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SEM imaging of chiral nematic films cast from cellulose nanocrystal suspensions

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Abstract

The chiral nematic self-assembly of aqueous suspensions of cellulose nanocrystals is partially preserved on evaporation of water, but the ordering of the rod-like nanoparticles may become distorted by changes in volume, ionic strength and surface and convective forces during evaporation, thus affecting the morphology and optical properties of the dried film. Proposed applications for these solids with chiral nematic order require confirmation of their structure. A SEM examination of the fracture surface of a slowly-dried film showed a surprisingly regular fan-like pattern which is shown to be characteristic of cross-sections of the left-handed helicoidal arrangement of nanocrystals, where the helicoidal axis was almost perpendicular to the film surfaces. Superimposed on this pattern was what appeared to be a regular porosity, which is postulated to result from pull-out of the nanocrystals oriented orthogonal to the fracture surface.

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Acknowledgments

We thank Dr. Mari Granström for insightful discussions. The work of J. Majoinen, E. Kontturi and O. Ikkala was supported by the Finnish Funding Agency for Technology and Innovation (TEKES) and Academy of Finland, as part of the Finnish Center of Nanocellulose, a joint project of Aalto University, UPM, and VTT. DGG thanks NSERC Canada and the Centre for Self-assembled Chemical Structures for support

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Authors and Affiliations

  1. Molecular Materials, Department of Applied Physics, Aalto University, P. O. Box 15100, 00076, Aalto, Espoo, Finland

    Johanna Majoinen & Olli Ikkala

  2. Department of Forest Products Technology, Aalto University, P. O. Box, 16300, 00076, Aalto, Espoo, Finland

    Eero Kontturi

  3. Department of Chemistry, McGill University, Pulp and Paper Bldg., 3420 University Street, Montreal, QC, H3A 2A7, Canada

    Derek G. Gray

Authors
  1. Johanna Majoinen
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  2. Eero Kontturi
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  3. Olli Ikkala
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  4. Derek G. Gray
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Correspondence to Derek G. Gray.

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Majoinen, J., Kontturi, E., Ikkala, O. et al. SEM imaging of chiral nematic films cast from cellulose nanocrystal suspensions. Cellulose 19, 1599–1605 (2012). https://doi.org/10.1007/s10570-012-9733-1

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  • DOI: https://doi.org/10.1007/s10570-012-9733-1

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