Blending with Non-responsive Polymers to Incorporate Nanoparticles into Shape-Memory Materials and Enable Photothermal Heating: The Effects of Heterogeneous Temperature Distribution

Blending a shape-memory polymer (SMP) (e.g., thermoplastic polyurethane) with an immiscible carrier polymer (e.g., poly(ethylene oxide) (PEO) or poly(vinyl alcohol) (PVA)) containing dispersed metal nanoparticles (AuNPs) is a simple approach to enable actuation via photothermal heating. For blends containing up to 90% carrier polymer, the shape-memory capability can be thermally triggered either conventionally or utilizing internal heating via application of light that is resonant with the particle’s surface plasmon resonance. When incorporating nanoparticles in this manner, neither chemical modifi cation of the shapememory moiety nor solvation of the SMP is necessary. Actuation times are determined by the particular heterogeneous temperature distribution, which generally occurs under both conventional and photothermal heating methods, but with different spatial patterns. Blending an SMP with PEO containing AuNPs imposes a higher transition temperature (the melting point of PEO), enabling heat generated within the nanoparticle-containing regions to equilibrate throughout the sample, resulting in performance under photothermal conditions comparable with that achieved in a conventional heating approach. SMP:PVA blends actuate at the SMP transition temperature and the response depends on the size of phase segregation between the PVA and SMP; when decreasing the characteristic size of the segregated regions, heat is effi ciently transferred and optimal photothermal performance is observed.