Synthesis and Characterization of Self-Healing, Dual-Network Hydrogels Based on Polyvinyl alcohol: StructureProperty Relationships in a Viscoelastic System

Hypothesis: Dual-network hydrogels, created by combining two interpenetrating polymer networks, demonstrate improved mechanical stability and selfhealing properties due to the presence of reversible dynamic bonds. These
bonds allow the hydrogel to regain its original structure after suffering damage or stress. The distinctive characteristics of this type of hydrogel offer significant potential for a variety of applications in fields such as medicine, materials engineering, and developed technology.
Methods: This study developed and investigated a self-healing hydrogel with a reversible dual-network structure made from polyvinyl alcohol (PVA) and varying amounts of acrylamide (AM). The hydrogel was synthesized using PVA, AM, borax as a crosslinker, and iron (III) ions, with ammonium persulfate (APS) serving as a radical
polymerization initiator. To evaluate the structure, morphology, and performance of the synthesized hydrogel, several tests were conducted, including Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energydispersive X-ray spectroscopy (EDX) for microscopic surface morphology analysis
thermogravimetric analysis (TGA), swelling behavior (in distilled water and 0/9% by wt saline solution), rheological measurements, and assessments of the hydrogel's self-healing capability.
Findings: The results of the FTIR analysis confirmed the formation of the hydrogel structure and the presence of functional groups. SEM images showed that as the concentration of acrylamide (AM) increased, the hydrogel's structure changed from a smooth, non-porous surface to a mesoporous and homogeneous structure. At even higher concentrations of AM, a more compact and dense structure was observed due to increased crosslinking density Swelling behavior tests indicated that the PVA/PAM_0.5 sample exhibited the highest equilibrium swelling. TGA results confirmed that the thermal stability of the hydrogels improved with higher concentrations of AM. Rheological evaluations revealed that the PVA/PAM_0.5 hydrogel maintained its viscoelastic properties and fully recovered its structure after mechanical degradation Additionally, it demonstrated self-healing capabilities within 2 h at ambient temperature, without external stimulation.