Multiscale flow alignment in cellulose nanocrystals controlled by surface topology.

Area of Science:

• Materials Science
• Polymer Science
• Rheology

Background:

• Cellulose nanocrystals (CNCs) are promising nanomaterials with unique flow alignment properties.
• Understanding multiscale flow alignment is crucial for controlling CNC suspension behavior.
• Surface modification significantly impacts CNC interactions and macroscopic properties.

Purpose of the Study:

• To investigate how surface topology influences multiscale flow alignment in CNC suspensions.
• To resolve the propagation of alignment from mesoscale to nanoscale.
• To establish linker topology as a key variable in CNC alignment behavior.

Main Methods:

• In-situ rheology combined with polarized light imaging (PLI) and small-angle X-ray scattering (SAXS).
• Systematic variation of azetidinium-based dialkyl linker topologies on CNC surfaces.
• Analysis using higher-order anisotropy parameters and a generalized Maier-Saupe-type anisotropy distribution function.

Main Results:

• Surface modification decouples mesoscale birefringence (PLI) from nanoscale alignment (SAXS).
• Maltese-cross pattern appearance in PLI systematically precedes detectable nanoscale alignment.
• Higher-order anisotropy parameters distinguish alignment regimes not discernible by S₂ alone.
• Alignment behavior is strongly dependent on linker topology.

Conclusions:

• Linker topology is a critical controlling variable for multiscale flow alignment in CNC systems.
• Higher-order anisotropy parameters are essential for characterizing CNC alignment behavior.
• The study provides insights into designing CNC-based materials with tailored flow properties.