Abstract:
This project was focused on the modications of cellulose using ionic liquids. Cellulose is the most highly abundant natural biopolymer on earth. However the utilisation of cellulose requires chemical modication or physical dissolution in a suitable solvent. Recently ionic liquids have become the solvent of choice for cellulose and other biopolymers. This is because of their unique solvency power and the desirable properties such as non-ammability, thermal stability, and recyclability. The use of cellulose/ionic liquid combinations not only supports the green chemistry concept but also helps in the development of sustainable resources which could be used as replacement for petroleum feed stocks. In this research ionic liquids were used to dissolve cellulose. The ionic liquids used in this study were 1-butyl-3-methylimidazolium chloride, 1-allyl-3- methylimidazolium chloride, and 1-ethyl-3-methylimidazolium acetate. Rheology, heating FTIR and Raman studies were performed with ionic liquids and cellulose solutions to understand the properties of ionic liquids and cellulose solutions. The spectra from the heating studies were subjected to two dimensional correlation analyses. The rheology studies suggest that the ionic liquids themselves exist in two states, liquid state and a network state and the two dimensional analyses of the heating spectra reveals that the hydrogen bonding between C2H of the imidazolium ring, anion and moisture was responsible for this network formation. The cellulose was regenerated or fractionally precipitated from solutions using water, ethanol or acetonitrile as non-solvent. This investigation suggests that protic solvents like water and ethanol are good solvents for gel formation and acetonitrile is a desirable solvent for fractionation. The regenerated and fractionated cellulose samples were characterised by SEM, NMR, FTIR, XRD, DSC, TGA and SEC-MALLS analyses. Nano/sub-micron sized particles of cellulose were produced from the fractionation of cellulose from solutions in 1-ethyl-3-methylimidazolium acetate. SEC-MALLS data indicate that fractionation according to molecular weight is possible with dilute solutions in ionic liquids. It was also observed that samples regenerated from solutions in 1-ethyl-3-methylimidazolium acetate were more ordered than the samples regenerated from chloride containing ionic liquids. These preliminary results show that the use of ionic liquids in the processing of cellulose has the potential to have many possible applications.