Rheology of Native Cellulose in Ionic Liquid/DMSO Solutions
Open Access
- Author:
- Belka, Victoria
- Area of Honors:
- Materials Science and Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Ralph H Colby, Thesis Supervisor
Robert Allen Kimel, Thesis Honors Advisor - Keywords:
- ionic liquids
cellulose dissolution
rheology - Abstract:
- As the world seeks to decrease its reliance on synthetic polymers, many have looked to cellulose as the future of textiles, fibers, and consumer products. Cellulose is the most abundant biopolymer on Earth, and is currently used in the manufacturing of a variety of materials and products. The biopolymer’s low cost, biocompatibility, and biodegradable nature have made it an attractive substitute for petroleum-based plastics in industries ranging from construction to cosmetics. However, the widespread usage of cellulose is severely restricted by its resistance to traditional methods of processing and dissolution. The extremely strong network of inter- and intramolecular hydrogen bonds in cellulose requires the use of toxic, volatile chemicals and expensive, energy-intensive processing methods. Since 2002, ionic liquids (ILs) have garnered interest as an alternative solvent for cellulose due to their nonvolatile, nontoxic, and non-derivatizing nature. Though ionic liquids such as 1-ethyl-3-methylimidazolium acetate (EMImAC) have been shown to effectively dissolve cellulose, the high viscosities of the resultant cellulose/IL systems have also limited their use in industry. Recent literature has suggested that a potential solution involves the addition of a cosolvent molecule like dimethyl sulfoxide (DMSO), which acts to further solvate the cations in the ionic liquid to increase the availability of the anions, the main agent responsible in cellulose dissolution. This thesis investigates the effect of adding the cosolvent DMSO to cellulose/IL solutions by evaluating and comparing the rheological behavior of solutions of varying concentrations of cellulose in either 100% EMImAC or 50% EMImAC and 50% DMSO. The intrinsic viscosities of samples with concentrations of 0.05wt%, 0.1wt%, 0.2wt%, and 0.3wt% cellulose in both solvent mixtures were calculated through capillary viscometry and the creation of a Huggins and Kraemer plot at 20°C and 80°C. The solutions containing DMSO were found to be less viscous than the solutions without DMSO, and it was determined that the quality of DMSO as a cellulose solvent increased with temperature. Additionally, the complex viscosity, loss modulus, and storage modulus of each sample were measured through interfacial rheology. The frequency sweeps of the solutions containing DMSO were found to have complex viscosities several orders of magnitude smaller than that of the 100% EMImAC solutions of the same concentration of cellulose. Ultimately, the conclusion that the addition of a cosolvent such as DMSO could increase the processability of cellulose/ionic liquid solutions by lowering the viscosity of the system was supported by the results of this study. These results may promote sustainability by reducing the reliance on nonrenewable resources such as petroleum through increasing the viability of biodegradable, sustainable systems like cellulose/ionic liquid solutions.