Scalable Fabrication of Porous Cellulose Microparticles with Tunable Crystallinity and Chain Accessibility

Cellulose is a versatile and sustainable biopolymer that can be used to make microparticles for various applications. However, its inherent crystallinity limits the surface access for sorption and functionalization. This study presents a one-step method for tuning the crystallinity and chain accessibility of cellulose microparticles using a reactive spray drying technique. The spray drying parameters (e.g., feed concentration, N₂ gas flow rate, and cross-linker dosage) were optimized to produce spherical, porous microparticles with a size distribution ranging from 0.54 to 5.65 μm. Among these parameters, feed concentration and N₂ gas flow rate were shown to have the greatest influence on the morphology and internal structure, while cross-linking reduced crystallinity and enhanced chain accessibility. The extent of the enhancement in the chain accessibility was directly linked to the epichlorohydrin cross-linker/glucose monomer (E/G) ratio in the feed solution. As a result, the improved chain accessibility led to greater solvent absorptivity, methylene blue adsorption, and dispersibility of the spray-dried cellulose microparticles compared to those of pristine cellulose. These findings highlight the potential of the method as a simple and scalable approach to producing cellulose microparticles with tunable properties.