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The build-up of polyelectrolyte multilayers of microfibrillated cellulose and cationic polyelectrolytes
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0001-8622-0386
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
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2008 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 3, 784-795 p.Article in journal (Refereed) Published
Abstract [en]

A new type of nanocellulosic material has been prepared by high-pressure homogenization of carboxymethylated cellulose fibers followed by ultrasonication and centrifugation. This material had a cylindrical cross-section as shown by transmission electron microscopy with a diameter of 5-15 nm and a length of up to 1 mu m. Calculations, using the Poisson-Boltzmann equation, showed that the surface potential was between 200 and 250 mV, depending on the pH, the salt concentration, and the size of the fibrils. They also showed that the carboxyl groups on the surface of the nanofibrils are not fully dissociated until the pH has reached pH = similar to 10 in deionized water. Calculations of the interaction between the fibrils using the Derjaguin-Landau-Verwey-Overbeek theory and assuming a cylindrical geometry indicated that there is a large electrostatic repulsion between these fibrils, provided the carboxyl groups are dissociated. If the pH is too low and/or the salt concentration is too high, there will be a large attraction between the fibrils, leading to a rapid aggregation of the fibrils. It is also possible to form polyelectrolyte multilayers (PEMs) by combining different types of polyelectrolytes and microfibrillated cellulose (MFC). In this study, silicon oxide surfaces were first treated with cationic polyelectrolytes before the surfaces were exposed to MFC. The build-up of the layers was monitored with ellipsometry, and they show that it is possible to form very well-defined layers by combinations of MFC and different types of polyelectrolytes and different ionic strengths of the solutions during the adsorption of the polyelectrolyte. A polyelectrolyte with a three-dimensional structure leads to the build-up of thick layers of MFC, whereas the use of a highly charged linear polyelectrolyte leads to the formation of thinner layers of MFC. An increase in the salt concentration during the adsorption of the polyelectrolyte results in the formation of thicker layers of MFC, indicating that the structure of the adsorbed polyelectrolyte has a large influence on the formation of the MFC layer. The films of polyelectrolytes and MFC were so smooth and well-defined that they showed clearly different interference colors, depending on the film thickness. A comparison between the thickness of the films, as measured with ellipsometry, and the thickness estimated from their colors showed good agreement, assuming that the films consisted mainly of solid cellulose with a refractive index of 1.53. Carboxymethylated MFC is thus a new type of nanomaterial that can be combined with oppositely charged polyelectrolytes to form well-defined layers that may be used to form, for example, new types of sensor materials.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2008. Vol. 24, no 3, 784-795 p.
Keyword [en]
molecular-dynamics simulations, aqueous environment, charged surfaces, ionic-strength, layer, films, adsorption, deposition, poly(ethylenimine), nanoscale
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:kth:diva-17283DOI: 10.1021/la702481vISI: 000252777700033Scopus ID: 2-s2.0-39449090645OAI: oai:DiVA.org:kth-17283DiVA: diva2:335326
Note

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Microfibrillated cellulose: Energy-efficient preparation techniques and key properties
Open this publication in new window or tab >>Microfibrillated cellulose: Energy-efficient preparation techniques and key properties
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This work describes three alternative processes for producing microfibrillated cellulose (MFC) in which pulp fibres are first pre-treated and then homogenized using a high-pressure homogenizer. In one process, fibre cell wall delamination was facilitated with a combined enzymatic and mechanical pre-treatment. In the two other processes, cell wall delamination was facilitated by pre-treatments that introduced anionically charged groups into the fibre wall, by means of either a carboxymethylation reaction or irreversibly attaching carboxymethyl cellulose (CMC) onto the fibres. All three processes are industrially feasible and enable production with low energy consumption. Using these methods, MFC can be produced with an energy consumption of 500–2300 kWh/tonne, which corresponds to a 91–98% reduction in energy consumption from that presented in earlier studies. These materials have been characterized in various ways and it has been demonstrated that the produced MFCs are approximately 5–30 nm wide and up to several microns long.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 49 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 38
Keyword
Microfibrillated cellulose, microfibrillar cellulose, nanofibrillated cellulose nanofibrillar cellulose, nanocellulose, MFC, NFC, production techniques, energy efficient, gel properties, films, enzymes, carboxymethylation, carboxymethyl cellulose, CMC, mechanical properties, oxygen barrier, homogenization
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-102949 (URN)978-91-7501-464-7 (ISBN)
Presentation
2012-10-17, STFI-salen, Innventia AB, Drottning Kristinas väg 61, KTH, Stockholm, 14:02 (Swedish)
Opponent
Supervisors
Note

QC 20120928

Available from: 2012-09-28 Created: 2012-09-28 Last updated: 2012-10-03Bibliographically approved
2. Microfibrillated cellulose: Energy-efficient preparation techniques and applications in paper
Open this publication in new window or tab >>Microfibrillated cellulose: Energy-efficient preparation techniques and applications in paper
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This work describes three alternative processes for producing microfibrillated cellulose (MFC; also referred to as cellulose nanofibrils, CNF) in which bleached pulp fibres are first pretreated and then homogenized using a high-pressure homogenizer. In one process, fibre cell wall delamination was facilitated by a combined enzymatic and mechanical pretreatment. In the two other processes, cell wall delamination was facilitated by pretreatments that introduced anionically charged groups into the fibre wall, by means of either a carboxymethylation reaction or irreversibly attaching carboxymethylcellulose (CMC) to the fibres. All three processes are industrially feasible and enable energy-efficient production of MFC. Using these processes, MFC can be produced with an energy consumption of 500–2300 kWh/tonne. These materials have been characterized in various ways and it has been demonstrated that the produced MFCs are approximately 5–30 nm wide and up to several microns long.

The MFCs were also evaluated in a number of applications in paper. The carboxymethylated MFC was used to prepare strong free-standing barrier films and to coat wood-containing papers to improve the surface strength and reduce the linting propensity of the papers. MFC, produced with an enzymatic pretreatment, was also produced at pilot scale and was studied in a pilot-scale paper making trial as a strength agent added at the wet-end for highly filled papers.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. 63 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:5
Keyword
Microfibrillated cellulose, microfibrillar cellulose, nanofibrillated cellulose, nanofibrillar cellulose, cellulose nanofibrils, nanocellulose, MFC, NFC, CNF, production techniques, energy efficient, gel properties, films, enzymes, carboxymethylation, carboxymethyl cellulose, CMC, mechanical properties, oxygen barrier, homogenization, linting, papermaking
National Category
Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-159222 (URN)978-91-7595-426-4 (ISBN)
Public defence
2015-02-27, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20150126

Available from: 2015-01-26 Created: 2015-01-26 Last updated: 2015-01-28Bibliographically approved

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