Using natural deep eutectic solvents to create smart colloids from biomass

Huy Vu Duc Nguyen

Research output: Thesisinternal PhD, WU

Abstract

In Chapter 1, we first argue that cellulose- and chitin-based materials will be important sustainable materials of the future. Next, we discuss solvents for cellulose and chitin that could possibly be used in producing such materials in a sustainable manner, specifically Natural Deep Eutectic Solvents (NADES). Finally, we discuss an approach (which we will use in this thesis) for creating very open and highly branched polymer structures via precipitation of dissolved polymers: antisolvent precipitation in highly turbulent flow fields.

In Chapter 2, we report a sustainable and facile method for cellulose dissolution. We propose to use a Natural Deep eutectic solvent (NADES), composed of choline chloride and malic acid (CM), as an efficient cosolvent for the industrial cellulose solvent N-Methyl morpholine-N-oxide (NMMO). We demonstrate the synergistic effect of the ternary solvent system, which prevents the NMMO monohydrate from crystallizing while at the same time retaining its capacity to dissolve cellulose. Finally, we exploit the new ternary cellulose solvent by demonstrating the room-temperature fabrication of various controlled microstructural particles using an anti-solvent precipitation.

In Chapter 3, we described a method for fabricating a new class of cellulose-based materials, cellulose soft dendritic colloids (cellulose SDCs), via antisolvent precipitation under highly turbulent conditions. We systematically investigate the effect of different types of antisolvents and initial cellulose concentrations on the microstructure of cellulose SDCs particles. We show that the newly prepared cellulose SDCs have very good water-structuring ability, enabling gelation at very low volume fractions of cellulose SDCs.

In Chapter 4, we investigate the use of cellulose SDCs as additives in combinations with other polymers. We first investigate the possibility of using cellulose SDCs as reinforcing agents for packaging applications when incorporated into films of a biobased polymer, carboxymethyl cellulose (CMC). Next, we investigate the potential of cellulose SDCs as a substitute for binders in paper products. Our results demonstrate that due to the chemical compatibility of the cellulose SDCs with the other polymers, and the unique microstructures of the cellulose SDCs, their addition leads to remarkable improvements of the mechanical properties of the composites as compared to those of the pure materials.

In Chapter 5, we develop a novel and green fabrication process for preparing chitin nanowhiskers (ChNW) using a combination of Natural Deep Eutectic Solvent (NADES) pretreatment and mild mechanical treatment. The NADES solvent used in this study is composed of the natural ingredient’s choline chloride and malic acid. We show that aqueous chitin nanowhisker suspensions produced by our approach (NADES-ChNW) have improved colloidal stability compared with chitin nanowhiskers suspensions prepared by acid hydrolysis (Ac-ChNW). In addition, we prepare nanocomposite films containing PVOH and NADES-ChNW or Ac-ChNW to investigate their behavior as reinforcing agents. We have shown that, as compared to the Ac-ChNW, for the NADES-ChNW, both compatibility with the PVOH polymer and reinforcement are much better.

Finally, in Chapter 6, we summarize our most significant results and critically reflect on which of the original aims were achieved and what remains to be done. Additionally, we place our findings in the broader context of the field of biobased sustainable and renewable materials and discuss outstanding challenges.

Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • de Vries, Renko, Promotor
  • Stoyanov, S.D., Co-promotor
Award date18 May 2022
Place of PublicationWageningen
Publisher
Print ISBNs9789464471274
DOIs
Publication statusPublished - 2022

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