## 3 Shape-Memory Polymer Nanocomposites (SMPNCs)
### Carbon-Based Nanocomposites
#### 3.2.4 Graphene Oxide Nanocomposites  
Graphene, a unique two-dimensional nanostructure of \(sp^{2}\) hybridized carbon atoms arranged in a well-organized honeycomb pattern, has garnered interest due to its outstanding electrical, optical, and thermal properties [225, 226]. Its substantial surface area and aspect ratio make it an ideal candidate for enhancing the performance of SMPCs [226, 227]. Furthermore, graphene and its derivatives have been effectively utilized as fillers in polymeric substrates, capitalizing on their superior heat and light absorption capabilities for light-controlled actuation and deformation [228, 229, 230]. For instance, [PERSON] et al. developed SMPCs by incorporating graphene oxide (GO) into thermosetting polyurethane, demonstrating a photo-induced SME with 95% shape recovery upon NIR light exposure, as well as exhibiting solid-state plasticity and self-healing capabilities [73]. Among various synthesis methods, the chemical reduction of GO stands out as a widely recognized approach for producing substantial quantities of reduced graphene oxide (rGO) [231, 232]. However, the limited dispersion capability of rGO in polymer matrices, attributed to the re-agglomeration of graphitic layers via strong \(\pi\)-\(\pi\) and van der Waals interactions, restricts its effective incorporation [233]. Consequently, enhancing stability and dispersibility necessitates the modification or functionalization of rGO. [PERSON] and colleagues utilized epoxy bisphenol A diglycidil ether (DGEBA)-functionalized rGO (DGEBA-f-rGO) to create cross-linked photothermal networks in hyperbranched polyurethane/epoxy (HBPU/EP) composites, enhancing their NIR light-driven actuation and mechanical properties (Figure 24a) [230]. Upon exposure to an 808 nm NIR laser, the composites displayed a significant increase in surface temperature and heating rate compared to the constant surface temperature of pure HBPU/EP. The DGEBA-f-rGO composites demonstrated superior photothermal performance and faster, more efficient shape recovery under NIR irradiation compared to their nonfunctionalized GO counterparts. Incorporating 1.0 wt.% DGEBA-f-rGO into the HBPU/EP matrix resulted in rapid shape recovery within 6 s and maintained a recovery ratio exceeding 95.0%, significantly outperforming DGEBA-f-GO composites. Figure 23: (**a**) Self-healing dynamic cross-linking network design; and (**b**) electrical healing process of the conductive device with an LED bulb. Reproduced with permission from ref. [223]. Copyright 2021 Elsevier. [PERSON] et al. investigated the mechanical properties and shape-memory performance of PCL-based polyurethane nanofibers by integrating GO, PCL-functionalized f-GO, and rGO [234]. The composites containing f-GO and rGO exhibited enhanced actuation in shape-memory tests, achieving a recovery time of 8 s for 1 wt.% f-GO or rGO nanofibers, in contrast to 13 s for nanofibers with incorporated GO. This enhancement highlights the pivotal role of functionalized GO in improving interfacial interactions and enabling reversible cross-linking, thus optimizing the shape-recovery process [230]. Polyimide (PI) emerges as a key material in SMPs, notable for its excellent mechanical properties, thermal stability, and shape-memory functions [235]. [PERSON] et al. developed thermosetting cross-linked polyimide SMP composites (TCPI/rGO) with a high transition temperature (T\({}_{\text{trans}}\)), achieving rapid NIR light-induced shape recovery [236]. The addition of 1 wt.% rGO significantly enhanced the mechanical properties of the composites, achieving a breaking strain of 44.1% and toughness of 41.7 MJ/m\({}^{3}\).