Effect of Ionic Strength and Surface Charge Density on the Kinetics of Cellulose Nanocrystal Thin Film Swelling

Publication year: 2017
Authors: Reid M.S. 1, Kedzior S.A. 1, Villalobos M. 2, Cranston E.D. 1
1 - Department of Chemical Engineering, McMaster University, Hamilton, Ontario, Canada L8S 4L8
2 - Cabot Corporation, Billerica, Massachusetts 01821, United States
Published in: Langmuir, 2017, Vol. 33 (30), p. 7403–7411
doi: 10.1021/acs.langmuir.7b01740

This work explores cellulose nanocrystal (CNC) thin films (in situ via surface plasmon resonance, and the kinetics of liquid uptake were quantified. The contribution of electrostatic double-layer forces to film swelling was elucidated by using CNCs with different surface charges (anionic sulfate half ester groups, high and low surface charge density, and cationic trimethylammonium groups). Total water uptake in the thin films was found to be independent of ionic strength and surface chemistry, suggesting that in the aggregated state van der Waals forces dominate over double-layer forces to hold the films together. However, the rate of swelling varied significantly. The water uptake followed Fickian behavior, and the measured diffusion constants decreased with the ionic strength gradient between the film and the solution. This work highlights that nanoparticle interactions and dispersion are highly dependent on the state of particle aggregation and that the rate of water uptake in aggregates and thin films can be tailored based on surface chemistry and solution ionic strength.

MP-SPR keywords: affect of ionic strengths, cationic CNCs, cellulose nanocrystal (CNC) thin films, film hydration, film swelling in aqueous solutions, partially desulfated CNC, rate of water uptake, SiO2 (silicon dioxide) sensor slide, spin coating