Facile Synthesis of Cellulose-Based Microgels for Enhancing Soil Function for Agriculture

Functional microgels that can enhance agricultural productivity are becoming popular due to challenges brought by climate change, soil degradation, and inefficient irrigation-fertilizer utilization. However, the scalable production of cellulose-based microgels remains limited by conventional fabrication methods that compromise process safety, crosslinking efficiency, or mechanical stability. In this study, a cellulose-based polycarbodiimide-crosslinked carboxymethyl cellulose microgel (PCM) was prepared by reactive spray-drying that couples particle formation with in situ crosslinking using a non-volatile, water-soluble, and non-toxic polycarbodiimide crosslinker. FTIR and XPS analyses supported the formation of stable N-acylurea linkages between polycarbodiimide and carboxymethyl cellulose (CMC), with crosslinking promoted under mildly acidic conditions. The resulting PCM exhibited a swelling ratio exceeding 2000, pH-responsive swelling behavior, and excellent mechanical stability under saline conditions. Water retention analysis revealed significantly improved water holding capacity in PCM-treated coarse sand, while plant growth experiments demonstrated enhanced biomass production and drought survival of Amaranthus tricolor seedlings. These findings demonstrate the potential of reactive spray-drying using polycarbodiimide and CMC as a safe, scalable, and efficient manufacturing strategy for producing mechanically robust cellulose-based microgels for enhancing soil function.