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

Abstract 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.