Synergistic Enhancement of Photothermal Conversion and Mechanical Properties in PVA Hydrogels via Co-Doping of Polydopamine and Gold Nanoparticles

Abstract Photothermally responsive hydrogels with excellent mechanical properties are highly desirable for applications in biomedical engineering, soft actuators, and wearable devices. This work offers a simple and effective strategy for constructing photothermally responsive hydrogels with enhanced mechanical behavior by incorporating polydopamine (PDA) and citrate-stabilized gold nanoparticles (Au NPs) via a freeze-thaw process. Polydopamine functioned as a broadband photothermal agent, while Au NPs provided localized surface plasmon resonance (LSPR) effects. In addition, both polydopamine and Au NPs acted as physical crosslinking points and stress transfer centers within the hydrogel network. The incorporation of Au NPs also facilitated charge carrier migration, further contributing to improved photothermal conversion. As a result, compared with pure PVA hydrogels, the PVA@PDA@Au hydrogels exhibited significantly enhanced photothermal conversion efficiency after three freeze-thaw cycles, owing to the synergistic effect between polyPDAmine, Au NPs and PVA network. Moreover, the mechanical strength was remarkably improved, with the maximum load, tensile strength, and yield stress increasing by 4.6-fold, 4.2-fold, and 8-fold, respectively.