Cellulose nanocrystals: insights into the preparation and incorporation into new materials templates

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School of Chemical Engineering | Doctoral thesis (article-based) | Defence date: 2021-10-08
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Authors

Date

2021

Department

Biotuotteiden ja biotekniikan laitos
Department of Bioproducts and Biosystems

Major/Subject

Mcode

Degree programme

Language

en

Pages

68 + app. 114

Series

Aalto University publication series DOCTORAL DISSERTATIONS, 123/2021

Abstract

This thesis is focused on a novel cellulose hydrolysis technique via gaseous HCl and on the utilization of that technique in building up different materials templates, namely, those in hybrid multilayered structures of cellulose nanocrystals (CNCs) and ZnO as well as in micron-sized, porous particles of cross linked CNCs that retain the native cellulose microfibrillar alignment. Cellulose hydrolysis, typically in liquid/solid systems, has been extensively studied due to its significance in the fields of biofuels, chemicals production, and renewable materials. Herein, we focused on a gas/solid system by constructing a reactor for HCl (g) to overcome the limitations in previously introduced HCl vapor hydrolysis systems. Cellulose fibers were hydrolyzed down to the leveling-off degree of polymerization (LODP), indicating degradation of the disordered segments in cellulose microfibrils without visibly affecting the fiber morphology. Yet prolonged exposure was found to induce a partial collapse of the fiber structure. The exposure of hardwood cellulose nanofiber (CNF) thin films deposited on silica to HCl (g) resulted in visualization of the order/disorder transitions in cellulose microfibrils.Bacterial cellulose (BC) aerogels were hydrolyzed under 1 bar of HCl (g) and subse-quently TEMPO-oxidized to isolate the CNCs in a stable dispersion in water. Comprehensive microscopic analysis provided proof of concept on CNC formation. Crosslinking of hydrolyzed fibers by citric acid led to the formation of crosslinked CNC particles that maintained the native cell wall alignment. Thermoporosimetry combined with high resolution microscopy revealed the formation of a well-defined, nanoporous network consisting of end-to-end connected CNCs. The preparation of ZnO/CNC multilayered structures took place by alternation of atomic layer deposition (ALD) and spin coating, resulting in discrete CNC layers between the ZnO laminates. Thermal conductivity measurements revealed the effective thermal insulation by CNCs. Even the incorporation of submonolayer amounts of CNCs was able to significantly reduce the thermal conductivity of the system.

Description

Defence is held on 8.10. 2021 12:00 – 15:00 https://aalto.zoom.us/j/64004385532

Supervising professor

Kontturi, Eero, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland

Thesis advisor

Tammelin, Tekla, Dr.,Technical Research Center of Finland - VTT, Finland
Solala, Iina, Dr., Aalto University, Finland

Keywords

cellulose nanocrystals, HCl (g) hydrolysis, crosslinking, ZnO/CNC hybrids

Other note

Parts

  • [Publication 1]: Pääkkönen, Timo; Spiliopoulos, Panagiotis; Knuts, Aaro; Nieminen, Karlo; Johansson, Leena-Sisko; Enqvist, Eric; Kontturi, Eero (2018). From vapour to gas: optimising cellulose degradation with gaseous HCl, React. Chem. Eng, volume 3, issue 3, pages 312-318.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201808014328
  • [Publication 2]: Spiliopoulos, Panagiotis; Spirk, Stefan; Pääkkönen, Timo; Viljanen, Mira; Svedström, Kirsi; Pitkänen, Leena; Awais, Muhammad; Kontturi, Eero (2021). Visualizing Degradation of Cellulose Nanofibers by Acid Hydrolysis, Biomacromolecules, volume 22, issue 4, pages 1399-1405.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202104286402
  • [Publication 3]: Pääkkönen, Timo; Spiliopoulos, Panagiotis; Nonappa; Kontturi, Katri S.; Penttilä, Paavo; Viljanen, Mira; Svedström, Kirsi; Kontturi, Eero (2019). Sustainable High Yield Route to Cellulose Nanocrystals from Bacterial Cellulose, ACS Sustain. Chem. Eng., volume 7, issue 17, pages 14384-14388.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201909205323
  • [Publication 4]: Spiliopoulos, Panagiotis; Solala, Iina; Pääkkönen, Timo; Seitsonen, Jani; Bochove, Bas V; Seppälä, Jukka V; Kontturi, Eero (2020). Native structure of the plant cell wall utilized for top-down assembly of aligned cellulose nanocrystals into micrometer-sized nanoporous particles, Macromol. Rapid Commun, volume 41, issue 15, pages 2000201.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202008214805
  • [Publication 5]: Spiliopoulos, Panagiotis; Gestranius, Marie; Zhang, Chao; Ghijasi, Ramin; Tomko, John; Arstila, Kai; Putkonen, Matti; Karppinen, Maarit; Tammelin, Tekla; Hopkins, E. Patrick; Kontturi, Eero. Cellulose-inorganic hybrids of strongly reduced thermal conductivity. Submitted to Cellulose in the year 2021.
    DOI: 10.21203/rs.3.rs-632419/v1 View at publisher

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https://urn.fi/URN:ISBN:978-952-64-0506-3

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[diss] Kemian tekniikan korkeakoulu / CHEM