Sequential and selective shape memory by remote electrical control

Stimuli-responsive materials are smart materials capable to adjust their properties (e.g. shape and size) in response to an external or internal stimulus including temperature, light, magnetic field, mechanical stress, and pH. Shape memory polymers (SMPs) are attractive class of stimuli-responsive, programmable smart materials with shape-memory behavior: memorize their original, permanent shape; deform and fix into a secondary, temporary shape; and recover the original, permanent shape upon applying an external stimulus. In recent years, advancing intelligent supercapacitors and batteries have attracted significant attention whereas stimuli-responsive materials were integrated to induce stimuli-responsive properties to introduce new properties or mitigate some of the existing issues such as thermal management, mitigating volume change-induced performance degradation, recovery from a mechanical deformation, self-healing, electrochromism. Indeed, integrating energy storage technologies with a variety of stimuli are a fascinating method to realize smart functions [1-3].Herein, we aim to develop a heat-responsive battery capable of mitigating the impact of incidental mechanical abuse or deformation. To achieve this, a shape-memory solid polymer electrolyte (SMSPE) is engineered and incorporated into lithium metal batteries (LMBs). In response to an external heat, the engineered SMSPEs recover their original shape and size from mechanical deformations such as bending and elongation. This study opens-up a promising approach for engineering intelligent batteries responsive to unfavorable internal or external stimuluses, with potential to have a broad impact on other energy storage technologies in different sizes and shapes. The Li|SPSPEs|LFP full cell batteries display a long-term cycle life with a discharge capacity of ~120 mAh g−1 at C/10 in ambient temperature with around 90% capacity retention after 100 cycles. Moreover, the Li|SPSPEs|Li symmetrical cells exhibit a long-term stability with a low voltage polarization at a current density of 0.05 mAh cm−2 for up to 1000 cycles.Overall, the proposed approach shows a promising design principle which can open up new possibilities for the next-generation batteries and their safe operation. With vast range of available SMPs with tunable chemistries, transition temperatures, and high shape-memory performance, and opens up new frameworks to address a variety of detrimental, unresolved issues such as thermal runaway, with potential expansion to the other energy storage technologies.

A finite deformation thermomechanical constitutive model for triple shape polymeric composites based on dual thermal transitions

Polycaprolactone-based shape memory foams as self-fitting vaginal stents

Four-dimensional design and programming of shape-memory magnetic helical micromachines

Polymers can demonstrate shape memory (SM) effects by being temporarily fixed in a nonequilibrium shape and then recover their permanent shape when exposed to heat, light, or other external stimuli. Many previously developed shape memory polymers (SMPs) use the dramatic molecular chain mobility change around the glass transition temperature Tg to realize the SM effect. In these materials, the temporary shape cannot be repeated unless it is reprogramed, and therefore the SM effect is one way. Recently, a semicrystalline SMP, which can demonstrate both one- and two-way SM effects, was developed by one of our groups (Chung, T., Rorno-Uribe, A., and Mather, P. T., 2008, “Two-Way Reversible Shape Memory in a Semicrystalline Network,” Macromolecules, 41(1), pp. 184–192). The main mechanism of the observed SM effects is due to stretch induced crystallization. This paper develops a one-dimensional constitutive model to describe the SM effect due to stretch induced crystallization. The model accurately describes the complex thermomechanical SM effect and can be used for the future development of three-dimensional constitutive models.

Auto‐programmable shape memory polymers (AP‐SMPs) can deform automatically without external manipulation, exhibiting either a free‐standing temporary shape or a permanent shape. The unique shape memory behaviors derive mainly from control by two factors, water and temperature. However, the control mechanism is unknown. This study analyzes and demonstrates the dual‐control mechanism of water and temperature in the three shape‐changing processes of AP‐SMPs. First, the AP‐SMP is immersed in warm water (50 °C). Asymmetric swelling of bilayer films provides the driving force for the shape auto‐programming of the AP‐SMP. The solvent effect of water reduces the glass transition temperature (Tg) of the AP‐SMP, which becomes lower than the medium temperature in warm water. AP‐SMP can be programmed automatically. Then, the AP‐SMP is removed from water and placed in air at room temperature. The Tg value of the matrix film increases notably in air and exceeds the medium temperature. The temporary shape of the AP‐SMP can thus be fixed. Finally, the AP‐SMP can quickly return to its permanent shape when the medium temperature exceeds the matrix film Tg in air. The dual control shape memory mechanism provides insights into the design and development of AP‐SMPs.

Summary While there have been various lost circulation materials (LCMs) available in the market for treating fractures during the drilling of oil and gas wells, there is still a demand for a technology to seal large fractures. Considering limitations on the size of the particles that can be circulated through the drilling equipment, especially the bottomhole assembly, simply enlarging conventional LCM particles becomes ineffective for sealing large vugs and fractures. In this study, we use shape memory polymers (SMPs) to prepare programmed LCMs with various temporary shapes, which can transform to their permanent shapes with much larger dimensions as compared to their temporary shapes. A series of steps for thermomechanical programming of SMP is designed to trigger their expansion at the reservoir temperature. The dimensions of the programmed shapes can be an order of magnitude smaller than the ones for the original shapes, making their transport through the flowlines feasible, and bridging wide-opened fractures possible. The basic idea is that, after recovery, the SMP-based LCMs form an entangled network across a large width of fracture, and SMP particles recovered within the network, filling in the pores to form an effective sealing. We seek the capability of entangled ladders and interwoven fibers in forming a network across the fracture. A permeability plugging apparatus (PPA) is used to examine the efficiency of developed LCMs. The technique of 3D X-ray computed tomography (CT) is used to visualize the internal structure of formed plugs, enabling us to understand the mechanisms of bridging, plugging, and sealing.

Robust POSS-PEG networks. Nanostructure, viscoelasticity and shape memory behavior

Shape-memory polymers (SMPs) are a widely-used class of smart materials capable of recovering a pre-defined permanent shape from a deformed
temporary configuration when exposed to external stimuli. A crucial step in this behavior is shape-programming, which enables the fixation of the temporary shape. Simulating this step through numerical models can be both computationally expensive and prone to inaccuracies. This is primarily due to the difficulty in identifying the appropriate set of boundary conditions needed to deform the structure into the desired temporary shape, often requiring multiple trial-and-error iterations. This paper proposes a computational approach that overcomes such a difficulty and enables an
accurate simulation of the shape-memory cycle. The core innovation lies in the use of mesh morphing techniques to directly impose the temporary shape, thereby eliminating the need to determine complex mechanical loading conditions during the programming step. This method is integrated within a finite element framework and applied to a representative 4D printed structure. Numerical results confirm the robustness and accuracy of the approach, which replicates the recovery behavior of the SMP while significantly reducing computational effort in finding and applying the right set of boundary conditions. This work provides a valuable tool for the design of SMP systems.

Shape memory polymers (SMPs) have the capacity of memorizing a temporary shape and recovering their initial shape in response to various external stimuli. As one of promising class of intelligent materials, it has attracted great attention because of its potential applications in many areas, such as biomaterials and biotechnology, automotive industry, and aerospace field. Aliphatic polymers play an important role in the molecular design of SMPs owing to its excellent biodegradability and biocompatibility, and suitable thermal transition temperature range. This review focuses on the recent progress of shape memory polymers based on the aliphatic polyesters such as poly(lactic acid) (PLA), poly ( p -dioxanone) (PPDO), poly(butylene succinate) (PBS), poly( ω -pentadecalactone) (PPDL) and poly( ɛ -caprolactone) (PCL) and so on. From the view of architecture design, different systems are classified by block copolymers, crosslinking networks and interpenetrating networks. The influence of architectural features on the shape memory behaviors is also discussed. The block copolymers have been identified a typical mature system in design of dual-shape material, and the crystalline aliphatic polyesters can be served as the netpiont or the molecular switch in a SMP, depending on its transition temperature range among the binary systems. The thermoplastic feature of block copolymers endows an easy processibility. The various architectures of crosslinking network meet the increasing demand of SMPs design. Constructing network with crystallizable polyester segment such as PCL may achieve SMPs in one-way and two-way mode, and the stress-free two-way mode can also be realized by an elaborate architecture with pre-programed treatment. Embedding two segments in one network may achieve a triple-shape memory effect, meanwhile, incorporating two segments in an interpenetrating polymer network may result in a triple-shape material with improved performance. Recently, the SMPs based on dynamic networks become the new trend, which may combine the self-healing with shape memory effect in one system, and both dynamic covalent bond and non-covalent bond have been concerned. In order to fulfill the increasing requirement of application, the SMPs with multi-shape memory effect, multi-responsibility and multi-functionality are highly expected.

Shape memory polymers (SMP) belong to the class of stimuli-responsive materials and have generated significant research interest. Their capability to retain an imposed, temporary shape and to recover the initial, permanent shape upon exposure to an external stimulus depends on the “functional determinants”, which in simplistic terms, can be divided into structural/morphological and processing/environmental factors. The primary aim of the first part of this review is to reflect the knowledge about these fundamental relationships. In a next step, recent advances in shape memory polymer composites are summarized. In contrast to earlier reviews, studies on the impairment of shape memory properties through various factors, such as aging, compression and hibernation, lubricants, UV light and thermo-mechanical cycling, are extensively reviewed. Apart from summarizing the state-of-the-art in SMP research, recent progress is commented.

Shape memory polymers (SMPs) have attracted significant research interest in robotic applications due to their tunable thermomechanical properties and ability to change shape and recover their original form upon exposure to external stimuli, primarily temperature. One‐way SMPs require reprogramming for each cycle, whereas two‐way SMPs (2W‐SMP) intrinsically exhibit shape memory behavior without additional programming. This study develops a cross‐linked polycaprolactone/dicumyl peroxide (PCL/DCP) based 2W‐SMP composite. The thermomechanical and thermal properties are characterized using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). To create a freestanding 2W‐SMP capable of shape change and recovery solely through temperature variations, without relying on external loads for actuation, the SMP is embedded in a low‐stiffness elastomeric matrix. The resulting composite material exhibits an intrinsic two‐way shape memory effect, enabling reversible shape transformations during heating and cooling cycles. The one‐way and two‐way shape memory behaviors are systematically investigated using DMA. The one‐way shape memory effect demonstrated exceptional shape fixity and strain recovery values of 96% and 96.8%, respectively, confirming the material's ability to fix a temporary shape and recover its permanent form upon external stimulus. The practical potential of the 2W‐SMP is demonstrated by testing it as a gripper device, which exhibited repeatable opening and closing responses during heating and cooling cycles, illustrating its reversible shape transformations and durability over multiple actuation cycles.

Shape-memory polymers can be deformed and fixed in a temporary shape. They only recover their original, permanent shape when exposed to an appropriate stimulus.1 Therefore, shape-memory polymers are stimuli-sensitive materials and belong to the group of smart polymers. The shape change from the temp...

Shape memory polymers (SMPs) are known as smart polymer materials which can be deformed and fixed in a temporary shape and can recover to its original shape upon an external stimulus such as temperature which is the main stimulus for general SMPs. In this research, a renewable natural resource based on vanillin-furfurylamine benzoxazine (V-fa) and eugenol-furfurylamine benzoxazine (E-fa) are developed to substitute the use of petroleum based polybenzoxazine. The as-synthesized V-fa and E-fa show the degradation temperature at 5% weight loss to be as high as 343 and 310?C and char content to be 66 and 54%, respectively. Effects of epoxidized castor oil (ECO) content at 10-50wt% filled in bio-based polybenzoxazine on thermal, mechanical and shape memory properties of bio-based polybenzoxazine/bio-based epoxy SMPs are thoroughly investigated. The results reveal that with increase in ECO content, storage modulus and glass transition temperature of V-fa/ECO and E-fa/ECO copolymer decreased providing the values of 2.27 GPa to 1.60 GPa and 158?C to 100?C, respectively for V-fa/ECO copolymer and 1.53 GPa to 1.16 GPa and 40?C to -17?C, respectively for E-fa/ECO copolymer. In shape memory properties, the V-fa/ECO SMPs show shape fixity values at a room temperature of 86-94% and the values decrease with increasing ECO content, while the temporary shape at room temperature of the E-fa/ECO SMPs cannot fixed. Additionally, the V-fa/ECO SMPs provided the shape recovery values at Tg+20?C of 81-96% and the values increase with increasing of ECO content. Furthermore, it was observed that the V-fa/ECO copolymer having 40wt% of V-fa content exhibits good balance properties between shape memory performance and thermomechanical properties and it can be greatly recovered to the original shape for 5 cycles.

ABSTRACTShape memory polymers (SMP) can be deformed to a stable, temporary shape and recovered to their original shape by applying a stimulus. These networks rely on the presence of two types of net points to establish their permanent and temporary shapes. Classical strategies to stabilize temporary shapes rely on cooling below Tg/Tm where macromolecules become pinned in a stressed state. Recovery of the SMP usually involves heating to above the transition temperature where the permanent shape is remembered. Employing reversible binding groups (RBGs) in SMPs has emerged as an alternative strategy for stabilizing temporary shapes or imparting recyclability of the permanent shape. The use of dynamic chemistry often engenders additional functionality such as intrinsic self‐healing characteristics or alternative shape recovery triggering strategies. SMPs bearing both supramolecular and covalent RBGs will be reviewed with an emphasis on hydrogen bonding, ionic interactions, metal–ligand coordination, and dynamic covalent exchange and addition reactions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1340–1364