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Issue 12, 2008
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Long and entangled native cellulose I nanofibers allow flexible aerogels and hierarchically porous templates for functionalities

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Abstract

Recently it was shown that enzymatic and mechanical processing of macroscopic cellulose fibers lead to disintegration of long and entangled native cellulose I nanofibers in order to form mechanically strong aqueous gels (Pääkkö et al., Biomacromolecules, 2007, 8, 1934). Here we demonstrate that (1) such aqueous nanofibrillar gels are unexpectedly robust to allow formation of highly porous aerogels by direct water removal by freeze-drying, (2) they are flexible, unlike most aerogels that suffer from brittleness, and (3) they allow flexible hierarchically porous templates for functionalities, e.g. for electrical conductivity. No crosslinking, solvent exchange nor supercritical drying are required to suppress the collapse during the aerogel preparation, unlike in typical aerogel preparations. The aerogels show a high porosity of ∼98% and a very low density of ca. 0.02 g cm−3. The flexibility of the aerogels manifests as a particularly high compressive strain of ca. 70%. In addition, the structure of the aerogels can be tuned from nanofibrillar to sheet-like skeletons with hierarchical micro- and nanoscale morphology and porosity by modifying the freeze-drying conditions. The porous flexible aerogel scaffold opens new possibilities for templating organic and inorganic matter for various functionalities. This is demonstrated here by dipping the aerogels in an electrically conducting polyaniline–surfactant solution which after rinsing off the unbound conducting polymer and drying leads to electrically conducting flexible aerogels with relatively high conductivity of around 1 × 10−2 S cm−1. More generally, we foresee a wide variety of functional applications for highly porous flexible biomatter aerogels, such as for selective delivery/separation, tissue-engineering, nanocomposites upon impregnation by polymers, and other medical and pharmaceutical applications.

Graphical abstract: Long and entangled native cellulose I nanofibers allow flexible aerogels and hierarchically porous templates for functionalities

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Publication details

The article was received on 18 Jun 2008, accepted on 31 Jul 2008 and first published on 23 Sep 2008


Article type: Paper
DOI: 10.1039/B810371B
Citation: Soft Matter, 2008,4, 2492-2499
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    Long and entangled native cellulose I nanofibers allow flexible aerogels and hierarchically porous templates for functionalities

    M. Pääkkö, J. Vapaavuori, R. Silvennoinen, H. Kosonen, M. Ankerfors, T. Lindström, L. A. Berglund and O. Ikkala, Soft Matter, 2008, 4, 2492
    DOI: 10.1039/B810371B

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