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Capillary condensation of moisture in fractal pores of native cellulose powders
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
2004 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 393, no 4-6, 389-392 p.Article in journal (Refereed) Published
Abstract [en]

This study was performed to investigate the applicability of the theory of capillary condensation of moisture in fractal nanopores of native cellulose powders of various origins. The characteristic fractal dimensions D were calculated and their physical meaning discussed. The method proved useful for obtaining versatile information about the water–cellulose interactions as well as the bulk structure of cellulose particles.

Place, publisher, year, edition, pages
2004. Vol. 393, no 4-6, 389-392 p.
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-92516DOI: 10.1016/j.cplett.2004.06.043OAI: oai:DiVA.org:uu-92516DiVA: diva2:165628
Available from: 2005-01-20 Created: 2005-01-20 Last updated: 2015-09-10Bibliographically approved
In thesis
1. Engineering of Native Cellulose Structure for Pharmaceutical Applications: Influence of Cellulose Crystallinity Index, Surface Area and Pore Volume on Sorption Phenomena
Open this publication in new window or tab >>Engineering of Native Cellulose Structure for Pharmaceutical Applications: Influence of Cellulose Crystallinity Index, Surface Area and Pore Volume on Sorption Phenomena
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cellulose powders from various sources were manufactured and characterized to investigate the influence of their crystallinity index, surface area, and pore volume on sorption phenomena and the relevant pharmaceutical functionality. The influence of the cellulose crystallinity index on moisture sorption was important at low and intermediate relative humidities. At high relative humidities, properties such as surface area and pore volume took precedence in governing the moisture sorption process.

The theory of physical adsorption of gases onto fractal surfaces was useful for understanding the distribution of water in cellulose and the inner nanoscale structure of cellulose particles. It was found that, as a consequence of swelling, moisture induces a fractal nanopore network in cellulose powders that have a low or intermediate degree of crystallinity. On the other hand, no swelling occurs in highly crystalline cellulose powders and moisture sorption is restricted to the walls of the open pores.

No correlation was found between the cellulose crystallinity index and the incorporation and release of nicotine in cellulose mixtures. By loading nicotine in highly porous matrices of the Cladophora sp. algae cellulose, higher stability against oxidative degradation, higher loading capacity, and more steady release into an air-stream was achieved than when commercially available microcrystalline cellulose was loaded.

It was also shown that, by manipulating the structure of cellulose, the undesired hydrolysis of acetylsalicylic acid in mixtures with cellulose can be avoided. It was suggested that a broad hysteresis loop between the moisture adsorption and desorption curves of isotherms at low relative humidities could be indicative of an improved compatibility between acetylsalicylic acid and cellulose.

In all, this thesis demonstrates how the pharmaceutical functionality of microcrystalline cellulose can be improved via engineering of the structure of native cellulose powders.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 57 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 1
Pharmaceutics, microcrystalline cellulose, Cladophora sp. algae, crystallinity index, surface area and pore volume, fractals, stability, Galenisk farmaci
National Category
Pharmaceutical Sciences
urn:nbn:se:uu:diva-4752 (URN)91-554-6130-1 (ISBN)
Public defence
2005-02-11, B41, Biomedical Center, Husargatan 3, Uppsala, 09:15
Available from: 2005-01-20 Created: 2005-01-20Bibliographically approved

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