# Impact of Silica Nanoparticles on Mechanical Properties and Self-Healing Performance of PVA Hydrogels

## TL;DR

This paper shows how adding silica nanoparticles improves the strength and self-healing ability of PVA hydrogels, making them more practical for real-world uses.

## Contribution

The study introduces a novel method using ultra-small silica nanoparticles to enhance both mechanical strength and self-healing performance of PVA hydrogels.

## Key findings

- PVA hydrogels with ~12 nm silica nanoparticles achieved 95% self-healing recovery and 1.45 MPa tensile strength.
- Optimal self-healing recovery (96%) was achieved at 60 °C for 60 minutes.
- Ultra-small silica nanoparticles acted as efficient nucleating agents without disrupting the self-healing mechanism.

## Abstract

Hydrogels are three-dimensional polymeric networks capable of retaining large amounts of water. Polyvinyl alcohol (PVA)-based hydrogels exhibit autonomous self-healing through reversible physical interactions within the hydrogel matrix, including hydrogen bonding, crystallite formation, and dynamic crosslinking. However, their long self-healing times and low strength limit practical application. Herein, we propose an effective strategy to simultaneously achieve excellent self-repairing and high mechanical strength. The tensile strength of uncut PVA hydrogel was 1.21 MPa; after cutting and rejoining for 12 h at room temperature (RT), it recovered 94% of the original uncut strength. To accelerate self-healing, hydrogels were treated at 40, 50, and 60 °C for 20, 40, and 60 min. Under optimal conditions (60 °C for 60 min), 96% recovery was achieved. Mechanical properties were further improved by silica (Si) nanoparticles of various sizes (~12, ~85, and ~200 nm). Si-loaded hydrogels, particularly ~12 nm, demonstrated increased mechanical properties, reaching a tensile strength of 1.45 MPa and a self-healing recovery of 95% of the uncut hydrogel strength. Ultra-small (~12 nm) Si nanoparticles enhanced the overall mechanical properties by acting as an efficient nucleating agent and did not hinder the existing self-healing mechanism. The developed strategy will pave the way for novel techniques in hydrogel research and will advance applications such as soft robotics and wound dressing.