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Hollow cellulose capsules from CO2 saturated cellulose solutions - Their preparation and characterization
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.ORCID iD: 0000-0002-4511-1076
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.ORCID iD: 0000-0001-9176-7116
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2013 (English)In: RSC Advances, ISSN 2046-2069, Vol. 3, no 7, 2462-2469 p.Article in journal (Refereed) Published
Abstract [en]

A new material consisting of mm-sized hollow cellulose spheres, for biomedical applications or for the preparation of low weight porous materials has been prepared by a unique solution precipitation (SP) method. The technique is based on three separate steps. In the first step, high molecular mass, non-modified cellulose is dissolved in a suitable solvent. This cellulose solution is then saturated with a suitable gas (CO2 or N2 in the present work) and finally this gas-saturated solution is drop-wise added to a water reservoir. In this step, the cellulose is precipitated and a gas bubble is nucleated in the center of the cellulose sphere. When stored in water, the hollow center is filled with water, indicating that the capsule wall is porous in nature. This was also supported by BET-area measurements as well as by high resolution SEM-images of broken capsule walls. The internal void volume of a capsule was about 5 μl and the wall volume was about 8 μl. It was also established that the properties of the cellulose capsules, i.e. wall and void volume, the specific surface area, the average pore size of the capsule wall, the wall density, and the compressive load capacity could be tuned by the choice of cellulose concentration in the solution before precipitation. The capsule wall volume and void volume were also affected by the choice of gas, the gas pressure and the gas dissolution time during the gas saturation step. The response of the cellulose wall of the prepared capsules to changes in pH and ion concentration in the surrounding solution was also investigated. The swelling-shrinking behavior was further investigated by introducing more charges to the capsule wall, via carboxymethylation of the cellulose. This was achieved by using carboxymethylated cellulose which increased the swelling-shrinking effect. The results show a typical polyelectrolyte gel behavior of the capsule wall and the wet modulus of the cellulose wall was determined to be between 0.09-0.2 MPa depending on the charge of the cellulose in the capsule wall. Furthermore, the freeze dried cellulose spheres had a modulus of 1.9-7.4 MPa, depending on the cellulose concentration during the preparation of the spheres. These cellulose capsules are suitable both for the preparation of porous materials, where these larger spheres are joined together in 3D-shaped materials, and for controlled release where the interior of the capsules is filled with active substances and these substances are released by controlling the pores in the capsule walls.

Place, publisher, year, edition, pages
2013. Vol. 3, no 7, 2462-2469 p.
Keyword [en]
Active substance, Biomedical applications, Carboxymethylation, Cellulose solutions, Compressive loads, Controlled release, Gas bubble, Gas dissolution, Gas pressures, Gas saturations, Gel behavior, High molecular mass, High resolution, Internal voids, Ion concentrations, Solution precipitation, Void volume, Wall density
National Category
Other Chemistry Topics
URN: urn:nbn:se:kth:diva-118295DOI: 10.1039/c2ra22020bISI: 000313812400052ScopusID: 2-s2.0-84872707086OAI: diva2:605815

QC 20130215

Available from: 2013-02-15 Created: 2013-02-14 Last updated: 2014-08-29Bibliographically approved
In thesis
1. Macro-, Micro- and Nanospheres from Cellulose: Their Preparation, Characterization and Utilization
Open this publication in new window or tab >>Macro-, Micro- and Nanospheres from Cellulose: Their Preparation, Characterization and Utilization
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The structure of a polymeric material has a great influence in many fundamental scientific areas as well as in more applied science, since it affects the diffusion, permeability, mechanical strength, elasticity, and colloidal properties of the materials. The results in this thesis demonstrate that it is possible to fabricate solid and hollow cellulose spheres with a cellulose shell and encapsulated gas, liquid or solid particles and with a sphere size ranging from a few hundreds of nanometres to several millimetres, all with a tailored design and purpose.

The sizes of the different spheres have been controlled by three different preparation methods: large cellulose macrospheres by a solution solidification procedure, hollow micrometre-sized cellulose spheres by a liquid flow-focusing technique in microchannels, and nanometre-sized cellulose spheres by a membrane emulsification technique. 

The spheres were then modified in different ways in order to functionalize them into more advanced materials. This thesis demonstrates how to control the cellulose sphere dimensions and the wall-to-void volume ratio, the elasticity and the functionality of the spheres as such, where they were prepared to be pH-responsive, surface specific and X-ray active. These modifications are interesting in several different types of final materials such as packaging materials, drug release devices or advanced in vivo diagnostic applications.

In the more fundamental science approach, surface-smooth solid cellulose spheres were prepared for characterization of the macroscopic work of adhesion when a cellulose surface is separated from another material. Using these ultra-smooth macroscopic cellulose probes, it is possible to measure the compatibility and the surface interactions between cellulose and other materials which provide an important tool for incorporating cellulose into different composite materials. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. 67 p.
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:32
Cellulose, sphere, capsule, functionalization
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
urn:nbn:se:kth:diva-149807 (URN)978-91-7595-231-4 (ISBN)
Public defence
2014-09-26, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20140829

Available from: 2014-08-29 Created: 2014-08-27 Last updated: 2014-08-29Bibliographically approved

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Carrick, ChristopherPettersson, BertLarsson, Per TomasWågberg, Lars
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