AKD-Modification of bacterial cellulose aerogels in supercritical CO2
Different approaches towards hydrophobic modification of bacterial cellulose aerogels with the alkyl ketene dimer (AKD) reagent are presented. If AKD modification was performed in supercritical CO2, an unexpectedly high degree of loading was observed. About 15 % of the AKD was bound covalently to the cellulose matrix, while the other part consisted of re-extractable AKD-carbonate oligomers, which are novel chemical structures described for the first time. These oligomers contain up to six AKD and CO2 moieties linked by enolcarbonate structures. The humidity uptake from environments with different relative humidity by samples equipped with up to 30 % AKD is strongly reduced, as expected due to the hydrophobization effect. Samples above 30 % AKD, and especially at very high loading between 100 and 250 %, showed the peculiar effect of increased humidity uptake which even exceeded the value of unmodified bacterial cellulose aerogels.
KeywordsCellulose aerogel Bacterial cellulose Surface modification Hydrophobization Supercritical carbon dioxide Alkyl ketene dimer (AKD) AKD-CO2-oligomers Humidity uptake
We would like to thank the Austrian Christian-Doppler-Society, Vienna and the FZMB GmbH, Bad Langensalza, Germany, for financial support within the “Christian Doppler Laboratory for Advanced Cellulose Chemistry and Analytics” and Walter Klug for recording the SEM pictures.
- Ek M, Gellerstedt G, Henriksson G (eds) (2009) Pulp and paper chemistry and technology, 1st edn. Walter de Gruyter, Berlin, p 400Google Scholar
- Liebner F, Potthast A, Rosenau T, Haimer E, Wendland M (2007) Ultralight-weight cellulose aerogels from NBnMO-stabilized Lyocell Dopes. Res Lett Mat Sci 4–8, article ID 73724Google Scholar
- Liebner F, Haimer E, Wendland M, Neouze M-A, Schlufter K, Miethe P, Heinze T, Potthast A, Rosenau T (2010) Aerogels from unaltered bacterial cellulose: application of scCO2 drying for the preparation of shaped, ultra-lightweight cellulosic aerogels. Macromol Biosci 10(4):349–352CrossRefGoogle Scholar
- Lindfors J, Salmi J, Laine J, Stenius P (2007) AKD and ASA model surfaces: preparation and characterization. Bioresources 2(4):652–670Google Scholar
- Odermatt J, Meyer R, Meier D, Ettl R (2003) Identification and quantification of alkyl ketene dimers by pyrolysis-gas chromatography/mass spectrometry and pyrolysis-gas chromatography/flame ionization detection. J Pulp Paper Sci 29(1):1–6Google Scholar
- Roberts JC (1996) The chemistry of paper. RSC paperbacks. The Royal Society of Chemistry, CambridgeGoogle Scholar
- Rosenau T, Russler A (2012) Novel CO2-containing oligomers by processing of alkylketene dimer (AKD) in supercritical carbon dioxide. Tewtrahedron Lett (in press)Google Scholar
- Russler A, Miethe P, Liebner F, Potthast A, Rosenau T (2011) In: Proceedings of the 16th international symposium on wood, fiber and pulping chemistry (ISWFPC), June 08–10, Tianjin, China, VII/1. Modification of bacterial cellulose aerogelsGoogle Scholar
- Seo WS, Cho NS, Ohga S (2008a) Possibility of hydrogen bonding between AKD and cellulose molecules during AKD sizing. J Fac Agricult (Kyushu University) 53(2):405–410Google Scholar
- Seo WS, Cho NS, Ohga S (2008b) Surface chemical states of sizing agents on AKD/cellulose blends by X–ray photoelectron spectroscopy. J Fac Agricult (Kyushu University) 53(2):411–416Google Scholar