Change search
ReferencesLink to record
Permanent link

Direct link
Fabrication of nanocellulose-based materials: Liquid crystalline phase formation and design of inorganic–nanocellulose hybrids
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The increasing need to replace fossil fuels as a source of energy and raw material is resulting in extensive research efforts towards identifying and developing high performance materials and devices based on renewable sources. Cellulose being the most versatile and abundant biopolymer in nature is one of the obvious choices. Cellulose, due to its properties that arise from the hierarchical structure, has been used for millennia by mankind although it is currently used, in the form of microfibers, mainly in the paper and pulp industry. However, many efforts are being directed towards retrieving even smaller cellulose constituents such as nanofibers and nanocrystals (i.e., nanocellulose), which can actually be used in high performance materials. In order to do so, a better understanding of the behavior and interactions between these novel nanomaterials are required. Moreover, the combination of nanocellulose with inorganic nanoparticles bears a great potential that can open the door to multifunctional materials based on a renewable component.

In this work, the anisotropic behavior, i.e., the formation of a chiral nematic phase, of cellulose nanocrystals (CNC) initially dispersed in aqueous media spanning a wide volume fraction range has been studied by small angle X-ray scattering (SAXS) and laser diffraction. The analysis shows that the twist angle between neighboring CNCs increased from ~1° up to ~4° as the CNC volume fraction increased from 2.5 to 6.5 vol%.

Also, the drying of an aqueous CNC droplet immersed in a binary toluene/ethanol mixture was studied and monitored in-situ by polarized video microscopy, where the influence of the water dissolution rate on the morphology of the resulting microbeads was investigated by scanning electron microscopy. The morphology of the microbeads depends not only on the drying speed but also on the initial starting CNC volume fraction. In this regard, the influence of the degrees of liquid crystallinity on the formation of a chiral nematic phase on films has also been studied.

Lastly, the fabrication and various properties of hybrids and composites prepared from cellulose nanofibers (CNF) and inorganic constituents are presented. The structure and chemistry of a museum sample of a traditional African textile (Bogolan) is analyzed and the chemical foundation of the dyeing method is outlined. This Bogolan dyeing method was used to pattern CNF films, and to study the details of how the surface-bound iron-tannin complexes are formed on the cellulose surface.

Also, the formation of transparent, hard and flexible films based on CNF-titania (anatase) nanoparticle hybrids was studied, where the influence of the composition of the hybrids on the optical and mechanical properties is discussed on the basis of results from electron microscopy, spectrophotometry and nanoindentation.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University , 2015. , 60 p.
National Category
Materials Chemistry
Research subject
Materials Chemistry
Identifiers
URN: urn:nbn:se:su:diva-116517ISBN: 978-91-7649-064-8OAI: oai:DiVA.org:su-116517DiVA: diva2:806712
Public defence
2015-05-29, Magnéli Hall, Arrhenius Laboratory, Svante Arrhenius Väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 2: Submitted. Paper 4: Manuscript.

Available from: 2015-05-07 Created: 2015-04-21 Last updated: 2015-10-27Bibliographically approved
List of papers
1. Rod Packing in Chiral Nematic Cellulose Nanocrystal Dispersions Studied by Small-Angle X-ray Scattering and Laser Diffraction
Open this publication in new window or tab >>Rod Packing in Chiral Nematic Cellulose Nanocrystal Dispersions Studied by Small-Angle X-ray Scattering and Laser Diffraction
Show others...
2015 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 23, 6507-6513 p.Article in journal (Refereed) Published
Abstract [en]

The packing of cellulose nanocrystals (CNC) in the anisotropic chiral nematic phase has been investigated over a wide concentration range by small-angle X-ray scattering (SAXS) and laser diffraction. The average separation distance between the CNCs and the average pitch of the chiral nematic phase have been determined over the entire isotropic-anisotropic biphasic region. The average separation distances range from 51 nm, at the onset of the anisotropic phase formation, to 25 nm above 6 vol % (fully liquid crystalline phase) whereas the average pitch varies from approximate to 15 mu m down to approximate to 2 mu m as phi increases from 2.5 up to 6.5 vol %. Using the cholesteric order, we determine that the twist angle between neighboring CNCs increases from about 1 degrees up to 4 degrees as phi increases from 2.5 up to 6.5 vol %. The dependence of the twisting on the volume fraction was related to the increase in the magnitude of the repulsive interactions between the charged rods as the average separation distance decreases.

National Category
Materials Chemistry
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-118952 (URN)10.1021/acs.langmuir.5b00924 (DOI)000356755300027 ()
External cooperation:
Available from: 2015-07-22 Created: 2015-07-21 Last updated: 2016-08-25Bibliographically approved
2. Confined self-assembly of cellulose nanocrystals in a shrinking droplet
Open this publication in new window or tab >>Confined self-assembly of cellulose nanocrystals in a shrinking droplet
Show others...
2015 (English)In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 11, no 26, 5374-5380 p.Article in journal (Refereed) Published
Abstract [en]

We have studied how cellulose nanocrystals (CNC) self-assemble into liquid crystalline phases in shrinking, isolated droplets. By adjusting the water dissolution rate of an aqueous CNC droplet immersed in a binary toluene-ethanol mixture we can control the final morphology of the consolidated microbead. At low ethanol concentration in the surrounding fluid dense microbeads of spherical morphology are produced while collapsed core-shell particles are obtained at high ethanol concentration. Polarized light microscopy was used to follow the spatial evolution and coalescence of birefringent spheroids during droplet shrinkage. Electron microscopy reveals the resultant nematic microstructure. This method of confined CNC assembly provides thus the possibility to prepare ordered microbeads, which can be useful as templates or for their optical properties.

National Category
Chemical Sciences Materials Engineering Physical Sciences
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-119021 (URN)10.1039/c5sm00886g (DOI)000356806200021 ()
Available from: 2015-07-28 Created: 2015-07-24 Last updated: 2015-10-27Bibliographically approved
3. Macroscopic Control of Helix Orientation in Films Dried from Cholesteric Liquid-Crystalline Cellulose Nanocrystal Suspensions
Open this publication in new window or tab >>Macroscopic Control of Helix Orientation in Films Dried from Cholesteric Liquid-Crystalline Cellulose Nanocrystal Suspensions
Show others...
2014 (English)In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 15, no 7, 1477-1484 p.Article in journal (Refereed) Published
Abstract [en]

The intrinsic ability of cellulose nanocrystals (CNCs) to self-organize into films and bulk materials with helical order in a cholesteric liquid crystal is scientifically intriguing and potentially important for the production of renewable multifunctional materials with attractive optical properties. A major obstacle, however, has been the lack of control of helix direction, which results in a defect-rich, mosaic-like domain structure. Herein, a method for guiding the helix during film formation is introduced, which yields dramatically improved uniformity, as confirmed by using polarizing optical and scanning electron microscopy. By raising the CNC concentration in the initial suspension to the fully liquid crystalline range, a vertical helix orientation is promoted, as directed by the macroscopic phase boundaries. Further control of the helix orientation is achieved by subjecting the suspension to a circular shear flow during drying.

Keyword
film growth, helical structures, liquid crystals, nanocrystalline cellulose, optical properties
National Category
Chemical Sciences
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-105198 (URN)10.1002/cphc.201400062 (DOI)000335515900025 ()
Funder
Knut and Alice Wallenberg Foundation
Note

AuthorCount:7;

Available from: 2014-07-04 Created: 2014-06-24 Last updated: 2015-04-21Bibliographically approved
4. Bogolanfini dyeing – a traditional nanotechnology from West Africa
Open this publication in new window or tab >>Bogolanfini dyeing – a traditional nanotechnology from West Africa
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-116516 (URN)
Available from: 2015-04-21 Created: 2015-04-21 Last updated: 2016-01-29Bibliographically approved
5. Hard and Transparent Films Formed by Nanocellulose-TiO2 Nanoparticle Hybrids
Open this publication in new window or tab >>Hard and Transparent Films Formed by Nanocellulose-TiO2 Nanoparticle Hybrids
Show others...
2012 (English)In: PLoS ONE, ISSN 1932-6203, Vol. 7, no 10, e45828Article in journal (Refereed) Published
Abstract [en]

The formation of hybrids of nanofibrillated cellulose and titania nanoparticles in aqueous media has been studied. Their transparency and mechanical behavior have been assessed by spectrophotometry and nanoindentation. The results show that limiting the titania nanoparticle concentration below 16 vol% yields homogeneous hybrids with a very high Young's modulus and hardness, of up to 44 GPa and 3.4 GPa, respectively, and an optical transmittance above 80%. Electron microscopy shows that higher nanoparticle contents result in agglomeration and an inhomogeneous hybrid nanostructure with a concomitant reduction of hardness and optical transmittance. Infrared spectroscopy suggests that the nanostructure of the hybrids is controlled by electrostatic adsorption of the titania nanoparticles on the negatively charged nanocellulose surfaces.

National Category
Chemical Sciences
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-82432 (URN)10.1371/journal.pone.0045828 (DOI)000309388500016 ()
Note

AuthorCount:10;

Available from: 2012-11-14 Created: 2012-11-14 Last updated: 2015-09-10Bibliographically approved

Open Access in DiVA

fulltext(87647 kB)4202 downloads
File information
File name FULLTEXT01.pdfFile size 87647 kBChecksum SHA-512
80ca07b8ac9dc3d9a99f8af8bfd797ea537436d2327352919d1253e3e77356ad6ca96af6857ed4f4b1c41592a759f6860fda5da3c6b03a56a38ab4abaab03298
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Schütz, Christina
By organisation
Department of Materials and Environmental Chemistry (MMK)
Materials Chemistry

Search outside of DiVA

GoogleGoogle Scholar
Total: 4202 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 1314 hits
ReferencesLink to record
Permanent link

Direct link