## 3 Shape-Memory Polymer Nanocomposites (SMPNCs)
### Other Non-Metal Nanocomposites  
Various types of non-metallic nanofillers have been employed to enhance the properties of SMPNCs to meet specific application requirements. [PERSON] et al. developed novel polyurethane-based NIR light-activated SMPCs by incorporating polydopamine nanoparticles (PDANPs) with polycaprolactone (PCL), hexamethylene diisocyanate (HDI), and 1,4-butanediol (BDO) [260]. The abundant benzene rings, catechol, and amine groups in PDANPs facilitate both covalent and noncovalent interactions with the polymer matrix, such as hydrogen bonding, coordination, and \(\pi\)-\(\pi\) stacking, thereby enhancing compatibility [261]. Due to its exceptional thermal stability and photothermal properties, PDA serves as an ideal photothermal agent for the construction of NIR light-triggered thermally-sensitive SMPCs, particularly suited for biomedical applications [262]. The PCL-PDA polyurethanes, containing 0.17 wt.% PDANPs, exhibited nearly 100% NIR light-triggered shape recovery within 20 s at laser intensities of 0.66 and 1.00 W/cm\({}^{2}\), while a lower intensity of 0.33 W/cm\({}^{2}\) required approximately 60 s for full recovery (Figure 26a). Further tests under an 808 nm laser at 0.33 W/cm\({}^{2}\), adhering to the American National Standard for safe skin exposure [263], confirmed the composite's precise and controllable shape recovery, achieving complete shape restoration within 60 s. In another study, [PERSON] et al. synthesized SMPCs by incorporating PDA nanospheres as a photothermal filler into the PCL/TPU matrix via solution blending [264]. The light-responsive SME of the PCL/TPU/PDA nanocomposites was examined under visible light at a fixed intensity of 200 mW/cm\({}^{2}\), revealing that the shape-recovery rate accelerated with an increase in PDA nanosphere content. Specifically, the composite (PCL/TPU/PDA) with 3 wt.% PDA (P/T/D-3) achieved 100% recovery within 50 s, demonstrating the efficacy of PDA nanospheres as light-absorbing fillers for efficient light-to-heat conversion. Polypyrrole (PPy), a conjugated organo-polymeric NP, has garnered significant interest for its technological applications, including roles in electrodes, electronic devices, sensors, actuators, biomaterials, and light-to-heat conversion materials, due to its unique properties and functionalities [265]. [PERSON] et al. enhanced the ethylene-vinyl acetate copolymer (EVA)/PCL composite by incorporating PPy NPs as photothermal fillers, achieving exceptional photo-induced shape-memory performance with a 100% recovery ratio (R\({}_{\text{r}}\)) [266]. In samples containing less than 0.5 wt.% PPy, rapid and complete shape recovery was observed under laser exposure, with the recovery time diminishing as the PPy content increased, culminating in full recovery within 7 s at a concentration of 1 wt.% PPy. Additionally, the nanocomposite demonstrated the capability for precise and selective self-healing of damaged areas, without adversely affecting the performance of intact regions. Once healed, the cut sample resisted re-fracture, even after repeated bending, and could support a weight of 3846 times its own, without significant deformation or damage. (Figure 26b) [266]. In another study, [PERSON] et al. developed PPy NP-filled PLA/PCL nanocomposites, exhibiting exceptional triple shape-memory properties, with shape-recovery rates (R\({}_{\text{r}}\)1, R\({}_{\text{r}}\)2, and R\({}_{\text{r}}\)3) of 92%, 87%, and 93%, respectively, in an 80:20 PLA/PCL blend [267]. The study revealed that under constant NIR irradiation, the surface temperature of composites increased, and the shape-recovery time decreased with higher PPy content, demonstrating the significant photo-induced SME of PPy NPs selectively distributed in the PCL component. [PERSON] et al. synthesized SMPU nanocomposites by incorporating modified silica nanoparticles (SNPs) into polyurethane using an in situ two-step polymerization method.