Cellulose nanocrystals (CNCs) exhibit self-assembly into higher-ordered chiral nematic liquid crystal (LC) structures. Understanding their dynamic behavior during phase transitions is crucial for advancing nanomaterial applications in photonics, biomaterials, and coatings. In this study, we employ X-ray Photon Correlation Spectroscopy (XPCS) to investigate the real-time self-assembly dynamics of CNC suspensions at varying concentrations, ranging from the isotropic to the arrested glass phase.
We prepared CNC suspensions in propylene glycol (PG), spanning a range of concentrations, and complemented XPCS with dynamic light scattering (DLS) and polarized optical microscopy (POM) to track phase transitions. Our findings reveal a three-stage decay in particle dynamics, coinciding with self-assembly transitions. The diffusion rate of CNCs decreases by four orders of magnitude as the system transitions from the isotropic to the arrested LC phase—an effect much greater than expected for repulsive Brownian rods.Furthermore, coarse-grained molecular dynamics (MD) simulations were performed to interpret XPCS results, showing that while simple crowding effects slow diffusion by a factor of 2–4, the experimentally observed slowdown is nearly 10,000 times greater, underscoring the role of collective ordering and interparticle interactions. These findings extend beyond CNC-PG systems, suggesting that similar dynamic behavior may occur in other polar solvents such as water, where low viscosity limitations have hindered direct XPCS observations.
This study represents a significant step in directly quantifying CNC self-assembly dynamics and highlights the feasibility of using XPCS to probe nanoscale dynamics in concentrated colloidal suspensions. The insights gained contribute to the design and manufacturing of CNC-based functional materials, paving the way for tailored self-assembly in nanostructured systems.