Editorial

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2 pages, 161 KiB

Open AccessEditorial

Editorial on Special Issue: “Dynamics of Gels and Its Applications”

by Yiming Yang and Di Jia

Gels 2022, 8(12), 805; https://doi.org/10.3390/gels8120805 - 08 Dec 2022

Viewed by 758

Abstract

Gels are polymer networks swollen in various solvents [...] Full article

(This article belongs to the Special Issue Dynamics of Gels and Its Applications)

Research

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15 pages, 4922 KiB

Open AccessArticle

Fabrication of Textile Waste Fibers Aerogels with Excellent Oil/Organic Solvent Adsorption and Thermal Properties

by Chunlei Dong, Yangzhao Hu, Yuxuan Zhu, Jiale Wang, Xuerui Jia, Jianbing Chen and Jingliang Li

Gels 2022, 8(10), 684; https://doi.org/10.3390/gels8100684 - 21 Oct 2022

Cited by 7 | Viewed by 2421

Abstract

In recent years, the treatment of textile waste has attracted more and more attention around the world. The reuse of textile waste can contribute to the reduction of carbon emissions and the sustainable development of the economy. Herein, we proposed a facile and [...] Read more.

In recent years, the treatment of textile waste has attracted more and more attention around the world. The reuse of textile waste can contribute to the reduction of carbon emissions and the sustainable development of the economy. Herein, we proposed a facile and cost-effective approach to fabricating aerogel by using textile waste fibers as the matrix and polyvinyl alcohol (PVA) and glutaraldehyde (GA) as crosslinking agents. After being modified with methyltrimethoxysilane (MTMS) via chemical vapor deposition, both the interior and exterior of the textile waste aerogels exhibit a hydrophobic property with a water contact angle of up to 136.9° ± 2.3°. A comprehensive investigation of the structure, thermal properties, mechanical properties and oil absorption capacity of this aerogel shows its potential for building insulation and oil spill cleanup. The textile waste fibers aerogels have low density and high porosity, good thermal stability and outstanding heat insulation properties (K_avg. = 0.049–0.061 W/m·K). With a maximum oil absorption value of 26.9 ± 0.6 g/g and rapid and effective oil/water mixture separation, the aerogel exhibits competitive commercial application value. Full article

(This article belongs to the Special Issue Dynamics of Gels and Its Applications)

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11 pages, 1779 KiB

Open AccessCommunication

Enhancing Mechanical Performance of a Polymer Material by Incorporating Pillar[5]arene-Based Host–Guest Interactions

by Chengdi Huang, Hanwei Zhang, Ziqing Hu, Youping Zhang and Xiaofan Ji

Gels 2022, 8(8), 475; https://doi.org/10.3390/gels8080475 - 28 Jul 2022

Cited by 5 | Viewed by 1741

Abstract

Polymer gels have been widely used in the field for tissue engineering, sensing, and drug delivery due to their excellent biocompatibility, hydrophilicity, and degradability. However, common polymer gels are easily deformed on account of their relatively weak mechanical properties, thereby hindering their application [...] Read more.

Polymer gels have been widely used in the field for tissue engineering, sensing, and drug delivery due to their excellent biocompatibility, hydrophilicity, and degradability. However, common polymer gels are easily deformed on account of their relatively weak mechanical properties, thereby hindering their application fields, as well as shortening their service life. The incorporation of reversible non-covalent bonds is capable of improving the mechanical properties of polymer gels. Thus, here, a poly(methyl methacrylate) polymer network was prepared by introducing host–guest interactions between pillar[5]arene and pyridine cation. Owing to the incorporated host–guest interactions, the modified polymer gels exhibited extraordinary mechanical properties according to the results of the tensile tests. In addition, the influence of the host–guest interaction on the mechanical properties of the gels was also proved by rheological experiments and swelling experiments. Full article

(This article belongs to the Special Issue Dynamics of Gels and Its Applications)

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12 pages, 2620 KiB

Open AccessArticle

Spatially-Resolved Network Dynamics of Poly(vinyl alcohol) Gels Measured with Dynamic Small Angle Light Scattering

by Sujata Dhakal, Zehao Chen, Daniel Estrin and Svetlana Morozova

Gels 2022, 8(7), 394; https://doi.org/10.3390/gels8070394 - 22 Jun 2022

Cited by 2 | Viewed by 1800

Abstract

Hydrogels are cross-linked polymer networks swollen in water. The large solvent content enables hydrogels to have unique physical properties and allows them to be used in diverse applications such as tissue engineering, drug delivery, and absorbents. Gel properties are linked to internal dynamics. [...] Read more.

Hydrogels are cross-linked polymer networks swollen in water. The large solvent content enables hydrogels to have unique physical properties and allows them to be used in diverse applications such as tissue engineering, drug delivery, and absorbents. Gel properties are linked to internal dynamics. While bulk gel dynamics have been studied extensively, how gel networks respond locally to deformation has yet to be understood. Here, poly(vinyl alcohol) (PVA) gels have been stretched to study the effects of deformation on gel dynamics parallel and perpendicular to the stretching direction using dynamic small angle light scattering (DSALS). The implementation of DSALS is described and compared to traditional DLS for PVA gels with different crosslink densities, ranging from 0.75–2%. Despite the orders of magnitude difference in the scattering vector, q, range of the techniques, the dynamics match, and the apparent elastic diffusion coefficient, D_A increases linearly with the crosslink density for unstretched gels at a constant 2 wt% concentration. We observe that the elastic motion depends on the direction of stretch, decreasing perpendicular to stretching and increasing at parallel direction. Using DSALS can therefore be an effective tool to evaluate local hydrogel response to deformation. Full article

(This article belongs to the Special Issue Dynamics of Gels and Its Applications)

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17 pages, 4709 KiB

Open AccessArticle

Emulsion Gels as Precursors for Porous Silicones and All-Polymer Composites—A Proof of Concept Based on Siloxane Stabilizers

by Carmen Racles, Adrian Bele, Ana-Lavinia Vasiliu and Liviu Sacarescu

Gels 2022, 8(6), 377; https://doi.org/10.3390/gels8060377 - 14 Jun 2022

Cited by 3 | Viewed by 1775

Abstract

In spite of its versatility, the emulsion templating method is rather uncommon for the preparation of porous silicones. In this contribution, two siloxane-containing stabilizers, designed to be soluble in polar (water) and non-polar (toluene) solvents, respectively, were used in low concentrations to produce [...] Read more.

In spite of its versatility, the emulsion templating method is rather uncommon for the preparation of porous silicones. In this contribution, two siloxane-containing stabilizers, designed to be soluble in polar (water) and non-polar (toluene) solvents, respectively, were used in low concentrations to produce stable emulsions, wherein polysiloxane gels were obtained by UV-photoinitiated thiol-ene click cross-linking. The stabilizers exhibited negative interfacial tension, as measured by Wilhelmy plate tensiometry. The emulsion gels evolved into porous silicones (xerogels), with tunable morphology and properties. According to TEM and SEM investigations, the emulsion template was preserved in the final materials. Several parameters (e.g., the structure of the polysiloxane precursors, composition of the emulsion gels, nature of the continuous phase, cross-linking conditions, or additives) can be varied in order to obtain porous elastic materials with desired properties, such as Janus membranes, absorbent monoliths, all-polymer porous composites, or silicone-swollen gels. The feasibility of these types of materials was tested, and exemplary porous silicones were briefly characterized by contact angle measurements, mechanical testing, and absorption tests. The proposed method is simple, fast, and economic, uses very little amounts of stabilizers, and can be adjusted as a green technique. In this contribution, all the silicon-based materials with a convenient design were prepared in house. Full article

(This article belongs to the Special Issue Dynamics of Gels and Its Applications)

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10 pages, 1648 KiB

Open AccessArticle

Poly(ethylene oxide) Is Positively Charged in Aqueous Solutions

by Chao Zhou, Chunda Ji, Yuchen Nie, Jingfa Yang and Jiang Zhao

Gels 2022, 8(4), 213; https://doi.org/10.3390/gels8040213 - 31 Mar 2022

Cited by 6 | Viewed by 1921

Abstract

There have been controversies about the binding of cations to poly(ethylene oxide) (PEO) chains in aqueous solutions. In the current study, single molecular evidence of charging PEO chains by cation binding in aqueous solutions is provided. From the adoption of the photon-counting histogram [...] Read more.

There have been controversies about the binding of cations to poly(ethylene oxide) (PEO) chains in aqueous solutions. In the current study, single molecular evidence of charging PEO chains by cation binding in aqueous solutions is provided. From the adoption of the photon-counting histogram method, it is discovered that the local pH value at the vicinity of the PEO chain is higher than the bulk solution, showing that the PEO chain is positively charged. Such a situation exists with and without the presence of salt (NaCl) in the solution, presumably due to the binding of cations, such as hydronium and sodium ions. Single molecular electrophoresis experiments using fluorescence correlation spectroscopy demonstrate that the PEO chains are weakly charged with a charging extent of ~5%. In comparison to the salt-free condition, the addition of external salt (NaCl) at moderate concentrations further charges the chain. The charging causes the PEO chains to expand and a further increase in the salt concentration causes the chain to shrink, exhibiting a polyelectrolyte-like behavior, demonstrated by the hydrodynamic radii of a single PEO chain. The effect of ion identity is discovered with alkali cations, with the order of the charging capacity of Li⁺ < Na⁺ < Cs⁺ < K⁺. Full article

(This article belongs to the Special Issue Dynamics of Gels and Its Applications)

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11 pages, 12553 KiB

Open AccessArticle

Formation of Hydrogels Based on a Copolymer of N-Vinyl-2-pyrrolidone and Glycidyl Methacrylate in the Presence of the Reaction Product of 1,3-Dimethylmidazolium Dimethylphosphate and Elemental Sulfur

by Natalia Tarasova, Efrem Krivoborodov, Alexey Zanin, Ekaterina Pascal, Ilya Toropygin, Alexander Artyukhov, Samson Muradyan and Yaroslav Mezhuev

Gels 2022, 8(2), 136; https://doi.org/10.3390/gels8020136 - 21 Feb 2022

Cited by 3 | Viewed by 2146

Abstract

The aim of the study is to search for a reaction that provides the possibility of tandem “one-pot” formation of polymer networks during radical copolymerization of N-vinyl-2-pyrrolidone and glycidyl methacrylate. It was shown that the addition of recently synthesized 1,3-dimethylimidazolium (phosphonooxy-)oligosulfanide makes [...] Read more.

The aim of the study is to search for a reaction that provides the possibility of tandem “one-pot” formation of polymer networks during radical copolymerization of N-vinyl-2-pyrrolidone and glycidyl methacrylate. It was shown that the addition of recently synthesized 1,3-dimethylimidazolium (phosphonooxy-)oligosulfanide makes it possible to obtain a cross-linked copolymer in one stage as a result of radical copolymerization of N-vinyl-2-pyrrolidone and glycidyl methacrylate with a molar ratio of monomers less than 1.4. The structure of the copolymerization products of N-vinyl-2-pyrroldione and glycidyl methacrylate formed in the presence of 1,3-dimethylimidazolium (phosphonooxy-)oligosulfanide was characterized by ¹H NMR, FTIR and MALDI spectroscopy. ¹H NMR spectroscopy revealed an interaction under moderate heating between glycidyl methacrylate and 1,3-dimethylimidazolium (phosphonooxy-)oligosulfanide, accompanied by the formation of a mixture of unsaturated products of complex structure, presumably acting as crosslinking agents. It is shown that when the molar ratio of N-vinyl-2-pyrroldione/glycidyl methacrylate comonomers is 0.89, a densely crosslinked copolymer is formed, capable of limited swelling in water with a velocity constant of 5.06 × 10⁻² min⁻¹ and an equilibrium degree of swelling of about 227%. Full article

(This article belongs to the Special Issue Dynamics of Gels and Its Applications)

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11 pages, 22416 KiB

Open AccessArticle

Nickel (II) and Cobalt (II) Alginate Biopolymers as a “Carry and Release” Platform for Polyhistidine-Tagged Proteins

by Andrei-Mihai Dumitrașcu, Iuliana Caraș, Cătălin Țucureanu, Andreea-Laura Ermeneanu and Vlad-Constantin Tofan

Gels 2022, 8(2), 66; https://doi.org/10.3390/gels8020066 - 18 Jan 2022

Cited by 3 | Viewed by 2377

Abstract

Protein immobilization using biopolymer scaffolds generally involves undesired protein loss of function due to denaturation, steric hindrance or improper orientation. Moreover, most methods for protein immobilization require expensive reagents and laborious procedures. This work presents the synthesis and proof of concept application of [...] Read more.

Protein immobilization using biopolymer scaffolds generally involves undesired protein loss of function due to denaturation, steric hindrance or improper orientation. Moreover, most methods for protein immobilization require expensive reagents and laborious procedures. This work presents the synthesis and proof of concept application of two alginate hydrogels that are able to bind proteins with polyhistidine tags by means of interaction with the crosslinking cations. Nickel (II) and cobalt (II) alginate hydrogels were prepared using a simple ionic gelation method. Hydrogels were characterized by optical microscopy and AFM, and evaluated for potential cytotoxicity. In addition, binding capacity was tested towards proteins with or without HisTAG. Hydrogels had moderate cytotoxicity and were able to exclusively bind polyhistidine-tagged proteins with a binding capacity of approximately 300 µg EGFP (enhanced green fluorescent protein) per 1 mL of hydrogel. A lyophilized hydrogel-protein complex dissolved upon the addition of PBS and allowed the protein release and regain of biological activity. In conclusion, the nickel (II) and cobalt (II) alginate biopolymers provided an excellent platform for the “carry and release” of polyhistidine-tagged proteins. Full article

(This article belongs to the Special Issue Dynamics of Gels and Its Applications)

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17 pages, 9728 KiB

Open AccessArticle

Preparation and Evaluation of Polymer-Based Ultrasound Gel and Its Application in Ultrasonography

by Sadia Afzal, Muhammad Zahid, Zulfiqar Ahmad Rehan, H. M. Fayzan Shakir, Hamza Javed, Meshari M. H. Aljohani, Syed Khalid Mustafa, Maqsood Ahmad and Montaser M. Hassan

Gels 2022, 8(1), 42; https://doi.org/10.3390/gels8010042 - 06 Jan 2022

Cited by 11 | Viewed by 10636

Abstract

Ultrasound imaging is a widely used technique in every health care center and hospital. Ultrasound gel is used as a coupling medium in all ultrasound procedures to replace air between the transducer and the patient’s skin, as ultrasound waves have trouble in traveling [...] Read more.

Ultrasound imaging is a widely used technique in every health care center and hospital. Ultrasound gel is used as a coupling medium in all ultrasound procedures to replace air between the transducer and the patient’s skin, as ultrasound waves have trouble in traveling through air. This research was performed to formulate an inexpensive alternative to commercially available ultrasound gel as it is expensive and imported from other countries. Different formulations with different concentrations of carbopol 980 (CAR 980) and methylparaben were prepared with natural ingredients such as aloe vera gel and certain available chemicals that have no harmful effects on the skin. To justify the efficiency of the formulations; necessary physicochemical characteristics such as visual clarity, homogeneity, transparency, skin irritation, antibacterial activity, pH, stability, spreadability, conductivity, acoustic impedance, viscosity, and cost were evaluated. Moreover, a comparison study was also conducted with commercially available ultrasound gel that was utilized as a control. All samples showed excellent transparency and no microbial growth. S1 was the only formulation that met all of the requirements for commercial ultrasound gel and produced images that were similar to those produced by commercial ultrasound gel. So, this formulation could be used as an alternative to expensive commercial ultrasound gel for taking images in hospitals and medical centers. Full article

(This article belongs to the Special Issue Dynamics of Gels and Its Applications)

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23 pages, 3847 KiB

Open AccessArticle

Silicate-Based Electro-Conductive Inks for Printing Soft Electronics and Tissue Engineering

by Sadaf Samimi Gharaie, Amir Seyfoori, Bardia Khun Jush, Xiong Zhou, Erik Pagan, Brent Godau and Mohsen Akbari

Gels 2021, 7(4), 240; https://doi.org/10.3390/gels7040240 - 27 Nov 2021

Cited by 8 | Viewed by 4329

Abstract

Hydrogel-based bio-inks have been extensively used for developing three-dimensional (3D) printed biomaterials for biomedical applications. However, poor mechanical performance and the inability to conduct electricity limit their application as wearable sensors. In this work, we formulate a novel, 3D printable electro-conductive hydrogel consisting [...] Read more.

Hydrogel-based bio-inks have been extensively used for developing three-dimensional (3D) printed biomaterials for biomedical applications. However, poor mechanical performance and the inability to conduct electricity limit their application as wearable sensors. In this work, we formulate a novel, 3D printable electro-conductive hydrogel consisting of silicate nanosheets (Laponite), graphene oxide, and alginate. The result generated a stretchable, soft, but durable electro-conductive material suitable for utilization as a novel electro-conductive bio-ink for the extrusion printing of different biomedical platforms, including flexible electronics, tissue engineering, and drug delivery. A series of tensile tests were performed on the material, indicating excellent stability under significant stretching and bending without any conductive or mechanical failures. Rheological characterization revealed that the addition of Laponite enhanced the hydrogel’s mechanical properties, including stiffness, shear-thinning, and stretchability. We also illustrate the reproducibility and flexibility of our fabrication process by extrusion printing various patterns with different fiber diameters. Developing an electro-conductive bio-ink with favorable mechanical and electrical properties offers a new platform for advanced tissue engineering. Full article

(This article belongs to the Special Issue Dynamics of Gels and Its Applications)

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18 pages, 6351 KiB

Open AccessArticle

Dynamics of a Gel-Based Artificial Tear Film with an Emphasis on Dry Disease Treatment Applications

by Hamza Mehdaoui, Hamid Ait Abderrahmane, Clement de Loubens, Faïçal Nait Bouda and Sofiane Hamani

Gels 2021, 7(4), 215; https://doi.org/10.3390/gels7040215 - 16 Nov 2021

Cited by 3 | Viewed by 1627

Abstract

This paper discusses the spreading of gel-based ophthalmic formulation on the cornea surface assumed to be flat. We show that gel-based formulations exhibit rheological behaviors that the Herschel–Bulkley model can describe. The continuity and momentum equations are solved numerically using the monofluid formulation [...] Read more.

This paper discusses the spreading of gel-based ophthalmic formulation on the cornea surface assumed to be flat. We show that gel-based formulations exhibit rheological behaviors that the Herschel–Bulkley model can describe. The continuity and momentum equations are solved numerically using the monofluid formulation and the volume-of-fluid (VOF) method. We investigated the influence of the rheological properties, namely the consistency, the yield stress, and the flow behavior index, on the spreading of a gel-based artificial tear over the cornea surface. We propose optimal values of these properties for efficient gel-based artificial tears. Full article

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14 pages, 5239 KiB

Open AccessArticle

Production of Porous Agarose-Based Structures: Freeze-Drying vs. Supercritical CO₂ Drying

by Mariangela Guastaferro, Lucia Baldino, Ernesto Reverchon and Stefano Cardea

Gels 2021, 7(4), 198; https://doi.org/10.3390/gels7040198 - 05 Nov 2021

Cited by 18 | Viewed by 2985

Abstract

In this work, the effect of two processes, i.e., freeze-drying and supercritical CO₂ (SC-CO₂) drying, on the final morphology of agarose-based porous structures, was investigated. The agarose concentration in water was varied from 1 wt% up to 8 wt%. Agarose [...] Read more.

In this work, the effect of two processes, i.e., freeze-drying and supercritical CO₂ (SC-CO₂) drying, on the final morphology of agarose-based porous structures, was investigated. The agarose concentration in water was varied from 1 wt% up to 8 wt%. Agarose cryogels were prepared by freeze-drying using two cooling rates: 2.5 °C/min and 0.1 °C/min. A more uniform macroporous structure and a decrease in average pore size were achieved when a fast cooling rate was adopted. When a slower cooling rate was performed instead, cryogels were characterized by a macroporous and heterogenous structure at all of the values of the biopolymer concentration investigated. SC-CO₂ drying led to the production of aerogels characterized by a mesoporous structure, with a specific surface area up to 170 m²/g. Moreover, agarose-based aerogels were solvent-free, and no thermal changes were detected in the samples after processing. Full article

(This article belongs to the Special Issue Dynamics of Gels and Its Applications)

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