Solvent-free mechanochemical synthesis of superabsorbent polymers derived from paramylon and zein

Bio-based superabsorbent polymers (SAPs) were successfully prepared through a sustainable solvent-free and catalyst-free mechanochemical esterification of paramylon and zein using succinic anhydride as the esterification reagent. By optimizing the reaction temperature and raw material composition, a paramylon-to-zein weight ratio of 4:6 exhibited a porous morphology and achieved a maximum water absorption capacity of approximately 60 g/g, comparable to that of a commercial bio-based SAP. The optimized SAP also exhibited favorable biodegradability and showed no observable phytotoxicity in seed germination tests. Furthermore, incorporation of only 0.5 wt% SAP into soil improved soil water retention and promoted maize growth under drought conditions, increasing plant height and root length compared with the untreated control. These results demonstrate that solvent-free mechanochemical processing provides an effective and environmentally friendly strategy for producing bio-based SAPs with promising potential for sustainable agricultural water management.