Dynamical Mechanical Analysis and Micromechanics Simulations of Spin-Crossover@Polymer Particulate Composites: Toward Soft Actuator Devices

Recently, soft actuators have been increasingly considered for applications in various technological fields, such as soft robotics, artificial muscles, wearable technologies, medical devices, and smart textiles. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] These devices are inspired by human muscles, which are agile, reconfigurable, physically adaptive, lightweight, and multifunctional. The development of new stimuli-responsive materials, including the optimization of their properties and their integration into actuator systems, plays a central role in this endeavor. [15][16][17][18][19][20][21][22] Among the different kinds of functional materials used in soft actuators, the most studied are electroactive polymers, gels, piezopolymers, shape memory polymers, and soft magnetic composites. [23][24][25][26][27][28][29][30][31][32] Each material has pros and cons and none of them can fulfill the numerous and sometimes even disparate technological requirements (e.g., mechanical compliance, high work density, efficiency, reliability, speed, accuracy, scalability, controllability). Depending on the physical mechanisms underlying the actuation, they can be operated by different stimuli, including electric fields, temperature, pressure, magnetic field, humidity, or light irradiation, but electrical current or tension are the most relevant due to their ease of use. [33,34] Molecular spin-crossover (SCO) complexes of iron(II) ions exhibiting substantial volume change upon stimuli-induced switching between their high-spin (HS) and low-spin (LS) states appear promising candidates in this context. [35,36] Indeed, the SCO phenomenon is not only accompanied by a large spontaneous strain [37] (up to 22 vol% [38] ) and associated large strain energy densities (up to a few tens of J cm À3[36] ), but provides also unique multifunctionality (concomitant change of mechanical, optical, caloric, and magnetic properties), multiresponsiveness (to temperature, pressure, light, and chemical stimuli), and large compositional and morphological versatility. [39][40][41] To enhance their processability, SCO compounds are frequently embedded into polymer matrices to form particulate composites. [42,43] Based on this approach, conventional bending bimorph actuators were recently fabricated in our team using SCO@polymer composites by means of solvent casting, [44] spray coating, [45] blade casting [46,47] and 3D printing. [48] Since nearly all SCO@polymer composite materials are electrically insulating, in practice, they are used in combination with a conducting material to achieve electrothermal actuation. [44,46]

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“…As shown in Table 1, the computed values of

ε_{comp}^{SCO}

are in reasonably good agreement with the transformation strain assessed using thermal expansion measurements,

ε_{exp}^{SCO}

, which are reported in ref. [59]. This result provides confidence for our numerical approach.…”

Section: Resultssupporting

confidence: 73%

Soft Actuators Based on Spin‐Crossover Particles Embedded in Thermoplastic Polyurethane

Zan

Piedrahita‐Bello

Alavi

et al. 2023

Advanced Intelligent Systems

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“…Recently, we have investigated the mechanical properties of composite polymers based on spin crossover materials using both tensile test and Dynamical Mechanical Analysis (DMA). , Both techniques were also used to characterize the TPU and SCO@TPU composite polymers, and the pertinent mechanical parameters are gathered in Table . According to the result of the DMA for both the pure TPU polymer and the SCO@TPU composite, the glass transition temperature, which corresponds to the maximum value of tan Delta, is around 30 °C (Figure S5).…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Self-Healing Composite Polymers Based on Spin Crossover Materials for Multidirectional Preprogrammed Actuation

Enriquez-Cabrera,

Yang,

Alavi

et al. 2024

ACS Appl. Polym. Mater.

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A dimethylglyoxime−urethane-based self-healing polyurethane elastomer with a distinct two-phase morphology combining high extensibility (>500%), a high Young's modulus (40 MPa), and a high healing efficiency based on dual dynamic bonds at room temperature was obtained. Such a polymer was used for fabrication by blade casting and/or self-healing bilayer actuators incorporating a composite layer formed by anisometric spin crossover particles presenting anisotropic volume change and showing large transformation strain above room temperature. Thus, the self-healing polymer, generally used for damage reparation, is also useful for the shaping of the bilayer composite actuator as well as to guide its preprogrammed motion.

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Constructing Alkyl Chain Modified Fe^II Spin Crossover Complexes through Complementary Pair Strategy

Peng,

Lu,

Shang

et al. 2024

Eur J Inorg Chem

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Four alkyl chains and cyclohexane modified FeII complexes [Fe(Ln)(L’)](ClO4)2⋅solv (n=1, 2, 3, 4) were synthesized and characterized. X‐ray diffraction study showed that these complexes were constituted by asymmetric mononuclear FeII entities, incorporating alkyl‐chain‐modified bppCOOH (2,6‐bis(1H‐pyrazol‐1‐yl)isonicotinic acid) ligands and 6,6’’‐2,6‐dimethoxyphenyl‐substituted terpy ligand (L’). Magnetic susceptibility measurements revealed that complexes 1, 2, and 3 were in the high spin state across the measured temperature range, whereas complex 4 displayed an incomplete spin crossover phenomenon, with a transition temperature (T1/2) at 240 K. Investigations into variable‐temperature structure and magneto‐structural correlations revealed that the integration of alkyl‐chain‐modified bipyridyl units fostered the π⋅⋅⋅π intra‐ and intermolecular interactions, contributing to distinct crystal stacking and spatial configurations in complex 4 when compared to its counterparts. These findings underscore the pivotal influence of intramolecular interactions on the FeII spin states and highlight the significance of designing flexible ligands for modulating spin‐crossover characteristics.

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Dynamical Mechanical Analysis and Micromechanics Simulations of Spin-Crossover@Polymer Particulate Composites: Toward Soft Actuator Devices

Cited by 6 publications

References 74 publications

Soft Actuators Based on Spin‐Crossover Particles Embedded in Thermoplastic Polyurethane

Soft Actuators Based on Spin‐Crossover Particles Embedded in Thermoplastic Polyurethane

Self-Healing Composite Polymers Based on Spin Crossover Materials for Multidirectional Preprogrammed Actuation

Constructing Alkyl Chain Modified Fe^II Spin Crossover Complexes through Complementary Pair Strategy

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Dynamical Mechanical Analysis and Micromechanics Simulations of Spin-Crossover@Polymer Particulate Composites: Toward Soft Actuator Devices

Cited by 6 publications

References 74 publications

Soft Actuators Based on Spin‐Crossover Particles Embedded in Thermoplastic Polyurethane

Soft Actuators Based on Spin‐Crossover Particles Embedded in Thermoplastic Polyurethane

Self-Healing Composite Polymers Based on Spin Crossover Materials for Multidirectional Preprogrammed Actuation

Constructing Alkyl Chain Modified FeII Spin Crossover Complexes through Complementary Pair Strategy

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Constructing Alkyl Chain Modified Fe^II Spin Crossover Complexes through Complementary Pair Strategy