Phosphate-Containing Interpenetrating Polymer Networks as Slow-Release Fertilizer Hydrogels

Purpose：The study increases phosphorus content in hydrogels without substantially sacrificing water regain and evaluates phosphate-containing interpenetrating networks as slow-release fertilizer carriers.

System and methods：2-Methacryloyloxyethyl phosphate was used as the first network in a phosphorus-containing IPN hydrogel and compared with a terpolymer of MEP, bis(methacryloyloxyethyl) phosphate and acrylic acid. Swelling, mechanical behavior and release performance were examined.

Key findings and mechanism：Phosphorus-containing IPN hydrogels with MEP as the first network were compared with a terpolymer of MEP, BMEP and acrylic acid. At equal monomer ratios, the IPN showed better swelling; it also allowed higher phosphorus content without major loss of water regain, a key requirement for agricultural release materials. Phosphate groups introduce hydrophilicity and ionic interactions that participate in water partitioning, while the interpenetrating network provides mechanical support and prevents excessive collapse at high phosphorus content. Phosphorus also serves as a nutrient-release source.

Application value and limits：The study illustrates ionic interactions and release control by phosphate groups in highly hydrated materials. It is less directly related to industrial coatings but useful for understanding phosphate hydrophilicity, crosslinking and ion-responsive design. This is an agricultural slow-release hydrogel rather than a coating or structural adhesive. Any transfer of the chemistry requires new validation of ionic strength, pH, hydrolysis and mechanical strength, and the goal shifts from nutrient release to interfacial anchoring.