Swelling Process Research Articles

Preparation of Peanut Shell Cellulose Double-Network Hydrogel and Its Adsorption Capacity for Methylene Blue

To achieve optimal recovery and value-added utilisation of cellulose in peanut shells, the cellulose in peanut shells was first extracted using the sodium hydroxide-sodium chlorite method. Then, cellulose hydrogel was prepared by graft copolymerisation using N, N’-methylenebisacrylamide as the cross-linking agent, sodium persulfate as the initiator, and acrylic acid as the monomer. Orthogonal optimisation experiments were designed to obtain optimal process parameters for hydrogel preparation with the cellulose dosage of 0.40 g, initiator dosage of 0.20 g, polymerisation temperature of 70°C, cross-linking agent of 0.25 g, and monomer dosage of 3.0 mL. The effect of initiator dosage on hydrogel synthesis was the most significant, followed by monomer dosage and reaction temperature. Characterisation using X-ray diffraction analysis and scanning electron microscopy revealed that the hydrogel was amorphous and exhibited a distinct three-dimensional double network structure. Hydrogel swelling kinetic analysis showed that the hydrogel swelling process was divided into three stages, and fitted the Schott secondary swelling kinetic model. The prepared hydrogel had a good adsorption effect on methylene blue; the adsorption of methylene blue by the hydrogel was 1.259 mg/g at 25°C when the initial concentration of methylene blue was 5 mg/L. The adsorption kinetics of the hydrogel fit the pseudo-first-order kinetic model, pseudo-second-order kinetic model, Eovich model and particle diffusion model. The best fitting effect was obtained with the pseudo-second-order kinetic model. The adsorption isotherm analysis of methylene blue on hydrogel showed that the adsorption process was consistent with Langmuir and Freundlich models. The correlation coefficient of the Freundlich isotherm model was higher, indicating that the adsorption of methylene blue on hydrogel was mainly chemisorption.

Swelling and Antimicrobial Activity Characterization of a GO-Reinforced Gelatin-Whey Hydrogel.

Whey-based hydrogel samples with increasing concentrations of graphene oxide (GO) were studied, against a control sample (M), for swelling behavior in light of nuclear magnetic resonance (NMR) and mathematical models of the diffusion process and for antibacterial activity. Graphene oxide (GO) is an optimal filler for whey-based hydrogels, giving them improved mechanical and swelling properties at low concentrations. Crosslinking induces a certain stiffness of the hydrogels, which is why only the first part of the swelling process (<60%) follows the first-order model, while during the whole time interval, the swelling process follows the second-order diffusion model. The NMR relaxometry results are consistent with the swelling behavior of GO-reinforced whey−gelatin composite hydrogels, showing that higher GO concentrations induce a higher degree of cross-linking and, therefore, lower swelling capacity. Only hydrogel samples with higher GO concentrations demonstrated antibacterial activity.

Optical and mechanical properties of PNIPAm‐MWCNTs and PNIPAm‐GO composites

AbstractThe aim of this study is to investigate drying, swelling, elastic properties, and to produce optical band gap energies on the performance of Poly (N‐Isopropyl acrylamide) ‐ Multi walled carbon nanotubes (PNIPAm – MWCNTs) and Poly (N‐Isopropyl acrylamide)‐ Graphene Oxide (PNIPAm‐GO) composites, respectively. The composites were prepared by free radical crosslinking copolymerization. Drying and swelling of PNIPAm‐MWCNTs and PNIPAm‐ GO composites were performed by using steady state fluorescence technique. Firstly, the desorption coefficients of the composites were modeled by using Fick's Law. Cooperative diffusion coefficients were calculated by employing Li‐Tanaka Model. When composite doped with 10 wt% of MWCNTs has a higher desorption coefficient than composite doped with the same amount of GO, 40 wt% of GO content in the PNIPAm has a higher diffusion coefficient than the composite that has 40 wt% of MWCNTs content in the swelling process. Secondly, the composite that has 40 wt% of MWCNTs content has a higher modulus before swelling than the composite that has the same amount of GO contents. Lastly, optical band gap energies were calculated by using Tauc's approach, and Urbach's relation by using the data performed UV Spectroscopy. We found that PNIPAm ‐GO has a much narrower band gap value.

Investigation on storage stability and rheological properties of environment-friendly devulcanized rubber modified asphalt

The application of conventional rubber modified asphalt was limited to its high viscosity, poor storage stability, and environmental pollution. This study proposed a preparation process of environment-friendly devulcanized rubber modified asphalt (DRMA) with superior performance. The storage stability and rheological properties of base asphalt, rubber modified asphalt (RMA), and DRMA with different modifier content were evaluated by segregation test, frequency scanning test, multiple stress creep recovery test (MSCR), linear amplitude scanning (LAS) test, and bending beam rheometer (BBR) test. Modification mechanisms of DRMA were detected by scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), and four-component analysis. Test results indicated that interaction between crumb rubber and asphalt was mainly physical and has slight chemical reaction. The swelling process of devulcanized rubber (DVR) was adequate and absorbs more light components, which was crucial to improve rheological properties. The storage stability of DRMA was less susceptible to the content of DVR. Besides the crack resistance of DRMA with 18% DVR dosage, the storage stability, high-temperature performance, fatigue resistance, and low-temperature performance of DRMA were markedly superior to that of RMA if the modifier dosage is the same. The rutting and fatigue resistance of RMA was reinforced and then weakened slightly with the increase of CR content, while that of DRMA was enhanced continuously, implying that more waste crumb rubber can be added to asphalt after devulcanization. DRMA was expected to be widely applied owing to its superior performance and environmental features.

Swelling-based gelation of wet cellulose nanopaper evaluated by single particle tracking

ABSTRACT Nanopapers fabricated from cellulose nanofibers (CNFs) drastically swell to form hydrogels when they are in contact with water. This gelation makes contrast with conventional papers that simply deform without drastic volume increase. While the volume increase is qualitatively obvious from the macroscopic visual inspection, its quantitative understanding is nontrivial because of the difficulty in the detection of the boundary between the nanopaper hydrogel and the residual or extra water. In this study, we use single particle tracking (SPT) to reveal the swelling-based gelation phenomenon of cellulose nanopapers. The diffusive dynamics of probe particles uncovers the transient process of swelling, and equilibrium analysis reveals the dependence of volume increase fundamentally dependent on the amount of water to be in contact with the nanopapers. Comparison with the aqueous CNF dispersion without drying reveals the difference in the texture of the nanopaper hydrogels from them.

Inhibition of the LRRC8A channel promotes microglia/macrophage phagocytosis and improves outcomes after intracerebral hemorrhagic stroke.

Promoting microglial/macrophage (M/Mφ) phagocytosis accelerates hematoma clearance and improves the prognosis of intracerebral hemorrhagic stroke (ICH). Cation channels such as Piezo1 modulate bacterial clearance by regulating M/Mφ. Whether LRRC8A, an anion channel, affects M/Mφ erythrophagocytosis and functional recovery after ICH was investigated here. We found that LRRC8A is highly expressed on M/Mφ in the perihematomal region of ICH mice. Conditional knockout of Lrrc8a in M/Mφ or treatment with an LRRC8A channel blocker accelerated hematoma clearance, reduced neuronal death, and improved functional recovery after ICH. Mechanistically, the LRRC8A channel inhibition promoted M/Mφ phagocytosis by activating AMP-activated protein kinase (AMPK), thereby inducing nuclear translocation of nuclear factor-erythroid 2 related factor 2 (Nrf2) and increasing Cd36 transcription. Our findings illuminate the regulation of M/Mφ phagocytosis by the LRRC8A channel via the AMPK-Nrf2-CD36 pathway after ICH, suggesting that LRRC8A is a potential target for hematoma clearance in ICH treatment.

Compression Relaxation of Multi-Structure Polymer Composites in Penetrating Liquid Medium.

Multi-structural polymer composites are widely used in the mechanical engineering, automotive, aviation and oil refining industries, as well as in the printing industry as a shock-absorbing deckle on the offset cylinders of printing machines. During offset printing, composites come into contact with inks and washing solutions, the components of which penetrate the material and cause the polymers to swell. This process degrades the print quality, and for this reason the study of its features is relevant. The prerequisites for this work are the study of the fundamental laws of diffusion and sorption of liquids by polymers with different micro- and macro-structures in different physical states and in different forms (e.g., films, sheets, fibers and fabrics). The combination of polymer materials in the composition of multi-structural fabric blankets makes it possible to obtain materials with unique mechanical properties and high resistance to liquid penetrating media and to use them in high-tech processes of multi-color printing with high resolution and color rendering. This article reports for the first time the kinetics and thermodynamics results obtained from the swelling of multi-structural polymeric blankets in solvents used in printing, and the effect of sorption of different polar liquids on the viscoelastic strain under compression during the operation of the damping systems of printing machines. Using mathematical models of activated liquid diffusion in polymers and deformation of a viscoelastic body, the swelling rate constants, solvent diffusion coefficients (the kinetic characteristics of the swelling process) and Flory−Huggins parameters (the thermodynamic characteristics of the interaction of the solvent with the composite) for composite−solvent systems with several chemical composition variants were determined. The elastic modulus and the viscosity coefficient of the composite under liquid saturation were calculated based on the experimental cyclic compression data. The range of change in the compression and restoration times of the polymeric blankets (0.09 s ÷ 0.78 s) was determined. It was shown that the composite swelled to a limited extent in all the studied liquids. All solvents used were thermodynamically poor (χ > 0.5). It has been established that rubber−fabric blankets coated with nitrile rubber are the least resistant to the action of dichloroethane, and that blankets with layers of polyolefins are not resistant to ethyl acetate. Water significantly affects the physicochemical properties of rubber−fabric blankets with a large proportion of cotton fabric layers. The data obtained can serve as a basis for optimizing the compositions of inks and cleaning solutions, as well as a theoretical basis for the thermodynamics of composite−solvent systems.

Effect of Solvents on the Color Recovery Responses of Swollen Structural-Color Epoxy Films Based on Inverse Opal Photonic Crystals.

Photonic crystal (PC) films have been widely applied in color displays and the anticounterfeiting field due to their facile fabrication process and easily tunable properties. However, the method for improving the reusability of the color-changed swollen PC films is still a challenge. In this paper, we report the color recovery behavior of epoxy resin inverse opal photonic crystal (EP-IOPC) films, which show different responses after being infiltrated with ethanol, acetone, and dimethyl sulfoxide (DMSO) based on the swelling and deswelling process. DMSO achieved the best effect on the color recovery of the swollen EP-IOPC films compared to ethanol and acetone, and the reflection spectrum blue-shifted in a small range and finally stabilized at a 60 nm deviation from the original spectrum after 10 times recovery. This strategy of color recovery not only solved the problem that the swollen EP-IOPC film's color changes to a certain extent but also showed promising potential in the color display and anticounterfeiting field.

A soluble-fluorescent surface molecularly imprinted polymer sensor based on combined soluble solid phase-and liquid–liquid-microextraction

The rigid and highly cross-linked nature of fluorescent molecularly imprinted polymer (FMIP) make it dispersive in solution and cause scattering of source light which limits the application of FMIP in photoluminescence sensors. In addition, the distribution of FMIPs in the solution is unstable and in some cases their rapid settlement deviate the accuracy and precision of measurement. In this work, a miniaturized probe based on the soluble-fluorescent surface molecularly imprinted polymer (S-FSMIP) was developed and conveniently implemented to detect sertraline (SER), as a model target, in human urine. The developed probe synthesis was conducted in two main steps: i) design of FSMIP with hydrophobic core and hydrophilic surface, ii) swelling process of FSMIP at a high temperature in the presence of a high boiling hydrophobic deep eutectic solvent (HDES). Employment of HDES as a green solvent for solvation of FSMIP minimizes the consumption of hazardous chemicals and also improves analyte transfer to surface of FMIP. The adsorption isotherm and adsorption kinetic of the S-FSMIP were also studied and compared with FSMIP. Accordingly, the analytical parameters such as linearity, limits of detection, limits of quantification, relative standard deviations and the absolute recovery values were provided for this rapid and green-oriented method.

Study on SBS Optimal Block Ratio Based on Molecular Simulation.

The block ratio of SBS is an important factor influencing the swelling effect of modified asphalt, but the effect of the block ratio in the swelling process cannot be accurately studied by macro testing. In order to solve this problem and screen out the optimal SBS block ratio, molecular models of asphalt and SBS with different block ratios were established by molecular simulation technology at the microscopic level, and an asphalt-SBS interaction layer system was established on this basis. The diffusion and adhesion effects of SBS with different block ratios were evaluated by calculating the immersion depth, diffusion coefficient, and adhesion work of SBS in asphalt. The results show that SBS has a physical cross-linking reaction with asphalt during swelling, and SBS with a higher butadiene block ratio exhibits a deeper immersion depth; thus, SBS with a 3/7 block ratio has the best performance in the modification process, which is superior to SBS with other block ratios, in terms of both the diffusion and adhesion effect. The performance of asphalt modified by SBS with different block ratios was tested using penetration, softening point, and ductility, and the results were consistent with the simulation results, which proved the reliability of the microscopic conclusions from a macro perspective.

Swelled Mechanism of Crumb Rubber and Technical Properties of Crumb Rubber Modified Bitumen.

Crumb rubber modified bitumen (CRMB) has excellent high-temperature performance and fatigue resistance, and is widely used in asphalt pavement to cope with increasing traffic axle load and changing climate. Under conventional preparation conditions, the swelling degree of CR can directly impact the comprehensive properties of CRMB; however, physical and chemical properties research on swelling crumb rubber (SCR) and crumb rubber recycled bitumen (CRRB) in CRMB is relatively lacking. In this paper, the working performance of CRMB and CRRB in high-temperature and low-temperature conditions were studied through physical and working performance testing of bitumen. The CR and SCR were tested by scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIR), gel permeation chromatography (GPC), and particle size distribution (PSD) tests to study the physicochemical behavior and microscopic effects before and after CR swelling. The results showed that CR dosage was in the range of 10%, 15%, and 20%, as well as that CR dosages have a positive effect on the high- and low-temperature performance, storage stability, and elastic recovery of bitumen. The high-temperature PG grades of bitumen were directly improved by four grades, and the elastic recovery rate increased by 339.9%. CR improved the ultra-low temperature crack resistance of bitumen. Due to the absorption of lighter components by CR, the relative content of the heavy component of bitumen increased; however, its low-temperature performance decreased significantly. After swelling, the CR particle size increased and the range became wider, the surface complexity of CR became higher, and the specific surface area was larger. At the same time, CR carried out the transformation process from large and medium molecules to small molecules. During the swelling process, a new benzene ring structure appeared in the CR, and the C-C bond and C-S bond of CR broke, forming part of the C=C bond.

Correlation of ground penetrating radar and 2-D resistivity imaging methods towards shallow subsurface layer at coastal area

There is potential for a long-term subsidence trend on reclaimed land from the shoreline that may cause a geohazard in the future. This study conducted ground penetrating radar (GPR) and the 2-D resistivity method within the residential area in Teluk Kumbar, Pulau Pinang. This residential area is built on reclaimed land about 100 m from the shoreline. The purpose of this study is to identify subsidence in the coastal environment by considering the impact of seasonal variations using both surveys. The influence of wet and dry seasons on GPR and resistivity for the subsurface condition can be determined precisely after evaluating the attenuation of electromagnetic and resistivity values. The resistivity results show three lithology classes: reclaimed soil (>600 Ωm), original soil (<400 Ωm) and hard material (>1000 Ωm) during the dry season. Meanwhile, GPR signals support resistivity results with clear interfaces between reclaimed-original soil and original soil-hard material. GPR signals on layer interfaces have significantly reduced during the wet season due to the increased conductivity. The resistivity results also show decreases as the conductivity increases. Besides, a thick saturated zone of original soil formation has expanded in size during this season with a low resistivity value (<100 Ωm) and weak amplitude reflection. This zone tends to undergo shrink and swell processes due to moisture content changes, which can also correspond to subsidence. Overall, this study provides a good correlation between the performance of geophysical techniques and seasonal changes that accurately characterize the subsurface layer.

The Shrink–Swell Process of the Granite Residual Soil with Different Weathering Degree in a Gully System in Southern China

The soil shrink–swell phenomenon produces crack networks and slope instability. However, few studies have involved the continuous shrink–swell process of granite residual soils. The objective of the study is to explore the shrink–swell process of weathered granite soils and its effects on gully development in southern China. The bulk density, soil water content (SWC), shrink–swell ratio (SSR), clay mineral content, and mechanical composition, etc., of soil samples from five soil layers (at depths of 0.3 m, 3.0 m, 7.0 m, 12.0 m, and 16.0 m) along a profile in Yudu County was analyzed. After quantifying the soil properties at different soil depths, we analyzed these data statistically in an effort to identify strong parametric relationships. The results indicated that some properties such as bulk density and shear stress increased with soil depth, while other soil properties, such as plasticity index and liquid limit, were inversely related to depth. Soil cohesion, the angle of internal friction, and shear stress were closely related to the SWC. Every 1% decrease in the SWC resulted in a shear stress reduction of 6.62 kPa. The SSR values exhibited significant variation between the three dry–wet cycles and were closely related to the bulk density values of our kaolin and montmorillonite samples. As an environmental factor, the SWC can trigger changes in internal soil properties such as shear stress and the SSR. Using these data and observations made during our field survey, it can be proposed that continuous shrink–swell variation in deep granite-weathering crust can result in crack formation and gully erosion. It can be inferred that crack development velocity and gully retreat rate may be affected by the soil’s shrink–swell process. Consequently, this information provides insight to understanding the mechanism of gully development in southern China.

The effect of binder molecular weight and talc mineral filler on expansion ratio and hardness in intumescent material

AbstractIntumescent flame retardant coatings were prepared including binder (acrylic resin), solvent, TiO2, talc and flame retardant system (ammonium polyphosphate‐APP, pentaerythritol‐PEN, and melamine‐MEL). To evaluate the effect of molecular weight on the swelling process as well as the hardness of the charred layer, the acrylic resins with different molecular weights were applied. In particular, by incorporating of talc mineral, the performance of the APP‐PEN‐MEL system is significantly improved. The results showed that the highest molecular weight acrylic resin has the best expansion ratio (53.72 times) and the highest hardness of charred layer (15.5 N at the compression of 30 %). The coating with 2.5 % talc powder can be considered as an optimized content of the char layer.

Recovery of carbon fiber-reinforced polymer waste using dimethylacetamide base on the resin swelling principle.

The mechanical recycling method of the carbon fiber-reinforced polymer (CFRP) has the advantages of simple process, less pollution and low cost, but only low utilization value of carbon fibers in powder or short fibers form can be obtained. To reduce the length and strength loss of the recycled carbon fibers, a novel and cost-effective dimethylacetamide (DMAC) swelling technique was developed to achieve rapid delamination of the CFRP laminates under mild conditions (120°C-160°C, 1h). The corresponding swelling ratios and mass-loss rates of cured epoxy resin (CEP) were about 121.39%-157.39% and 0-0.69%, respectively. Excessive swelling of CEP in DMAC resulted in the cracking of the resin matrix between the adjacent carbon fiber layers. Thus the CFRP laminates were delaminated into soft single carbon fiber layers, which showed excellent cutting performance and reinforcing properties. The delamination products were cut into thin strips of different sizes and vacuum bag molded into new CFRP laminates. The flexural strength and tensile strength of the newly produced CFRP laminates were about 76.38%-90.98% and 94.61%-98.54% of the original CFRP laminates, respectively. More importantly, the chemical compositions of DMAC and CEP were unchanged during the physical swelling process. No organic pollutants (caused by resin degradation) were generated. And the used DMAC can be easily recycled by filtration. Therefore, this study provides a strategy for low-cost and high-valued recycling of CFRP waste.

Application of the Maxwell–Stefan theory in modeling gas diffusion experiments into isolated oil droplets by water

We have used the Maxwell–Stefan diffusion theory to model the mass transfer between tertiary-injected gas and residual oil blocked by water, in order to predict the time required for the rupture of the water barrier due to oil swelling. We have also designed and conducted a set of visualization micromodel experiments on various pure and multicomponent oil–gas systems to measure the water rupture time in tertiary gas injection processes. The experimental results show that the initial pressure and dimensions of the system, the oil and gas composition, and the gas solubility in water control the oil swelling process. The experimentally measured rupture times are then employed to evaluate the reliability of the model and to compare its accuracy with that of a similar one using classical Fick's law. Our modeling results show that both models are able to estimate the water rupture time for pure systems with an acceptable precision. As for multicomponent mixtures, however, only the Maxwell–Stefan theory is capable of modeling the molecular diffusion process correctly and yields values close to reality, while the use of Fick's law would lead to erroneous results. Deficiency of the latter model becomes more acute when the diffusion direction in reality is contrary to what the model indicates, which leads to failure in calculating any value for rupture time at all for these cases.

Reversible and pH-modulated changes in microgel size triggered by electrochemical stimuli

A novel microgel, the volume of which can be reversibly changed by using an electrochemical trigger, was successfully synthesized. To this end, a monomer based on N-(3-aminopropyl)methacrylamide modified with ferrocenecarboxylic acid was obtained and co-polymerized with acrylic acid and N,N′–methylenebisacrylamide. Using the distillation precipitation polymerization method, spherical, smooth-surfaced microgel particles ca. 500 nm in diameter were obtained. The presence of ferrocene groups in the microgel was shown with nuclear magnetic resonance spectroscopy, energy dispersive X-ray spectroscopy, and cyclic voltammetry methods. Dynamic light scattering experiments showed that the microgel size strongly depends on the oxidation state of the ferrocene groups. Next, cyclic voltammetry and chronoamperometry combined with quartz crystal microbalance measurements, obtained with an Au electrochemical quartz crystal microbalance electrode modified with the microgel, proved that the microgel size could be controlled by an electrochemical trigger. More interestingly, the electro-response was found to strongly depend on pH. In acidic pH, where almost all carboxylic groups are protonated, the oxidation of ferrocene groups led to a decrease in the registered frequency shift, related to the microgel swelling process. In alkaline pH, where many carboxylic groups are ionized, the oxidation of ferrocene led to an increase in frequency, related to the microgel shrinking process. These processes were found to be reversible and relatively fast.

Preparation of Spherical Cellulose Nanocrystals from Microcrystalline Cellulose by Mixed Acid Hydrolysis with Different Pretreatment Routes

Spherical cellulose nanocrystal (CNC), as a high value cellulose derivative, shows an excellent application potential in biomedicine, food packaging, energy storage, and many other fields due to its special structure. CNC is usually prepared by the mixed acid hydrolysis method from numerous cellulose raw materials. However, the pretreatment route in preparing spherical CNC from cellulose fiber is still used when choosing microcrystalline cellulose (MCC) as the raw material, which is not rigorous and economical. In this work, pretreatment effects on the properties of spherical CNC produced from MCC by mixed acid hydrolysis were systematically studied. Firstly, the necessity of the swelling process in pretreatment was examined. Secondly, the form effects of pretreated MCC (slurry or powder form) before acid hydrolysis in the preparation of spherical CNC were carefully investigated. The results show that the swelling process is not indispensable. Furthermore, the form of pretreated MCC also has a certain influence on the morphology, crystallinity, and thermal stability of spherical CNC. Thus, spherical CNC with different properties can be economically prepared from MCC by selecting different pretreatment routes through mixed acid hydrolysis.

Anti-inflammatory effects and potential mechanisms of Mitragyna speciosa methanol extract on λ-karagenan-induced inflammation model

Introduction: Mitragyna speciosa is known to have beneficial effects, such as antinociceptive and anti-inflammatory effects. There are some components that involve in inflammatory, such as Inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX-2) enzymes, and also cytokines. This study aimed to investigate the anti-inflammatory effect and its mechanism of Mitragyna speciosa leaf. Methods: Carrageenan-induced rat paw edema model was used for inflammation induction. Rats were given Mitragyna speciosa leaf methanol extract at a dose of 75, 150, and 200 mg/kg. Results: Intraplantar injection of carrageenan led to the development of time-dependent peripheral inflammation, which, in turn, was a significant increase in the swelling process as measured by a plethysmometer. However, administration of EMS (75,150 and 200mg/kg) can reduce edema in a dose-dependent manner. We also demonstrated that skin histology on EMS administration significantly preserved skin thickness at 4 h after carrageenan injection. Conclusion: In conclusion, we reveal the role of Mytragyna speciosa methanol extract as anti-inflammatory and maintain skin thickness in the inflammatory process.

Anion-Induced Reversible Actuation of Squaramide-Crosslinked Polymer Gels.

Supramolecular anion binding to squaramide crosslinkers in poly(N,N-dimethylacrylamide) gel networks enhances swelling and allows reversible chemically driven actuation. The volume swelling ratio of the gels is shown to depend on both the type of anion and its concentration. 1H NMR and UV–vis titrations with the squaramide crosslinkers reveal a relationship between anion binding affinity and the concentration-dependent swelling behavior. Gel swelling is shown to be reversible, and by embedding a solid support into rod-shaped gels, soft actuators are fabricated that undergo forward and backward bending motion in response to changing anion concentration. The swelling and bending process, which is accompanied by intense green coloration of the gel, is achieved by using only low amounts of crosslinker. This macroscopic actuation achieved by anion binding to specific molecular entities in the polymer network will open new opportunities in the field of chemically responsive materials.