Sustainable and environment Friendlier carrageenan-based pH-responsive hydrogels: swelling behavior and controlled release of fertilizers

Herein, a series of pH-responsive composite hydrogels based on carrageenan (CG) and synthetic polymer poly (N-vinyl-2-pyrrolidone) (PVP) was developed by using 3-aminopropyl triethoxysilane (APTES) as cross-linker. The formation of the hydrogel was confirmed with the help of Fourier-transform infrared spectroscopy (FTIR). The FTIR spectra revealed the presence of all functionalities at their specific wavenumbers. The thermal stability of the as prepared composite hydrogels and pristine carrageenan and PVP was evaluated with the help of thermogravimetric analysis (TGA). The obtained thermo-grams portrays that the composite hydrogels are thermally more stable as compared to the pristine hydrogels. Furthermore, antibacterial investigations exhibit good activities against S. aureus a gram-positive strain indicating that the as prepared hydrogels can be employed for the biological applications. Additionally, the time-dependent sustainability of the composite hydrogels was confirmed by biodegradation analysis. The results obtained are in well agreement with the reported results. Also, the swelling behavior of the hydrogels was examined against different media using different concentrations of the APTES. The percentage of swelling in water for hydrogel samples was increased with the quantity of APTES. The different pH of the same solutions explains the swelling behavior in dependable way as hydrogels exhibit inverse relation of swelling with pH; in acidic medium, i.e., at low pH, maximum swelling was observed and vice versa. This idiosyncratic behavior of these synthesized hydrogels and its sustainability favors their use for control release of fertilizers. The release pattern was studied by spectrophotometer using indophenol blue at 640 nm showed 86.82% of fertilizer release over a period of 216 h in a phosphate buffer saline (PBS) in a controlled manner. Graphical Abstract: [Figure not available: see fulltext.].