Interactions of nanocrystalline cellulose with an oppositely charged surfactant in aqueous medium

The interaction between negatively charged nanocrystalline cellulose (NCC) and a cationic surfactant, tetradecyl trimethyl ammonium bromide (TTAB) was examined by isothermal titration calorimetry (ITC), conductometric and potentiometric titrations and surface tensiometry. The interaction is controlled by electrostatic and hydrophobic interactions. ITC and surface tension measurements confirmed the formation of electrostatically driven NCC–TTAB complexes in the bulk and at the interface, which was followed by hydrophobically driven polymer-induced micellization of TTAB on NCC rods. The critical micelle concentration (CMC) of TTAB was shifted from 1.1 to 1.3 g/L in the presence of 0.655 g/L NCC. The settling and phase separation characteristics were quantified by determining the height of NCC flocs as a function of time, which describe the stability of NCC in the presence of TTAB. Zeta potential results revealed a charge reversal from negative to positive values with increasing TTAB concentration, confirming the formation of NCC–TTAB complexes in aqueous solutions. Based on the results, a physical mechanism on the interaction of NCC and TTAB is proposed.

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► Positively charged surfactant binds to negatively charged nanocrystalline cellulose.
► Electrostatic attraction, reorganization, polymer induced and bulk micellization occur.
► NCC solutions become unstable and phase separate in the presence of TTAB.