Entropy‐Mediated Polymer–Cluster Interactions Enable Dramatic Thermal Stiffening Hydrogels for Mechanoadaptive Smart Fabrics

Abstract

Thermal stiffening materials that are naturally soft but adaptively self‐strengthen upon heat are intriguing for load‐bearing and self‐protection applications at elevated temperatures. However, to simultaneously achieve high modulus change amplitude and high mechanical strength at the stiffened state remains challenging. Herein, entropy‐mediated polymer–mineral cluster interactions are exploited to afford thermal stiffening hydrogels with a record‐high storage modulus enhancement of 13 000 times covering a super wide regime from 1.3 kPa to 17 MPa. Such a dramatic thermal stiffening effect is ascribed to the transition from liquid‐liquid to solid–liquid phase separations, and at the molecular level, driven by enhanced polymer–cluster interactions. The hydrogel is further processed into sheath–core fibers and smart fabrics, which demonstrate self‐strengthening and self‐powered sensing properties by co‐weaving another liquid metal fiber as both the joule heater and triboelectric layer.

Recent developments in artificial spider silk and functional gel fibers

“…Wen et al successfully produced high-performance stretchable TE-fibers comprising poly (3,4-ethylenedioxythiophene): poly (styrenesulfonic acid) (PEDOT:PSS) and WPU by a simple one-step wet-spinning approach. 80 Wu et al 81 exploited entropy-mediated polymer-mineral cluster interactions to prepare thermal stiffening hydrogels with a record-high storage modulus enhancement of 13,000 times, covering a superwide region from 1.3 kPa to 17 MPa. Such a dramatic thermal stiffening effect was attributed to the transition from liquid-liquid to solid-liquid phase separation, which was governed by the enhanced polymer-cluster interactions on the molecular level.…”

“…Reproduced with permission: Copyright 2022, Wiley-VCH GmbH. 81 GA, glutaraldehyde; SA, spider-silk-inspired wet adhesive.…”

Innovations in spider silk‐inspired artificial gel fibers: Methods, properties, strengthening, functionality, and challenges

“…The disruption and reestablishment of non-covalent cross-links in response to environmental changes can result in modifications to the structures and morphologies of the fibers, subsequently impacting their additional properties. 100,104 For example, Wu et al 105 reported entropy-driven interactions between polymers and clusters for the production of mineral hydrogels that demonstrate a remarkable increase in stiffness when exposed to heat. This stiffening response can be harnessed in mineral hydrogel-based smart textiles and sheath core fibers, allowing them to dynamically adapt their stiffness to varying temperatures (Figure 3A).…”

Aqueous coordination polymer complexes: From colloidal assemblies to bulk materials

“…Ligand structure Metal source Applications Carboxylate Cu 2+ , Zn 2+ [57]; CaCO 3 NP [58,59]; Eu 3+ [60]; Fe 3+ -cluster [61] Smart fabrics [58]; Adhesives [59] Pyridine Ag + [62] Phenanthroline Cu + [63,64] Artificial enzymes [63] Histidine Zn 2+ , Cu 2+ , Co 2+ , Ni 2+ [65][66][67] Dipicolinic acid Zn 2+ [43,51]; Fe 2+ [13]; Fe 3+ [68] Mn 2+ [69]; Co 2+ [70]; Eu 3+ [71,72]; Gd 3+ [73] MRI agents [69]; Drug delivery [73]; Security ink [71]；Catalytic nanoreactors [70] Pyridine-carboxylic acid Eu 3+ , Tb 3+ [74] Hydrogel actuators [74] Catechol Zn 2+ [75]; Fe 3+ [17,76,77]; Fe 3 O 4 NP [78] Adhesives [75,77] Iminodiacetate Eu 3+ [18,79] Terpyridine Co 2+ [80] Para-bispyridyl / Meta-bispyridyl Pd 2+ [81,82] Open-form bis-pyridyl dithienylethene/ Closed-form bis-pyridyl dithienylethene Pd 2+ [83] 4…”

“…The gels with smaller sizes of Fe 3 O 4 NPs relax faster due to the limited chain bonds in the cross-linking center. More recently, Sun and coworkers used very small amorphous CaCO 3 (ACC) nanoparticles to create bio-inspired mineral-based hybrid hydrogel materials, including "mineral plastics" [118], hybrid adhesive [59] and mechanoadaptive smart fabrics [58] (Fig. 19b).…”