Abstract
The adsorption of carboxymethylcellulose (CMC) on cellulose surfaces is one of the most studied examples of the adsorption of an anionic polyelectrolyte on a like-charged surface. It has been suggested that divalent ions can act as a bridge between CMC chains and the surface of cellulose and enhance the CMC adsorption: they can, however, also alter the structure of CMCs in the solution. In previous investigations, the influence of cations on solution properties has been largely overlooked. This study investigates the effect of Ca2+ ions on the properties of CMC solutions as well as the influence on cellulose nanofibers (CNFs), which was studied by dynamic light scattering and correlated with the adsorption of CMC on a cellulose surface probed using QCM-D. The presence of Ca2+ facilitated the multichain association of CMC chains and increased the hydrodynamic diameter. This suggests that the adsorption of CMCs at high concentrations of CaCl2 is governed mainly by changes in solution properties rather than by changes in the cellulose surface. Furthermore, an entropy-driven mechanism has been suggested for the adsorption of CMC on cellulose. By comparing the adsorption of CMC from H2O and D2O, it was found that the release of water from the cellulose surface is driving the adsorption of CMC.
Highlights
The adsorption of polymers on cellulose surfaces has been of interest for decades due to its applications in papermaking
This study investigates the effect of Ca2+ ions on the properties of CMC solutions as well as the influence on cellulose nanofibers (CNFs), which was studied by dynamic light scattering and correlated with the adsorption of CMC on a cellulose surface probed using QCMD
It has been shown that anionic polyelectrolytes such as carboxymethylcellulose can adsorb on cellulose surfaces irrespective of their expected electrostatic repulsion.[4−8] Carboxymethylcellulose (CMC) is the most versatile semisynthetic polyelectrolyte derived from cellulose[9,10] and has been used in a wide range of applications, including mineral processing,[11−13] pharmaceutics,[14] and as a viscosity modifier.[15]
Summary
The adsorption of polymers on cellulose surfaces has been of interest for decades due to its applications in papermaking. The adsorption of CMC on cellulose has been used to improve the wet mechanical properties of cellulose.[4,5,16] Apart from conventional applications, the adsorption of CMC on cellulose has been used to create biofunctional interfaces for diagnostic platforms and bone-healing scaffolds.[6,17,18]
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