Using the ionic liquid 1-ethyl-3-methylimidazolium acetate as a solvent for fabricating cellulose lignin composite films
File(s)
Author(s)
Othman, Farhana
Type
Thesis or dissertation
Abstract
Plastic is lightweight and durable, making it suitable for many applications, including packaging. Nonetheless, its petroleum-based, non-biodegradable properties have resulted in significant global waste issues. Regenerated cellulose film, often referred to as cellophane, provides a sustainable alternative as it is produced from cellulose wood or cotton fibers. Lignin is a promising material because of its abundant functional groups, such as phenolic and aliphatic hydroxyls, carbonyls, which determine its reactivity and processing capabilities. This study aimed to substitute hazardous solvents for the dissolving of cellulose and lignin with the ionic liquid 1-ethyl-3-methylimidazolium acetate, [C₂C₁im][OAc], together with DMSO as a co-solvent. [C₂C₁im][OAc] was synthesized by several methods, and green metrics were assessed to evaluate sustainability. Films composed of cellulose-lignin (cel-lig) and cellulose-lignin-glycerol (cel-lig-gly) were produced using solution casting. Their physicochemical, thermal, and surface properties were determined, along with hydroxyl group quantification and compositional analysis (CA) to determine structure–property correlations. The ion-exchange synthetic method demonstrated the highest efficiency for synthesizing [C₂C₁im][OAc], with an atom economy of 62.8% and an E-factor of 107.8. The NMR tests indicating that four and five washing cycles for cel and cel-lig film, respectively. 31P NMR analysis indicated that hardwood lignins have a greater hydroxyl content compared to softwood lignins. Conversely, cellulose-softwood lignin (i.e. 10cel-4iSL) films exhibited significant surface roughness, resulting in the greatest water contact angle of 88.7°. CA indicated that softwood lignin consisted of approximately 99.9% pure lignin, whereas ionosolv hardwood lignin (iHL) contained around only 60% lignin along with carbohydrate residues. Simultaneously, addition plasticiser of 5 wt.% glycerol produced optimal mechanical performance, increasing tensile yield by 120% in cel-lig-gly, with a tensile stress of 75.8 MPa. CA and hydroxyl content was essential for tailoring the properties of cel-lig films, enabling applications that require superior water-barrier or UV blocking capabilities.
Version
Open Access
Date Issued
2026-02-01
Date Awarded
2026-09-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Welton, Tom
Brandt-Talbot, Agnieszka
Sponsor
Ministry of Higher Education Malaysia
Publisher Department
Department of Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)