High Temperature Shape Memory Polymers Research Articles

4D-printing of high-temperature shape-memory polymers based on polyimide, N,N-dimethylacrylamide and photoactive cross-linkers

Thermally responsive shape memory polyimides (PIs) have attracted significant attention in the high-tech fields like aerospace industry. At the same time creating of materials and approaches to the formation of three-dimensional (3D) shape memory structures containing PIs remains an urgent task. In this work we have developed new photopolymeric compositions (PPCs) based on high-performance readily soluble PI, reactive solvent (N,N-dimethylacrylamide) and photoactive cross-linker (bisphenol A ethoxylate diacrylate (BAEDA) or tris[2-(acryloyloxy)ethyl] isocyanurate (TAI)). The resulting PPCs were used to form 3D-structures using LCD 3D-printing. It has been found that the nature of the cross-linker and post-processing temperature have a significant impact on the thermal and mechanical properties of the materials. The tensile strength has the maximum value after the thermal post-curing at 250°С for 1 h (83.3 ± 7.4 MPa and 60.8 ± 4.8 MPa for PPCs with TAI and BAEDA, respectively). Moreover, 4D-printed PI-containing materials exhibit an excellent shape memory performance at recovery temperatures >150 °C, with shape fixity ratio >99% and shape recovery ratio up to 95.6%.

4D-printing of mechanically durable high-temperature shape memory polymer with good irradiation resistance

4D-printing of mechanically durable high-temperature shape memory polymer with good irradiation resistance

A photosensitive composition based on an aromatic polyamide for LCD 4D printing of shape memory mechanically robust materials

High-temperature shape memory polymers (SMPs) draw growing interest from researchers due to their potential as materials for application in the field of high-temperature smart devices. However, in the majority of cases the processing of high-temperature SMPs is limited by fabrication of two-dimensional films. Here, we have prepared a photosensitive composition based on high-performance heat resistant poly-N,N′-(m-phenylene)isophthalamide (MPA) and photosensitive components (N,N-dimethylacrylamide and bisphenol A ethoxylate diacrylate (BAEDA)). It has been shown by IR spectroscopy, that LCD 3D printing followed by post-curing at 150 °C results in the formation of semi-interpenetrating polymer networks, while thermal processing at a temperature ≥200 °C leads to the formation of fully crosslinked structures due to the interaction of NH groups from MPA and acrylic groups from BAEDA via the Michael addition. The post-curing temperature has a significant effect on the thermal and mechanical properties of materials. Thermal post-curing of 3D printed samples at 250 °C for 1 h results in the fabrication of materials with the highest tensile strength (92.4 ± 6.1 MPa), glass transition temperature (148 °C) and thermal decomposition temperature (above 350 °C). Remarkably, MPA-based materials exhibit an excellent shape memory performance at temperatures >150 °C, with fixity ratio (Rf) of 99.7 % and recovery ratio (Rr) of 99.9 %. Moreover, we showed that the glass transition temperature decreased by no more than 1 % after γ-radiation of 200 Gy. In addition, the material maintains a high storage modulus and good shape memory performance after being irradiated, and thus has a great potential in the field of aerospace structural materials.

Experimental analysis of high-temperature shape memory polymers for deployable structures

Shape memory polymers (SMPs) continue to capture interest in the aerospace industry due to their unique properties. In general, the focus has been on SMPs with low transformation temperatures below 100 °C. However, certain aerospace applications require shape memory polymers with higher transformation temperatures to prevent undesirable actuation upon heat exposure. Moreover, and despite significant work on characterizing mechanical and recovery properties of shape memory polymers, the literature lacks full-field characterization of recovery properties, in particular at elevated temperatures. In this work, a high-temperature thermoset epoxy SMP (Tg ≈ 130 °C), named EPON SMP, is thoroughly investigated. This study provides a comprehensive experimental analysis of the mechanical and shape memory properties of the aforementioned high-temperature epoxy SMP. In addition, this study uses a full-field characterization technique, Digital Image Correlation (DIC), to provide further insight on localization, heterogeneity, and local recovery of shape memory strains. Furthermore, the study evaluates the recovery properties of the EPON SMP at different loading conditions (i.e., bending and tensile) and proposes shape-recovery evaluation methods that can be later implemented on other SMPs. • An epoxy-based shape memory polymer with high switching temperature (Tg ≈ 130 °C) was considered in this work. • The temperature dependant mechanical properties were evaluated across a wide temperature range around Tg. • The shape recovery properties were studied under simple tensile and complex bending conditions. • The heterogeneities in the accumulated and recovery strains were evaluated using full-field deformation measurements. • A deep insight into the local accumulation of programmed, thermal, mechanical, and recovery strains is provided.

High temperature shape memory aliphatic polybenzimidazole

High-temperature shape memory polymers have attracted significant attention in the fields of aerospace and structural components industries. Here, we present a new type of high-performance shape memory polybenzimidazole based on 3,3′-diaminobenzidine and sebacic acid (C8-PBI). Polycondensation in Eaton's reagent allowed obtaining high-strength (97.7 ± 5.1 MPa) C8-PBI-based films with high glass-transition temperature (243 °C) and thermal stability up to 466 °C. The combination of soft aliphatic and hard benzimidazole segments in the macromolecular structure and strong intermolecular hydrogen bonds that serve as physical crosslinking points in the polymer network, thereby imparting shape memory properties to C8-PBI. Shape fixity ratio and shape recovery ratio of C8-PBI reach 99.8% and 97.0%, respectively.

A Thermoset Shape Memory Polymer-Based Syntactic Foam with Flame Retardancy and 3D Printability.

Here we report a thermoset shape memory polymer-based syntactic foam inherently integrated with flame retardancy, good mechanical properties, excellent shape memory effect, and 3D printability. The syntactic foam is fabricated by incorporating a high-temperature shape memory polymer (HTSMP) as the matrix, with 40 vol % hollow glass microspheres (HGM) K20, K15, and K1 as fillers. Compressive behavior, strain-controlled programming followed by free recovery, stress recovery, and flame retardancy of these three syntactic foams were studied. Dynamic mechanical analysis and thermal characterization validate their high glass transition temperature (Tg = ∼250 °C) and excellent thermal stability. Our results suggest that the foam consisting of K20 HGM exhibits high compressive strength (81.8 MPa), high recovery stress (6.8 MPa), and excellent flame retardancy. Furthermore, this syntactic foam was used for three-dimensional (3D) printing by an extruder developed in our lab. Honeycomb, sinusoidal shapes, and free-standing helical spring were printed for demonstration. This high-temperature photopolymer-based syntactic foam integrated with high Tg, flame retardancy, high recovery stress, and 3D printability can be beneficial in different sectors such as aerospace, construction, oil and gas, automotive, and electronic industries.

Bio-based adenine-containing copolyimides with high switching temperatures and high-strain storage

High switching temperature shape memory polymers were developed from copolyimides via a facile random copolymerization strategy.

Design of recyclable, fast-responsive and high temperature shape memory semi-aromatic polyamide

Development of high temperature shape memory polymers with fast response time and recyclable performance is highly desired. In this study, a new semi-aromatic tri-amine (TRIA) containing thioether unit is prepared through the reaction of trifluoro-monomer and p-mercaptoaniline (p-MA). It is conducted to polymerize with 4,4′-thiodibenzoyl chloride (TDC) and different ratios of diamine (both of them contained flexible thioether group) to supply a series of slightly crosslinking semi-aromatic polyamide. It is found that the resultant polymers had excellent thermal properties (Tg, 237.9–245.8 °C, Td, 430.9–436.5 °C) and mechanical properties (tensile strength, 74–100 MPa). Because of the introduction of the large amount of flexible thioether group, the resultant polyamides can be dissolved in some aprotic solvents, and can be processed with solution method to fabricate a series of fast-responsive shape memory film (SMF) with a responsive time of 6–8 s, recovery rate of 98–99.5% after 20 cycles. What's more, the oxidized film can even lift a weight equal to about 2–3 times (vertical direction) and 5–8 times (horizontal direction) of its own weight. Interestingly, unlike other shape memory polymers, these SMF after multiple processes (after bending-recovery cycle at high temperature) can still be processed repeatedly with a solution route, which supplies a novel and recyclable candidate for excellent performance SMP. It is expected to be used in solar cell wingspan actuator to light the satellite weight.

Enhancing recovery speed and anti-wear capability of high-temperature shape memory polymer with modified boron nitride nanoparticles

Glass transition temperature (Tg) is important for the application of shape memory polymers (SMPs), and here shape memory polyimide (SMPI) with high Tg of 363 °C is reported. High shape recovery speed can improve reliability performance of SMP, and the introduction of modified boron nitride (M-BN) nanoparticles into SMPI matrix can enhance the recovery speed obviously. The faster recovery speed is mainly caused by the increase in thermal diffusivity, which enhances from 0.147 mm2 s−1 for primitive SMPI to 0.190 mm2 s−1 for the composite with 10% M-BN (SMPI/10% M-BN). Anti-wear capability is important for service life and performance reliability of materials, and wear rate decreases from 7.5 × 10−9 g N−1 r−1 for primitive SMPI to 0.83 × 10−9 g N−1 r−1 for SMPI/10% M-BN. The enhanced anti-wear capability is ascribed to high hardness, self-lubricating property and thermal conductivity of BN. Wear mechanism is studied, and it evolves from adhesive and fatigue wear for primitive SMPI to slight adhesive wear for SMPI/10% M-BN.

Self-healing high temperature shape memory polymer

Self-healing can improve reliability and extend service lifetime of materials while shape memory polymers (SMPs) have potential in many smart applications, and here self-healing shape memory polyimide (SHSMPI) that can heal damages at high temperature is fabricated for the first time. SHSMPI is synthesized by incorporating fusible thermoplastic polystyrene (PS) at 8% weight content into shape memory polyimide (SMPI) matrix, and it exhibits excellent shape memory effect. SHSMPI can self-heal crack, pierced hole, and cut effectively at heal-temperature of 243 °C. Self-healing mechanism of SHSMPI is discussed, and SMPI matrix produces spatial proximity through shape memory effect while PS acts as healing agent to heal the damages. SHSMPI can produce stored energy of 0.105 J g−1 at the efficiency of 33.1% upon triggering. The designing of SHSMPI at macroscale makes it suitable for mass production, and the self-healing performance will greatly expand application areas of SMPI.

High temperature shape memory polymer with high wear resistance

High temperature shape memory polymers (SMP) have potentials in aerospace and electronic industries, while wear resistance can enhance reliability and service life of products. Here high temperature SMP with high resistance are prepared for the first time by introducing 3-aminopropyltriethoxysilane modified SiO2 nanoparticles (A-SiO2) into new shape memory polyimide (SMPI) matrix. The composite with 10% A-SiO2 exhibits high glass transition temperature (Tg) of 256 °C, complete shape fixity and shape recovery of 100%, and low wear rate of 1.67 × 10−9 g N−1 r−1. In comparison, neat SMPI exhibits poor wear resistance with serious damages after the same dry sliding, and its wear rate is 5.83 × 10−9 g N−1 r−1. The wear mechanism is studied and the wear evolves from adhesive and fatigue wear of neat SMPI to slight adhesive wear of the composite with 10% A-SiO2.

Utilizing Polyhexahydrotriazine (PHT) to Cross-Link Polyimide Oligomers for High-Temperature Shape Memory Polymer

Integrating good strength and toughness, high thermostability, and easy processability into one shape memory polymers is highly desirable yet challenging. Herein, we demonstrate an approach to fabr...

High-Temperature Shape Memory Behavior of Semicrystalline Polyamide Thermosets.

We have explored semicrystalline poly(decamethylene terephthalamide) (PA 10T) based thermosets as single-component high-temperature (>200 °C) shape memory polymers (SMPs). The PA 10T thermosets were prepared from reactive thermoplastic precursors. Reactive phenylethynyl (PE) functionalities were either attached at the chain termini or placed as side groups along the polymer main chain. The shape fixation and recovery performance of the thermoset films were investigated using a rheometer in torsion mode. By controlling the Mn of the reactive oligomers, or the PE concentration of the PE side-group functionalized copolyamides, we were able to design dual-shape memory PA 10T thermosets with a broad recovery temperature range of 227–285 °C. The thermosets based on the 1000 g mol–1 reactive PE precursor and the copolyamide with 15 mol % PE side groups show the highest fixation rate (99%) and recovery rate (≥90%). High temperature triple-shape memory behavior can be achieved as well when we use the melt transition (Tm ≥ 200 °C) and the glass transition (Tg = ∼125 °C) as the two switches. The recovery rate of the two recovery steps are highly dependent on the crystallinity of the thermosets and vary within a wide range of 74%–139% and 40–82% for the two steps, respectively. Reversible shape memory events could also be demonstrated when we perform a forward and backward deformation in a triple shape memory cycle. We also studied the angular recovery velocity as a function of temperature, which provides a thermokinematic picture of the shape recovery process and helps to program for desired shape memory behavior.

Crosslinking of Semiaromatic Polyesters toward High-Temperature Shape Memory Polymers with Full Recovery.

In this work, high-temperature shape memory polymers are realized by end-group crosslinking of the semiaromatic polyesters polyethylene terephthalate as well as polybutylene terephthalate. Both networks exhibit trigger temperatures distinctly higher than 200 °C and excellent shape memory properties such as storable strains of 200%, full fixity of the applied strain in the temporary shape, and full recovery of the permanent shape.

High-Temperature Shape Memory Behavior of Novel All-Aromatic (AB)n-Multiblock Copoly(ester imide)s

Thermoplastic and thermoset all-aromatic liquid crystal (LC) (AB)n-multiblock copoly(ester imide)s based on N-(3′-hydroxyphenyl)trimellitimide (IM), 4-hydroxybenzoic acid (HBA), and 6-hydroxy-2-naphthoic acid (HNA) were investigated as single-component high-temperature (≥250 °C) shape memory polymers (SMPs). A high Tg (∼200 °C) HBA/IM block embedded in a low Tg (∼120 °C) HBA/HNA matrix creates a stable rubbery plateau that can be extended to ∼240 °C by cross-linking. The shape fixation (Rf) and shape recovery efficiency (Rr) of the thermoplastic and thermoset films were investigated using a rheometer in torsion mode. Thermoplastic LC copoly(ester imide) films showed excellent dual SM behavior (Rf and Rr ∼ 100%) at 170 °C. After cross-linking the thermoplastic films a single component system as obtained that exhibited high-temperature (≥250 °C) tunable triple SM and one-way reversible SM behavior.

Facile control of high temperature shape memory polymers

ABSTRACTGlass transition temperature (Tg) is crucial in determining application areas of high temperature shape memory polymers (SMPs), but some Tgs are difficult or uneconomic to be obtained. Here we introduce a facile way to prepare high temperature SMPs with controllable Tgs from 183 to 230 °C by copolymerization of polyimides, and relationships between Tgs and diamine components of the shape memory copolyimides agree with Fox Equation. These copolyimides can fix temporary shape and return to original shape nicely, and the possible mechanisms of their high shape fixity and shape recovery are analyzed on the basis of thermomechanical properties and molecular structures. The copolymerization of shape memory polyimides has offered an effective way to obtain high temperature SMPs with desired properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44902.

High temperature shape memory polyimide ionomer

ABSTRACTIn this work, a high temperature shape memory polymer based on polyimide (PI) ionomer is prepared by introducing ionic crosslinked interaction. The ionic crosslinked points are introduced to polymer networks through the reaction between polyamic acid and calcium hydroxide before thermal imidization. The crosslinked reaction, microtopography, mechanical, thermal, and shape memory properties of PI ionomers are systematically investigated. The results show the introduction of ionic crosslinked interaction could enhance the glass transition temperature, mechanical, and shape recovery performance of ODA‐ODPA, a PI. The prepared ionomers exhibit good high temperature shape memory properties around 270 °C. The shape fixation and shape recovery ratio are over 99% and 90%, respectively. This method provided a new sight of preparing high temperature shape memory polymer, which could be used in severe conditions, like aerospace industry field. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43630.

Optically transparent high temperature shape memory polymers.

Optically transparent shape memory polymers (SMPs) have potential in advanced optoelectronic and other common shape memory applications, and here optically transparent shape memory polyimide is reported for the first time. The polyimide possesses a glass transition temperature (Tg) of 171 °C, higher than the Tg of other transparent SMPs reported, and the influence of molecular structure on Tg is discussed. The 120 μm thick polyimide film exhibits transmittance higher than 81% in 450-800 nm, and the possible mechanism of its high transparency is analyzed, which will benefit further research on other transparent high temperature SMPs. The transparent polyimide showed excellent thermomechanical properties and shape memory performances, and retained high optical transparency after many shape memory cycles.

Shape-Memory Polymers with Adjustable High Glass Transition Temperatures

Shape-memory polymers (SMPs) are synthesized with adjustable glass transition temperature (Tg) ranging from 299 to 322 °C, higher than those reported previously. The polyimide containing thermal stable but flexible linkages within the backbone act as reversible phase, and high molecular weight (Mn) is necessary to form physical cross-links as fixed phase of thermoplastic shape-memory polyimide. The critical Mn is 21.3 kg/mol, and the relationship between Mn and Tg is explored. Thermoset polyimides show higher storage modulus and better shape-memory effects than thermoplastic counterparts due to covalent cross-linking, and the effective cross-link density with the influence on their physical properties is studied. The mechanism of high-temperature shape-memory effect of polyimide on the basis of chain flexibility, molecular weight, and cross-link density is proposed, which will benefit further research on high-temperature SMPs.

Synthesis, structure and tunable shape memory properties of polytriazoles: dual-trigger temperature and repeatable shape recovery

Click assisted synthesis resulted in low, high and dual trigger temperature shape memory polymers. They exhibit high shape recovery and repeatability in shape memory properties.