Optimising Photothermal Silver Nanoparticles for Efficient Light-Activated Shape Memory Response in AgNP-Polymer Composites

The study presents the synthesis and integration of silver nanoparticles (AgNPs) into a polyurethane (PU) matrix to create a light-activated shape memory polymer (SMP). AgNPs were synthesized using a microwave-assisted solvothermal method with polyvinylpyrrolidone (PVP) as a stabilizer, where varying the molecular weight of PVP and the AgNO₃/PVP ratio influenced nanoparticle size and distribution. Characterisation via scanning electron microscopy (SEM) and dynamic light scattering (DLS) confirmed the irregular morphology and size consistency of AgNPs, with smaller particles exhibiting narrow size distributions and enhanced photothermal response. Among the samples, PVP with an average molecular weight (M_n) of 10,000 and an AgNO₃/PVP mole ratio of 14.7 demonstrated optimal UV-blue light absorption, which facilitated efficient local heating under irradiation. The AgNP-PU composite exhibited a reliable shape memory effect when exposed to UV-blue light.