Temperature-dependent interactions between hydrophobically modified ethyl(hydroxyethyl)cellulose and methyl nanocellulose

The temperature-dependent association between methyl nanocellulose and hydrophobically modified ethyl(hydroxyethyl)cellulose (EHEC) was determined. Methyl nanocellulose was mixed under different concentrations with EHEC in aqueous media. The hydrophobic association, cloud point and temperature-dependent flocculation were studied using turbidity, rheometry and laser diffraction analysis. The phase separation of EHEC samples containing different amounts of methyl nanocellulose in 1.0 wt% solution was measured between 20 and 70 °C, showing that the cloud point of the solutions increased with increasing nanocellulose content. An increase in the low shear viscosity and gelation behavior of the mixture with the highest methyl nanocellulose content in conjunction with changes in cloud point indicated that the hydrophobic nanocellulose strengthened the hydrophobic association and the gel network. A bimodal particle size distribution was observed for both the pure EHEC and hydrophobically modified nanocellulose reference solutions, whereas the mixture had a trimodal particle size distribution when being diluted. The colloidal stability and re-structuring mechanism of the dilute methyl nanocellulose suspension after shear and the role of birefringence are discussed.