Anisotropic Diffusion and Phase Behavior of Cellulose Nanocrystal Suspensions
Jonas Van Rie1, Christina Schütz2, Alican Gençer1
1Renewable Materials and Nanotechnology Research Group, Department of Chemical Engineering , KU Leuven , Campus Kortrijk, Etienne Sabbelaan 53 , B-8500 Kortrijk , Belgium.
Langmuir : the ACS Journal of Surfaces and Colloids
|January 24, 2019
Summary
Concentrated cellulose nanocrystal suspensions transition from isotropic to anisotropic states. Parallel diffusion coefficients peak at this transition, revealing how rod alignment impacts particle movement and entropy.
Area of Science:
- Materials Science
- Colloid Science
- Soft Matter Physics
Background:
- Cellulose nanocrystals (CNCs) are rodlike nanoparticles with potential applications in advanced materials.
- Understanding their behavior in concentrated suspensions is crucial for controlling material properties.
- Phase transitions in CNC suspensions influence their macroscopic characteristics.
Purpose of the Study:
- To investigate the phase transition of concentrated CNC suspensions.
- To determine the translational and rotational diffusion coefficients of CNCs.
- To elucidate the relationship between particle alignment and diffusion dynamics.
Main Methods:
- Dynamic light scattering (DLS) in polarized and depolarized modes.
- Polarized light microscopy.
- Viscosity measurements.
- Small-angle neutron scattering (SANS).
Main Results:
- A phase transition from isotropic to anisotropic (nematic) state was observed between 1-5 wt % CNCs.
- Rotational and translational diffusion coefficients generally decreased with increasing concentration.
- A local maximum in parallel translational diffusion was found at the isotropic-to-nematic transition.
- Unusual dispersive behavior in fast mode translational diffusion was observed, linked to particle length and twist fluctuations.
Conclusions:
- Rodlike particle alignment enhances translational entropy at the phase transition.
- Diffusion dynamics are significantly influenced by CNC alignment and inter-particle spacing.
- Two distinct length scales govern diffusion relaxation in aligned CNC systems.
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