ABSTRACT A series of semi‐interpenetrating polymer network (semi‐IPN) hydrogels were prepared by free‐radical polymerization of N,N′‐dimethylacrylamide (DMA) and maleic acid (MA) in the presence of linear polyacrylamide (PAM). The ternary PAM/DMA/MA semi‐IPN structure was designed to combine network reinforcement, swelling regulation, soil moisture retention, and phosphate adsorption/release within a single hydrogel platform. The influence of MA content on the properties of the hydrogels was systematically investigated. FTIR analyses confirmed the successful incorporation of MA, while SEM images revealed its effect on the internal network morphology. TGA, DSC, mechanical, and rheological results showed that increasing MA content raised thermal stability, the Tg, improved compressive strength and storage modulus. Swelling experiments showed a maximum equilibrium swelling ratio of 3240.16% in deionized water, along with clear responsiveness to pH and ionic strength. The hydrogels also exhibited effective phosphate adsorption/release performance, achieving a cumulative phosphate release of 78.75% after 6000 min, with the release behavior best described by the Zero‐order kinetic model. Furthermore, soil application tests indicated that hydrogel‐amended soils maintained a residual moisture content of approximately 16.5% after five repeated wetting‐drying cycles, each lasting about 12 days, while showing negligible variation in soil pH.
Phan et al. (Tue,) studied this question.