Dielectric contrast driven phase transitions in cellulose microfibril dispersions

A. Kuijk, C. Klik, G. van den Brink, S. Mohan, K.P. Velikov
Unilever R&D Vlaardingen B.V.,
Netherlands

Keywords: cellulose microfibrils

Summary:

Fibre-like particles depending on their interaction potential can form both ordered and disordered networks with an interesting rheological response. Cellulose microfibrils dispersion are naturally strongly attractive due to strong interfibrillar hydrogen bonding and Van der Waals interactions. These attractive interactions, in combination with the high aspect ratio of the particles, cause the formation of extended networks when the microfibrils are dispersed in polar solvents. In this paper, we present a study on the effect of dielectric contrast aqueous dispersions of cellulose microfibrils. Decreasing the dielectric index difference between the solvent and the microfibrils was found to make more homogeneous dispersions by decreasing the intefibrillar forces. This leads to prevention of the shear-induced aggregation and even to a decrease of the concentration of macroscopic aggregates. Glycerol decreases the attractive interactions between the cellulose microfibrils to such an extent that they are able to align and form liquid crystal gel-like phases.