Two-Way and Multiple-Way Shape Memory Polymers for Soft Robotics: An Overview

Scalet, Giulia

doi:10.3390/act9010010

Cited by 152 publications

(125 citation statements)

References 291 publications

(395 reference statements)

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“…The material was prepared by stoichiometric reaction of an acrylate-capped, linear poly(caprolactone) prepolymer with a tetra-functional thiol. 5,13 The resulting network has a well-defined architecture comprising of a cross-link functionality of four, with a theoretical cross-link density of 0.12 mol cm −3 and a chain length between cross-links of 4.5 kg mol −1 .…”

Section: Resultsmentioning

confidence: 99%

“…2,3 Cross-linked semicrystalline polymers combine chain crystallization and entropy elasticity, forming thermosets or elastomers that are important to the burgeoning topics of artificial muscles 4 and soft robotics. 5,6 While crystallization of linear polymers has been extensively studied, the topic of chain crystallization within cross-linked networks has received far less attention. The presence of cross-links increases the rate of crystallization at early stages because of the reduced configurational entropy of network strands compared to free polymer chains.…”

Section: Introductionmentioning

confidence: 99%

“…17 We have previously developed and studied poly(caprolactone) shape-memory elastomers that, upon crystallization, can store large amounts of recoverable elastic strain energy. 5,13,[18][19][20] The network's shape-memory properties are attributed to the backbone's high enthalpy of crystallization as well as the network's uniform cross-link functionality and monodisperse strand molecular weight between cross-links. Crystallization of the strained network is the key to shapefixing, however, the relationship between crystallization kinetics and tensile stress reduction during a shape-memory cycle is unclear, especially at strains beneath 100%.…”

Section: Introductionmentioning

confidence: 99%

“…By controlling the magnitude and direction of crystallization, polymer morphology can be tuned for applications including packaging materials 1 and organic semiconductors 2,3 . Cross‐linked semicrystalline polymers combine chain crystallization and entropy elasticity, forming thermosets or elastomers that are important to the burgeoning topics of artificial muscles 4 and soft robotics 5,6 …”

Section: Introductionmentioning

confidence: 99%

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On the nature of s hape‐fixing in semicrystalline shape‐memory networks

Yang

Anthamatten

2020

Polymer Crystallization

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Crystallization of polymer strands within elastically strained cross-linked networks can lower tension, leading to stabilization of mechanically deformed states. This process, referred to as shape-fixing, is sensitive to thermomechanical path because both mechanical strain and thermal undercooling affect crystallization kinetics. In the present study, shape-fixing of a well-defined poly(caprolactone) network is examined at fixed strains ranging from 25 to 100%. Isothermal crystallization kinetics were studied using wide angle X-ray scattering while simultaneously monitoring tension loss. Plots of tensile stress versus degree of crystallization show that significant stress reduction occurs at only a few percent crystallinity (<0.05). The development of Young's modulus under identical conditions was evaluated, and results are combined to estimate the shape-fixity at different crystallization conditions and times. This study contributes to understanding the interrelationship between crystallization, stress reduction, and material stiffening to support further development of semicrystalline shape-memory networks.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On the nature of s hape‐fixing in semicrystalline shape‐memory networks

Yang

Anthamatten

2020

Polymer Crystallization

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“…Mechanistically, directional crystallization and melting of the switching segment enables the actuation of programmed SMPs, same as entropy elasticity, as well-known from actuation experiments under a constant external load [ 24 , 28 , 29 ]. Against this background, recent studies focused on the development of concepts to introduce bidirectional actuation to novel polymeric systems [ 30 , 31 ] and addressed several technological fields like biomedical applications [ 32 ], soft robotics [ 33 ] and 4D printing [ 34 ].…”

Section: Introductionmentioning

confidence: 99%

Shape Memory Polymer Foam with Programmable Apertures

et al. 2020

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In this work, a novel type of polyester urethane urea (PEUU) foam is introduced. The foam was produced by reactive foaming using a mixture of poly(1,10–decamethylene adipate) diol and poly(1,4–butylene adipate) diol, 4,4′-diphenylmethane diisocyanate, 1,4–butanediol, diethanolamine and water as blowing agent. As determined by differential scanning calorimetry, the melting of the ester-based phases occurred at temperatures in between 25 °C and 61 °C, while the crystallization transition spread from 48 °C to 20 °C. The mechanical properties of the foam were simulated with the hyperplastic models Neo-Hookean and Ogden, whereby the latter showed a better agreement with the experimental data as evidenced by a Pearson correlation coefficient R² above 0.99. Once thermomechanically treated, the foam exhibited a maximum actuation of 13.7% in heating-cooling cycles under a constant external load. In turn, thermal cycling under load-free conditions resulted in an actuation of more than 10%. Good thermal insulation properties were demonstrated by thermal conductivities of 0.039 W·(m·K)−1 in the pristine state and 0.052 W·(m·K)−1 in a state after compression by 50%, respectively. Finally, three demonstrators were developed, which closed an aperture or opened it again simply by changing the temperature. The self-sufficient material behavior is particularly promising in the construction industry, where programmable air slots offer the prospect of a dynamic insulation system for an adaptive building envelope.

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