Anti-swelling Properties Research Articles

Self-Cross-Linking of MXene-Intercalated Graphene Oxide Membranes with Antiswelling Properties for Dye and Salt Rejection.

Membrane-based water purification is poised to play an important role in tackling the potable water crisis for safe and clean water access for the general population. Several studies have focused on near two-dimensional membranes for this purpose, which is based on an ion rejection technique. However, membrane swelling in these materials has emerged as a significant challenge because it leads to the loss of function. Herein, we report a self-cross-linked MXene-intercalated graphene oxide (GO) membrane that retains ion and dye rejection properties because the physical cross-linking interaction between Ti-O-Ti and neighboring nanosheets effectively suppresses the swelling of the membrane. In addition to the associative Ti-O-Ti bonds, C-O-C, O=C-O, and C-OH bonds are also formed, which are important for inhibiting the swelling of the membrane. To ensure the longevity of these membranes in a service context, they were subjected to heat pressurization and subsequent thermal annealing. The membrane subjected to this novel processing history exhibits minimal swelling upon immersion in solutions and retains function, rejecting salt and dyes over a wide range of salt and dye concentrations. Furthermore, these membranes successfully rejected dye and salt over a period of 72 h without a degradation of function, suggesting that these membranes have the requisite durability for water filtration applications.

An injectable magnesium-coordinated phosphate chitosan-based hydrogel loaded with vancomycin for antibacterial and osteogenesis in the treatment of osteomyelitis.

Microbial infections of bones, particularly after joint replacement surgery, are a common occurrence in clinical settings and often lead to osteomyelitis (OM). Unfortunately, current treatment approaches for OM are not satisfactory. To address this issue, this study focuses on the development and evaluation of an injectable magnesium oxide (MgO) nanoparticle (NP)-coordinated phosphocreatine-grafted chitosan hydrogel (CMPMg-VCM) loaded with varying amounts of vancomycin (VCM) for the treatment of OM. The results demonstrate that the loading of VCM does not affect the formation of the injectable hydrogel, and the MgO-incorporated hydrogel exhibits anti-swelling properties. The release of VCM from the hydrogel effectively kills S.aureus bacteria, with CMPMg-VCM (50) showing the highest antibacterial activity even after prolonged immersion in PBS solution for 12 days. Importantly, all the hydrogels are non-toxic to MC3T3-E1 cells and promote osteogenic differentiation through the early secretion of alkaline phosphatase and calcium nodule formation. Furthermore, in vivo experiments using a rat OM model reveal that the CMPMg-VCM hydrogel effectively kills and inhibits bacterial growth, while also protecting the infected bone from osteolysis. These beneficial properties are attributed to the burst release of VCM, which disrupts bacterial biofilm, as well as the release of Mg ions and hydroxyl by the degradation of MgO NPs, which inhibits bacterial growth and prevents osteolysis. Overall, the CMPMg-VCM hydrogel exhibits promising potential for the treatment of microbial bone infections.

An anti-swelling chitosan-based hydrogel driven by balance of hydrophilic segment and hydrophobic segment strategy for underwater detection of human motion

Hydrogel-based flexible strain sensors have gained rapid development. However, most of traditional hydrogels were prone to undergo swelling behavior underwater as solvent molecules continuously penetrated, which limited their application scenarios. To make up this deficiency, a chitosan-based anti-swelling hydrogel cross-linked by ionic liquid are presented. The hydrogel is consisted of chitosan (CS) and copolymer of acrylic acid (AA), 2-hydroxyethyl methacrylate (HEMA), butyl acrylate (BA) and dimethylaminoethyl methacrylate maleate (DMAEMA-MA). The P(HEMA-BA-AA)/ILs/CS hydrogel exhibited excellent anti-swelling properties driven by balance of hydrophilic segment and hydrophobic segment strategy (equilibrium swelling rate of −3.79 % in water for 100 days). The ionic liquid was introduced into the hydrogel system as cross-linking agent, which could effectively prevent the loss of conductivity of the hydrogel after soaking in water. The synergy effect chain entanglement, H-bonds and electrostatic interactions endowed the hydrogel with excellent mechanical property. Surprisingly, the modulus and toughness of the hydrogel were significantly boosted after a week of submersion. Thus, this anti-swelling hydrogel was employed as wireless strain sensor, which implemented underwater motion monitoring and safety alarms. It is expected that the anti-swelling hydrogel driven by balance of hydrophilic and hydrophobic effects would inspire the development of underwater sensors.

A gelatin-based ionogel with anti-swelling properties for underwater human physiological signal detection.

A hydrogel is an ideal matrix material for flexible electronic devices, electronic skin and health detection devices due to its outstanding flexibility and stretchability. However, hydrogel-based flexible electronic devices swell once they are placed in a high humidity or underwater environment. The swelling behavior could damage the internal structure of hydrogels, ultimately leading to the reduction or complete loss of mechanical properties, electrical conductivity and sensing function. In order to resolve the above problems, a double network ionogel with remarkable anti-swelling behavior, stretchability and conductive properties was prepared. The ionogel consisted of gelatin (G) and copolymerization of acrylic acid (AA), 2-hydroxyethyl methacrylate (HEMA), butyl acrylate (BA), dimethylaminoethyl methacrylate maleate (D) and N,N'-methylene-bis-acrylamide (MBAA). Due to the dense crosslinking network and hydrophobic interaction, the ionogel exhibited remarkable anti-swelling properties (7.64% of the 30-day equilibrium swelling ratio in deionized water). D and MBAA were simultaneously introduced into the ionogel system as cross-linking agents to provide a large number of cross-linking points, improving the cross-linking density of the ionogel. Importantly, the introduction of D avoided ionic leakage by free radical copolymerization. Furthermore, the ionogel maintained stable mechanical properties and conductivity after being submerged in deionized water owing to remarkable anti-swelling performance. The mechanical properties of the ionogel retained 89.75% of the initial mechanical properties after a 5-day immersion in deionized water. Therefore, this ionogel could be employed as an underwater flexible wearable sensor for high humidity or underwater motion monitoring.

Mussel-inspired adhesive and anti-swelling hydrogels for underwater strain sensing.

The application of hydrogels in an underwater environment is limited due to their swelling behavior and the existence of a hydration layer. In this study, a hydrogel based on poly(sulfobetaine methacrylate) (PSBMA), tannic acid (TA) and montmorillonite (MMT) was prepared with excellent anti-swelling properties and underwater self-adhesion properties. The PSBMA hydrogel has excellent anti-swelling properties due to the strong electrostatic interaction between charged groups of PSBMA chains. Inspired by marine mussels, tannic acid modified montmorillonite (TA@MMT) was introduced. Natural polyphenol tannic acid, as a catechol donor, provides a large number of catechol groups for hydrogels. Montmorillonite acts as the physical cross-linking point of PSBMA chains through electrostatic interaction to improve the cohesion of the hydrogel. By combining the adhesion mechanism of zwitterions and catechol, the hydrogel maintains adhesion in air and underwater environments. In addition, a strain sensor was prepared based on the PSBMA/TA@MMT hydrogel, which can closely fit the human skin and stably monitor different movements in air and in underwater environments. Through a Bluetooth communication system, long-distance information transmission can be achieved. Therefore, the PSBMA/TA@MMT hydrogel broadens the application prospect of wearable devices in the underwater environment.

Efficient adsorption of chloroquine phosphate by a novel sodium alginate/tannic acid double-network hydrogel in a wide pH range

In this work, a novel double-network composite hydrogel (SA/TA), composed of sodium alginate (SA) and tannic acid (TA), was designed and fabricated by a successive cross-linking method using Ti(IV) and Ca(II) as crosslinkers. SA/TA exhibited reinforced mechanical strength and anti-swelling properties because of the double-network structure. SA/TA was used as an adsorbent for removal of a popular antiviral drug, chloroquine phosphate (CQ), in water. The adsorption performance of SA/TA was systematically investigated, to study various effects including those of TA mass content, solution pH, adsorption time, and initial CQ concentration. Adsorption was also examined in presence of inorganic and organic coexisting substances commonly found in wastewater, and under different actual water samples. Batch experimental results indicated that SA/TA could maintain higher and more stable CQ uptakes within a wide solution pH range from 3.0 to 10.0, compared to its precursor, SA hydrogel, owing to the addition of TA-Ti(IV) coordination network. The maximum experimental CQ uptake exhibited by the 1:1 (by wt) SA/TA (SA/TA2) was as high as 0.699 mmol/g at the initial pH of 9.0. A high concentration of coexisting NaCl evidently reduced the CQ uptakes of SA/TA2 due to the electrostatic shielding effect, moreover, divalent cations including Ca(II) and Mg(II) also inhibited the adsorption of CQ due to competitive adsorption. However, humic acid had little effect on this adsorption. Considering the apparent adsorption performance, the aforementioned effects of various factors and the spectroscopic characterizations, multi-interactions are suggested for adsorption including chelation, electrostatic interactions, π-π electron donor-acceptor interaction and hydrogen bonding. SA/TA showed a slight loss in adsorption capacity toward CQ and sustained physicochemical structural stability, even after six adsorption–desorption cycles. In addition to CQ, SA/TA could be efficiently used for adsorption of two other antivirus drugs, namely, hydroxychloroquine sulfate and oseltamivir phosphate. This work provides an effective strategy for the design and fabrication of novel adsorbents that can effectively adsorb antiviral drugs over a wide pH range.

Insight of multifunctional Cu-alginate hydrogel membrane for precise molecule/ion separation applications

Membrane technology has garnered significant attention for its role in addressing the challenges of molecule/ion separation processes, yet it remains hindered by issues such as membrane fouling, including organic and biofouling. While calcium alginate (CaAlg) membranes have demonstrated remarkable antifouling and molecule/ion separation properties, they suffer from high swell ability and poor mechanical performance. This study introduces a one-step ion-crosslinking method to fabricate a series of copper alginate (CuAlg) hydrogel membranes. These membranes are then assembled into a dual-layer structure with a modified hydrophilic and mechanically robust microfiltration fiber support layer (MHSL). Notably, the CuAlg/MHSL membrane exhibits excellent separation performance, characterized by high selectivity and flux recovery rate. This membrane significantly enhances the long-term molecule/ion separation performance through improved mechanical strength, anti-swelling properties, and antimicrobial capabilities. In addition, the decreased thickness of the CuAlg/MHSL membrane enables higher flux rates, proving beneficial in cases of CaAlg membranes' inability to perform well under high-salt conditions. To further investigate the pore structure and anti-swelling mechanism of the CuAlg membrane, molecular dynamics (MD) simulations are conducted. Additionally, a life cycle analysis comparing the CuAlg hydrogel with various traditional polymers assesses their respective environmental impacts, highlighting the eco-friendliness of the hydrogel as a membrane substrate. These findings provide valuable insights for developing sustainable hydrogel membranes with stable performance and high separation efficiency in molecular/ion separation applications.

Collagen fibril-like injectable hydrogels from self-assembled nanoparticles for promoting wound healing

Soft hydrogels are excellent candidate materials for repairing various tissue defects, yet the mechanical strength, anti-swelling properties, and biocompatibility of many soft hydrogels need to be improved. Herein, inspired by the nanostructure of collagen fibrils, we developed a strategy toward achieving a soft but tough, anti-swelling nanofibrillar hydrogel by combining the self-assembly and chemical crosslinking of nanoparticles. Specifically, the collagen fibril-like injectable hydrogel was subtly designed and fabricated by self-assembling methylacrylyl hydroxypropyl chitosan (HM) with laponite (LAP) to form nanoparticles, followed by the inter-nanoparticle bonding through photo-crosslinking. The assembly mechanism of nanoparticles was elucidated by both experimental and simulation techniques. Due to the unique structure of the crosslinked nanoparticles, the nanocomposite hydrogels exhibited low stiffness (G’< 2 kPa), high compressive strength (709 kPa), and anti-swelling (swelling ratio of 1.07 in PBS) properties. Additionally, by harnessing the photo-crosslinking ability of the nanoparticles, the nanocomposite hydrogels were processed as microgels, which can be three-dimensionally (3D) printed into complex shapes. Furthermore, we demonstrated that these nanocomposite hydrogels are highly biocompatible, biodegradability, and can effectively promote fibroblast migration and accelerate blood vessel formation during wound healing. This work presents a promising approach to develop biomimetic, nanofibrillar soft hydrogels for regenerative medicine applications.

Applications of pteridophytes in Himachal Pradesh, Western Himalaya: An ethnobotanical perspective

Ferns exhibit wide distribution in the Indian Himalayan Region (IHR), with Himachal Pradesh providing optimal climatic conditions for diverse fern species. This study documents the ethnobotanical applications of 45 pteridophyte species, spanning 16 families and 21 genera in Himachal Pradesh. Pteridophytes hold economic importance due to their edibility, ornamental appeal, and medicinal properties. Local communities extensively employ Pteridophytes with medicinal attributes to address various health concerns, including boils, wounds, colds, coughs, gastrointestinal diseases, gonorrhea, typhoid, urinary problems, uterine disorders, and hair loss. Moreover, Pteridophytes exhibit anti-inflammatory and anti-swelling properties, where plant paste is directly applied to the skin for swelling reduction. The monsoon season sees substantial growth of ferns in moisture-rich soil. Apart from their utilitarian purposes, ferns contribute to aesthetic values and serve as outdoor and ornamental plants. Noteworthy ornamental ferns, such as Adiantum capillus-veneris, Pteris cretica, Pteris multifida, Polypodium polypodioides, and Lepisorus thunbergianus, are acknowledged for their potential to enhance air quality. Diplazium esculentum, an edible fern, stands out as a popular and nutritious cuisine in Himachal Pradesh. The article concludes with recommendations for the conservation and sustainable utilization of ethnobotanically significant Pteridophytes in Himachal Pradesh.

Water-Induced Phase Separation for Anti-Swelling Hydrogel Adhesives in Underwater Soft Electronics.

The development of hydrogel-based underwater electronics has gained significant attention due to their flexibility and portability compared to conventional rigid devices. However, common hydrogels face challenges such as swelling and poor underwater adhesion, limiting their practicality in water environments. Here, a water-induced phase separation strategy to fabricate hydrogels with enhanced anti-swelling properties and underwater adhesion is presented. By leveraging the contrasting affinity of different polymer chains to water, a phase-separated structure with rich hydrophobic and dilute hydrophilic polymer phases is achieved. This dual-phase structure, meticulously characterized from the macroscopic to the nanoscale, confers the hydrogel network with augmented retractive elastic forces and facilitates efficient water drainage at the gel-substrate interface. As a result, the hydrogel exhibits remarkable swelling resistance and long-lasting adhesion to diverse substrates. Additionally, the integration of carboxylic multiwalled carbon nanotubes into the hydrogel system preserves its anti-swelling and adhesion properties while imparting superior conductivity. The conductive phase-separated hydrogel exhibited great potential in diverse underwater applications, including sensing, communication, and energy harvesting. This study elucidates a facile strategy for designing anti-swelling underwater adhesives by leveraging the ambient solvent effect, which is expected to offer some insights for the development of next-generation adhesive soft materials tailored for aqueous environments.

Molecular dynamics simulation of the mechanical properties and thermal conductivity of aromatic electrolytes in proton exchange membrane fuel cells

Evaluation of mechanical and thermodynamic properties and understanding of the influence mechanism are crucial for the fuel cell membranes. The molecular dynamics simulation are performed to quantitatively study the variation of the absorption, swelling rates, tensile compression, and thermal conductivity for four membranes containing three typical aromatic polymers, namely sulfonated poly-ether-ether-ketone (PEEK), polysulfone acid-phenol-F (PAEF), phosphoric-pyridine-polyethers (PEP), and typical Nafion 213 (perfluorinated sulfonic acid PFSA). A microscopic model is constructed to establish the relationship between the hydrophobicity of the functional groups, water cluster distribution, and swelling properties. PFSA (Nafion) exhibits the best antiswelling properties. Main chain hydrophobicity and side chain hydrophilicity can enhance water aggregation, which leads to uneven water distribution during water absorption. The membrane swelling rate decreases when the water distribution is inhomogeneous. The sensitivity of the membrane thermal conductivity is more apparent when the water distribution is inhomogeneous. Nanoscale cavities and rearrangements in the molecular chain orientations along the stretching direction are identified based on microscopic morphological analysis. Aromatic polymer films exhibit higher thermal conductivity than that of Nafion, but their large water swelling rates and relatively low tensile-compression properties need to be improved by further research for realizing widescale practical applications.

Easy-to-Prepare Flexible Multifunctional Sensors Assembled with Anti-Swelling Hydrogels.

Recent years have witnessed the development of flexible electronic materials. Flexible electronic devices based on hydrogels are promising but face the limitations of having no resistance to swelling and a lack of functional integration. Herein, we fabricated a hydrogel using a solvent replacement strategy and explored it as a flexible electronic material. This hydrogel was obtained by polymerizing 2-hydroxyethyl methacrylate (HEMA) in ethylene glycol and then immersing it in water. The synergistic effect of hydrogen bonding and hydrophobic interactions endows this hydrogel with anti-swelling properties in water, and it also exhibits enhanced mechanical properties and outstanding self-bonding properties. Moreover, the modulus of the hydrogel is tissue-adaptable. These properties allowed the hydrogel to be simply assembled with a liquid metal (LM) to create a series of structurally complex and functionally integrated flexible sensors. The hydrogel was used to assemble resistive and capacitive sensors to sense one-, two-, and three-dimensional strains and finger touches by employing specific structural designs. In addition, a multifunctional flexible sensor integrating strain sensing, temperature sensing, and conductance sensing was assembled via simple multilayer stacking to enable the simultaneous monitoring of underwater motion, water temperature, and water quality. This work demonstrates a simple strategy for assembling functionally integrated flexible electronics, which should open opportunities in next-generation electronic skins and hydrogel machines for various applications, especially underwater applications.

Zero-waste preparation of supramolecular hydrogels and films comprising tannic acid and ultra-high-molecular-weight polyethylene oxide

Recently, tannic acid (TA) has been attracting attention as a component for supramolecular hydrogels. In fact, TA was reported to form viscous hydrogels with polyethylene oxide (PEO) (∼10 kDa), a typical macromolecule; however, little is known about hydrogels consisting of TA with ultra-high-molecular-weight (UHMW) PEO (≥100 kDa). In this study, TA/PEO hydrogels containing PEO of various molecular weights are prepared to investigate the effects of the molecular weight of PEO on the structure and characteristic physical properties of TA/PEO hydrogels. Interestingly, UHMW PEOs (≥100 kDa) formed stretchable hydrogel aggregates (TaPeO Gel), which were completely different from existing viscous TA/PEO gels (∼10 kDa). The mechanical properties of the TaPeO Gel (500 kDa) include high elongation, strong adhesive ability, and anti-swelling properties. In addition, the TaPeO Gel dried at 40 °C for 8 days was a lightweight and rigid material that exhibited shape memory and self-healing properties. Furthermore, a highly stretchable film (TaPeO Film) was obtained during the preparation of the TaPeO Gel by drying the unwanted supernatant from the TA/PEO mixture. These results suggest that advanced supramolecular gels and films can be prepared simultaneously from TA and UHMW PEO in a zero-waste process.

Strong, Tough, and Anti-Swelling Supramolecular Conductive Hydrogels for Amphibious Motion Sensors.

Conductive polymer hydrogels (CPHs) are widely employed in emerging flexible electronic devices because they possess both the electrical conductivity of conductors and the mechanical properties of hydrogels. However, the poor compatibility between conductive polymers and the hydrogel matrix, as well as the swelling behavior in humid environments, greatly compromises the mechanical and electrical properties of CPHs, limiting their applications in wearable electronic devices. Herein, a supramolecular strategy to develop a strong and tough CPH with excellent anti-swelling properties by incorporating hydrogen, coordination bonds, and cation-π interactions between a rigid conducting polymer and a soft hydrogel matrix is reported. Benefiting from the effective interactions between the polymer networks, the obtained supramolecular hydrogel has homogeneous structural integrity, exhibiting remarkable tensile strength (1.63MPa), superior elongation at break (453%), and remarkable toughness (5.5MJ m-3 ). As a strain sensor, the hydrogel possesses high electrical conductivity (2.16S m-1 ), a wide strain linear detection range (0-400%), and excellent sensitivity (gauge factor = 4.1), sufficient to monitor human activities with different strain windows. Furthermore, this hydrogel with high swelling resistance has been successfully applied to underwater sensors for monitoring frog swimming and underwater communication. These results reveal new possibilities for amphibious applications of wearable sensors.

Zwitterionic polymer brush-functionalized dual-crosslinked hydrogel via subsurface-initiated atom transfer radical polymerization for anti-fouling applications

In this work, a double-network (DN) hydrogel embedded with initiator (HHyBr) was prepared and then reinforced with Fe3+, after which the antifouling polymer (poly-sulfobetaine vinyl imidazole, PSBVI) was successfully grafted onto the HHy-Br substrate via subsurface-initiated atom transfer radical polymerization (sSI-ATRP) to obtain PSBVI-functionalized HHy-Br (HHy-PSBVI). It has been demonstrated that Fe3+ can increase the crosslinking density of HHyBr; as a result, the tensile strength of the as-prepared hydrogel was increased from 0.07 to 1.75 MPa, as well as its anti-swelling properties were improved (from 648 % to 219 %). In addition, the presence of Fe3+ can efficiently promote the sSI-ATRP process. Compared with HHyBr, the PSBVI-functionalized HHy-Br manifested a significant decrease in friction coefficient, as the grafted high-thickness PSBVI brush (about 200 μm) has excellent hydrophilicity and can form a strong hydration layer for lubrication. Furthermore, the as-prepared HHy-PSBVI also exhibits outstanding antibacterial properties against E. coli (nearly 100 % were removed) and S. aureus (99 % were removed), as well as a satisfactory antifouling effect against microalgae (93 % Dunaliella and 92 % Chlorella were removed), which is attributed to the synergistic effect between the strong hydration of the zwitterionic polymer and the good bactericidal effect of the cationic imidazole group.

Confined Ionic-Liquid-Mediated Cation Diffusion through Layered Membranes for High-Performance Osmotic Energy Conversion.

Ion-selective membranes act as the core components in osmotic energy harvesting, but remain with deficiencies such as low ion selectivity and a tendency to swell. 2D nanofluidic membranes as competitive candidates are still subjected to limited mass transport brought by insufficient wetting and poor stability in water. Here, an ionic-liquid-infused graphene oxide (GO@IL) membrane with ultrafast ion transport ability is reported, and how the confined ionic liquid mediates selective cation diffusion is revealed. The infusion of ionic liquids endows the 2D membrane with excellent mechanical strength, anti-swelling properties, and good stability in aqueous electrolytes. Importantly, immiscible ionic liquids also provide a medium, allowing partial dehydration for ultrafast ion transport. Through molecular dynamics simulation and finite element modeling, that GO nanosheets induce ionic liquids to rearrange, bringing in additional space charges, which can be coupled with GO synergistically, is proved. By mixing 0.5/0.01m NaCl solution, the power density can achieve a record value of ≈6.7W m-2 , outperforming state-of-art GO-based membranes. This work opens up a new route for boosting nanofluidic energy conversion because of the diversity of the ILs and 2D materials.

Fabrication of a High-Strength, Tough, Swelling-Resistant, Conductive Hydrogel via Ion Cross-Linking, Directional Freeze-Drying, and Rehydration.

Conductive hydrogels have been in huge demand in biomedical and wearable electronics. However, the application of traditional conductive hydrogels is largely limited due to their poor mechanical properties. Here, a conductive hydrogel with excellent mechanical strength and swelling resistance properties is prepared by ion cross-linking, directional freeze-drying, and rehydration. First, the acrylamide and acrylic acid are polymerized in the κ-carrageenan solution to form the hydrogel. Then, the obtained hydrogel is cross-linked with Fe3+ by soaking in ferric chloride solution. Finally, the ionic cross-linked hydrogels are reinforced by directional freeze-drying and rehydration. The resulting hydrogel has excellent tensile strength (5.67 MPa) and high toughness (7.63 MJ/m3). It is worth noting that the hydrogel also had excellent anti-swelling properties. Its mechanical strength and volume almost show no changes after soaking in deionized water for 40 days. In addition, the hydrogel exhibits good ionic conductivity (0.091 S/m), high sensitivity, and excellent stability when applied as a strain sensor. This work proposes a simple method to fabricate a conductive hydrogel with great mechanical properties and swelling resistance, which displays huge potential in varied fields.

Using a Novel Pervaporative Sequential-Co-immobilized Two-Sectional Bioreactor with an Ultralow Fouling–Biofouling Superhydrophobic Silicallite-1/PDMS Membrane to Enhance Bioethanol Production

This study is on the efficient fermentation of high glucose (G) and xylose (X) levels (G/X ratio of 1.5:1), simulating the hydrolysate of lignocellulosic wastes, via an innovative integrated two-stage fermentation–pervaporation process. Immobilized Zymomonas mobilis (Z) and Pichia stipitis (P) were exploited in a sequential-co-immobilized culture (Z in the first stage and Z and P in second stage) to simultaneously increase bioethanol productivity and lessen the inhibitions. The threshold inhibition was evaluated in 100 mL shake flasks by raising the initial total sugar concentration from 50 to 200 g/L where complete inhibition was observed at 200 g/L. Subsequently, fermentation (G: 120 g/L, X: 80 g/L) was examined in a sequential-co-immobilized two-sectional bioreactor (ITB-2L) during 200 h. ITB resulted in 100% glucose and 16% xylose conversion, showing ethanol productivity of 0.26 g/L·h and yield of 0.4 ge/gs. To investigate the effect of reducing inhibitions, a tubular superhydrophobic silicalite-1/PDMS pervaporative (TSP) autoclavable membrane with antiswelling properties was fabricated. The pervaporative sequential-co-immobilized two-sectional bioreactor (PITB) using TSP enhanced xylose conversion (57%), ethanol productivity (0.39 g/L·h), and yield (0.47 ge/gs). The membrane surface was probed after 161 h of usage, and the limited presence of only negative ions on its surface proved its superior ultralow fouling–biofouling formation. PITB proved itself as a robust integrated process for the second-generation bioethanol production.

One-Step Soaking Strategy toward Anti-Swelling Hydrogels with a Stiff "Armor".

Double-network (DN) hydrogels consisting of noncovalent interacting networks are highly desired due to their well-controlled compositions and environmental friendliness, but the low water resistance always impairs their mechanical strength. Here, an anti-swelling hydrogel possessing the core/shell architecture through rational regulation of multiple weak noncovalent interactions is prepared. A composite hydrogel consists of chitosan (CS) and poly(N-acryloyl 2-glycine) (PACG), readily forming the shell-structured DN hydrogel after soaking in a FeCl3 solution because of in situ formation of chain entanglements, hydrogen bonds, and ionic coordination. The produced DN hydrogels exhibit excellent anti-swelling behaviors and mechanical durability for over half a year, even in some strict situations. Taking the merits of noncovalent bonds in adjustability and reversibility, the swelling property of these hydrogels can be easily customized through control of the ion species and concentrations. A dynamically reversible transition from super-swelling to anti-swelling is realized by breaking up and rebuilding the metal-coordination complexes. This facile but efficient strategy of turning the noncovalent interactions and consequently the mechanics and anti-swelling properties is imperative to achieve the rational design of high-performance hydrogels with specific usage requirements and expand their applicability to a higher stage.

TFC membrane with in-situ crosslinked ultrathin chitosan layer for efficient water/ethanol separation enabled by multiple supramolecular interactions

Chitosan (CS) membranes have been widely applied in water/ethanol separation via membrane-based pervaporation, but a bottleneck in the practical application always exists due to their severe swelling behavior in aqueous solution and consequently low permeation flux due to the large membrane thickness. Here, thin film composite (TFC) hollow fiber (HF) membrane with an in-situ-crosslinked ultrathin CS selective layer is developed via multiple supramolecular interaction-crosslinking strategy for efficient water/ethanol separation via pervaporation. With Fe3+-phytic acid (PhA) complex pre-deposited on the substrate, the subsequently introduced CS selective layer is in-situ crosslinked via multiple supramolecular interactions, including coordination, electrostatic, and hydrogen bonding interactions. By varying the cycle number of Fe3+/PhA assembly and the species of employed organophosphorus acid, the anti-swelling properties of the resultant TFC CS membrane is enhanced and the separation performance is maximized. The optimal TFC-CS-Fe2PhA2 membrane with two cycles of Fe3+/PhA assembly has a selective layer thickness of 60 ​nm and a corresponding ultrahigh flux of 2.87 ​kg/m2 h, coupled with a permeate water concentration of 99.5 ​wt% and good long-term stability for the dehydration of 85 ​wt% ethanol aqueous solution at 50 ​°C. The supramolecular interaction-crosslinking presented in this work provides an efficient and promising strategy for the construction of TFC CS membrane with excellent anti-swelling property and superior separation performance.