Cellulose nanocrystals in aqueous suspensions: rheology of lyotropic chiral liquid crystals

A thorough rheological study of the behavior of cellulose nanocrystals (CNC) in water was undertaken, focusing on the main characteristics of rod-like suspensions that allign under flow and can display liquid crystal behavior at rest, in at least a range of concentrations. The effect of adding a dis...

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Bibliographic Details
Published in:Cellulose (London) 2019-03, Vol.26 (4), p.2317-2332
Main Authors: Buffa, Juan M., Casado, Ulises, Mucci, Verónica, Aranguren, Mirta I.
Format: Article
Language:English
Subjects:
Bioorganic Chemistry
Cellulose
Ceramics
Chemistry
Chemistry and Materials Science
Composites
Dispersion
Glass
Liquid crystals
Nanocrystals
Natural Materials
Organic Chemistry
Original Research
Oscillations
Physical Chemistry
Polymer Sciences
Reagents
Rheological properties
Rheology
Shear tests
Sustainable Development
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Summary:A thorough rheological study of the behavior of cellulose nanocrystals (CNC) in water was undertaken, focusing on the main characteristics of rod-like suspensions that allign under flow and can display liquid crystal behavior at rest, in at least a range of concentrations. The effect of adding a dispersing agent (gum arabic, GA) to the suspension was analyzed, and different surface treatments were also performed on the CNC using TEMPO, chloro(dodecyl)dimethylsilane and trimethoxysilyl propylmethacrylate, named as TCNC, DCNC and MCNC respectively. The CNC, TCNC and the suspensions prepared with added GA formed stable suspensions with a concentration range in which isotropic and anisotropic (self-organized) phases coexisted in equilibrium. On the other hand, the aqueous suspensions of the two silanized CNCs only displayed flow-induced ordering, with a similar type of rheological behavior to the other nanocrystal suspensions, although with obvious quantitative differences. These latter ones were not stable suspensions and precipitated after a few hours of rest. The rheological tests included steady shear, dynamic oscillations and start-up of steady shear that were performed for all the nanocrystals suspensions prepared at different concentrations. Differences observed were related to the crystals surface modifications or addition of the dispersing agent. A persistent periodic oscillation of the viscosity was measured in the start-up of steady shear tests and the periods of the oscillations were determined and related to the different types of crystals considered. Graphical abstract
ISSN:0969-0239
1572-882X
DOI:10.1007/s10570-019-02278-3