Change search
ReferencesLink to record
Permanent link

Direct link
Nanoscale Cellulose Films with Different Crystallinities and Mesostructures: Their Surface Properties and Interaction with Water
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0001-8622-0386
2009 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 13, 7675-7685 p.Article in journal (Refereed) Published
Abstract [en]

A systematic study of the degree of molecular ordering and swelling of different nanocellulose model films has been conducted. Crystalline cellulose II surfaces were prepared by spin-coating of the precursor cellulose solutions onto oxidized silicon wafers before regeneration in water or by using the Langmuir-Schaefer (LS) technique. Amorphous cellulose films were also prepared by spin-coating of a precursor cellulose solution onto oxidized silicon wafers. Crystalline cellulose I surfaces were prepared by spin-coating wafers with aqueous suspensions of sulfate-stabilized cellulose nanocrystals and low-charged microfibrillated cellulose (LC-MFC). In addition, a dispersion of high-charged MFC was used for the buildup of polyelectrolyte multilayers with polyetheyleneimine on silica with the aid of the layer-by-layer (LbL) technique. These preparation methods produced smooth thin films on the nanometer scale Suitable for X-ray diffraction and swelling measurements. The surface morphology and thickness of the cellulose films were characterized in detail by atomic force microscopy (AFM) and ellipsometry measurements, respectively. To determine the surface energy of the cellulose surfaces, that Is, their ability to engage in different interactions with different materials, they were characterized through contact angle measurements against water, glycerol, and methylene iodide. Small incidence angle X-ray diffraction revealed that the nanocrystal and MFC films exhibited a cellulose I crystal structure and that the films prepared from N-methylmorpholine-N-oxide (NMMO), LiCl/DMAc solutions, using the LS technique, possessed a cellulose II structure. The degree of crystalline ordering was highest in the nanocrystal films (similar to 87%), whereas the MFC, NMMO, and LS films exhibited a degree of crystallinity of about 60%. The N,N-dimethylacetamide(DMAc)/LiCl film possessed very low crystalline ordering (<15%). It was also established that the films ha different mesostructures, that is, structures around 10 nm, depending on the preparation conditions. The LS and LiCl/DMAc films are smooth without any clear mesostructure, whereas the other films have a clear mesostructure in which the dimensions are dependent oil the size of the nanocrystals, fibrillar cellulose, and electrostatic charge of the MFC. The swelling of the films was studied using a quartz crystal microbalance with dissipation. To understand the swelling properties of the films, it was necessary to consider both the difference in crystalline ordering and the difference in mesostructure of the films.

Place, publisher, year, edition, pages
2009. Vol. 25, no 13, 7675-7685 p.
Keyword [en]
National Category
Paper, Pulp and Fiber Technology
URN: urn:nbn:se:kth:diva-11498DOI: 10.1021/la900323nISI: 000267533800074ScopusID: 2-s2.0-67650089781OAI: diva2:277306
QC 20100623Available from: 2009-11-17 Created: 2009-11-17 Last updated: 2010-12-03Bibliographically approved
In thesis
1. Novel oil resistant cellulosic materials
Open this publication in new window or tab >>Novel oil resistant cellulosic materials
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this study has been to prepare and characterise oil resistant cellulosic materials, ranging from model surfaces to papers and aerogels. The cellulosic materials were made oil resistant by chemical and topographic modifications, based on surface energy, surface roughness and barrier approaches. Detailed wetting studies of the prepared cellulosic materials were made using contact angle measurements and standardised penetration tests with different alkanes and oil mixtures.

A significant part of the activities were devoted to the development of model cellulosic surfaces with different degrees of crystalline ordering for the wetting studies. Crystalline cellulose I, II and amorphous cellulose surfaces were prepared by spin-coating of cellulose nanocrystal or microfibrillated cellulose (MFC) dispersions, with Langmuir-Schaefer (LS) films or by a layer-by-layer (LbL) deposition technique. The formation of multilayers consisting of polyethyleneimine (PEI)/anionic MFC or cationic MFC/anionic MFC was further studied and optimized in terms of total layer thickness and adsorbed amount by combining Dual Polarization Interferometry (DPI) or Stagnation Point Adsorption Reflectrometry (SPAR) with a Quartz Crystal Microbalance with Dissipation (QCM-D).

The smooth cellulosic surfaces prepared had different molecular and mesostructure properties and different surface energies as shown by X-ray diffraction, Atomic Force Microscopy (AFM) imaging, ellipsometry measurements and contact angle measurements.

The cellulose model surfaces were found to be ideal for detailed wetting studies, and after the surface has been coated or covalently modified with various amounts of fluorosurfactants, the fluorinated cellulose films were used to follow the spreading mechanisms of different oil mixtures. The viscosity and surface tension of the oil mixtures, as well as the dispersive surface energy of the cellulose surfaces, were found to be essential parameters governing the spreading kinetics. A strong correlation was found between the surface concentration of fluorine, the dispersive surface energy and the measured contact angle of the oil mixtures.

Silicon surfaces possessing structural porous characteristics were fabricated by a plasma etching process. The structured silicon surfaces were coated with sulfate-stabilized cellulose I nanocrystals using the LbL technique. These artificial intrinsically oleophilic cellulose surfaces were made highly oleophobic when coated with a thin layer of fluorinated silanes. By comparison with flat cellulose surfaces, which are oleophilic, it is demonstrated that the surface energy and the surface texture are essential factors preventing oil from spreading on the surface and, thus, inducing the observed macroscopic oleophobic properties.

The use of the MFC for surface coating on base papers demonstrated very promising characteristics as packaging materials. Environmental-Scanning Electron Microscopy (E-SEM) micrographs indicated that the MFC layer reduced the sheet porosity, i.e. the dense structure formed by the nanofibers resulted in superior oil barrier properties. Attempts were made to link the procedure for preparation of the MFC dispersions to the resulting microstructure of the coatings, and film porosity and the film moisture content to the resulting permeability properties.

Finally, MFC aerogels were successfully prepared by freeze-drying. The surface texture of the porous aerogels was carefully controlled by adjusting the concentration of the MFC dispersion used for the freeze-drying. The different scales of roughness of the MFC aerogels were utilised, together with the very low surface energy created by fluorination of the aerogel, to induce highly oleophobic properties.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. ix, 55 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2009:57
oleophobic, MFC, cellulose, oil resistant, contact angle, XPS, SEM
National Category
Paper, Pulp and Fiber Technology
urn:nbn:se:kth:diva-11494 (URN)978-91-7415-476-4 (ISBN)
Public defence
2009-12-04, F3, Lindstedtvägen 26, KTH, Stockholm, 10:00 (English)
QC 20100623Available from: 2009-11-17 Created: 2009-11-17 Last updated: 2012-03-13Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Aulin, ChristianJosefsson, PeterWågberg, Lars
By organisation
Fibre TechnologyFibre and Polymer Technology
In the same journal
Paper, Pulp and Fiber Technology

Search outside of DiVA

GoogleGoogle Scholar
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

Altmetric score

Total: 219 hits
ReferencesLink to record
Permanent link

Direct link