Direct Determination of Cross-Link Density and Its Correlation with the Elastic Modulus of a Gel with Slidable Cross-Links

Katō, K.; Ikeda, Yuta; Ito, Kohzo

doi:10.1021/acsmacrolett.9b00238

Cited by 56 publications

(59 citation statements)

References 28 publications

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“…In previous reports, Young’s modulus in slide-ring gels showed a similar value regardless of the number of threaded cyclic molecules in PRXs, although Young’s modulus increased with a higher cross-linking density [24,41]. In the present study, at the 1% strain point, Young’s modulus was controlled by the amount of EDC/NHS regardless of the type of cross-linker used (Table 2).…”

Section: Resultssupporting

confidence: 72%

Mechanically Reinforced Gelatin Hydrogels by Introducing Slidable Supramolecular Cross-Linkers

et al. 2019

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Tough mechanical properties are generally required for tissue substitutes used in regeneration of damaged tissue, as these substitutes must be able to withstand the external physical force caused by stretching. Gelatin, a biopolymer derived from collagen, is a biocompatible and cell adhesive material, and is thus widely utilized as a component of biomaterials. However, the application of gelatin hydrogels as a tissue substitute is limited owing to their insufficient mechanical properties. Chemical cross-linking is a promising method to improve the mechanical properties of hydrogels. We examined the potential of the chemical cross-linking of gelatin hydrogels with carboxy-group-modified polyrotaxanes (PRXs), a supramolecular polymer comprising a poly(ethylene glycol) chain threaded into the cavity of α-cyclodextrins (α-CDs), to improve mechanical properties such as stretchability and toughness. Cross-linking gelatin hydrogels with threading α-CDs in PRXs could allow for freely mobile cross-linking points to potentially improve the mechanical properties. Indeed, the stretchability and toughness of gelatin hydrogels cross-linked with PRXs were slightly higher than those of the hydrogels with the conventional chemical cross-linkers 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS). In addition, the hysteresis loss of gelatin hydrogels cross-linked with PRXs after repeated stretching and relaxation cycles in a hydrated state was remarkably improved in comparison with that of conventional cross-linked hydrogels. It is considered that the freely mobile cross-linking points of gelatin hydrogels cross-linked with PRXs attenuates the stress concentration. Accordingly, gelatin hydrogels cross-linked with PRXs would provide excellent mechanical properties as biocompatible tissue substitutes exposed to a continuous external physical force.

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Section: Resultssupporting

confidence: 72%

Mechanically Reinforced Gelatin Hydrogels by Introducing Slidable Supramolecular Cross-Linkers

et al. 2019

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“…Gels 2021, 7, x FOR PEER REVIEW 2 of 18 gels exhibit low Young's modulus [20][21][22][23][24][25][26][27], high toughness [20,23,[28][29][30][31][32], and elastic mechanical response (low hysteresis) [20,23,28,33], overcoming the trade-off between toughness and elasticity for conventional polymeric elastomers. Herein, we review the mechanical and fracture properties of SR gels to clarify the correlation of the sliding of the movable cross-links with the softness, elasticity, and toughness.…”

Section: Preparation Of Sr Gelsmentioning

confidence: 99%

“…The slidability of the cross-linking points leads to a softer mechanical response of SR gels compared with that of FC gels with fixed cross-links [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. Figure 2 shows stress–strain curves of FC and SR gels with various cross-linker concentrations [ 23 ].…”

Section: Softness Of Sr Gelsmentioning

confidence: 99%

“…In SR gels, the axial polymer chains are cross-linked by figure-of-eight cross-links, and the cross-linking points can slide along the polymer chains. Interestingly, SR gels exhibit low Young’s modulus [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ], high toughness [ 20 , 23 , 28 , 29 , 30 , 31 , 32 ], and elastic mechanical response (low hysteresis) [ 20 , 23 , 28 , 33 ], overcoming the trade-off between toughness and elasticity for conventional polymeric elastomers.…”

Section: Introductionmentioning

confidence: 99%

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Softness, Elasticity, and Toughness of Polymer Networks with Slide-Ring Cross-Links

Mayumi

Liu

Yasuda

et al. 2021

Gels

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Slide-ring (SR) gels cross-linked by ring molecules are characterized by softness (low Young’s modulus), elasticity (low hysteresis loss), and toughness (large fracture energy). In this article, the mechanical and fracture properties of SR gels are reviewed to clarify the physical understanding of the relationship between the molecular-level sliding dynamics of the slide-ring cross-links and macroscopic properties of SR gels. The low Young’s modulus and large fracture energy of SR gels are expressed by simple equations as a function of the degree of sliding movement. The dynamic fracture behaviors of SR gels gives us the time scale of the sliding dynamics of the cross-links, which is at the micro-sec scale. The fast sliding motion of the cross-links leads to the elasticity of the SR gels. The SR concept can be applied to solvent-free elastomers and composite materials.

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“…Since the discovery of the remarkable properties of rotaxane‐crosslinked polymers (RCPs) composed of α‐cyclodextrin and poly(ethylene glycol) by Ito and coworkers, [ 4 ] a variety of similar structures have been reported. [ 5–26 ] We previously developed vinyl polymer‐based RCPs displaying high mechanical performance by free‐radical polymerization of conventional vinyl monomers in the presence of rotaxane‐type crosslinkers bearing polymerizable vinyl groups on each axle and wheel component. [ 7–9,13,20,21 ] Notably, our method enables the application of various vinyl monomers; therefore, it could be used for the fabrication of versatile functionalized materials with excellent toughness.…”

Section: Methodsmentioning

confidence: 99%

Rotaxane‐Based Difunctional Nitrile N‐Oxide Crosslinker: Synthesis and Direct Introduction of Movable Crosslinking Points into Ethylene‐Propylene‐Butadiene Monomer (EPDM) Rubber

Sogawa

Tsutsuba

Sakiyama

et al. 2020

Macromol. Rapid Commun.

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Incorporation of rotaxane scaffolds into the crosslinking points of polymer networks significantly affects their rheological and mechanical properties. The present study involves the synthesis of a new rotaxane‐type crosslinker containing nitrile N‐oxide functional groups on both the axle and wheel components. The prepared crosslinker is highly reactive; however, it can be isolated and applied in the crosslinking reaction of a commercially important polymer, namely ethylene‐propylene‐butadiene monomer rubber (EPDM), in the absence of additives and catalysts. Tensile tests reveal that compared to a network containing conventional crosslinking points, both breaking strength and strain of the network structure prepared herein are improved due to the incorporation of movable crosslinking points. The synthesized network structure also exhibits five times higher fracture energy. The developed post‐crosslinking methodology for the direct introduction of movable crosslinking points into pre‐formed polymers will be valuable in the production of rotaxane materials for various applications.

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Direct Determination of Cross-Link Density and Its Correlation with the Elastic Modulus of a Gel with Slidable Cross-Links

Cited by 56 publications

References 28 publications

Mechanically Reinforced Gelatin Hydrogels by Introducing Slidable Supramolecular Cross-Linkers

Mechanically Reinforced Gelatin Hydrogels by Introducing Slidable Supramolecular Cross-Linkers

Softness, Elasticity, and Toughness of Polymer Networks with Slide-Ring Cross-Links

Rotaxane‐Based Difunctional Nitrile N‐Oxide Crosslinker: Synthesis and Direct Introduction of Movable Crosslinking Points into Ethylene‐Propylene‐Butadiene Monomer (EPDM) Rubber

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