Facile tuning of hydrogel properties by manipulating cationic-aromatic monomer sequences

Fan, Hailong; Cai, Yirong; Gong, Jian Ping

doi:10.1007/s11426-021-1010-3

Cited by 20 publications

(18 citation statements)

References 21 publications

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“…By contrast, hydrogels with random cationic/aromatic sequences exhibit poor adhesion in seawater. [118] However, as a polyelectrolyte, poly(cation-adj-π) hydrogels significantly swell in water because of the high ionic osmotic pressure of the dissociated counterions. [119] Thus, the highly swollen hydrogels are fragile in water and have poor underwater adhesion.…”

Section: Adhesives Based On Molecular Interactionsmentioning

confidence: 99%

Bioinspired Underwater Adhesives

2021

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adhesive, causing plasticization, swelling, erosion, degradation, or hydrolysis of adhesives, which eventually leads to cohesive failure. [8,9] Therefore, the development of underwater adhesives remains a significant challenge.An efficient way of developing underwater adhesives is by taking inspiration from nature. For instance, sessile marine organisms such as mussels and sandcastle worms use L-3,4-dihydroxyphenylalanine (DOPA) to achieve permanent underwater adhesion, whereas aquatic creatures such as remora and clingfish use unique microstructures for temporary underwater attachment. [10][11][12][13] Inspired by these unique underwater adhesion strategies, significant progress has been made in the design and fabrication of novel underwater adhesives in the past decade.Previous reviews on underwater adhesion have mainly focused on the micromechanics and bonding mechanisms. Adhesives for soft and wet tissues and hydrogels have been discussed in other recent reviews. [1,[14][15][16] However, only a few have been devoted to bulk underwater adhesives. [10,12,13,[16][17][18][19][20] In this review, we summarize the currently reported adhesives that show macroscopic adhesion to mainly, but not limited to, solid surfaces under wet and underwater conditions. We provide an overview of the development and performance of underwater adhesives based on different bonding methods and mechanisms. In addition, we discuss the possible research directions and perspectives for underwater adhesives. Current Design Strategies for Underwater AdhesionThe keys to achieving wet adhesion are the breaking down of the hydration layer and interaction with the substrate surface, which can be designed at different length scales (Figure 1). [21][22][23] To achieve dehydration at the molecular level (∼nm), hydrophobic organic solvents, monomers, and polymers have been used to remove the hydration layer and facilitate surface wetting, especially for hydrophobic substrates. [24,25] The use of water-absorbing fillers, including inorganic substances and hydrophilic polymers, is an alternative strategy that is widely used for wet surfaces. [26][27][28] At a larger length scale (μm to mm), surface microstructures can promote water drainage to prevent permanent water trapping. [29] Accompanied by the dehydration process, the interfacial bonding of adhesives is achieved by the formation of covalent/ non-covalent bonds (∼nm), which highly depends on the interfacial chemistry between the adherend and the adhesive. [10] For Underwater adhesives are in high demand in both commercial and industrial sectors. Compared with adhesives used in dry (air) environments, adhesives used for wet or submerged surfaces in aqueous environments have specific challenges in development and performance. In this review, focus is on adhesives demonstrating macroscopic adhesion to wet/underwater substrates. The current strategies are first introduced for different types of underwater adhesives, and then an overview is provided of the development and performance of underwater ad...

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Section: Adhesives Based On Molecular Interactionsmentioning

confidence: 99%

Bioinspired Underwater Adhesives

2021

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“…For example, it can take more than 15 days to achieve solvent exchange equilibrium in the case of the poly(methyl acrylate) (PMA) hydrogel. Similarly, three-block copolymerized hydrogels 21 and cation−π hydrogels 22 are also associated with long solvent exchange times, impeding the practical application of the hydrophobic hydrogels.…”

Section: Introductionmentioning

confidence: 99%

Tough Hydrophobic Hydrogels for Monitoring Human Moderate Motions in Both Air and Underwater Environments

et al. 2023

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Hydrophobic hydrogels with high strength and great stretchability hold immense potential in various fields, such as soft robots, 3D printing, and flexible sensors. However, the formation of large hydrophobic domains in a hydrophobic hydrogel can lead to a heterogeneous structure in the bulk hydrogel. This phenomenon will result in the hydrophobic hydrogel becoming opaque, having a large energy hysteresis during stretching, poor strain-sensitivity, and slow self-recovery. In this study, we successfully developed a series of transparent hydrophobic hydrogels that exhibit excellent mechanical properties (low hysteresis and high toughness of ∼1.8−2.5 MJ m −3 ) with a desirable strain-sensitivity. The key factor in achieving this was the ability to tune large, inhomogeneous hydrophobic structures into small, well-ordered domains at the scale of 16.50−52.08 nm by introducing a small number of electrostatic groups into the hydrophobic networks. The hydrophobic hydrogels were able to form strong dual physical interactions, including electrostatic interactions and hydrophobic associations, making them ideal materials for fabricating wearable sensors with both in air and underwater applications. This facile and effective approach provides a novel method to prepare hydrophobic hydrogels with good mechanical performance, low hysteresis, and good strain-sensitivity, opening up new potential for their applications in various fields.

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“…The strength of the underwater adhesion of hydrogels can be improved through the synergy of ionic and hydrophobic interactions. − The hydrophobic domains can repel water molecules and provide a less polar environment, enhancing the electrostatic attraction between the cationic groups on the hydrogel and the anionic groups on surfaces like metals, glasses, and biotic tissues. For example, Fan et al constructed a hydrogel with adjacent cationic and aromatic monomers, showing a fast and strong adhesion in seawater; − Han et al prepared a hydrogel with a hydrophilic monomer and a hydrophobic monomer through a micellar copolymerization in the presence of Fe 3+ , where Fe 3+ induces a self-hydrophobization to the hydrogel surface and enhances the underwater adhesion on a diverse range of substrates . Albeit this progress, a few attempts have been made to enhance the stretchability and underwater adhesiveness simultaneously. , Toward the applications of tissue adhesives, wound dressings, or monitors for large-range human motions, there is a need for a facile method to prepare a stretchable and salt-resistant hydrogel adhesive.…”

Section: Introductionmentioning

confidence: 99%

Synergy of Host–Guest and Cation−π Interactions for an Ultrastretchable, pH-Tunable, Surface-Adaptive, and Salt-Resistant Hydrogel Adhesive

Yang

Jin

et al. 2022

Chem. Mater.

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The adhesion to wet, acidic, and saline biointerfaces with large deformation is important in the fields of wound dressing and motion monitoring but has proven to be extremely challenging. There is a need for a facile method to improve the stretchability and salt resistance simultaneously. Here, an ultrastretchable, pH-tunable, surface-adaptive, and salt-resistant hydrogel adhesive is reported. The hydrogel adhesive is prepared through cross-linking acrylamide with a supramolecular complex of poly(β-cyclodextrin) (PCD) and benzimidazole (BI). The dynamic association between PCD and BI causes an extra energy dissipation and improves the breaking strain to be larger than 4000%. The hydrogel exhibits stable adhesiveness to varieties of surfaces due to the multiple types of hydrogel–surface interactions, including ionic bond, π–π stacking, and hydrogen bond. Notably, the adhesive strength of the hydrogel gets significantly enhanced in an acidic environment and shows no attenuation in a saline environment. This is due to the unique adjacent cation−π structure of BI: the imidazole can be protonized upon acidification, and the phenyl group can repel water and enhance the ionic attraction with the substrates. The ultrastretchability, the stable adhesion on biointerfaces, and the salt resistance render the hydrogel a promising candidate for the surgical patch and motion sensors that serve in wet, acidic, and dynamic environments.

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Facile tuning of hydrogel properties by manipulating cationic-aromatic monomer sequences

Cited by 20 publications

References 21 publications

Bioinspired Underwater Adhesives

Bioinspired Underwater Adhesives

Tough Hydrophobic Hydrogels for Monitoring Human Moderate Motions in Both Air and Underwater Environments

Synergy of Host–Guest and Cation−π Interactions for an Ultrastretchable, pH-Tunable, Surface-Adaptive, and Salt-Resistant Hydrogel Adhesive

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