Shape memory polymers (SMPs), due to the programmable deformation and recovery ability, exhibit widespread potential in fields of biomedical devices, smart actuators, and engineering structures. Thermoplastic SMPs, which possess the intrinsic linear molecular chain structures, are able to be processed through diverse methods, in addition to being re-processed after process-forming, compared with thermoset SMPs. The environmental recycling characteristics for thermoplastic SMPs describe their wide use potential and prospect. In this paper, a comprehensive description of mechanism, matrix polymers, actuations, and applications for thermoplastic SMPs and composites was reviewed. Furthermore, two promising potential developing directions, 4D printing metamaterial and dynamic covalent networks, were proposed. The multifunctionality and enhanced performances of thermoplastic SMPs and composites exhibited excellent application value, which is significant for future advancements.

Shape memory polymers (SMPs) are a class of smart materials that exhibit unique shape-fixing and recovery abilities, attracting wide attention for applications in electronics, aerospace, and biomedical engineering. Chitosan (CS) as a renewable biopolymer, possessing good biocompatibility, biodegradability, and antimicrobial properties; its use as a matrix enhances the environmental compatibility and bio-adaptability of SMPs. MXene, as a novel two-dimensional material, is characterized by high electrical conductivity, abundant surface functional groups and good hydrophilicity, showing potential in energy storage, electromagnetic shielding and sensing. In this work, CS and poly (vinyl alcohol) (PVA) were used as the polymer matrix, and carbon nanotubes (CNTs) together with MXene were introduced as co-fillers to construct multifunctional composites. The effect of the CNTs/MXene hybrid fillers on mechanical properties, electromagnetic shielding and multi-stimuli-responsive shape memory behavior was systematically investigated. After ratio optimization, the composites showed excellent comprehensive performance: tensile strength reached up to 20.0 MPa, Young’s modulus up to 292.2 MPa, and maximum elongation at break of 23.2%; electromagnetic interference shielding effectiveness (SE_T) in the X-band (8.2–12.4 GHz) reached a maximum of 10.6 dB; shape fixation rates exceeded 90%; under thermal stimulation, a shape recovery ratio of 98.3% was achieved within 41.7 s; light-driven recovery rate reached 86.5% with a minimal recovery time of 82.3 s; under electrical stimulation the highest recovery rate was 94.1% with a shortest recovery time of 30 s. This study successfully prepared functional multi-stimuli-responsive shape memory composite films and provided a new strategy for the design of green smart materials.