Tuning the morphology of aerosolised cellulose nanocrystal particulates via controlled aggregation

Cellulose nanocrystals (CNCs) are polycrystalline, rod-shaped nanoparticles isolated from cellulose that have attracted increasing attention for a wide variety of applications. While there has been significant research into CNCs in suspensions, hydrogels and films, there have been remarkably few studies that investigated their properties during and after aerosolisation. Here, we studied how the surface functionality of different CNC suspensions impacts the size and morphology of the CNC particulates formed when the initial suspensions are aerosolised. By building a new experimental setup, we observed that colloidally-metastable aqueous CNC suspensions - achieved by carboxylation of the surface hydroxy groups or by exposure to high-intensity ultrasonication - yield large particulates upon aerosolisation under ambient temperatures. In contrast, aqueous suspensions of unfunctionalised CNCs tend to produce smaller particulates upon aerosolisation, despite suffering from poor colloidal stability in liquid suspension. These results demonstrate that both the aerosolisation process and the properties of the CNC suspension play a crucial role in determining the final size and morphology of CNC particulates. This highlights the need to consider colloidal stability and surface functionality when designing CNC-based materials for applications involving aerosol delivery or spray-drying.