4D-printed materials are an emerging field of research because the physical structure of these novel materials respond to environmental changes. 3D printing techniques have been employed to print a base material with shape memory properties. Geometrical deformations can be observed once an external stimulus triggers the shape memory effect (SME) integrated into the material. The plasticizing effect is a well-known phenomenon where the microscopic polymer chain movements have been altered and reflected in different shape memory behaviour. It has been suggested that a 4D material with localized actuation behaviour can be fabricated by utilizing functionally graded layers made from different degrees of plasticizing. This study demonstrated that a novel 4D material can be fabricated from material extraction continuous printing technique with different loadings of poly(ethylene glycol) (PEG) plasticize, achieving localized thermal recovery. The results indicate that a plasticized functional layer is an effective technique for creating next generation 4D materials.
Polymeric blend shape memory polymers (SMPs) can be constructed from two immiscible polymeric matrices. The shape recovery behavior of these composite systems can be easily controlled by varying the ratio of the polymer blends. It has been recently discovered that the functionality of SMPs can be further enhanced with electroactive ability through the use of conductive fillers. However, the fillers may negatively interact with the SMPs and cause a reduction in the elongation at failure thereby diminishing the shape recovery performance. It is proposed that a plasticizer can be utilized to alter the microstructure of the SMPs with conductive fillers. In this study, a new hybrid SMP is developed by combining single‐walled carbon nanotubes (SWCNT) into a poly(lactic acid) (PLA) and thermoplastic polyurethane (TPU) SMP system containing poly(ethylene glycol) (PEG) plasticizer. The incorporation of PEG is able to lower the activation temperature, while enhancing dispersion of SWCNT. The presence of SWCNT can stabilize the SMP system and significantly enhance the shape‐fixing capability after deformation at room temperature conditions. By carefully controlling the formulation, an electroactive SMP can be created by optimizing the amount of SWCNT and PEG plasticizer.
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