PH-responsive chitosan nanoparticles for controlled-release nitrogen fertilizer: Template-tampering free radical graft copolymerization under energetic radiation study

Abstract

Macromolecular template-tampering free radical graft copolymerization under energetic radiation is studied as a controlled process for fabricating and nanosizing chitosan-graft-polyacrylic acid interpolymer complex (CS-PAA IPC) nanoparticles. The CS-PAA IPC nanoparticles is proposed as a pH-responsive vehicle for water absorption and controlled release of nitrogen (N) fertilizer. Roles of chitosan macromolecular template and absorbed energy for controlling free radical graft copolymerization in an aqueous solution were studied. Controlling graft copolymerization, nanostructure, nanosize, and size distribution of the CS-PAA IPC nanoparticles were followed by varying different parameters, i.e., CS template chain length, AA concentrations (0.03–0.15 M), and absorbed energies (10–30 kJ/kg, kGy). The CS-PAA IPC nanoparticles have well-defined in spherical shape with the size in the range of 30–200 nm. The pre-irradiated CS template provides a crucial role for narrowing size distribution of the CS-PAA IPC nanoparticles. Kinetic swelling behavior, water absorption/diffusion mechanism, nitrogen (N) fertilizer (ammonium nitrate, NH4NO3) entrapment/controlled release based on pH-responsive characteristic were investigated in acidic to basic ranges (pH 5, 7 and 9). The diffusion mechanism of the CS-PAA IPC nanoparticles exhibited a non-Fickian diffusion. The N content was 23 g per 100 g of CS-PAA IPC nanoparticles fertilizer. Pot-testing was carried out through the baby corn growth in different soil conditions, i.e., sandy soil (SS), SS/ NH4NO3, SS/NH4NO3-entrapped CS-PAA, and cultivation soil/NH4NO3. The CS-PAA IPC nanoparticles is a promising water absorption and pH-responsive platform for N fertilizer entrapment and controlled-release for soil amending, enhancing fertilizer utilization efficiency, and reducing environmental impact due to N loss.