Novel Biodegradable Nanocomposite Hydrogels Based on Biopolymers and Montmorillonite as Low-Cost and High-Strength Coating Membranes for Efficient Slow-Release Fertilizers

Preparation and characterization of hydrogels based on glycidyl methacrylate (GMA)‐grafted NR and modified cassava starch as eco‐friendly materials for sustainable agriculture

“…Figure 4B shows the TG and DTA (inset) curves for CSt powder, NRG film, and both semi‐IPN hydrogels: CSt‐g‐PAA/NRG and CSt‐g‐PAM. The CSt powder exhibited three weight loss step at: (a) 25–120°C (moisture evaporation), (b) 250–400°C (chain scission) with a maximum degradation temperature ( T d,max ) of 303°C, and (c) 400–500°C (C–C chain degradation) 21,22,26 . The NRG film presented a single step weight loss that took place at 250–450°C with T d,max of 359°C, possibly caused by the decomposition of NRG main chains (chain scission) and GMA grafted chains.…”

“…Fundamentally, the pH and salt solutions are key factors that significantly influence the swelling behavior of hydrogels 22,26,45 . Consequently, possessing a clear understanding of these factors would greatly facilitate the customization and application of hydrogels across a wide range of fields.…”

“…At lower pH values (especially pH <4), there was a significant decrease in swelling properties, possibly due to the protonation of carboxylate groups in AA and amide groups in AM. This protonation, resulting in –COO − to COOH conversion in CSt‐g‐PAA/NRG and –CONH 2 to –CONH 3 + conversion in CSt‐g‐PAM/NRG, led to reduced hydrogen bonding with water molecules, enhancing the physical crosslinking level in the semi‐IPN networks through hydrogen bonding of –COOH groups and –CONH 3 + groups, and reducing the anion‐anion repulsions, finally diminishing the water swelling capacity of both semi‐IPN hydrogel films 5,21,22 …”

“…Distilled water (50 mL) was introduced to the soil every 3 days. At intervals of 0, 15, 30, 45, and 60 days, the buried samples were carefully retrieved, washed with distilled water, and dried at 50°C until a constant weight was achieved 22 . The biodegradability of the hydrogel films was determined by weight loss of the specimens.…”

“…Additionally, the epoxy groups in GMA can potentially react with hydroxyl or carboxyl groups in polyesters, leading to improved compatibility 25 . Also, it has been found that the most frequently employed monomers to graft with starch are acrylic acid (AA) and acrylamide (AM), having hydroxy (‐OH) and amide functionality (‐CONH 2 ‐), respectively, for improving the hydrogel swelling properties 22,24–26 . Furthermore, while GMA is typically grafted onto NR (NRG) or blended with other polymers as a compatibilizer, only a few studies have reported the synthesis of hydrogels using NRG and CSt 17,24,25,27 …”