The shape-memory effect in ionic elastomers: fixation through ionic interactions

Jiménez, Antonio González; Malmierca, M. A.; Bernal-Ortega, Pilar; Posadas, Paula; Pérez-Aparicio, Roberto; Marcos‐Fernández, Ángel; Mather, Patrick T.; Valentín, Juan López

doi:10.1039/c7sm00104e

Cited by 27 publications

(22 citation statements)

References 58 publications

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“…In addition to utilizing chemical crosslinking as the permanent network in SMPs, physical crosslinking with sufficiently long relaxation time can also be used as the fixed permanent phase, such as the ionic aggregates in ionomers . Strong ionic interactions in ionomers generally impose strong restriction on the segmental dynamics of surrounding polymer chains, therefore, those ionic crosslinking can act as permanent anchor points if deformation temperature is below the ionic transition temperature . In general, the incorporation of ions into the SMPs is aimed to act as a crosslinking anchor of the network, while it is rarely reported to incorporate ions into vitrimers for achieving dual cross‐linked network with triple‐shape‐memory effects.…”

Section: Methodsmentioning

confidence: 99%

Dual Cross‐linked Vinyl Vitrimer with Efficient Self‐Catalysis Achieving Triple‐Shape‐Memory Properties

Niu

Wang

Kui

et al. 2019

Macromol. Rapid Commun.

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As an emerging class of dynamic cross‐linked network, vitrimers have attracted much attention due to the combination of mechanical advantages of thermosets and recyclability of thermoplastics at an elevated temperature. In particular, most vitrimers with multi‐shape memory properties usually involve more than one thermal transition or molecular switch, which might pose a challenge for facile sample fabrication and potentially limits their applications. In pursuit of a more universal and simple route, utilizing commercially available and inexpensive reagents to prepare shape‐memory vitrimers with dual cross‐linked network from vinyl monomer‐derived prepolymers is reported here. Copolymerization of desired vinyl monomers gives prepolymers containing carboxyl and zinc carboxylate groups, which are later converted into vitrimers in a single step by post‐curing with diglycidylether of bisphenol A. The Zn2+ ions can not only act as physical crosslinking points through ionic coordination interactions, thus providing the triple‐shape‐memory properties, but also play the role of catalyst to activate transesterification in the dynamic covalent network. This new self‐catalyzed vitrimer has excellent transesterification efficiency, triple‐shape‐memory properties, and can be sufficiently healed and reprocessed at an elevated temperature. The proposed molecular design of self‐catalyzed materials opens a new avenue toward commercially relevant fabrication of high‐performance vitrimers with multiple shape‐memory properties.

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Section: Methodsmentioning

confidence: 99%

Dual Cross‐linked Vinyl Vitrimer with Efficient Self‐Catalysis Achieving Triple‐Shape‐Memory Properties

Niu

Wang

Kui

et al. 2019

Macromol. Rapid Commun.

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“…To observe the reaction of the carboxylic groups with MgO, FTIR-ATR was used. As studied in previous works, the formation of covalent crosslinks (by adding DCP to the system) does not influence the IR band of the carboxylic groups of the rubber matrix [ 32 , 68 ]. Therefore, it can be used to study the reaction of these moieties with metal oxide.…”

Section: Resultsmentioning

confidence: 95%

“…According to the experimental procedure described in [ 32 ], shape-memory tests with four memory cycles were carried out for each sample with an increase of 50% in strain for the temporary shape. Figure 6 shows the complete characterization of one of the samples (containing 15 phr CNT).…”

Section: Resultsmentioning

confidence: 99%

“…All these materials presented rigid behavior at room temperature, as their shape-memory fixing mechanism was based on crystallization. To solve this, in a previous study conducted by our group, ionic elastomers based on a carboxylated nitrile rubber (XNBR) were obtained, where ionic transition was the switching mechanism of the shape-memory effect and elastomeric behavior was preserved in all ranges of temperature [ 32 ]. These materials possess strong, physically crosslinked networks featuring the phase separation of ion-rich domains, where trapped polymer chains around ionic associations act as reinforcing points [ 33 ].…”

Section: Introductionmentioning

confidence: 99%

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Shape-Memory Composites Based on Ionic Elastomers

et al. 2022

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Shape-memory polymers tend to present rigid behavior at ambient temperature, being unable to deform in this state. To obtain soft shape-memory elastomers, composites based on a commercial rubber crosslinked by both ionic and covalent bonds were developed, as these materials do not lose their elastomeric behavior below their transition (or activation) temperature (using ionic transition for such a purpose). The introduction of fillers, such as carbon black and multiwalled carbon nanotubes (MWCNTs), was studied and compared with the unfilled matrix. By adding contents above 10 phr of MWCNT, shape-memory properties were enhanced by 10%, achieving fixing and recovery ratios above 90% and a faster response. Moreover, by adding these fillers, the conductivity of the materials increased from ~10−11 to ~10−4 S·cm−1, allowing the possibility to activate the shape-memory effect with an electric current, based on the heating of the material by the Joule effect, achieving a fast and clean stimulus requiring only a current source of 50 V.

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“…[10] The fixed phase needs physical (e.g., microphase separation) [11] or chemical [12,13] cross-links to produce the netpoints, so as to determine the permanent shape. [14] And the reversible phase is responsible for the temporary shape fixation by crystallization/melting transition, [13] glass transition, [12] dynamic covalent bonding, [15] hydrogen bonding, [16] metal-ligand coordination, [17] etc. SMPs DOI: 10.1002/mame.202100370 possess the advantages of high elastic deformation, low cost, low density, and potential biocompatibility and biodegradability.…”

Section: Introductionmentioning

confidence: 99%

Bio‐Based, Self‐CrosslinkableEucommia ulmoidesGum/Silica Hybrids with Body Temperature Triggering Shape Memory Capability

Jia

et al. 2021

Macro Materials & Eng

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At present, the synthesis of body temperature triggering shape memory polymers usually requires elaborate structural design, which limits their wide application. Herein, starting from bio-based Eucommia ulmoides gum (EUG), a series of EUG/silica hybrids (ESHs) are prepared through a facile one-pot process, in which EUG is epoxied and then self-crosslinked with SiO 2 by epoxy ring-open reaction. Varying the amount of H 2 O 2 , the shape memory transition temperature (T trans ) of ESHs is adjusted to 47.4-36.6 °C, which is close to human body temperature (37 °C). Among them, ESH-17 exhibited the best body temperature triggering shape memory ability (T trans = 36.6 °C), which can restore the permanent shape within 60 s at 37 °C with a shape fixity ratio of 99% and shape recovery ratio near 100%. In addition, the shape memory mechanism is discussed and shows some application scenarios of ESHs. The as-produced materials can be used as smart biomaterials such as self-tightening sutures, self-sealing root canal filling materials, and so on.

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The shape-memory effect in ionic elastomers: fixation through ionic interactions

Cited by 27 publications

References 58 publications

Dual Cross‐linked Vinyl Vitrimer with Efficient Self‐Catalysis Achieving Triple‐Shape‐Memory Properties

Dual Cross‐linked Vinyl Vitrimer with Efficient Self‐Catalysis Achieving Triple‐Shape‐Memory Properties

Shape-Memory Composites Based on Ionic Elastomers

Bio‐Based, Self‐CrosslinkableEucommia ulmoidesGum/Silica Hybrids with Body Temperature Triggering Shape Memory Capability

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