Triphase Equilibria in Cellulose Nanocrystal Suspensions Containing Neutral and Charged Macromolecules

Abstract

The effect of added nonadsorbing macromolecules on the phase behavior of suspensions of electrostatically stabilized cellulose nanocrystals is examined. Triphasic isotropic−isotropic−nematic equilibria develop in cellulose nanocrystal suspensions to which a mixture of dextran and blue dextran is added. Phase diagrams for different combinations of uncharged dextran and anionically charged blue dextran are presented. The range of dextran concentrations at which the triphase equilibrium is produced is strongly influenced by the molecular weight of the blue dextran. Reentrant phenomena as well as regions of biphase coexistence are present in the phase diagrams. A threshold difference in charge density between two blue dextrans of varying degree of dye substitution is necessary for triphase equilibrium to occur at a given number density of each polymer species. Different repulsive electrostatic and attractive entropic forces may dominate at different concentrations of the dextrans, contributing to the rich phase behavior of these suspensions.

Patterning of Nanocrystalline Cellulose Gel Phase by Electrodissolution of a Metallic Electrode

“…It is already well known that solutions of CNCs in water can form a gel phase in the presence of ions [12]–[14]. In this study we demonstrated that the electrodissolution of a metallic electrode controlled the growth of such a gel phase.…”

“…At high CNCs concentration around 10wt% the liquid crystalline phase dominates and the suspension turns to a gel. Increasing the ionic strength of a CNCs suspension can also result in phase separation into isotropic and gel phase [12]–[14]. In this context, aqueous suspensions of carboxylated CNCs (cCNCs) displayed birefringence patterns but did not flocculate or sediment owing to the polyanionic character imparted by the negative charges on the cCNCs surface [15].…”

Gelation of crystalline nanocellulose in the presence of hydroxyethyl cellulose

“…These results are complementary to the findings of Lekkerkerker and coworkers who mainly studied the effect of non‐adsorbed polymer chains on the phase change of different colloidal particles such as platelets or rods . This effect was also studied by Beck‐Candenado et al using CNC suspensions . They could obtain a transition from two phases (isotropic and nematic) to three phases (two isotropic and one nematic) when adding more Blue Dextran in a 8.7 g/g CNC suspension.…”

Liquid Crystals of Cellulosics: Fascinating Ordered Structures for the Design of Functional Material Systems

“…In this phase separation, blue dextran was partitioned preferentially into the upper isotropic phase; however, the lower dextran-poor chiral nematic phase exhibited a rather distorted fingerprint texture with numerous disclinations. Further investigation of these lines demonstrated that the "isotropic-isotropic-chiral nematic" phase equilibrium developed when an undyed neutral dextran was added along with the anionically charged blue dextran to a biphasic CNC suspension (e.g., 8.7 wt%) [95]. The concentrations of the two dextrans needed to produce the three-phase equilibrium were strongly influenced by their molecular weights and overall charge density.…”