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Dernière mise à jour : Mai 2018

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Cellulose nanowhiskers strengthen agarose gel properties

cellulose nanowhiskers in an agarose hydrogel
Hydrogels are materials made from a polymeric network and an aqueous solvent. They have various properties that can be modified by the presence of nanoparticles to be used for new applications.

Nanowhiskers, obtained by hydrolysis with sulfuric acid, are nanocrystalline cellulose particles. They carry sulfate groups that make it possible to obtain stable aqueous suspensions through electrostatic repulsions. Agarose is a polysaccharide extracted from algae that forms gels by aggregation of helixes and that has considerable viscoelastic properties. In this study, we attempted to modulate the properties of composite gels by controlling the electrostatic charge of nanoparticles and by varying their concentration.

The addition of nanowhiskers to agarose at concentrations lower than their percolation threshold (0.25% in volume) strongly reinforces (x10) the mechanical properties of the gel. Stress transfer between nanowhiskers and the matrix can affect the connectivity of the agarose network. Varying the charge density at the nanowhisker surface alters the interactions: a weakly charged nanowhisker surface leads to aggregation and a less efficient strengthening effect. At a higher charge density, nanowhiskers are more effectively dispersed and strengthen the agarose network. Nevertheless, besides a maximum density of SO3- groups, topology modifications and/or network connectivity changes could lead to a less efficient strengthening.These results suggest that matrix properties can also play a role. Replacing agarose with carrageenans, also extracted from algae and sulfated, could provide an interesting option.

Partnership :

This work was conducted as part of the thesis of Kevin Jacques Le Goff led by Thierry Aubry (University of Western Brittany, 2014), hosted at the Laboratory of Materials Engineering of Brittany (Brest) and the team of ISD UR BIA Nantes. 

References :

K.J. Le Goff, D. Jouanneau, C. Garnier, T. Aubry (2014) Gelling of cellulose nanowhiskers in aqueous suspension

Journal of Applied Polymer Science,131, 40676. doi: 10.1002/app.40676

K.J. Le Goff, C. Gaillard, W. Helbert, C. Garnier, T. Aubry (2015) Rheological study of reinforcement of agarose hydrogels by cellulose nanowhiskers

Carbohydrate Polymers,116, 117-123.

K.J. Le Goff, C. Gaillard, C. Garnier, T. Aubry (2016) Electrostatically driven modulation of the reinforcement of agarose hydrogels by cellulose nanowhiskers

Journal of Applied Polymer Science, 43063.doi : 10.1002/app.43063

K.J. Le Goff Etude des propriétés rhéologiques et structurales d’hydrogels d’agarose chargés de nanowhiskers de cellulose. Thèse de l’école doctorale SICMA. Université de Bretagne Occidentale. 148 p.