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1.
A double hydrogen bonding (DHB) hydrogel is constructed by copolymerization of 2‐vinyl‐4,6‐diamino‐1,3,5‐triazine (hydrophobic hydrogen bonding monomer) and N,N‐dimethylacrylamide (hydrophilic hydrogen bonding monomer) with polyethylene glycol diacrylates. The DHB hydrogels demonstrate tunable robust mechanical properties by varying the ratio of hydrogen bonding monomer or crosslinker. Importantly, because of synergistic energy dissipating mechanism of strong diaminotriazine (DAT) hydrogen bonding and weak amide hydrogen bonding, the DHB hydrogels exhibit high toughness (up to 2.32 kJ m−2), meanwhile maintaining 0.7 MPa tensile strength, 130% elongation at break, and 8.3 MPa compressive strength. Moreover, rehydration can help to recover the mechanical properties of the cyclic loaded–unloaded gels. Attractively, the DHB hydrogels are responsive to CO2 in water, and demonstrate unprecedented CO2‐triggered shape memory behavior owing to the reversible destruction and reconstruction of DAT hydrogen bonding upon passing and degassing CO2 without introducing external acid. The CO2 triggering mechanism may point out a new approach to fabricate shape memory hydrogels.  相似文献   

2.
Spherical polymer brushes, poly(acrylic acid) (PAA)‐grafted polystyrene nanoparticle (PAA@PS), are employed as the macro‐crosslinker to prepare PAA hydrogels. Benefitting from the innumerable hydrogen bonds between highly entangled PAA chains both in bulk and on the polymer brush, the PAA/PAA@PS hydrogels combine desirable stretchability, toughness, and notch‐insensitivity. The uniaxial tensile tests show a very high fracture elongation up to 9.1 × 103% while the fracture toughness reaches 3.0 MJ m−3 and the maximum swelling ratio of the hydrogel can be 2.0 × 103 as well. After being loaded with silver nanoparticles, the PAA/PAA@PS hydrogels are employed as a recyclable catalyst successfully.  相似文献   

3.
In this work, acrylamide/itaconic acid copolymeric hydrogels are prepared by free radical polymerization initiated by redox initiators of potassium persulfate and N ,N ,N ′,N ′‐tetramethyl ethylene diamine; N ,N ′methylene bisacrylamide was employed as a crosslinking agent. Aniline monomer was absorbed in the network of poly(acrylamide‐co‐itaconic acid) P(AAm‐co‐IA) hydrogel and followed by gamma radiation induced polymerization at room temperature. The novel semi‐interpenetrating network was comprised of linear polyaniline immersed in P(AAm‐co‐IA) matrix. Electrical conductivity of the hydrogels was measured using four‐probe technique. The conductivities for the prepared hydrogels are found to increase from 5.5 × 10?7 S cm?1 for P(AAm‐co‐IA) alone to 4.4 × 10?3 S cm?1 for semi‐interpenetrating polymer network P(AAm‐co‐IA)/polyaniline. Thus, a new composite hydrogel with good conductive properties also displaying enhanced mechanical strength and pH sensitivity was prepared. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

4.
Flexible hydrogel strain sensors have made great progress in medical applications, human motion detection, and human-machine interactions. However, the design of hydrogels to realize the synergistic responses of excellent mechanical properties, robust adhesion, and stable sensing is still a highly challenging task. Herein, we report a multifunctional hydrogel (PAMT hydrogel) by crosslinking acrylic acid (AA), 2-methacryloyloxyethyl phosphorylcholine (MPC) and tannic acid (TA) to form a polymer network via a simple one-pot free radical polymerization. Among them, the dynamic bonding with hydrogen bonding between PAA chains and TA significantly improved the stretch ability of the hydrogels (700%), and the abundant catechol groups on TA endowed the hydrogels with strong and stable adhesion properties (the adhesion strength to glass reached 248 N m−1). When applied to human skin, the hydrogel can be easily peeled off without leaving any residue. Furthermore, the strain sensor assembled using PAMT hydrogel could not only effectively detect the movement in different parts of the human body, but also be used for precise handwritten recognition and electric skin of silicone prosthetic hand. Due to the addition of MPC and TA, the conductive hydrogel has good biocompatibility and no harm to human body. Therefore, PAMT hydrogel has opened up a new vision for the development of intelligent detection and bionic intelligent robots.  相似文献   

5.
Double network (DN) hydrogels as one kind of tough gels have attracted extensive attention for their potential applications in biomedical and load-bearing fields. Herein, we import more functions like shape memory into the conventional tough DN hydrogel system. We synthesize the PEG-PDAC/P(AAm-co-AAc) DN hydrogels, of which the first network is a well-defined PEG (polyethylene glycol) network loaded with PDAC (poly(acryloyloxyethyltrimethyl ammonium chloride)) strands, while the second network is formed by copolymerizing AAm (acrylamide) with AAc (acrylic acid) and cross-linker MBAA (N, N'-methylenebisacrylamide). The PEG-PDAC/P(AAm-co-AAc) DN gels exhibits high mechanical strength. The fracture stress and toughness of the DN gels reach up to 0.9 MPa and 3.8 MJ/m3, respectively. Compared with the conventional double network hydrogels with neutral polymers as the soft and ductile second network, the PEG-PDAC/P(AAm-coAAc) DN hydrogels use P(AAm-co-AAc), a weak polyelectrolyte, as the second network. The AAc units serve as the coordination points with Fe3+ ions and physically crosslink the second network, which realizes the shape memory property activated by the reducing ability of ascorbic acid. Our results indicate that the high mechanical strength and shape memory properties, probably the two most important characters related to the potential application of the hydrogels, can be introduced simultaneously into the DN hydrogels if the functional monomer has been integrated into the network of DN hydrogels smartly.  相似文献   

6.
One of the significant challenges in bone tissue engineering (BTE) is the healing of traumatic tissue defects owing to the recruitment of local infection and delayed angiogenesis. Herein, a 3D printable multi-functional hydrogel composing polyphenolic carbon quantum dots (CQDs, 100 µg mL−1) and gelatin methacryloyl (GelMA, 12 wt%) is reported for robust angiogenesis, bone regeneration and anti-tumor therapy. The CQDs are synthesized from a plant-inspired bioactive molecule, 1, 3, 5-trihydroxybenzene. The 3D printed GelMA-CQDs hydrogels display typical shear-thinning behavior with excellent printability. The fabricated hydrogel displayed M2 polarization of macrophage (Raw 264.7) cells via enhancing anti-inflammatory genes (e.g., IL-4 and IL10), and induced angiogenesis and osteogenesis of human bone mesenchymal stem cells (hBMSCs). The bioprinted hBMSCs are able to produce vessel-like structures after 14 d of incubation. Furthermore, the 3D printed hydrogel scaffolds also show remarkable near infra-red (NIR) responsive properties under 808 nm NIR light (1.0 W cm−2) irradiation with controlled release of antitumor drugs (≈49%) at pH 6.5, and thereby killing the osteosarcoma cells. Therefore, it is anticipated that the tissue regeneration and healing ability with therapeutic potential of the GelMA-CQDs scaffolds may provide a promising alternative for traumatic tissue regeneration via augmenting angiogenesis and accelerated immunomodulation.  相似文献   

7.

In order to develop a new functional product from lignin, sodium lignosulfonate (LS)-based polyurethane (LSPU) hydrogels were prepared from LS and hexamethylene diisocyanate (HDI) derivatives in water. Isocyanate/hydroxyl group ratio (NCO/OH ratio) was varied from 0.05 to 0.8 mol mol−1, and water content (Wc = mass of water/mass of dry sample) of the obtained LSPU hydrogels was varied from 0 to 3.0 g g−1. Phase transition behavior of hydrogels with various Wc’s was investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG). In DSC heating curve of LSPU hydrogels, glass transition, cold crystallization, melting and liquid crystallization were observed. Cold crystallization, two melting peaks and variation of melting enthalpy indicate that three kinds of water, i.e., non-freezing water, freezing bound water and free water, exist in LSPU hydrogel. Glass transition temperature (Tg) decreased from 230 to 190 K in a Wc range where non-freezing water was formed in the hydrogel. Tg increased when freezing bound water was formed in the system. Tg leveled off in a Wc range where normal ice was formed. The effect of NCO/OH ratio on molecular motion of LSPU hydrogel is examined based on Tg and heat capacity difference at TgCp). Water vaporization curve measured by TG also indicates the presence of bound water which evaporates at a temperature higher than ca. 410 K. By atomic force microscopic observation, the size of molecular bundle of LSPU hydrogel is calculated and compared with that of LS-water system. By cross-linking, the height of molecular bundle decreased from ca. 3–1 nm and lignin molecules extend in a flat structure.

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8.

The present study aimed to synthesize poly(acrylic acid) hydrogel embedded with magnetic cobalt (Co) nanoparticles and to investigate their potential in adsorption and catalysis. The hydrogel was prepared by facile free radical polymerization reaction and Co nanoparticles were fabricated within hydrogel by reducing Co (II) ions using NaBH4 as reducing agent. Co nanoparticles within hydrogel system imparted magnetic properties to the resulting composite gel and also increased the adsorption capacity. The swelling study of hydrogel was carried out by gravimetric analysis. Different functional groups were identified by Fourier Transform Infrared Spectroscopy and Transmission Electron Microscopy analysis was done to investigate dispersion of Co nanoparticles in hydrogel. The bare hydrogel along with Co nanoparticles loaded gel were tested as adsorbent systems for the removal of a cationic dye (methylene blue) from aqueous solution. 95% removal of methylene blue was achieved with a highest adsorption capacity of 836.5 mg/g of adsorbent. The famous adsorption isotherms were used to evaluate adsorption data. Results showed that Freundlich isotherm model was followed with R2 value of 0.95. The hydrogel was also used for catalytic reduction in a toxic pollutant, i.e., 4-nitrophenol. Experimental data for 4-nitrophenol reduction followed pseudo first order kinetics model. Activation energy and apparent rate constant were calculated as 9.24 kJ/mol and 0.24 min−1, respectively. Recycling of the magnetic poly(acrylic acid) hydrogel fabricated with Cobalt nanoparticles was carried out for four consecutive cycles and no significant loss in catalytic activity was observed.

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9.
Low-grade heat is ubiquitous in the environment and its thermoelectric conversion by the ionic conductors remains a challenge because of the low efficiency and poor sustainability. Here we demonstrate that the thermoelectric performances can be boosted by combining the Soret effect of protons and proton-coupled electron transfer (PCET) reaction of benzoquinone and hydroquinone in hydrogels. An overall enhancement of thermopower (25.9 mV K−1), power factor (5 mW m−1 K−2), figure of merit (>2.4) and continuity of power output is achieved. Moreover, an energy-storage function can be achieved by the redox couple, and a retained power output of 27.7 %, or 14 mW m−2 for more than 3 hours is obtained by the re-balance of PCET reactants in the hydrogel after the removal of the temperature gradient.  相似文献   

10.
Tough hydrogels have great potentials in soft robotics, artificial muscles, tissue replacement, and so on. Here we introduce novel tough hydrogels crosslinked by triblock copolymer (F127DA) micelles and metal coordination. The gels showed outstanding tensile strength (∼1–11 MPa), toughness (∼4–32 MJ m−3), and excellent self‐recovery properties (∼56.8–87.2% toughness recovery in 9 min at room temperature). The mechanical and self‐recovery properties could be manipulated by varying contents of micelles and/or COO groups. Dynamic mechanical analysis of the hydrogels revealed apparent activation energy and relaxations for both physical interactions. In situ small‐angle X‐ray scattering measurements on hydrogels upon stretching revealed micelle deformations. XPS measurements on hydrogels before and after stretching revealed significant changes in the binding energy of Fe3+ ions in the gels, suggesting the rupture of coordination bonds. The experimental results strongly suggest a synergistic effect from the micelle‐crosslinking and Fe3+–COO coordination on the strength, toughness, and self‐recovery of the hydrogels. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 865–876  相似文献   

11.
《中国化学快报》2023,34(10):108262
To achieve smart and personalized medicine, the development of hydrogel dressings with sensing properties and biotherapeutic properties that can act as a sensor to monitor of human health in real-time while speeding up wound healing face great challenge. In the present study, a biocompatible dual-network composite hydrogel (DNCGel) sensor was obtained via a simple process. The dual network hydrogel is constructed by the interpenetration of a flexible network formed of poly(vinyl alcohol) (PVA) physical cross-linked by repeated freeze-thawing and a rigid network of iron-chelated xanthan gum (XG) impregnated with Fe3+ interpenetration. The pure PVA/XG hydrogels were chelated with ferric ions by immersion to improve the gel strength (compressive modulus and tensile modulus can reach up to 0.62 MPa and 0.079 MPa, respectively), conductivity (conductivity values ranging from 9 × 10−4 S/cm to 1 × 10−3 S/cm) and bacterial inhibition properties (up to 98.56%). Subsequently, the effects of the ratio of PVA and XG and the immersion time of Fe3+ on the hydrogels were investigated, and DNGel3 was given the most priority on a comprehensive consideration. It was demonstrated that the DNCGel exhibit good biocompatibility in vitro, effectively facilitate wound healing in vivo (up to 97.8% healing rate) under electrical stimulation, and monitors human movement in real time. This work provides a novel avenue to explore multifunctional intelligent hydrogels that hold great promise in biomedical fields such as smart wound dressings and flexible wearable sensors.  相似文献   

12.
In this article, we report a synergistic strategy to develop dual physically cross-linked tough hydrogels via one-pot bulk copolymerization of N-vinyl-2-pyrrolidone, acrylic acid, and stearyl methylacrylate (SMA) without any adscititious surfactant. Due to synergic effects of hydrogen bonding and hydrophobic association, the resulted dual physically cross-linked hydrogels (DP Gel) with ultra-wide range adjustable Young's modulus (0.08–45.6 MPa), tensile stress (0.7–6.9 MPa), and toughness (3.3–23.1 MJ m−3). Stretching to 300%, DP Gel exhibited fast recoverability that remained ~95% of initial dissipated energy after resting in 60 °C for 3 min. Finally, scanning electron microscopy revealed that the microstructure of hydrogel changed from phase separation structure to micro phase separation as SMA added, which accounted for excellent performance of DP Gel. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1469–1474  相似文献   

13.
Novel amphoteric pH-sensitive hydrogels with pendant carboxyl and backbone tertiary amine groups were designed and synthesized. First, ethylenediaminetetraacetic dianhydride (EDTAD) reacted with butanediamine (BDA) via N-acylation reaction to give a polyamide prepolymer with pendant carboxyl groups (PEB–COOH); then amino-terminated poly(ethylene glycol) 500 (ATPEG500) was added as a cross-linking agent to produce the desired network polymer (PEB–ATPEG500–COOH). The obtained hydrogels are potentially degradable and non-toxic since its backbone and cross-linking sections are both linked by amide bonds and all monomers have been proved as safe. FTIR, 1H NMR, 13C NMR and ninhydrin reaction method were employed to qualitatively and quantitatively characterize the obtained polymers. The effect of cross-linking agent amount, characterized by the molar ratios (Rm) of NH2 groups in ATPEG500 to pendant COOH groups in PEB–COOH, on the swelling behavior of the proposed hydrogel was examined. The results indicate that the equilibrium swelling ratio decreases and the pH-sensitivity becomes retarded with the increase of Rm. For PEB–ATPEG500–COOH hydrogels with Rm no more than 0.42, they exhibited three SRe variation zones at pH 2–4, pH 6–7 and pH 9–11, respectively, suggesting obvious and interesting amphoteric pH-sensitivity. In addition, the swelling kinetics tests on PEB–ATPEG500–COOH with Rm = 0.32 reveal that the swelling kinetics of proposed hydrogel follows a Fickian diffusion process in media of pH 7, and an anomalous diffusion process in media of pH 2 and 11. The above obtained results will facilitate the application of this proposed hydrogel in biomedical fields, particularly in the drug controlled release.  相似文献   

14.
The N-arylation of chiral amino acid esters with minimal racemization is a challenging transformation because of the sensitivity of the α-stereocenter. A versatile synthetic method was developed to prepare N-arylated amino acid esters using cyclohexanones as aryl sources under continuous-flow conditions. The designed flow system, which consists of a coil reactor and a packed-bed reactor containing a Pd(OH)2/C catalyst, efficiently afforded the desired N-arylated amino acids without significant racemization, accompanied by only small amounts of easily removable co-products (i. e., H2O and alkanes). The efficiency and robustness of this method allowed for the continuous synthesis of the desired product in very high yield and enantiopurity with high space-time yield (74.1 g L−1 h−1) and turnover frequency (5.9 h−1) for at least 3 days.  相似文献   

15.

Chitosan is a biopolymer that forms hydrogels after swell in acid medium. The environment of the three-dimensional network of the chitosan-based hydrogels can be modified by its degree of swelling and crosslinking. In this way, nicotine was incorporated in the hydrogel formulations, with or without crosslinking with glutaraldehyde (0.01%), in different swollen states. Transdermal delivery of nicotine by chitosan-based hydrogels was studied in order to achieve the prolonged administration of the drug. Thermal analysis indicated a preliminary stability of these formulations, and the mechanism of drug release from hydrogels was dependent of the swelling degree and crosslinking. These formulations were able to control the transdermal flux of nicotine for up to 48 h following zero-order kinetics. The hydrogels with higher amounts of water or the partially dried crosslinked hydrogels reduced the partition of nicotine into the skin, leading to a minor transdermal flux of the drug (<3.4 µg cm−2 h−1). On the other hand, the partially dried non-crosslinked hydrogels lead to a major transdermal flux of the drug (20.19 µg cm−2 h−1) due to modifications of the environment into the hydrogel. In this way, these transdermal formulations were promising vehicles for prolonged administration of nicotine.

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16.
To provide prominent accessibility of fishmeal to the European population, the currently available, time- and cost-extensive feeding trials, which evaluate fish feed, should be replaced. The current paper reports on the development of a novel 3D culture platform, mimicking the microenvironment of the intestinal mucosa in vitro. The key requirements of the model include sufficient permeability for nutrients and medium-size marker molecules (equilibrium within 24 h), suitable mechanical properties (G' < 10 kPa), and close morphological similarity to the intestinal architecture. To enable processability with light-based 3D printing, a gelatin-methacryloyl-aminoethyl-methacrylate-based biomaterial ink is developed and combined with Tween 20 as porogen to ensure sufficient permeability. To assess the permeability properties of the hydrogels, a static diffusion setup is utilized, indicating that the hydrogel constructs are permeable for a medium size marker molecule (FITC-dextran 4 kg mol−1). Moreover, the mechanical evaluation through rheology evidence a physiologically relevant scaffold stiffness (G' = 4.83 ± 0.78 kPa). Digital light processing-based 3D printing of porogen-containing hydrogels results in the creation of constructs exhibiting a physiologically relevant microarchitecture as evidenced through cryo-scanning electron microscopy. Finally, the combination of the scaffolds with a novel rainbow trout (Oncorhynchus mykiss) intestinal epithelial cell line (RTdi-MI) evidence scaffold biocompatibility.  相似文献   

17.
Tissue engineering approach aims to overcome the transplant drawbacks and facilitate tissue repair and regeneration. Here, a new conductive, highly porous, and flexible polycaprolactone/gelatin/polypyrrole/graphene 3D scaffolds for nerve tissue repair is presented. A simple and efficient porogen leaching fabrication method is applied to create a 3D network with a pore radius of 3.8 ± 0.7 to 4.2 ± 0.8 μm with an exceptional uniform circular porous structure. The conductivity of the polymeric scaffold without graphene, in wet conditions, was found to be 0.78 ± 0.1 S.m−1 and it increased to 3.3 ± 0.2 S.m−1 for the optimized sample containing 3wt% graphene (G3). Tensile strength was measured at 163 KPa for the base sample (without graphene) and improved to 526 KPa for G3 sample. Following 42 days of incubation in PBS, 32.5% degradation for the base sample (without graphene) was observed. The cell study demonstrated a non-cytotoxic nature of all scaffolds tested and the cells had mostly stretched and covered the surface. Overall, the sum of results presented in this study demonstrate a simple fabrication platform with extraordinary aspects that can be utilized to mimic the native conductive tissue properties, and also because of its flexibility it can easily be rolled into a nerve conduit to fill gaps in nerve tissue regeneration.  相似文献   

18.
Supramolecular polymers from the bolaamphiphilic L ‐histidine ( BolaHis ) and benzene dicarboxylic acids (o‐phthalic acid, OPA ; isophthalic acid, IPA and terephthalic acid, TPA ) were found to form hydrogels although neither of the single components could gel water. It was suggested that the hydrogen bond and ionic interactions among different imidazole and carboxylic acid groups are responsible for the formation of the supramolecular polymer as well as the hydrogel formation. Depending on the structures of the dicarboxylic acids, different behaviors of the gels were observed. The hydrogels from OPA / BolaHis and IPA / BolaHis showed thixotropic properties, that is, the hydrogel was destroyed by hand shaking and then slowly gelated again at room temperature. However, the hydrogels of TPA / BolaHis could not. Interestingly, when EuIII was doped into IPA / BolaHis supramolecular polymers, very strong luminescence enhancement was observed. FT‐IR spectroscopies and XRD analysis revealed that the strong luminescence enhancement could be attributed to the matched supramolecular nanostructures, which render the correct binding and a good dispersion of EuIII ions. The work offers a new approach for fabricating functional hydrogels through the supramolecular polymers.  相似文献   

19.
《化学:亚洲杂志》2017,12(18):2374-2378
We report a new approach of in situ assembling gold nanoclusters (AuNCs) into hydrogel networks by exploiting the triple roles of protein as a gelator, a reducing agent as well as a template. The strategy simply involves the mixing of BSA and AuCl4 under alkaline condition. The obtained AuNCs‐protein nanocomposite hydrogels with injectable and moldable features can be made into semi‐transparent films or N‐doped C/Au composites. Our work demonstrates the feasibility of fabricating AuNCs in situ embedded in hybrid hydrogels, which can serve as multifunctional precursors for constructing diverse nanocomposite materials.  相似文献   

20.
Indole-3-acetic acid (IAA) based biopolymeric hydrogels with tunable anti-oxidant and anti-fungal character has been synthesized via condensation polymerization as pH-sensitive hydrophilic material.The present study focused on the synthesis of antifungal heterocyclic hydrogel using citric acid (CA), indole-3-acetic acid (IAA) and ethylene glycol (EG) by condensation polymerization. The hydrogels revealed a pH-sensitive swelling behavior, with increased swelling in acidic media, which in turn has decreased the swelling in the basic media.The hydrogel samples were tested for antifungal activity against Aspergillus fumigates, Rhizopusoryzae and Candida albicans at different concentrations (500, 1000, 1500, 2000 μg/well). Ketoconazole was used as positive control and DMSO as negative control for antifungal activity. Fungi were increasingly identified as major pathogens in various infections. Hydrogels with antifungal properties may constitute an important restriction to fungal infections. The biopolymeric hydrogels were characterized by Fourier transform infrared (FT-IR) spectroscopy, 1H-NMR,13C-NMR, TGA, DSC followed by scanning electron microscopy (SEM). The increased antifungal activity was monitored in equimolar composition more than that of other compositions. The antioxidant activity of ICE with DPPH and NO radicals has been compared with rutin. Such antifungal hydrogels with antioxidant properties is recommended for medical applications such as bandages, catheters, drains and tubes to prevent infection.  相似文献   

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