Intramolecular and intermolecular crosslinked poly(vinyl alcohol)–borate complexes for the sustained release of fertilizers and enzymes

Abstract

Therapeutic agents or agricultural fertilizers captured in polymer colloids (PCs) give rise to interesting applications, which are typically related to sustained release. We synthesized crosslinked polymer structures with poly(vinyl alcohol) (PVA) and borax precursors. Fourier transform infrared spectroscopy showed that a polymer-boron ion complex was formed with the crosslinking reaction at the OAH site of PVA; thereby, PCs were formed. Field-emission scanning electron microscopy showed that a uniform mesoporous two-dimensional structure formed via intermolecular and intramolecular crosslinking. Trypsin enzyme and phosphate fertilizer were trapped in these PCs independently to study sustained release. Fertilizer-incorporated PCs were mixed with soil samples, in which seeds of fenugreek were sown, and the plant growth was monitored a duration of 15 days. The fertilizer release, studied with UV-visible spectroscopy, showed a sustained signature of the fertilizer (at 690 nm) in the water extracts of soil, with much healthier plant growth compared to the control. For the trypsinincorporated PC samples, the released enzyme was made to interact with bovine serum albumin protein to monitor the released percentage with UV absorption spectroscopy. A systematic increase in the enzyme signature (at 280 nm) was observed for a duration of 60 min; this indicated the potential of PC for sustained drug release. The swelling calculations predicted that the mechanism involved was composed of pseudo-swelling behavior. We envisaged that the hydroxyl groups of the PC broke in water and formed a complex with water. This complex slowly dissolved in water to release the entrapped molecules.

Extremely Stretchable Strain Sensors Based on Conductive Self‐Healing Dynamic Cross‐Links Hydrogels for Human‐Motion Detection

“…The –OH stretching peak is sensitive to hydrogen bonding. Compared with pure PVA, the –OH stretching peak shifts to a higher wavenumber and the peak is enhanced after formation of the hydrogel, indicating the presence of hydrogen bonding interactions between the hydroxyl groups on the PVA molecular chains and tetrafunctional borate ion . In addition, dynamic mechanical measurements of the pure hydrogel and SWCNT/hydrogel were carried out to investigate their rheological properties.…”

Self-Healing Nanophotonics: Robust and Soft Random Lasers

“…The isolation of dye and self-assembled Ag NPs from the air prevents the oxidation and thus guarantees the stability of the laser materials. To gain insight into the nature of the hydrogel, Fourier transform infrared spectroscopy is provided in Figure c, ,, and the broad and strong peak around 3330 cm –1 demonstrates the presence of the hydrogen-bonding interaction between the PVA and the tetrafunctional borate. , Self-healability is resultant from the lateral movement of the underlying self-healing hydrogel, which is attributed to the dynamical association and dissociation of hydrogen bonds. Figure d presents the strain–stress curve of the composite, showing the stretchability of the device.…”

Preparation and properties of a degradable interpenetrating polymer networks based on starch with water retention, amelioration of soil, and slow release of nitrogen and phosphorus fertilizer

“…It is well known that diammonium phosphate and urea dissolve quickly in water after being added to soil, and the nutrient released out with that. The SF swelled slowly because of hydrogen bonding and polymer–boron ion complex formation with the crosslinking reaction at the OH site of starch, as revealed by FTIR 20. This restricted the relaxation of polymer chains and brought about a decrease in the diffusion of water molecules and a subsequent reduction in the solution of phosphate.…”

“…After the coating polymer slowly absorbed the water in the soil and swelled, there was an increase in the pore size of the three‐dimensional network, which benefitted the diffusion of the fertilizer solution. SF in the core of SAAmF swelled slowly because of the breakage of the interaction of hydroxyl groups and boron ions in water absorbed in hydrogel network, and the entrapped molecules dissolved slowly 20. There existed a dynamic exchange between the free water in the hydrogel and the one in soil,21, 22 and then, the nutrient was released slowly into the soil through the grids with dynamic exchange 14, 23…”