Simple preparation of stimuli-responsive hydrogels with good mechanical properties and mild stimuliresponsiveness is essential for their applications as smart soft robots. Mechanically strong Janus poly(N-isopropylacrylamide)/graphene oxide (PNIPAM/GO) nanocomposite hydrogels with stimuli-responsive bending behaviors are prepared through a simple one-step method by using molds made of a Teflon plate and a glass plate. Residual oxygen in the air bubbles on the Teflon plate surface affects the polymerization and hence the cross-linking density, leading to the different swelling/deswelling rates of the two sides of the gels. Therefore, the hydrogels exhibit bending/unbending behaviors upon heating/cooling in water. The incorporation of GO nanosheets dramatically enhances the mechanical properties of Janus hydrogels. Meanwhile, the photo-responsive property of the GO nanosheets also imparts the hydrogels with remotecontrollable deformation under IR irradiation. The application of the Janus PNIPAM/GO hydrogels as thermo-responsive grippers is demonstrated. 相似文献
In this study, a facile way has been proposed to prepare transparent, tough and flexible polyacrylamide (PAM) hydrogels which is composed of a dually crosslinked single network by chemical crosslinking of N,N'-methylenebisacrylamide (BIS) and physical crosslinking of hydrophilic hexagonal boron nitride (hBN) nanosheets. The resulting h-BN/PAM nanocomposite hydrogels are highly transparent, and exhibit significantly enhanced mechanical properties compared to the dark (GO)/PAM nanocomposite hydrogels or chemical crosslinking PAM hydrogels. Thus it opens up new opportunities for developing nextgeneration transparent, tough and flexible hydrogels that hold great promise in such important applications as light responsive soft robot and liquid microlenses. 相似文献
A new type of stimuli-responsive organic/inorganic nano-composite hydrogel was prepared by introducing fibrillar attapulgite into poly(2-hydroxyethyl methacrylate-co-poly(ethylene glycol) methyl ether methacrylate-co-methacrylic acid) network, in which the nanosized attapulgite fibril worked as the cross-linker instead of conventional chemical cross-linker. In the preparation process, a prepolymerization route was adopted to effectively stabilize the dispersion of attapulgite. The structure and morphology of the nano-composite hydrogels were characterized by SEM, FTIR and DSC. The swelling/deswelling behaviors and tensile mechanical properties of the nano-composite hydrogels were compared with that of the corresponding chemically cross-linked hydrogel. The results showed that the nano-composite hydrogels had much greater equilibrium-swelling ratio, much faster response rate to pH and significantly improved tensile mechanical properties. As the content of AT increased, the tensile strength, effective cross-link chain density and glass transition temperature increased, while the equilibrium swelling ratio, deswelling rate and elongation at break decreased. 相似文献
In this study, we chose corn stover hemicellulose for the preparation of hydrogels with admirable adsorption properties under mild alkaline conditions. Clay nanosheets were introduced to this system and hemicellulose/clay hybrid hydrogels were prepared. Morphological, mechanical properties and the methylene blue adsorption behaviors of the prepared hydrogels were studied. Results suggested that the addition of clay not only improved the mechanical strength of hemicellulose-based hydrogels, but also increased the adsorption capacity on methylene blue. Moreover, the adsorptions were confirmed to follow pseudo-second order equation for both gels with and without clay. The maximum adsorption capacities on methylene blue for hemicellulose-based hydrogels with or without clay reached 148.8 and 95.6 mg/g, respectively. These results implied that hemicellulose-based hydrogels could be used as promising adsorbents for the removal of methylene blue from waste water. 相似文献
We have developed a facile strategy to fabricate model multicolor hydrogels via a straightforward mixing process of poly acrylonitrile-grafted methacrylamide (PANMAM), polymethacrylic acid (PMAA) and doped lanthanide (Eu/Tb) and zinc ions to form the interpenetrating dual-polymer gel networks. The hydrogels exhibit excellent tunability of multi-spectrum emission colors (including white light) by simply varying the stoichiometry of metal ions. Furthermore, taking the advantage of different metal ion response mechanisms, we have demonstrated the reversible acidity/alkalinity stimuli-responsive behaviors of white-light-emitting hydrogel (WLE gel). Meanwhile, the unique cross-linked network formed through hydrogen-bonding, metal-ligand coordination and ionic interaction is introduced to achieve favorable mechanical strength of hydrogels. These properties enable the possibility in obtaining fluorescent patterns on hydrogels, which are promising candidate for encrypted information with improved security. 相似文献
A facile and versatile method for the synthesis of Janus graphene oxide (GO) nanosheets with different structures is reported. Based on electrostatic assembly, Janus GO nanosheets can be easily functionalized with a template polymer or be defunctionalized by altering the ionic strength. By using this approach, Janus GO nanosheets are prepared successfully with hydrophobic polystyrene chains on one side and hydrophilic poly(2‐(dimethylamino)ethyl methacrylate) chains on the other side.
Although significant progress has been made in the design and application of injectable hydrogels for biomedical applications, concurrent control of rheological and mechanical properties of injectable hydrogels has remained as an open challenge to the researchers. In this work, we introduce and put into practice a photo‐curable poloxamer (also known as Pluronic)/graphene oxide (Plu/GO) injectable hydrogel with well‐controlled rheological and mechanical properties. Acrylate group was anchored to hydrogel structure to endow photo‐crosslinking ability through decelerating degradation rate of poloxamer hydrogels after injection. It was found that the modified Plu remains stable in biological media for a long‐term period without significant weight loss. Rheological properties of hydrogels were also carried out as essential prerequisite for an ideal injectability via frequency sweep, flow curve, recovery, and yield stress before and after modification, signifying shear‐thinning behavior of Plu/GO hydrogels with high recoverability. The viscosity of shear‐thinning‐like hydrogels dropped at higher shear stress, which facilitated injection process. Moreover, mechanical behavior of Plu was optimized by manipulating the content of Plu, degree of modification with reactive precursor, curing, and particularly incorporation of GO without deteriorating effects on rheological behavior of Plu. 相似文献
With the ever-increasing demands for personalized drugs, disease-specific and condition-dependent drug delivery systems, four-dimensional (4D) printing can be used as a new approach to develop drug capsules that display unique advantages of self-changing drug release behavior according to the actual physiological circumstances. Herein, a plant stomata-inspired smart hydrogel capsule was developed using an extrusion-based 4D printing method, which featured with UV cross-linked poly(N-isopropylacrylamide) (PNIPAM) hydrogel as the capsule shell. The lower critical solution temperature (LCST) of the PNIPAM hydrogels was approximately 34.9 °C and macroporous PNIPAM hydrogels were prepared with higher molecular weight polyethylene glycols (PEGs) as the pore-forming agents. Owing to the LCST-induced shrinking/swelling properties, the prepared PNIPAM hydrogel capsules exhibited temperature-responsive drug release along with the microstructure changes in the PNIPAM hydrogels. The in vitro drug release test confirmed that the PNIPAM hydrogel capsules can autonomously control their drug release behaviors on the basis of ambient temperature changes. Moreover, the increased PEG molecular weights in the macroporous PNIPAM hydrogel capsules caused an obvious improvement of drug release rate, distinctly indicating that the drug release profiles can be well programmed by adjusting the internal pore size of the hydrogel capsules. In vitro biocompatibility studies confirmed that the PNIPAM hydrogel capsules have great potential for biomedical applications. The bioinspired 4D printed hydrogel capsules pioneer the paradigm of smart controlled drug release. 相似文献
Carbonaceous nanocomposite hydrogels are prepared with an aid of a suspension polymerization method and are used as anodes in microbial fuel cells (MFCs). (Poly N‐Isopropylacrylamide) (PNIPAM) hydrogels filled with electrically conductive carbonaceous nanomaterials exhibit significantly higher MFC efficiencies than the unfilled hydrogel. The observed morphological images clearly show the homogeneous dispersion of carbon nanotubes (CNTs) and graphene oxide (GO) in the PNIPAM matrix. The complex formation of CNTs and GO with NIPAM is evidenced from the structural characterizations. The effectual MFC performances are influenced by combining the materials of interest (GO and CNTs) and are attributed to the high surface area, number of active sites, and improved electron‐transfer processes. The obtained higher MFC efficiencies associated with an excellent durability of the prepared hydrogels open up new possibilities for MFC anode applications.
A novel stimuli-responsive organic/inorganic nanocomposite hydrogel (NC hydrogel) with excellent mechanical properties was synthesized by in situ polymerization of 2-(2-methoxyethoxy) ethyl methacrylate (MEO(2)MA), oligo (ethylene glycol) methacrylate (OEGMA) and acrylic acid (AAc), as the polymeric matrix (PMOA), and fibrillar attpulgite (AT), as the reinforcer and cross-linker. The effect of the AT content on the mechanical properties for the swollen and dried NC hydrogels was determined by tensile testing and dynamic mechanical analysis (DMA), respectively. The tensile testing results showed that the incorporation of AT nanoparticles significantly enhanced the mechanical properties of NC hydrogels. As the content of AT increased, the tensile strength, tensile modulus and effective cross-linked chain density increased. The DMA results showed that the storage modulus of AT/PMOA NC hydrogels was increased and the glass transition temperatures shifted to higher temperature compared to the pure PMOA hydrogel, which further indicated that the enhancement of mechanical property depended upon the presence and content of AT. In addition, the faster swelling rates of the NC hydrogels were observed in comparison with the corresponding physically cross-linked PMOA hydrogel, except for 1% AT/PMOA sample. However, the deswelling kinetics of NC hydrogels was obviously retarded. 相似文献
Graphene is a two-dimensional sp2 hybridized carbon material that has attracted tremendous attention for its stimuli-responsive applications, owing to its high surface area and excellent electrical, optical, thermal, and mechanical properties. The physicochemical properties of graphene can be tuned by surface functionalization. The biomedical field pays special attention to stimuli-responsive materials due to their responsive abilities under different conditions. Stimuli-responsive materials exhibit great potential in changing their behavior upon exposure to external or internal factors, such as pH, light, electric field, magnetic field, and temperature. Graphene-based materials, particularly graphene oxide (GO), have been widely used in stimuli-responsive applications due to their superior biocompatibility compared to other forms of graphene. GO has been commonly utilized in tissue engineering, bioimaging, biosensing, cancer therapy, and drug delivery. GO-based stimuli-responsive platforms for wound healing applications have not yet been fully explored. This review describes the effects of different stimuli-responsive factors, such as pH, light, temperature, and magnetic and electric fields on GO-based materials and their applications. The wound healing applications of GO-based materials is extensively discussed with cancer therapy and drug delivery. 相似文献
In recent years, intelligent hydrogels which can change their swelling behavior and other properties in response to environmental stimuli such as temperature, pH, solvent composition and electric fields, have attracted great interest. The hydrogels based on polysaccharides incorporated with thermo-responsive polymers have shown unique properties such as biocompatibility, biodegradability, and biological functions in addition to the stimuli-responsive characters. These "smart" hydrogels exhibit single or multiple stimuli-responsive characters which could be used in biomedical applications, including controlled drug delivery, bioengineering or tissue engineering. This review focuses on the recent developments and future trends dealing with stimuli-responsive hydrogels based on grafting/blending of polysaccharides such as chitosan, alginate, cellulose, dextran and their derivatives with thermo-sensitive polymers. This review also screens the current applications of these hydrogels in the fields of drug delivery, tissue engineering and wound healing. 相似文献
Development of high‐strength hydrogels has recently attracted ever‐increasing attention. In this work, a new design strategy has been proposed to prepare graphene oxide (GO)/polyacrylamide (PAM)/aluminum ion (Al3+)‐cross‐linked carboxymethyl hemicellulose (Al‐CMH) nanocomposite hydrogels with very tough and elastic properties. GO/PAM/Al‐CMH hydrogels were synthesized by introducing graphene oxide (GO) into PAM/CMH hydrogel, followed by ionic cross‐linking of Al3+. The nanocomposite hydrogels were characterized by means of FTIR, X‐ray diffraction (XRD), and scanning electron microscopy/energy‐dispersive X‐ray analysis (SEM‐EDX) along with their swelling and mechanical properties. The maximum compressive strength and the Young's modulus of GO3.5/PAM/Al‐CMH0.45 hydrogel achieved values of up to 1.12 and 13.27 MPa, increased by approximately 6488 and 18330 % relative to the PAM hydrogel (0.017 and 0.072 MPa). The as‐prepared GO/PAM/Al‐CMH nanocomposite hydrogels possess high strength and great elasticity giving them potential in bioengineering and drug‐delivery system applications. 相似文献