Enhanced Mechanical Properties in Cellulose Nanocrystal–Poly(oligoethylene glycol methacrylate) Injectable Nanocomposite Hydrogels through Control of Physical and Chemical Cross-Linking

The paper focuses on the obtaining of novel nanocomposite hydrogels based on polyacrylamide and layered double hydroxides (LDHs) modified with double bonds. The modification of LDH clay was investigated by FTIR, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses. Mechanical properties of the nanocomposite hydrogels were employed by compression and rheological measurements. The formation of exfoliated and intercalated structures was evidenced in transmission electron microscopy (TEM). Chemical cross-linking of hydrogels using both classical cross-linker and modified clay was an efficient method to improve the mechanical properties of novel nanocomposite hydrogels. These hydrogels with improved mechanical properties could be further tested for biomedical applications such as tissue engineering.

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A facile one-step gelation approach simultaneously combining physical and chemical cross-linking for the preparation of injectable hydrogels

Journal of Materials Chemistry B ◽

10.1039/c7tb00396j ◽

2017 ◽

Vol 5 (17) ◽

pp. 3145-3153 ◽

Cited By ~ 3

Author(s):

Haofang Zhu ◽

Xiaojun Cai ◽

Lihuang Wu ◽

Zhongwei Gu

Keyword(s):

Cross Linking ◽

Injectable Hydrogels ◽

One Step ◽

Physical And Chemical ◽

Chemical Cross Linking

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Analysis of the Effect of Processing Conditions on Physical Properties of Thermally Set Cellulose Hydrogels

Materials ◽

10.3390/ma12071066 ◽

2019 ◽

Vol 12 (7) ◽

pp. 1066 ◽

Cited By ~ 4

Author(s):

Tim Huber ◽

Sean Feast ◽

Simone Dimartino ◽

Wanwen Cen ◽

Conan Fee

Keyword(s):

Mechanical Properties ◽

Network Formation ◽

Aqueous Sodium Hydroxide ◽

Cross Linking ◽

Processing Conditions ◽

Hot Press ◽

Thermal Gelation ◽

Complex Shapes ◽

Bond Network ◽

Chemical Cross Linking

Cellulose-based hydrogels were prepared by dissolving cellulose in aqueous sodium hydroxide (NaOH)/urea solutions and casting it into complex shapes by the use of sacrificial templates followed by thermal gelation of the solution. Both the gelling temperatures used (40–80 °C), as well as the method of heating by either induction in the form of a water bath and hot press or radiation by microwaves could be shown to have a significant effect on the compressive strength and modulus of the prepared hydrogels. Lower gelling temperatures and shorter heating times were found to result in stronger and stiffer gels. Both the effect of physical cross-linking via the introduction of additional non-dissolving cellulosic material, as well as chemical cross-linking by the introduction of epichlorohydrin (ECH), and a combination of both applied during the gelation process could be shown to affect both the mechanical properties and microstructure of the hydrogels. The added cellulose acts as a physical-cross-linking agent strengthening the hydrogen-bond network as well as a reinforcing phase improving the mechanical properties. However, chemical cross-linking of an unreinforced gel leads to unfavourable bonding and cellulose network formation, resulting in drastically increased pore sizes and reduced mechanical properties. In both cases, chemical cross-linking leads to larger internal pores.

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Chemical Cross-Linking of Anatase Nanoparticle Thin Films for Enhanced Mechanical Properties

Langmuir ◽

10.1021/acs.langmuir.8b00479 ◽

2018 ◽

Vol 34 (21) ◽

pp. 6109-6116 ◽

Cited By ~ 5

Author(s):

A. Salmatonidis ◽

J. Hesselbach ◽

G. Lilienkamp ◽

T. Graumann ◽

W. Daum ◽

...

Keyword(s):

Thin Films ◽

Mechanical Properties ◽

Cross Linking ◽

Chemical Cross Linking

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Differentiation of physical and chemical cross-linking in gelatin methacryloyl hydrogels

Scientific Reports ◽

10.1038/s41598-021-82393-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Lisa Rebers ◽

Raffael Reichsöllner ◽

Sophia Regett ◽

Günter E. M. Tovar ◽

Kirsten Borchers ◽

...

Keyword(s):

Near Infrared ◽

Cross Linking ◽

Cross Link ◽

Scanning Calorimetry ◽

Link Density ◽

Double Bond Conversion ◽

Cross Links ◽

Physical And Chemical ◽

The Impact ◽

Chemical Cross Linking

AbstractGelatin methacryloyl (GM) hydrogels have been investigated for almost 20 years, especially for biomedical applications. Recently, strengthening effects of a sequential cross-linking procedure, whereby GM hydrogel precursor solutions are cooled before chemical cross-linking, were reported. It was hypothesized that physical and enhanced chemical cross-linking of the GM hydrogels contribute to the observed strengthening effects. However, a detailed investigation is missing so far. In this contribution, we aimed to reveal the impact of physical and chemical cross-linking on strengthening of sequentially cross-linked GM and gelatin methacryloyl acetyl (GMA) hydrogels. We investigated physical and chemical cross-linking of three different GM(A) derivatives (GM10, GM2A8 and GM2), which provided systematically varied ratios of side-group modifications. GM10 contained the highest methacryloylation degree (DM), reducing its ability to cross-link physically. GM2 had the lowest DM and showed physical cross-linking. The total modification degree, determining the physical cross-linking ability, of GM2A8 was comparable to that of GM10, but the chemical cross-linking ability was comparable to GM2. At first, we measured the double bond conversion (DBC) kinetics during chemical GM(A) cross-linking quantitatively in real-time via near infrared spectroscopy-photorheology and showed that the DBC decreased due to sequential cross-linking. Furthermore, results of circular dichroism spectroscopy and differential scanning calorimetry indicated gelation and conformation changes, which increased storage moduli of all GM(A) hydrogels due to sequential cross-linking. The data suggested that the total cross-link density determines hydrogel stiffness, regardless of the physical or chemical nature of the cross-links.

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High-Strength Nanocomposite Hydrogels with Swelling-Resistant and Anti-Dehydration Properties

Polymers ◽

10.3390/polym10091025 ◽

2018 ◽

Vol 10 (9) ◽

pp. 1025 ◽

Cited By ~ 2

Author(s):

Bo Xu ◽

Yuwei Liu ◽

Lanlan Wang ◽

Xiaodong Ge ◽

Min Fu ◽

...

Keyword(s):

Mechanical Properties ◽

Mechanical Performance ◽

High Strength ◽

Alumina Nanoparticles ◽

Cross Linking ◽

Free Radical Copolymerization ◽

Application Range ◽

Practical Applications ◽

Nanocomposite Hydrogels ◽

Al2o3 Nps

Hydrogels with excellent mechanical properties have potential for use in various fields. However, the swelling of hydrogels under water and the dehydration of hydrogels in air severely limits the practical applications of high-strength hydrogels due to the influence of air and water on the mechanical performance of hydrogels. In this study, we report on a kind of tough and strong nanocomposite hydrogels (NC-G gels) with both swelling-resistant and anti-dehydration properties via in situ free radical copolymerization of acrylic acid (AA) and N-vinyl-2-pyrrolidone (VP) in the water-glycerol bi-solvent solutions containing small amounts of alumina nanoparticles (Al2O3 NPs) as the inorganic cross-linking agents. The topotactic chelation reactions between Al2O3 NPs and polymer matrix are thought to contribute to the cross-linking structure, outstanding mechanical performance, and swelling-resistant property of NC-G gels, whereas the strong hydrogen bonds between water and glycerol endow them with anti-dehydration capacity. As a result, the NC-G gels could maintain mechanical properties comparable to other as-prepared high-strength hydrogels when utilized both under water and in air environments. Thus, this novel type of hydrogel would considerably enlarge the application range of hydrogel materials.

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Mechanically Reinforced Gelatin Hydrogels by Introducing Slidable Supramolecular Cross-Linkers

Polymers ◽

10.3390/polym11111787 ◽

2019 ◽

Vol 11 (11) ◽

pp. 1787 ◽

Cited By ~ 6

Author(s):

Dae Hoon Lee ◽

Atsushi Tamura ◽

Yoshinori Arisaka ◽

Ji-Hun Seo ◽

Nobuhiko Yui

Keyword(s):

Mechanical Properties ◽

Stress Concentration ◽

Cross Linking ◽

Supramolecular Polymer ◽

Poly Ethylene Glycol ◽

Physical Force ◽

Adhesive Material ◽

Cell Adhesive ◽

Poly Ethylene ◽

Chemical Cross Linking

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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