Reversible heat induced sol-gel transition of anionic cellulose

Cellulose is an abundant polymer in agricultural wastes, thus, representing an excellent candidate for eco-sustainable components. It is biocompatible, has good mechanical properties and has the ability to stabilize oil-in-water emulsions via Pickering stabilization. As such, cellulosic materials can provide functional properties in multiple commercial products (e.g.cream, lotion, food).
Anionic cellulose (AC) fibrils have a negative charge (ζ-potential of -60 ± 2 mV) which allows a prompt dispersibility and a high stability of dispersed fibrils in polar media. Cation-induced gelation is observed for AC fibrils due to charge screening. It results in shear thinning gels with good network recoverability upon breakage (weak thixotropy) and a long term stability.
We present the possibility to form heat-induced hydrogels using AC fibrils in absence of salt. The rheological characterization of the gels shows a strong gel structure irreversibility upon breakage (strong thixotropy) with a permanent gel-liquid transition upon vigorous shaking. UV-vis spectroscopy and conductivity
analysis suggested weak interfibrillar aggregation while differential scanning
calorimetry (DSC) confirmed the absence of covalent crosslinks between
AC fibrils upon heating. Further characterization of fibril aggregation
was conducted via small angle X-ray scattering (SAXS). In addition,
hydrophobic interactions of the AC fibrils before and after heating were
probed via fluorescent probe PRODAN.