, showed superior adhesion strength and were flexible. Cyrene showed up to ten times better extraction capacity of flavonoids (hesperidin and rutin) when mixed with water than using established ethanol-water mixtures and an increase to 91% when heated up to 65 °C. Cyrene demonstrated an efficient liquid media to disperse carbon nanotubes and reached concentrations up to 0.27 mg mL-1, which were stable for up to six months. Cyrene produced membranes tailored for applications from reverse osmosis (˂0.001 µm pore size) to microfiltration (0.1-10 µm) by changing polymers employed and the viscosity of the casting solution. Cyrene-based membranes showed higher porosity than usual and formed pores without the use of additives. Hansen Solubility Parameters were employed in this work to predict polymer dissolutions and discover new viable blends of Cyrene with other green solvents for these applications. This study has demonstrated the applicability of Cyrene across a broad range of applications involving polymer synthesis and fabrication of advanced materials, especially those which do not require rapid evaporation of the solvent or where higher viscosity is essential.