## 3 Shape-Memory Polymer Nanocomposites (SMPNCs)
### Metal-Based Nanocomposites
#### 3.1.3 Silver Nanoparticle (AgNP) Nanocomposites
Figure 10: (**a**) Illustration of the network formation in the PmBz-PCL-Ag nanocomposite using SS-PCL modified AgNPs, along with photographs depicting the shape recovery of PmBz-PCL (1), PmBz-PCL-Ag0.001 (2), PmBz-PCL-Ag0.01 (3), PmBz-PCL-Ag0.1 (4), and PmBz-PCL-Ag0.3 (5) upon light activation. Reproduced with permission from ref. [57]. Copyright 2020 Elsevier. (**b**) UV\(-\)vis spectra of CNC-ad-AgNPs and CNC-g-AgNPs. Reproduced with permission from ref. [32]. Copyright 2018 American Chemical Society. Figure 9: (**a**) Diagram illustrating the preparation process of PAF alongside images of its fractured surface. (**b**) Graph depicting PAF’s recovery time and rate under various applied voltages. (**c**) Digital photos and infrared thermal images showing the electric/moisture actuation process and its recovery, with corresponding infrared images (left) and digital photos demonstrating the 10-s recovery process of PAF at 2 V (right). Reproduced with permission from ref. [44]. Copyright 2020 Elsevier. In another study, [PERSON] et al. designed light-activated SMP composites by incorporating 1 wt.% AgNPs into PCL [32]. The study employed two methods for synthesizing plasmonic AgNPs: (i) adsorption of AgNPs onto the surface of cellulose nanocrystals (CNCs) through direct reduction of Ag ions with NaBH\({}_{4}\), labeled CNC-ad-AgNPs, and (ii) grafting of AgNPs onto CNCs after modifying the CNC surface with thiol groups, followed by subsequent Ag ion reduction, referred to as CNC-g-AgNPs. The light absorbance capability of the CNC-ad-AgNPs and CNC-g-AgNPs composites were illustrated in Figure 10b. CNC-ad-AgNPs exhibited a single absorption band at 400 nm, indicative of adsorbed spherical nanostructures. In contrast, CNC-g-AgNPs displayed a redshift of the band to 415 nm, suggesting plasmon excitation along the nanofiller's longer axis, and a second absorption band of low intensity at 930 nm, indicative of a nanorod-like structure. This design strategy for incorporating plasmonic AgNPs onto CNCs enables efficient, fast, and remotely triggered shape-memory actuation under IR light, demonstrating the potential of such systems for advanced applications. [PERSON] et al. employed a method to decrease the shape-memory recovery times and improve the recovery ratio of thermoplastic potato starch (PS) by incorporating AgNPs [118]. AgNPs act as anchor points within the starch matrix through hydrogen bonds between the hydroxyl groups of the starch and the AgNPs [119]. This interaction increased the shape-recovery ratio from 85% to 98% as the AgNP concentration increased from 0% to 2 wt.%, attributed to mechanical reinforcement and increased number of netpoints between the polymer chains [118]. Additionally, the presence of AgNPs reduced recovery times to two minutes for PS20 AgNP with 2 wt.% AgNPs. Initial recovery of over 75% of the original shape occurred within the first 20 s for composites with lower AgNP content, while those with 2 wt.% AgNPs achieved over 85% recovery. After one minute, both the PS and the PS05 AgNP with 0.5 wt.% AgNPs reached similar recovery ratios (85% and 87%, respectively), likely affected by water absorption. In contrast, composites with higher AgNP content (1 wt.% and 2 wt.%) exhibited higher recovery ratios (approximately 98%) and demonstrated lower water absorption n rates. In another study, [PERSON] et al. utilized a direct green synthesis technique to produce SMPNCs embedded with AgNPs [120]. The composite material was fabricated using a solution casting method, combining a PLA/PCL blend with AgNPs synthesized through the environmentally friendly reduction of silver salts using _Rubus caesius_ L. leaves. It was observed that the shape-recovery properties of the nanocomposite films improved with increasing AgNP content. The smart superhydrophobic surfaces of SMPs with tunable wettability have attracted extensive attention due to their widespread applications. [PERSON] et al.