Aggregation behavior of aqueous cellulose nanocrystals: the effect of inorganic salts
Journal article, 2016

Natural anisotropic building-blocks such as cellulose nanocrystals (CNCs) have attracted considerable attention due to their biodegradability and nanometer-size. In this work the colloidal behavior of CNCs, obtained from sulfuric acid hydrolysis of microcrystalline cellulose, has been studied in presence of salts of different valences. The influence on the colloidal stability and nature of aggregates has been investigated for monovalent salts (LiCl, NaCl, KCl, CsCl), divalent salts (CaCl2 and MgCl2), and a trivalent salt (AlCl3), both experimentally by means of turbidity and small angle X-ray scattering (SAXS) measurements, as well as by Monte Carlo simulations using a simple coarse-grained model. For the entire salt series, a critical aggregation concentration (CAC) could be determined by turbidity measurements, as a result of the reduction of effective Coulomb repulsions due to the presence of sulfate groups on the CNC surface. The CACs also followed the Schulze-Hardy law, i.e. the critical aggregation concentration decreased with increasing counterion valence. For the monovalent ions, the CACs followed the trend Li+ > Na+ > K+ > Cs+, which could be rationalized in terms of matching affinities between the cation and the sulfate groups present at the surface of CNCs. From the SAXS measurements it was shown that the density of the aggregates increased with increasing salt concentration and ion valence. In addition, these findings were rationalized by means of simulation, which showed a good correlation with experimental data. The combination of the experimental techniques and the simulations offered insight into interaction-aggregation relationship of CNC suspensions, which is of importance for their structural design applications.

Coarse-grained model

Aggregation

SAXS

Schulze-Hardy rule

Cellulose nanocrystal

Hofmeister

Author

Tuan Phan Xuan

Chalmers, Physics, Condensed Matter Physics

A. Thuresson

Lund University

M. Skepo

Lund University

A. Labrador

MAX IV Laboratory

Romain Bordes

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Applied Surface Chemistry

Aleksandar Matic

Chalmers, Physics, Condensed Matter Physics

Cellulose

0969-0239 (ISSN)

Vol. 23 6 3653-3663

Subject Categories

Physical Chemistry

DOI

10.1007/s10570-016-1080-1

More information

Latest update

9/6/2018 1